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• Accelerated cardiac MR stress perfusion with radial sampling after physical exercise with an MR-compatible supine bicycle ergometer.

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  Accelerated cardiac MR stress perfusion with radial sampling after physical exercise with an MR-compatible supine bicycle ergometer.

  Author(s)

  Pflugi S, Roujol S, Akçakaya M, Kawaji K, Foppa M, Heydari B, Goddu B, Kissinger K, Berg S, Manning WJ, Kozerke S, Nezafat R.

  Date

  2014-08-08

  Source

  Magnetic resonance in medicine

  PURPOSE:
  To evaluate the feasibility of accelerated cardiac MR (CMR) perfusion with radial sampling using nonlinear image reconstruction after exercise on an MR-compatible supine bike ergometer.

  METHODS:
  Eight healthy subjects were scanned on two separate days using radial and Cartesian CMR perfusion sequences in rest and exercise stress perfusion. Four different methods (standard gridding, conjugate gradient SENSE [CG-SENSE], nonlinear inversion with joint estimation of coil-sensitivity profiles [NLINV] and compressed sensing with a total variation constraint [TV]) were compared for the reconstruction of radial data. Cartesian data were reconstructed using SENSE. All images were assessed by two blinded readers in terms of image quality and diagnostic value.

  RESULTS:
  CG-SENSE and NLINV were scored more favorably than TV (in both rest and stress perfusion cases, P < 0.05) and gridding (for rest perfusion cases, P < 0.05). TV images showed patchy artifacts, which negatively influenced image quality especially in the stress perfusion images acquired with a low number of radial spokes. Although CG-SENSE and NLINV received better scores than Cartesian sampling in both rest and exercise stress perfusion cases, these differences were not statistically significant (P > 0.05).

  CONCLUSION:
  We have demonstrated the feasibility of accelerated CMR perfusion using radial sampling after physical exercise using a supine bicycle ergometer in healthy subjects. For reconstruction of undersampled radial perfusion, CG-SENSE and NLINV resulted in better image quality than standard gridding or TV reconstruction. Further technical improvements and clinical assessment are needed before using this approach in patients with suspected coronary artery disease.

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• An MR-Compatible Treadmill for Exercise Stress Cardiac Magnetic Resonance Imaging

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  An MR-Compatible Treadmill for Exercise Stress Cardiac Magnetic Resonance Imaging

  Author(s)

  Eric L. Foster, John W. Arnold, Mihaela Jekic, Jacob Bender, Vijay Balasubramanian, Paaladinesh Thavendiranathan, Jennifer A. Dickerson, Subha V. Raman, and Orlando P. Simonetti

  Date

  2012-03-13

  Source

  Magnetic Resonance in Medicine. 2012 March; 67(3): 880–889.

  This article describes an MR-safe treadmill that enables cardiovascular exercise stress testing adjacent to the MRI system, facilitating cardiac MR imaging immediately following exercise stress. The treadmill was constructed of non-ferromagnetic components utilizing a hydraulic power system. Computer control ensured precise execution of the standard Bruce treadmill protocol commonly used for cardiovascular exercise stress testing. The treadmill demonstrated no evidence of ferromagnetic attraction and did not affect image quality. Treadmill performance met design specifications both inside and outside the MRI environment. Ten healthy volunteers performed the Bruce protocol with the treadmill positioned adjacent to the MRI table. Upon reaching peak stress (98% ± 8% of age-predicted maximum heart rate (APMHR)), the subjects lay down directly on the MRI table, a cardiac array coil was placed, an intravenous line connected, and stress cine and perfusion imaging performed. Cine imaging commenced on average within 24 ± 4 s and was completed within 40 ± 7 s of the end of exercise. Subject heart rates were 86% ± 9% of APMHR at the start of imaging and 81% ± 9% of APMHR upon completion of cine imaging. The MRI compatible treadmill was shown to operate safely and effectively in the MRI environment.

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• Arm exercise as an alternative to pharmacologic stress testing: arm exercise stress testing and outcome

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  Arm exercise as an alternative to pharmacologic stress testing: arm exercise stress testing and outcome

  Author(s)

  Martin WH 3rd, Xian H, Wagner D, Chandiramani P, Bainter E, Ilias-Khan

  Date

  2014-02-14

  Source

  American Heart Journal

  BACKGROUND:
  Treadmill exercise variables are powerful predictors of all-cause mortality but are unobtainable in at least 50% of patients because of disabilities precluding lower extremity exercise. Arm exercise stress testing is a potentially cost-effective alternative, but no long-term outcome data are available.

  METHODS:
  We performed arm ergometer stress tests on 446 veterans aged 64.0 (11.1) years (mean [SD]) between 1997 and 2002 and investigated whether arm exercise capacity in resting metabolic equivalents, heart rate recovery (in beats per minute), delta (peak resting) heart rate (in beats per minute), and other exercise variables predict long-term all-cause mortality, myocardial infarction (MI), or coronary revascularization.

  RESULTS:
  During follow-up of 12.0 (1.3) years, 255 patients died (57.2%), 70 had MI (15.7%), and 118 underwent coronary revascularization (26.4%). After adjustment for significant demographic and clinical variables, death was predicted by arm metabolic equivalents (hazard ratio/SD 0.59, 95% CI 0.46-0.75, P < .001), heart rate recovery (hazard ratio/SD 0.64, 95% CI 0.49-0.83, P < .001), and delta heart rate (hazard ratio/SD 0.75, 95% CI 0.63-0.91, P < .001). No exercise variables prognosticated MI, but coronary revascularization was predicted by stress-induced ST-segment deviations (hazard ratio 2.64, 95% CI 1.16-4.33, P < .001), limiting angina (hazard ratio 4.70, 95% CI 1.81-12.22, P < .001), and an abnormal perfusion imaging result (hazard ratio 2.0, 95% CI 1.14-3.51, P < .02).

  CONCLUSIONS:
  Arm exercise capacity, heart rate recovery, and delta heart rate predict 12-year all-cause mortality and arm exercise-induced ST changes, limiting angina, and an abnormal nuclear imaging result portend coronary revascularization in lower extremity disabled veterans.

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• Assessing exercise cardiac reserve using real-time cardiovascular magnetic resonance

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  Assessing exercise cardiac reserve using real-time cardiovascular magnetic resonance

  Author(s)

  Thu-Thao Le, Jennifer Ann Bryant, Alicia Er Ting, Pei Yi Ho, Boyang Su, Raymond Choon Chye Teo, Julian Siong-Jin Gan, Yiu-Cho Chung, Declan P. O’Regan, Stuart A. Cook, Calvin Woon-Loong Chin

  Date

  2017-07-19

  Source

  Journal of Cardiovascular Magnetic Resonance

  Background: Exercise cardiovascular magnetic resonance (ExCMR) has great potential for clinical use but its development has been limited by a lack of compatible equipment and robust real-time imaging techniques. We developed an exCMR protocol using an in-scanner cycle ergometer and assessed its performance in differentiating athletes from non-athletes.

  Methods: Free-breathing real-time CMR (1.5T Aera, Siemens) was performed in 11 athletes (5 males; median age 29 [IQR: 28–39] years) and 16 age- and sex-matched healthy volunteers (7 males; median age 26 [interquartile range (IQR): 25–33] years). All participants underwent an in-scanner exercise protocol on a CMR compatible cycle ergometer (Lode BV, the Netherlands), with an initial workload of 25W followed by 25W-increment every minute. In 20 individuals, exercise capacity was also evaluated by cardiopulmonary exercise test (CPET). Scan-rescan reproducibility was assessed in 10 individuals, at least 7 days apart.

  Results: The exCMR protocol demonstrated excellent scan-rescan (cardiac index (CI): 0.2 ± 0.5L/min/m2) and inter-observer (ventricular volumes: 1.2 ± 5.3mL) reproducibility. CI derived from exCMR and CPET had excellent correlation (r = 0.83,p < 0.001) and agreement (1.7 ± 1.8L/min/m2). Despite similar values at rest (P = 0.87), athletes had increased exercise CI compared to healthy individuals (at peak exercise: 12.2 [IQR: 10.2–13.5] L/min/m2 versus 8.9 [IQR: 7.5–10.1] L/min/m2, respectively; P < 0.001). Peak exercise CI, where image acquisition lasted 13–17 s, outperformed that at rest (c-statistics = 0.95 [95% confidence interval: 0.87–1.00] versus 0.48 [95% confidence interval: 0.23–0.72], respectively; P < 0.0001 for comparison) in differentiating athletes from healthy volunteers; and had similar performance as VO2max (c-statistics = 0.84 [95% confidence interval = 0.62–1.00]; P = 0.29 for comparison).

  Conclusions: We have developed a novel in-scanner exCMR protocol using real-time CMR that is highly reproducible. It may now be developed for clinical use for physiological studies of the heart and circulation.

  Keywords: Cardiovascular magnetic resonance, Supine bike ergometer, Exercise physiology, Cardiopulmonary exercise test

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• Assessing vascular response to exercise using a combination of real-time spiral phase contrast MR and noninvasive blood pressure measurements

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  Assessing vascular response to exercise using a combination of real-time spiral phase contrast MR and noninvasive blood pressure measurements

  Author(s)

  Steeden JA, Atkinson D, Taylor AM, Muthurangu V

  Date

  2010-04-30

  Source

  Journal of Magnetic Imaging (JMRI)

  PURPOSE:
  To measure the hemodynamic response to exercise using real-time velocity mapping magnetic resonance imaging (MRI), incorporating a high temporal resolution spiral phase contrast (PC) sequence accelerated with sensitivity encoding (SENSE).

  MATERIALS AND METHODS:
  Twenty healthy adults underwent MRI at rest and during supine exercise at two different exercise levels. Flow volumes were assessed in the ascending aorta using a spiral SENSE real-time PC sequence. The sequence was validated at rest against a vendor supplied gated PC sequence, and also at rest and during exercise against left ventricular volumes assessed using a radial k-t SENSE real-time sequence. Combining the measured flow volumes with simultaneous oscillometric blood pressure measurements, enabled the noninvasive calculations of systemic vascular resistance (SVR) and arterial compliance (C).

  RESULTS:
  Measured flow volumes correlated very well between the sequences at rest and during exercise. Cardiac output (CO) and heart rate were found to significantly increase during exercise, while SVR and C were found to decrease significantly.

  CONCLUSION:
  Hemodynamic response to exercise can be accurately quantified using a high temporal resolution spiral SENSE real-time flow imaging. This may allow early detection of hypertension and a greater understanding of the early changes in this condition.

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• Atrial volume and function during exercise in health and disease

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  Atrial volume and function during exercise in health and disease

  Author(s)

  Frédéric Schnell, Guido Claessen, André La Gerche, Piet Claus, Jan Bogaert, Marion Delcroix, François Carré, Hein Heidbuche

  Date

  2017-01-01

  Source

  Journal of Cardiovascular Magnetic Resonance

  Abstract
  Background: Although atrial function has prognostic significance in many cardiovascular conditions, changes during exercise have not previously been assessed. The aim of this study was to evaluate left atrial (LA) and right atrial (RA) volume and function during incremental exercise, both in normal individuals, healthy athletes, and in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

  Methods: Fifteen healthy non-athletes, 15 athletes and 15 CTEPH patients underwent multi-slice real-time cardiovascular magnetic resonance imaging at rest and during supine bicycle exercise with simultaneous invasive hemodynamic measurements.

  Results: At rest, athletes had larger indexed maximal RA and LA volumes (iRAVmax, iLAVmax) than CTEPH patients and non-athletes, the latter two groups having similar values. CTEPH patients had lower RA and LA emptying functions (EmF) at rest. During exercise, RA volumes (maximum and minimum) increased in CTEPH patients, whilst decreasing in athletes and non-athletes (P<0.001). The exercise-induced change in iLAVmax was similar between groups, but iLAVmin did not decrease in CTEPH patients. Thus exercise-induced increases in RAEmF and LAEmF, as seen in normal physiology, were significantly impaired in CTEPH patients. At peak exercise, RA volumes (maximum and minimum) and EmF correlated strongly with RA pressure (R=0.70;P=0.005;R=0.83;P<0.001;R=−0.87; P<0.001). On multivariate analysis, peak exercise RAEmF and iLAVmin were independent predictors of VO2peak in CTEPH patients and together explained 72% of the variance in VO2peak (ß =0.581 and ß=−0.515, respectively).

  Conclusions: In normal physiology, RAEmF and LAEmF increase with exercise, whereas CTEPH patients have impaired LAEmF and RAEmF, which becomes more apparent during exercise. Therefore, the changes in atrial volumes and function during exercise enable a far better distinction between physiological and pathological atrial remodeling than resting measures of volumes which are prone to confounding factors (e.g. endurance training). Peak exercise RAEmF is a good marker of poor functional state in CTEPH patients.

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• Automatic segmentation propagation of the aorta in real-time phase contrast MRI using nonrigid registration.

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  Automatic segmentation propagation of the aorta in real-time phase contrast MRI using nonrigid registration.

  Author(s)

  Freddy Odille, Jennifer A Steeden, Vivek Muthurangu, David Atkinson

  Date

  2011-01-03

  Source

  Journal of Magnetic Resonance Imaging (impact factor: 2.7). 01/2011; 33(1):232-8.

  To assess the use of a nonrigid registration technique for semi-automatic segmentation of the aorta from real-time velocity mapping MRI.
  Real-time phase contrast images were acquired to measure flow and stroke volumes in 10 subjects, during free breathing, at rest, and during exercise. A nonrigid registration algorithm was developed to propagate a manually drawn region of interest in the aorta from one frame to all other frames of the real-time sequence (148 images). Thus the technique provided a semi-automatic segmentation over the whole sequence of images. The accuracy was assessed by comparison with manual segmentations in terms of Dice overlap measures and stroke volumes (SV).
  Semi-automatic segmentations were comparable to manual ones (Dice score of 0.89 ± 0.04). Inter-observer reproducibility was similar for manual and semi-automatic segmentations (Dice score of 0.90 ± 0.04 in both cases, the difference was not significant). SV measurements also showed good agreement between manual and semi-automatic segmentations (correlation coefficient r > 0.94), and the differences were not statistically significant.
  Although real-time phase contrast images have compromised image quality, a fast and robust segmentation of the aorta was possible using the registration-based technique.

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• Biventricular response to supine physical exercise in young adults assessed with ultrafast magnetic resonance imaging

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  Biventricular response to supine physical exercise in young adults assessed with ultrafast magnetic resonance imaging

  Author(s)

  Arno A.W. Roest, Patrik Kunz, Hildo J. Lamb, Willem A. Helbing, Ernst E. van der Wall, Albert de Roos

  Date

  2001-03-01

  Source

  The American Journal of Cardiology Volume 87, Issue 5, 1 March 2001, Pages 601–605

  Simultaneous assessment of left ventricular (LV) and right ventricular (RV) response to exercise is limited with the current imaging modalities. Magnetic resonance imaging (MRI) techniques are now under development that allow near real-time evaluation of biventricular function under physical stress. This approach may open new avenues to study heart function in response to exercise in health and disease. The aim of this study was to evaluate biventricular response to supine physical exercise using ultrafast MRI. Biventricular volumes and function were examined in 16 healthy volunteers (mean age 18 ± 2 years) using an ultrafast MRI sequence at rest and during an exercise protocol on a MRI compatible bicycle ergometer. Exercise level was individualized at the workload corresponding to 60% of the maximal oxygen uptake. All subjects completed the exercise MRI examination, allowing functional evaluation. Stroke volume of both ventricles increased from rest to exercise (left ventricle, 89 ± 14 ml vs 102 ± 19 ml, p <0.05; right ventricle, 88 ± 14 ml vs 101 ± 16 ml, p <0.05). Ejection fraction also increased in both ventricles from rest to exercise (left ventricle, 63 ± 6% vs 74 ± 6%, p <0.05; right ventricle, 61 ± 6% vs 70 ± 6%, p <0.05). End-systolic volume of the left and right ventricles decreased from rest to exercise (left ventricle, −33 ± 12%, p <0.05; right ventricle, −25 ± 12%, p <0.05), whereas LV and RV end-diastolic volumes remained unchanged. The results fit well with current concepts of cardiac physiology, and therefore we conclude that ergometer-induced exercise MRI is a valid approach to assess physiologic changes in LV and RV function simultaneously.

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• Calf Muscle Perfusion at Peak Exercise in Peripheral Arterial Disease: Measurement by First-Pass Contrast-Enhanced Magnetic Resonance Imaging

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  Calf Muscle Perfusion at Peak Exercise in Peripheral Arterial Disease: Measurement by First-Pass Contrast-Enhanced Magnetic Resonance Imaging

  Author(s)

  David C. Isbell, Frederick H. Epstein, Xiaodong Zhong, Joseph M. DiMaria, Stuart S. Berr, Craig H. Meyer, Walter J. Rogers, Nancy L. Harthun, Klaus D. Hagspiel, Arthur Weltman, Christopher M. Kramer,

  Date

  2007-05-04

  Source

  Journal of Magnetic Resonance Imaging. 2007 May; 25(5): 1013–1020.

  Purpose
  To develop a contrast-enhanced magnetic resonance (MR) technique to measure skeletal muscle perfusion in peripheral arterial disease (PAD).
  Materials and Methods
  A total of 11 patients (age = 61 ± 11 years) with moderate symptomatic PAD (ankle-brachial index [ABI] = 0.75 ± 0.08) and 22 normals were studied using an MR-compatible ergometer. PAD and normalmax (Nlmax; N = 11) exercised to exhaustion. Nllow (N = 11) exercised to the same workload achieved by PAD. At peak exercise, 0.1 mm/kg of gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) was infused at 3–4 cm3/second followed by a saline flush at the same rate. A dual-contrast gradient echo (GRE) sequence enabled simultaneous acquisition of muscle perfusion and arterial input function (AIF). The perfusion index (PI) was defined as the slope of the time-intensity curve (TIC) in muscle divided by the arterial TIC slope.
  Results
  Median workload was 120 Joules in PAD, 210 Joules in Nllow, and 698 Joules in Nlmax (P < 0.001 vs. Nllow and PAD). Median PI was 0.29 in PAD (25th and 75th percentiles [%] = 0.20, 0.40), 0.48 in Nllow (25th, 75th % = 0.36, 0.62; P < 0.02 vs. PAD), and 0.69 in Nlmax (25th, 75th % = 0.5, 0.77; P < 0.001 vs. PAD). Area under the ROC-curve for PI differentiating patients from Nlmax was 0.95 (95% confidence interval [CI] = 0.77–0.99).
  Conclusion
  Peak-exercise measurement of lower limb perfusion with dual-contrast, first-pass MR distinguishes PAD from normals. This method may be useful in the study of novel therapies for PAD.

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• Cardiac MRI: a new gold standard for ventricular volume quantification during high-intensity exercise

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  Cardiac MRI: a new gold standard for ventricular volume quantification during high-intensity exercise

  Author(s)

  La Gerche A, Claessen G, Van de Bruaene A, Pattyn N, Van Cleemput J, Gewillig M, Bogaert J, Dymarkowski S, Claus P, Heidbuchel H.

  Date

  2013-01-07

  Source

  Circ Cardiovasc Imaging. 2013 Mar 1;6(2):329-38. doi: 10.1161/CIRCIMAGING.112.980037. Epub 2012 Dec 17.

  BACKGROUND:

  Accurate measures are critical when attempting to distinguish normal from pathological changes in cardiac function during exercise, yet imaging modalities have seldom been assessed against invasive exercise standards. We sought to validate a novel method of biventricular volume quantification by cardiac MRI (CMR) during maximal exercise.
  METHODS AND RESULTS:

  CMR was performed on 34 subjects during exercise and free-breathing with the use of an ungated real-time (RT-ungated) CMR sequence. ECG and respiratory movements were retrospectively synchronized, enabling compensation for cardiac cycle and respiratory phase. Feasibility of RT-ungated imaging was compared with standard exercise CMR imaging with ECG gating (gated); accuracy of RT-ungated CMR was assessed against an invasive standard (direct Fick); and reproducibility was determined after a second bout of maximal exercise. Ventricular volumes were analyzed more frequently during high-intensity exercise with RT-ungated compared with gated CMR (100% versus 47%; P<0.0001) and with better interobserver variability for RT-ungated (coefficient of variation=1.9% and 2.0% for left and right ventricular stroke volumes, respectively) than gated (coefficient of variation=15.2% and 13.6%; P<0.01). Cardiac output determined by RT-ungated CMR proved accurate against the direct Fick method with excellent agreement (intraclass correlation coefficient, R=0.96), which was highly reproducible during a second bout of maximal exercise (R=0.98).
  CONCLUSIONS:

  When RT-ungated CMR is combined with post hoc analysis incorporating compensation for respiratory motion, highly reproducible and accurate biventricular volumes can be measured during maximal exercise.

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• Characterizing blood oxygen level-dependent (BOLD) response following in-magnet quadriceps exercise

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  Characterizing blood oxygen level-dependent (BOLD) response following in-magnet quadriceps exercise

  Author(s)

  Caterini JE, Elzibak AH, St Michel EJ, McCrindle BW, Redington AN, Thompson S, Noseworthy MD, Wells GD.

  Date

  2015-06-01

  Source

  MAGMA

  Abstract
  OBJECT:

  There have been no studies to investigate the effects of cycling exercise protocols, as well as repeated bouts of exercise, on the blood oxygen level-dependent (BOLD) response in the quadriceps muscles. This study characterized BOLD signal recovery following non-ischemic bouts of exercise in the quadriceps muscles of healthy adults in order to provide a basis for application of a protocol for clinical populations.
  MATERIALS AND METHODS:

  Healthy male subjects (23.7 ± 2.0 years of age, n = 10) completed three cycles of one-minute exercise (65 % of maximum workload), with two minutes of rest between each bout, on an MRI-compatible ergometer. The BOLD responses during recovery were fitted to a sigmoid model, and response kinetics (post-exercise intensity [S0]), response time (α), change in baseline BOLD signal (κ), and inflection point (β)] were measured.
  RESULTS:

  The sigmoid function fit well to the post-exercise BOLD data (r (2) = 0.95 ± 0.04). The mean response time was 10.5 ± 3.8 seconds, change in baseline BOLD intensity was 0.15 ± 0.068, and time to half-peak was 20.2 ± 8.6 seconds.
  CONCLUSION:

  The proposed sigmoid model is a robust method for quantifying quadriceps BOLD response post-exercise without induced ischemia. Extension of this model to evaluate microvascular responses in patients with chronic disease could improve our understanding of exercise intolerance.

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• Design and testing of an MRI-compatible cycle ergometer for non-invasive cardiac assessments during exercise

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  Design and testing of an MRI-compatible cycle ergometer for non-invasive cardiac assessments during exercise

  Author(s)

  Silmara Gusso, Carlo Salvador, Paul Hofman, Wayne Cutfield, James C Baldi, Andrew Taberner, Poul Nielse

  Date

  2013-01-11

  Source

  BioMedical Engineering OnLine

  Background: Magnetic resonance imaging (MRI) is an important tool for cardiac research, and it is frequently used for resting cardiac assessments. However, research into non-pharmacological stress cardiac evaluation is limited.

  Methods: We aimed to design a portable and relatively inexpensive MRI cycle ergometer capable of continuously measuring pedalling workload while patients exercise to maintain target heart rates.

  Results: We constructed and tested an MRI-compatible cycle ergometer for a 1.5 T MRI scanner. Resting and sub-maximal exercise images (at 110 beats per minute) were successfully obtained in 8 healthy adults.

  Conclusions: The MRI-compatible cycle ergometer constructed by our research group enabled cardiac assessments at fixed heart rates, while continuously recording power output by directly measuring pedal force and crank rotation.

  Keywords: Cycle ergometer, Left ventricular function, Magnetic resonance imaging

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• Dynamic bicycle exercise to assess cardiac output at multiple exercise levels during magnetic resonance imaging

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  Dynamic bicycle exercise to assess cardiac output at multiple exercise levels during magnetic resonance imaging

  Author(s)

  Johan Heiberg, Benjamin Asschenfeldt, MarieMaagaarda, Steffen Ringgaard

  Date

  2017-07-17

  Source

  Clinical Imaging

  Abstract
  PURPOSE:
  The aim was to establish a method for performing dynamic exercise during magnetic resonance imaging (MRI) using a slowly increasing workload protocol.

  METHODS:
  An ergometer bicycle with a step-wise, exercise protocol was used. Real-time phase-contrast MRI images of the aorta were obtained at each exercise step.

  RESULTS:
  In total, 40 participants completed the exercise protocol to reach a mean maximum cardiac output of 13.7±3.7l/min and a heart rate of 150±16beats/min at the highest exercise level. Less than 1% of scans were discarded due to poor quality.

  CONCLUSIONS:
  Dynamic, high intensity exercise is feasible during MRI.

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• Effect of Fontan geometry on exercise haemodynamics and its potential implications

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  Effect of Fontan geometry on exercise haemodynamics and its potential implications

  Author(s)

  Tang E, Wei ZA, Whitehead KK, Khiabani RH, Restrepo M, Mirabella L, Bethel J, Paridon SM, Marino BS, Fogel MA, Yoganathan AP

  Date

  2017-05-18

  Source

  Heart (British Cardiac Society)

  OBJECTIVE:
  Exercise intolerance afflicts Fontan patients with total cavopulmonary connections (TCPCs) causing a reduction in quality of life. Optimising TCPC design is hypothesised to have a beneficial effect on exercise capacity. This study investigates relationships between TCPC geometries and exercise haemodynamics and performance.

  METHODS:
  This study included 47 patients who completed metabolic exercise stress test with cardiac magnetic resonance (CMR). Phase-contrast CMR images were acquired immediately following supine lower limb exercise. Both anatomies and exercise vessel flow rates at ventilatory anaerobic threshold (VAT) were extracted. The vascular modelling toolkits were used to analyse TCPC geometries. Computational simulations were performed to quantify TCPC indexed power loss (iPL) at VAT.

  RESULTS:
  A highly significant inverse correlation was found between the TCPC diameter index, which factors in the narrowing of TCPC vessels, with iPL at VAT (r=-0.723, p<0.001) but positive correlations with exercise performance variables, including minute oxygen consumption (VO2) at VAT (r=0.373, p=0.01), VO2 at peak exercise (r=0.485, p=0.001) and work at VAT/weight (r=0.368, p=0.01). iPL at VAT was negatively correlated with VO2 at VAT (r=-0.337, p=0.02), VO2 at peak exercise (r=-0.394, p=0.007) and work at VAT/weight (r=-0.208, p=0.17).

  CONCLUSIONS:
  Eliminating vessel narrowing in TCPCs and reducing elevated iPL at VAT could enhance exercise tolerance for patients with TCPCs. These findings could help plan surgical or catheter-based strategies to improve patients’ exercise capacity.

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• Effect of respiration on cardiac filling at rest and during exercise in Fontan patients: A clinical and computational modeling study

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  Effect of respiration on cardiac filling at rest and during exercise in Fontan patients: A clinical and computational modeling study

  Author(s)

  Alexander Van De Bruaene a,⁎, Guido Claessen b, Andre La Gerche b,c, Ethan Kung d, Alison Marsden e, Pieter De Meester a, Sarah Devroe f, Jan Bogaert g, Piet Claus h, Hein Heidbuchel i,Werner Budts a,MarcGewillig j

  Date

  2015-08-13

  Source

  IJC Heart & Vasculature

  Background: Due to the absence of a sub-pulmonary ventricle, the Fontan circulation is sensitive to respirationinduced changes in intrathoracic pressure. However, the importance of a ‘respiratory pump’ in creating forward flow remains controversial.We aimed at evaluating the effect of respiration on ventricular filling during exercise using clinical data and computational modeling predictions.
  Methods: Ten Fontan patients (6male, 20±4 years) underwent ungated cardiac magnetic resonance (CMR) imaging at rest and during supine bicycle exercise to evaluate systemic ventricular volumes (end-diastolic volume index (EDVi), end-systolic volume index (ESVi) and stroke volume index (SVi)) during normal respiration and a Valsalva maneuver. Respiratory-dependent SV was calculated. Clinical results were compared to predictions made by a closed-loop lumped-parameter (LPN) computational model of Fontan circulation.

  Results: Inspiration resulted in increased EDVi (98 ± 16 to 103 ± 15 mL; P=0.001), SVi (55 ± 9 to 59± 9 mL; P=0.001) and cardiac index (3.9±0.7 to 4.2±0.8 L/min; P=0.002),whereas ESVi (P=0.096) remained unchanged. The effect of inspiration on EDVi (mean effect+6±1mL; P b 0.0001) and SVi (+4±1 mL; P b 0.0001) was maintained during exercise. Respiratory-dependent SVi tended to increase during exercise (3 ± 2% to 5 ± 3%; P=0.084). Valsalva resulted in decreased EDVi (P=0.001), ESVi (P=0.003) and SVi (P=0.005). Computational modeling indicated higher EDV and SV at end-inspiration and expiration, showing a phased time delay between peak caval vein flow and peak SV.

  Conclusion: In Fontan patients, inspiration resulted in increased ventricular filling at rest and during exercise.
  Results were confirmed using a computational model indicating a phased time delay between peak SV and peak caval vein flow.

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• Effects of Exercise and Respiration on Blood Flow in Total Cavopulmonary Connection

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  Effects of Exercise and Respiration on Blood Flow in Total Cavopulmonary Connection

  Author(s)

  V.E. Hjortdal, K. Emmertsen, E. Stenbøg, T. Fründ, M. Rahbek. O. Dromann, K. Sørensen, E.M. Pedersen.

  Date

  2003-04-01

  Source

  Circulation.2003; 108: 1227-1231

  Background— Little is known about blood flow and its relationship to respiration during exercise in patients with total cavopulmonary connection (TCPC).
  Methods and Results— We studied 11 patients 12.4±4.6 years (mean±SD) of age 5.9±2.8 years (mean±SD) after TCPC operation. Real-time MRI was used to measure blood flow in the superior vena cava (SVC), inferior vena cava (IVC), and ascending aorta under inspiration and expiration during supine lower-limb exercise (rest, 0.5 and 1.0 W/kg) on an ergometer bicycle. IVC and aortic flow increased from 1.60±0.52 and 2.99±0.83 L/min per m2 at rest to 2.58±0.71 and 3.97±1.20 L/min per m2 at 0.5 W/kg and to 3.25±1.23 and 4.62±1.49 L/min per m2 at 1.0 W/kg (P≤0.05). SVC flow remained unchanged. Resting flow in the IVC was greater during inspiration (2.99±1.25 L/min per m2) than during expiration (0.83±0.44 L/min per m2) (inspiratory/mean flow ratio, 1.9±0.5), and retrograde flow was present during expiration (11±12% of mean flow). The predominance of inspiratory flow in IVC diminished with exercise to an inspiratory/mean flow ratio of 1.5±0.2 (P≤0.05) and 1.4±0.3 at 0.5 and 1.0 W/kg, respectively.
  Conclusions— In the TCPC, circulation IVC and aortic but not SVC flows increase with supine leg exercise. Inspiration facilitates IVC flow at rest but less so during exercise, when the peripheral pump seems to be more important.

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• Exercise capacity in single-ventricle patients after Fontan correlates with haemodynamic energy loss in TCPC

  ×

  Exercise capacity in single-ventricle patients after Fontan correlates with haemodynamic energy loss in TCPC

  Author(s)

  Khiabani RH, Whitehead KK, Han D, Restrepo M, Tang E, Bethel J, Paridon SM, Fogel MA, Yoganathan AP

  Date

  2014-09-02

  Source

  Heart (British Cardiac Society)

  OBJECTIVE:
  Elevated energy loss in the total cavopulmonary connection (TCPC) is hypothesised to have a detrimental effect on clinical outcomes in single-ventricle physiology, which may be magnified with exercise. This study investigates the relationship between TCPC haemodynamic energy dissipation and exercise performance in single-ventricle patients.

  METHODS:
  Thirty consecutive Fontan patients with TCPC and standard metabolic exercise testing were included. Specific anatomies and flow rates at rest and exercise were obtained from cardiac MR (CMR) and phase-encoded velocity mapping. Exercise CMR images were acquired immediately following supine lower limb exercise using a CMR-compatible cycle ergometer. Computational fluid dynamics simulations were performed to determine power loss of the TCPC anatomies using in vivo anatomies and measured flows.

  RESULTS:
  A significant negative linear correlation was observed between indexed power loss at exercise and (a) minute oxygen consumption (r=-0.60, p<0.0005) and (b) work (r=-0.62, p<0.0005) at anaerobic threshold. As cardiac output increased during exercise, indexed power loss increased in an exponential fashion (y=0.9671x(3.0263), p<0.0001).

  CONCLUSIONS:
  This is the first study to demonstrate the relationship between power loss and exercise performance with the TCPC being one of the few modifiable factors to allow for improved quality of life. These results suggest that aerobic exercise tolerance in Fontan patients may, in part, be a consequence of TCPC power loss.
  Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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• Exercise stress CMR reveals reduced aortic distensibility and impaired right-ventricular adaptation to exercise in patients with repaired tetralogy of Fallot

  ×

  Exercise stress CMR reveals reduced aortic distensibility and impaired right-ventricular adaptation to exercise in patients with repaired tetralogy of Fallot

  Author(s)

  Paul Habert, Zakarya Bentatou, e.a.

  Date

  2018-12-31

  Source

  PLoS One

  Background
  The aim of our study was to evaluate the feasibility of exercise cardiac magnetic resonance (CMR) in patients with repaired tetralogy of Fallot (RTOF) and to assess right and left ventricular adaptation and aortic wall response to exercise in comparison with volunteers.

  Methods
  11 RTOF and 11 volunteers underwent prospective CMR at rest and during exercise. A supine bicycle ergometer was employed to reach twice the resting heart rate during continuous exercise, blood pressure and heart rate were recorded. Bi-ventricular parameters and aortic stiffness were assessed using accelerated cine sequences and flow-encoding CMR. A t-test was used to compare values between groups. A Mann Whitney test was used to compare values within groups.

  Results
  In RTOF both ventricles showed an impaired contractile reserve (RVEF rest 36.2±8.3%, +1.3±3.9% increase after exercise; LVEF rest 53.8±6.1%, +5.7±6.4% increase after exercise) compared to volunteers (RVEF rest 50.5±5.0%, +10.4±7.1% increase after exercise, p = 0.039; LVEF rest 61.9±3.1%, +12.2±4.7% increase after exercise, p = 0.014).
  RTOF showed a reduced distensibility of the ascending aorta during exercise compared to volunteers (RTOF: 3.4±1.9 10-3.mmHg-1 vs volunteers: 5.1±1.4 10-3.mmHg-1; p = 0.027). Ascending aorta distensibility was correlated to cardiac work in the volunteers but not in RTOF.

  Conclusion
  RTOF showed an impaired contractile reserve for both ventricles. The exercise unmasked a reduced distensibility of the ascending aorta in RTOF, which may be an early sign of increased aortic rigidity.

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• Feasibility and Reproducibility of Biventricular Volumetric Assessment of Cardiac Function During Exercise Using Real-Time Radial k-t SENSE Magnetic Resonance Imaging

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  Feasibility and Reproducibility of Biventricular Volumetric Assessment of Cardiac Function During Exercise Using Real-Time Radial k-t SENSE Magnetic Resonance Imaging

  Author(s)

  Philipp Lurz, MD, Vivek Muthurangu, MD, Silvia Schievano, PhD, Johannes Nordmeyer, MD, Philipp Bonhoeffer, MD, Andrew M. Taylor, MD, Michael S. Hansen, PhD

  Date

  2009-01-01

  Source

  JOURNAL OF MAGNETIC RESONANCE IMAGING

  Purpose: To assess the feasibility and reproducibility of
  real-time radial k-t sensitivity encoding (SENSE) magnetic
  resonance imaging (MRI) for biventricular volumetric as-
  sessment during exercise.

  Materials and Methods: In all, 12 healthy young adults
  underwent MRI at rest and during supine exercise at three
  different workload intensities. Biventricular volumes and
  function were assessed with 1) a radial k-t SENSE real-time
  sequence and 2) a scanner vendor supplied (standard) real-
  time sequence. Global image quality, motion fidelity, and
  agreement in right ventricular (RV) and left ventricular (LV)
  stroke volume (SV) as a surrogate measure for accuracy
  were assessed. Exercise MR was repeated within 1 month
  for assessment of reproducibility.

  Results: Imaging scores were superior for radial real-time k-t
  SENSE images (P ⬍ 0.001). Agreement in RV and LV SV
  during exercise was better with radial k-t real-time (SD of
  difference ⫾3.43 vs. ⫾8.97 mL; P ⬍ 0.001). Agreement in
  cardiac output (CO) in the same subject at two different im-
  aging sessions was better for radial k-t SENSE. This was
  significant for the CO calculated for the RV (SD of difference
  ⫾0.6 vs. ⫾0.95 L/min; P ⫽ 0.01) and LV (⫾0.45 vs. ⫾0.92
  L/min; P ⬍ 0.001).

  Conclusion: Radial k-t SENSE real-time imaging repre-
  sents a feasible and reproducible imaging technique for
  biventricular assessment during exercise.

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• Flow during exercise in the total cavopulmonary connection measured by magnetic resonance velocity mapping.

  ×

  Flow during exercise in the total cavopulmonary connection measured by magnetic resonance velocity mapping.

  Author(s)

  Pedersen EM1, Stenbøg EV, Fründ T, Houlind K, Kromann O, Sørensen KE, Emmertsen K, Hjortdal VE

  Date

  2002-06-01

  Source

  Heart (British Cardiac Society)

  OBJECTIVE:
  To measure caval and pulmonary flows at rest and immediately after exercise in patients with total cavopulmonary connection (TCPC).

  DESIGN:
  An observational study using the patients as their own controls.

  SETTING:
  Using a combination of magnetic resonance (MR) phase contrast techniques and an MR compatible bicycle ergometer, blood flow was measured in the superior vena cava, the tunnel from the inferior vena cava, and in the left and right pulmonary arteries during rest and on exercise (0.5 W/kg and 1.0 W/kg).

  PATIENTS:
  Eleven patients aged 11.4 (4.6) years (mean (SD)) were studied 6.3 (3.8) years after TCPC operation.
  MAIN OUTCOME MEASURES:
  Volume flow measured in all four branches of the TCPC connection during rest and exercise.

  RESULTS:
  Systemic venous return (inferior vena cava plus superior vena cava) increased from 2.5 (0.1) l/min/m2 (mean (SEM)) to 4.4 (0.4) l/min/m2 (p < 0.05) during exercise, with even distribution to the two pulmonary arteries. At rest, inferior vena caval flow was higher than superior vena caval flow, at 1.4 (0.1) v 1.1 (0.1) l/min/m2 (p < 0.05). During exercise, inferior vena caval flow doubled (to 3.0 (0.3) l/min/m2) while superior vena caval flow only increased slightly (to 1.4 (0.1) l/min/m2) (p < 0.05). The increased blood flow mainly reflected an increase in heart rate. The inferior vena caval to superior vena caval flow ratio was 1.4 (0.1) at rest and increased to 1.8 (0.1) (p < 0.05) at 0.5 W/kg, and to 2.2 (0.2) at 1.0 W/kg (p < 0.05).

  CONCLUSIONS:
  Quantitative flow measurements can be performed immediately after exercise using MR techniques. Supine leg exercise resulted in a more than twofold increase in inferior vena caval flow. This was equally distributed to the two lungs, indicating that pulmonary resistance rather than geometry decides flow distribution in the TCPC circulation.

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• Heart Journal

  ×

  Heart Journal

  Author(s)

  A A W Roest, H J Lamb, E E van der Wall, H W Vliegen, J G van den Aardweg, P Kunz, A de Roos, W A Helbing

  Date

  2003-10-16

  Source

  Cardiovascular response to physical exercise in adult patients after atrial correction for transposition of the great arteries assessed with magnetic resonance imaging

  Objective: To assess with magnetic resonance imaging (MRI) cardiovascular function in response to exercise in patients after atrial correction of transposition of the great arteries (TGA).

  Methods: Cardiac function at rest and during submaximal exercise was assessed with MRI in 27 patients with TGA (mean (SD) age 26 (5) years) late (23 (2) years) after atrial correction and in 14 control participants (25 (5) years old).

  Results: At rest, only right ventricular ejection fraction was significantly lower in patients than in controls (56 (7)% v 65 (7)%, p , 0.05). In response to exercise, increases in right ventricular end diastolic (155 (55) ml to 163 (57) ml, p , 0.05) and right ventricular end systolic volumes (70 (34) ml to 75 (36) ml, p , 0.05) were observed in patients. Furthermore, right and left ventricular stroke volumes and ejection fraction did not increase significantly in patients. Changes in right ventricular ejection fraction with exercise correlated with diminished exercise capacity (r = 0.43, p , 0.05).

  Conclusions: In patients with atrially corrected TGA, MRI showed an abnormal response to exercise of both systemic right and left ventricles. Exercise MRI provides a tool for close monitoring of cardiovascular function in these patients, who are at risk for late death.

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• High-resolution phase-contrast MRI of aortic and pulmonary blood flow during rest and physical exercise using a MRI compatible bicycle ergometer

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  High-resolution phase-contrast MRI of aortic and pulmonary blood flow during rest and physical exercise using a MRI compatible bicycle ergometer

  Author(s)

  Tim Frederik Weber, Hendrik von Tengg-Kobligk, Annette Kopp-Schneider, Julia Ley-Zaporozhan, Hans-Ulrich Kauczor, Sebastian Ley

  Date

  2011-10-10

  Source

  European Journal of Radiology. Volume 80, Issue 1, October 2011, Pages 103–108

  Purpose
  To establish high-resolution phase-contrast magnetic resonance imaging (PC-MRI) using a MRI compatible bicycle ergometer to quantify aortic and pulmonary blood flow during resting conditions and exercise.
  Materials and methods
  In 20 healthy volunteers (mean age, 26.8 ± 5.0 years) high-resolution PC-MRI (mean temporal resolution, 7.4 ± 3.2 ms) was performed in the ascending aorta (AA) and main pulmonary artery (PA) during physical rest and three exercise stages: stage 1, no-load operation; stage 2, heart rate increase 40% compared to rest; stage 3, heart rate increase 80% compared to rest. Flow quantification in AA and PA included flow volume (FV), average velocity (AV), peak velocity (PV) and time to PV (TP).

  Results
  In stage 1 only TP demonstrated a significant change. With progression to stage 2, all parameters altered significantly. Flow measurements during stage 3 evidenced further alterations only of AV and TP regarding both AA and PA. The deviation of the heart rate from the desired target value was significantly higher for stage 3 compared to stage 2, and 15% of the subjects did not reach the desired target heart rate of stage 3 at all.
  Conclusion
  Flow quantification by high-resolution PC-MRI during exercise using a MRI compatible bicycle ergometer is feasible. Medium exercise stages are necessary and sufficient to demonstrate flow alterations in healthy volunteers. PC-MRI ergometry may give insights into aberrant hemodynamic conditions in patients with cardiovascular and pulmonary disease.

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• High-resolution phase-contrast MRI of aortic and pulmonary blood flow during rest and physical exercise using a MRI compatible bicycle ergometer.

  ×

  High-resolution phase-contrast MRI of aortic and pulmonary blood flow during rest and physical exercise using a MRI compatible bicycle ergometer.

  Author(s)

  Weber TF, von Tengg-Kobligk H, Kopp-Schneider A, Ley-Zaporozhan J, Kauczor HU, Ley S.

  Date

  2011-10-08

  Source

  European Journal of Radiology

  PURPOSE:
  To establish high-resolution phase-contrast magnetic resonance imaging (PC-MRI) using a MRI compatible bicycle ergometer to quantify aortic and pulmonary blood flow during resting conditions and exercise.

  MATERIALS AND METHODS:
  In 20 healthy volunteers (mean age, 26.8±5.0 years) high-resolution PC-MRI (mean temporal resolution, 7.4±3.2 ms) was performed in the ascending aorta (AA) and main pulmonary artery (PA) during physical rest and three exercise stages: stage 1, no-load operation; stage 2, heart rate increase 40% compared to rest; stage 3, heart rate increase 80% compared to rest. Flow quantification in AA and PA included flow volume (FV), average velocity (AV), peak velocity (PV) and time to PV (TP).

  RESULTS:
  In stage 1 only TP demonstrated a significant change. With progression to stage 2, all parameters altered significantly. Flow measurements during stage 3 evidenced further alterations only of AV and TP regarding both AA and PA. The deviation of the heart rate from the desired target value was significantly higher for stage 3 compared to stage 2, and 15% of the subjects did not reach the desired target heart rate of stage 3 at all.

  CONCLUSION:
  Flow quantification by high-resolution PC-MRI during exercise using a MRI compatible bicycle ergometer is feasible. Medium exercise stages are necessary and sufficient to demonstrate flow alterations in healthy volunteers. PC-MRI ergometry may give insights into aberrant hemodynamic conditions in patients with cardiovascular and pulmonary disease.

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• Improving the physiological realism of experimental models.

  ×

  Improving the physiological realism of experimental models.

  Author(s)

  Vinnakota KC, Cha CY, Rorsman P, Balaban RS, La Gerche A, Wade-Martins R, Beard DA, Jeneson

  Date

  2016-02-19

  Source

  Interface Focus 6: 20150076.

  The Virtual Physiological Human (VPH) project aims to develop integrative, explanatory and predictive computational models (C-Models) as numerical investigational tools to study disease, identify and design effective therapies and provide an in silico platform for drug screening. Ultimately, these models rely on the analysis and integration of experimental data. As such, the success of VPH depends on the availability of physiologically realistic experimental models (E-Models) of human organ function that can be parametrized to test the numerical models. Here, the current state of suitable E-models, ranging from in vitro non-human cell organelles to in vivo human organ systems, is discussed. Specifically, challenges and recent progress in improving the physiological realism of E-models that may benefit the VPH project are highlighted and discussed using examples from the field of research on cardiovascular disease, musculoskeletal disorders, diabetes and Parkinson’s disease.

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• Interaction between respiration and right versus left ventricular volumes at rest and during exercise: a real-time cardiac magnetic resonance study

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  Interaction between respiration and right versus left ventricular volumes at rest and during exercise: a real-time cardiac magnetic resonance study

  Author(s)

  Guido Claessen, Piet Claus, Marion Delcroix, Jan Bogaert, Andre La Gerche, Hein Heidbuchel1

  Date

  2014-01-24

  Source

  AJP Heart

  Breathing-induced changes in intrathoracic pressures influence left ventricular (LV) and right ventricular (RV) volumes, the exact nature and extent of which have not previously been evaluated in humans. We sought to examine this “respiratory pump” using novel real-time cardiac magnetic resonance (CMR) imaging. Eight healthy subjects underwent serial multislice real-time CMR during normal breathing, breath holding, and the Valsalva maneuver. Subsequently, a separate cohort of nine subjects underwent real-time CMR at rest and during incremental exercise. LV and RV end-diastolic volume (EDV) and end-systolic volume (ESV) and diastolic and systolic eccentricity indexes were determined at peak inspiration and expiration. During normal breathing, inspiration resultedinanincreaseinRVvolumes[RVEDV: 18  8%,RVESV: 14  12%, and RV stroke volume (SV): 21  10%, P  0.01] andanopposingdecreaseinLVvolumes(P  0.0001forinteraction). During end-inspiratory breath holding, RV SV decreased by 9  10% (P  0.046), whereas LV SV did not change. During the Valsalva maneuver, volumes decreased in both ventricles (RVEDV: 29  11%, RVESV: 16  14%, RV SV: 36  14%, LVEDV: 22  17%, and LV SV: 25  17%, P  0.01). The reciprocal effect of respiration on LV and RV volumes was maintained throughout exercise. The diastolic and systolic eccentricity indexes were greater during inspiration than during expiration, both at rest and during exercise (P  0.0001 for both). In conclusion, ventricular volumes oscillate with respiratory phase such that RV and LV volumes are maximal at peak inspiration and expiration, respectively. Thus, interpretation of RV versus LV volumes requires careful definition of the exact respiratory time point for proper interpretation, both at rest and during exercise

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• Leg lean mass correlates with exercise systemic output in young Fontan patients.

  ×

  Leg lean mass correlates with exercise systemic output in young Fontan patients.

  Author(s)

  Avitabile CM, Goldberg DJ, Leonard MB, Wei ZA, Tang E, Paridon SM, Yoganathan AP, Fogel MA, Whitehead KK

  Date

  2017-10-07

  Source

  Heart (British Cardiac Society)

  OBJECTIVE:
  We previously described lower leg lean mass Z-scores (LLMZ) in Fontan patients associated with worse peak oxygen consumption on metabolic exercise testing. We hypothesised that LLMZ correlates with indexed systemic flow (Qsi) and cardiac index (CI) on exercise cardiac magnetic resonance (eCMR).

  METHODS:
  Thirteen patients had LLM measured by dual-energy X-ray absorptiometry within mean 40 (range 0-258) days of eCMR. LLM was converted to sex and race-specific Z-scores based on healthy reference data. Ventricular volumes and flow measurements of the ascending and descending (DAO) aorta and superior vena cava (SVC) were obtained by CMR at rest and just after supine ergometer exercise to a heart rate associated with anaerobic threshold on prior exercise test. Baseline and peak exercise measures of Qsi (SVC+DAO/BSA) and CI, as well as change in Qsi and CI with exercise, were compared with LLMZ by linear regression.

  RESULTS:
  LLMZ was not correlated with resting flows, stroke volume or CI. There was a strong linear correlation between LLMZ and change in both CI (r=0.77, p=0.002) and Qsi (r=0.73, p=0.005) from rest to exercise. There was also a significant correlation between LLMZ and Qsi at exercise (r=0.70, p=0.008). The correlation between LLMZ and CI at exercise did not reach significance (r=0.3, p=0.07).

  CONCLUSIONS:
  In our cohort, there was a strong linear correlation between LLMZ and change in both CI and Qsi from rest to exercise, suggesting that Fontan patients with higher LLMZ may be better able to augment systemic output during exercise, improving performance.

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• Magnetic Resonance Augmented Cardiopulmonary Exercise Testing: Comprehensively Assessing Exercise Intolerance in Children with Cardiovascular Disease

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  Magnetic Resonance Augmented Cardiopulmonary Exercise Testing: Comprehensively Assessing Exercise Intolerance in Children with Cardiovascular Disease

  Author(s)

  Nathaniel J. Barber; Emmanuel O. Ako; Gregorz, T. Kowalik; Mun H. Cheang; Bejal Pandya; Jennifer A. Steeden; Shahin Moledina; Vivek Muthurangu

  Date

  2016-12-09

  Source

  Circulation: Cardiovascular Imaging December 2016, Volume 9, Issue 12

  Background
  Conventional cardiopulmonary exercise testing (CPET) can objectively measure exercise intolerance, but cannot provide comprehensive evaluation of physiology. This requires additional assessment of cardiac output (CO) and arterio-venous oxygen content difference (a-vO2). We developed magnetic resonance (MR) augmented CPET (MR-CPET) to achieve this goal and assessed children with right heart disease.

  Methods and Results
  Healthy controls (n=10) and children with pulmonary arterial hypertension (PAH) (n=10) and repaired Tetralogy of Fallot (ToF) (n=10) underwent MR-CPET. All exercise was performed on a MR-compatible ergometer and oxygen uptake (VO2) was continuously acquired using a modified metabolic cart. Simultaneous CO was measured using a real-time MR flow sequence and combined with VO2 to calculate avO2. Peak VO2 was significantly lower in the PAH group (12.6±1.31 ml/kg/min,
  p=0.01) and trended towards lower in the ToF group (13.5±1.29 ml/kg/min, p=0.06) compared to controls (16.7±1.37 ml/kg/min). Although ToF patients had the largest increase in CO, they had lower resting (3±1.2 l/min/m2) and peak (5.3±1.2 l/min/m2) values compared to controls (resting 4.3±1.2 l/min/m2, peak 6.6±1.2 l/ min/m2) and PAH patients (resting 4.5±1.1 l/min/m2, peak 5.9±1.1 l/min/m2). Both the PAH and ToF patients had blunted exercise induced increases in a-vO2. However, only the PAH patients had significantly reduced peak values (6.9±1.3 mlO2/100ml) compared to controls (8.4±1.4 mlO2/100ml, p= 0.005).

  Conclusions
  MR-CPET is feasible in both healthy children and children with cardiac disease. Using this novel technique we have demonstrated abnormal exercise patterns in VO2, CO and a-vO2.

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• Measurement of aortic and pulmonary flow with MRI at rest and during physical exercise.

  ×

  Measurement of aortic and pulmonary flow with MRI at rest and during physical exercise.

  Author(s)

  Niezen RA1, Doornbos J, van der Wall EE, de Roos A.

  Date

  1998-04-01

  Source

  Journal of computer assisted tomography

  PURPOSE:

  Our aim was to assess the feasibility of measuring great vessel flow during submaximal exercise using MR flow mapping.
  METHOD:

  In 16 healthy volunteers, MR measurements of great vessel flow were obtained at rest and during two levels of submaximal physical exercise using an MR-compatible bicycle ergometer.

  RESULTS:

  Great vessel flow showed good correlation at rest and during exercise (r = 0.9, p < 0.0005). Significant increase in heart rate was observed during exercise. Aortic flow volume increased from 64 +/- 13 ml/beat at rest to 71 +/- 11 ml/beat at 50 W (p < 0.0005) to 79 +/- 13 ml/beat at 100 W (p < 0.0005). Pulmonary flow volume increased from 63 +/- 14 ml/beat at rest to 70 +/- 13 ml/beat at 50 W (p < 0.005) to 76 +/- 12 ml/beat at 100 W (p = NS).

  CONCLUSION:

  Quantification of great vessel flow can be performed safely in healthy volunteers using MR flow measurements during submaximal physical exercise. These measurements may be used to study hemodynamic abnormalities in patients with cardiac disease.

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• MR augmented cardiopulmonary exercise testing-a novel approach to assessing cardiovascular function.

  ×

  MR augmented cardiopulmonary exercise testing-a novel approach to assessing cardiovascular function.

  Author(s)

  Barber NJ, Ako EO, Kowalik GT, Steeden JA, Pandya B, Muthurangu V.

  Date

  2015-04-22

  Source

  Physiological Measurements

  Abstract
  The purposes of this study were: (1) to evaluate feasibility and acceptability of MRI augmented cardiopulmonary exercise testing (MR-CPET) in healthy adults and (2) to test whether peak values obtained at conventional and MR-CPET correlate and to demonstrate variation in peak oxygen consumption (VO2) relates to both peak cardiac output (CO) and peak oxygen extraction (ΔcO2). Seventeen healthy adults underwent CPET and MR-CPET using an MR compatible ergometer and CPET system customised for MR use. Continuous aortic flow measurement used a validated UNFOLD-SENSE spiral phase contrast magnetic resonance (PCMR) sequence.Fifteen of 17 volunteers completed exercise; exclusions were due to claustrophobia and inability to effectively master exercise technique. Measures of acceptability were lower but still satisfactory for MR-CPET.There were strong correlations between conventional and MR-CPET for peak VO2 (r = 0.94, p < 0.001); VCO2 (r = 0.87, p < 0.001) and VE (r = 0.88, p < 0.001).Multiple linear regression analysis demonstrated peak CO and ΔcO2 were independent predictors of peak VO2 measured during MR-CPET (β = 0.73 and 0.38 p < 0.0001) and conventional CPET (β = 0.78, 0.28 p < 0.0001).MR-CPET is feasible, acceptable and demonstrates physiology not apparent with conventional CPET. MR-CPET allows differentiation of the contributions of CO and ΔcO2 to variation in peak VO2. We believe that this will be useful in understanding the origin of reduced exercise capacity in cardiac disease.

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• MRI evaluation of left ventricular volume in children and adults during in-scanner exercise.

  ×

  MRI evaluation of left ventricular volume in children and adults during in-scanner exercise.

  Author(s)

  James Enos, Robert McCarter and Russell Cross

  Date

  2018-02-01

  Source

  Journal of Biomedical Imaging and Bioengineering (2018) Volume 2, Issue 1

  Abstract
  Background: Real-time cardiac MRI (CMR) has been shown to accurately assess cardiac output during exercise when compared with the clinical gold-standard Fick technique; however, most strategies for exercise stress CMR have involved exercise outside of the MRI scanner with rapid transition into the magnet for imaging, which cannot capture active or peak exercise conditions. Novel re-binning reconstruction of real-time imaging data with robust automated motion correction and improved temporal resolution may be well-suited for CMR during in-scanner exercise. Methods: Real-time acquisitions with conventional and re-binning reconstructions were collected in healthy volunteers at rest and at two exercise workloads during in-scanner exercise using an MRIcompatible cycle ergometer. Bland-Altman analyses and intraclass correlation coefficients compared left ventricular volumes measured by each real-time technique during exercise. Results: Twenty-five volunteers were enrolled – demographics [mean ± SD (range)]: age 23.1 ± 11.2 years (10–59); weight, 65.9 ± 18.9 kg (27.1–109); 72% female. Bland-Altman analyses demonstrated no differences in left ventricular volumes obtained via each technique at rest or during exercise with a maximum mean difference of <6 ml (p ≥ 0.05) during exercise. Intraclass correlation coefficients (ICCs) indicated strong agreement between measurement techniques (all ICCs ≥ 0.85). Conclusions: Assessing left ventricular volumes during exercise using the re-binning technique is feasible and yields similar results in adults and children compared to conventional real-time imaging, which has been shown to correlate with measurement of cardiac output via the gold-standard Fick technique. Important advantages of the re-binning technique include improved temporal resolution and signal-to-noise compared to conventional real-time approaches. The re-binning technique also has the added benefit of presenting reconstructed images as a single cardiac cycle for more efficient cardiac functional assessments using standard clinical post-processing tools.

  Keywords
  Cardiac MRI, Exercise, Real-time imaging, Re-binning reconstruction, Left ventricular volume, Pediatric

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• Paradoxical Increase in Ventricular Torsion and Systolic Torsion Rate in Type I Diabetic Patients Under Tight Glycemic Control FREE

  ×

  Paradoxical Increase in Ventricular Torsion and Systolic Torsion Rate in Type I Diabetic Patients Under Tight Glycemic Control FREE

  Author(s)

  Jina Chung, MD; Paul Abraszewski, MD; Xin Yu, ScD; Wei Liu, ScD; Andrew J. Krainik, MD, MPH; Marvin Ashford, MD; Shelton D. Caruthers, PhD; Janet B. McGill, MD; Samuel A. Wickline, MD

  Date

  2006-01-09

  Source

  Clinical Research | January 2006

  Objectives This study sought to characterize the early features of diabetic cardiomyopathy by magnetic resonance imaging (MRI) tagging.
  Background The earliest manifestations of diabetic cardiomyopathy have not been well established, especially under tight glycemic management. We hypothesized that torsion measurements would identify subclinical contractile alterations in type I diabetics with normal left ventricular ejection fraction, mass, blood pressure, and aggressive glycemic control. We also sought to characterize the influence of elevated resting heart rates (HRs) of diabetics on torsion.
  Methods Sixteen patients with type I diabetes and 10 control patients underwent cine and tagged MRI with a 1.5-T scanner. Torsion, strain, and their rates were measured. To quantify the influence of chronotropic and inotropic stimulation on torsion, nine healthy volunteers underwent MRI tagging at rest, after atropine injection, and after exercise.
  Results Diabetic patients (hemoglobin A1c, 6.8 ± 0.4%) had a higher resting HR (77.0 ± 12.4 beats/min vs. 59.0 ± 5.6 beats/min; p < 0.01), higher maximal torsion by 23% (3.5 ± 0.9°/cm vs. 2.7 ± 0.4°/cm; p < 0.01) and higher maximal systolic torsion rate (TR-s) by 25% (0.013 ± 0.003°/cm/s vs. 0.010 ± 0.002°/cm/s, p = 0.01). Torsion did not significantly change with chronotropic stimulation (p = 0.30).
  Conclusions In diabetics under tight glycemic control, we observed a surprising increase in torsion and TR-s unrelated to chronotropic influences of HR. We propose that increased torsion and TR-s could represent early predictive markers of the propensity to cardiac dysfunction in asymptomatic type I diabetics. Furthermore, these findings seem fundamental to the diabetic state itself and unaccounted for by other comorbidities.

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• Peripheral arterial disease assessment: wall, perfusion, and spectroscopy

  ×

  Peripheral arterial disease assessment: wall, perfusion, and spectroscopy

  Author(s)

  Kramer CM

  Date

  2007-10-18

  Source

  Topics in magnetic resonance imaging (TMRI)

  INTRODUCTION:
  Peripheral arterial disease (PAD) is characterized by lower limb arterial obstruction due to atherosclerosis and is increasingly common. Presently used methods for diagnosis and follow-up as well as for assessment of novel therapies are limited.

  MATERIALS AND METHODS:
  Three distinct magnetic resonance examinations were developed. The first was high-resolution black-blood atherosclerotic plaque imaging of the superficial femoral artery using a surface coil and flow saturation. Second, first-pass contrast-enhanced dual-contrast perfusion imaging of the calf muscle was performed at peak exercise using a magnetic resonance (MR)-compatible pedal ergometer. Lastly, (31)P MR spectroscopy was also performed at peak exercise to measure phosphocreatine (PCr) recovery kinetics.

  RESULTS:
  Seventeen patients (age, 63 +/- 10 yrs) with mild to moderate PAD were studied with black-blood atherosclerotic plaque imaging. Mean atherosclerotic plaque volume measured was 7.27 +/- 3.73 cm(3). Eleven patients (age, 61 +/- 11 yrs) with mild to moderate symptomatic PAD and 22 normal control subjects were studied with first-pass contrast-enhanced perfusion imaging. Perfusion index was stepwise increased from patients to normal subjects with matched workload to normal subjects at maximal exercise. For PCr recovery kinetics, 20 patients with mild to moderate PAD and 14 controls were studied. The median recovery time constant of PCr was 34.7 seconds in the controls and 91.0 seconds in the PAD patients (P < 0.0001).

  CONCLUSIONS:
  Three distinct MR examinations of different aspects of peripheral arterial disease have been developed and tested and shown to differentiate patients with mild to moderate PAD from normal controls. Taken together, these tests are potential quantitative end points for clinical trials of novel therapies in PAD.

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• Quantitative abdominal aortic flow measurements at controlled levels of ergometer exercise

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  Quantitative abdominal aortic flow measurements at controlled levels of ergometer exercise

  Author(s)

  E.M. Pedersen, S. Kozerke, S. Ringgaard, M.B. Scheidegger, P. Boesiger

  Date

  1999-05-04

  Source

  Magnetic Resonance Imaging. Volume 17, Issue 4, May 1999, Pages 489-494

  Measuring the exercise-induced flow changes in the arteries of the body is a major challenge. The use of quantitative MR flow measurements for this purpose is hampered by movement artifacts and ECG triggering problems. To quantify exercise-induced flow changes in the abdominal aorta, we applied a fast hybrid phase contrast sequence with K-space segmentation and echo planar imaging readouts during a 12 heart beat, single breathhold post exercise scanning window after ergometer exercise in nine volunteers. Central k-space was acquired first. The changes in heart rate throughout the scanning window were quantified. The mean decrease in heart rate after six heart beats post exercise was less than 4% and less than 14% after 11 heart beats indicating that the exercise state was very well represented during the acquisition of central k-space. Abdominal aortic flow increased from 1.4 ± 0.3 l/min at rest to 7.9 ± 1.1 l/min at 131 watt. Retrograde flow reached a maximum value of 1.2 l/min at rest, and lasted 140 ms on average. Only for one out of the nine volunteers was there any retrograde flow present during exercise (at 33 watt and 65 watt exercise). It was concluded that retrograde flow patterns in the abdominal aorta associated with oscillating wall shear stresses and development of atherosclerosis disappeared with increasing levels of exercise. The feasibility of using fast quantitative phase contrast measurements during a post exercise scanning window to represent controlled exercise levels was demonstrated.

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• Respiratory Effects on Fontan Circulation during Rest and Exercise Utilizing Real Time Cardiac Magnetic Resonance Imaging

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  Respiratory Effects on Fontan Circulation during Rest and Exercise Utilizing Real Time Cardiac Magnetic Resonance Imaging

  Author(s)

  Zhenglun Wei, PhD, Kevin K. Whitehead, MD, PhD, Reza H. Khiabani, PhD, Michael Tree, Elaine Tang, Stephen M. Paridon, MD, Mark A. Fogel, MD, and Ajit P. Yoganathan, PhD

  Date

  2017-05-01

  Source

  Ann Thorac Surg. 2016 May; 101(5): 1818–1825.

  Background
  It is known that respiration modulates cavopulmonary flows, but there is little data comparing mean flows under breath holding and free breathing conditions to isolate the respiratory effects, as well as effects of exercise on the respiratory modulation.

  Methods
  Real time phase contrast magnetic resonance combined with a novel method to track respiration on the same image acquisition was used to investigate respiratory effects on Fontan caval and aortic flows under breath holding, free breathing and exercise conditions. Respiratory phasicity indices based on beat-averaged flow was employed to quantify the respiratory effect.

  Results
  Flow during inspiration was significantly higher than expiration under the free breathing and exercise conditions for both inferior vena cava (inspiration/expiration: 1.6±0.5 and 1.8±0.5, respectively) and superior vena cava (inspiration/expiration: 1.9±0.6 and 2.6±2.0, respectively). Changes from rest to exercise in the respiratory phasicity index for these vessels further showed the impact of respiration. Total systemic venous flow showed no significant statistical difference between the breath holding and free breathing conditions. In addition, no significant difference was found between the descending aorta and inferior vena cava mean flows under either resting or exercise conditions.

  Conclusions
  This study demonstrated that inferior vena cava and superior vena cava flow time variance is dominated by respiratory effects, which can be detected by the respiratory phasicity index. However, the minimal respiration influence on net flow validates the routine use of breath holding techniques to measure mean flows in Fontan patients. Moreover, the mean flows in the inferior vena cava and descending aorta are interchangeable.

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• The effect of supine exercise on the distribution of regional pulmonary blood flow measured using proton MRI

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  The effect of supine exercise on the distribution of regional pulmonary blood flow measured using proton MRI

  Author(s)

  E. T. Hall, R. C. Sá, S. Holverda, T. J. Arai, D. J. Dubowitz, R. J. Theilmann, G. K. Prisk, and S. R. Hopkins

  Date

  2015-02-15

  Source

  Journal of Applied Physiology

  The Zone model of pulmonary perfusion predicts that exercise reduces perfusion heterogeneity because increased vascular pressure redistributes flow to gravitationally nondependent lung, and causes dilation and recruitment of blood vessels. However, during exercise in animals, perfusion heterogeneity as measured by the relative dispersion (RD, SD/mean) is not significantly decreased. We evaluated the effect of exercise on pulmonary perfusion in six healthy supine humans using magnetic resonance imaging (MRI). Data were acquired at rest, while exercising (∼27% of maximal oxygen consumption) using a MRI-compatible ergometer, and in recovery. Images were acquired in most of the right lung in the sagittal plane at functional residual capacity, using a 1.5-T MR scanner equipped with a torso coil. Perfusion was measured using arterial spin labeling (ASL-FAIRER) and regional proton density using a fast multiecho gradient-echo sequence. Perfusion images were corrected for coil-based signal heterogeneity, large conduit vessels removed and quantified (in ml·min−1·ml−1) (perfusion), and also normalized for density and quantified (in ml·min−1·g−1) (density-normalized perfusion, DNP) accounting for tissue redistribution. DNP increased during exercise (11.1 ± 3.5 rest, 18.8 ± 2.3 exercise, 13.2 ± 2.2 recovery, ml·min−1·g−1, P < 0.0001), and the increase was largest in nondependent lung (110 ± 61% increase in nondependent, 63 ± 35% in mid, 70 ± 33% in dependent, P < 0.005). The RD of perfusion decreased with exercise (0.93 ± 0.21 rest, 0.73 ± 0.13 exercise, 0.94 ± 0.18 recovery, P < 0.005). The RD of DNP showed a similar trend (0.82 ± 0.14 rest, 0.75 ± 0.09 exercise, 0.81 ± 0.10 recovery, P = 0.13). In conclusion, in contrast to animal studies, in supine humans, mild exercise decreased perfusion heterogeneity, consistent with Zone model predictions.
  Keywords: functional magnetic resonance imaging, pulmonary perfusion, exercise

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• The response of the pulmonary circulation and right ventricle to exercise: exercise-induced right ventricular dysfunction and structural remodeling in endurance athletes

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  The response of the pulmonary circulation and right ventricle to exercise: exercise-induced right ventricular dysfunction and structural remodeling in endurance athletes

  Author(s)

  La Gerche A, Roberts T, Claessen G

  Date

  2014-09-04

  Source

  Pulmonary Circulation

  Abstract
  There is unequivocal evidence that exercise results in considerable health benefits. These are the result of positive hormonal, metabolic, neuronal, and structural changes brought about by the intermittent physiological challenge of exercise. However, there is evolving evidence that intense exercise may place disproportionate physiological stress on the right ventricle (RV) and the pulmonary circulation. Both echocardiographic and invasive studies are consistent in demonstrating that pulmonary arterial pressures increase progressively with exercise intensity, such that the harder one exercises, the greater the load on the RV. This disproportionate load can result in fatigue or damage of the RV if the intensity and duration of exercise is sufficiently prolonged. This is distinctly different from the load imposed by exercise on the left ventricle (LV), which is moderated by a greater capacity for reductions in systemic afterload. Finally, given the increasing RV demand during exercise, it may be hypothesized that chronic exercise-induced cardiac remodeling (the so-called athlete’s heart) may also disproportionately affect the RV. Indeed, there is evidence, although somewhat inconsistent, that RV volume increases may be relatively greater than those for the LV. Perhaps more importantly, there is a suggestion that chronic endurance exercise may cause electrical remodeling, predisposing some athletes to serious arrhythmias originating from the RV. Thus, a relatively consistent picture is emerging of acute stress, prolonged fatigue, and long-term remodeling, which all disproportionately affect the RV. Thus, we contend that the RV should be considered a potential Achilles’ heel of the exercising heart.

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• UNDERSTANDING THE CARDIOPULMONARY CIRCULATION IN SICKLE CELL DISEASE: USING AN MR AUGMENTED CARDIOPULMONARY EXERCISE TESTING TECHNIQUE

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  UNDERSTANDING THE CARDIOPULMONARY CIRCULATION IN SICKLE CELL DISEASE: USING AN MR AUGMENTED CARDIOPULMONARY EXERCISE TESTING TECHNIQUE

  Author(s)

  Emmanuel Ako, Nathaniel Barber, Grzegorz T. Kowalik, Jennifer Steeden, John Porter, John Walker, Vivek Muthurangu

  Date

  2016-04-05

  Source

  https://jcmr-online.biomedcentral.com/articles/10.1186/1532-429X-18-S1-O69

  Background:
  Exercise intolerance is a common feature of many diseases. The causes are difficult to determine and often multifactorial,
  including secondary cardiac-respiratory dysfunction, as well as skeletal muscle abnormalities. We have developed MR augmented
  cardiopulmonary exercise testing (CPET) that allows simultaneous evaluation of cardiac output, estimate mean pulmonary artery pressures
  and tissue oxygen extraction in addition to conventional CPET measures. To demonstrate the utility of this technique we performed MRCPET on patients with sickle cell disease (SCD). The aim of this study was to demonstrate that MR-CPET could be used to define the
  physiological factors associated with their poorly understood exercise intolerance.

  Methods:
  14 patients with homozygous sickle cell disease (age: 35.3, 30-41 yrs) and 14 healthy ethnic matched volunteers (age: 30.8,
  25-37 yrs) underwent MR-CPET. Exercise was performed on MR-compatible ergometer (Lode, The Netherlands) and VE, VO2, and VCO2
  were assessed using a respiratory gas analyser (Ultima, MedGraphics, USA). Aortic flow and septal curvature ratio (an index of mean
  pulmonary artery pressure) were measured during exercise. MR data was used to derive CO, HR, SV and Septal Curvature Ratio (SCR)
  during exercise. Tissue oxygen extraction was calculated using the Fick principle.

  Results:
  Peak VO2 (0.7±0.2 vs 1.1±0.3 L/min, p<0.001), CO (12±1.4 vs 13±1.3 L/min, p<0.05), SCR (0.6±0.1 vs 0.8±0.1, p<0.001)
  and tissue oxygen extraction (0.51±0.13 vs 0.90±0.19 mlO2/mlBlood, p<0.001) were all significantly lower in SCD patients compared to
  controls.

  Conclusions:
  Using MR-CPET we have been able to show for the first time that exercise intolerance in SCD is due to reduced skeletal
  muscle oxygen extraction and increased pulmonary pressures during exercise. This may be due to vascular network rarefaction,
  muscle and lung fibrosis, or reduced mitochondrial function; all of which have been demonstrated in histology specimens in SCD. This
  demonstrates the power of MR-CPET and we believe this technique could aid in better understanding of exercise intolerance and possibly
  better therapeutic interventions.

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