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Dissociation between peak exercise oxygen consumption and hemodynamic dysfunction in potential heart transplant
J R Wilson1, G Rayos, T K Yeoh
1Cardiology Division, Vanderbilt University Medical Center, Nashville, Tennessee 37232-2170, USA.
Journal of the American College of Cardiology
|August 1, 1995
Summary
Peak exercise oxygen consumption (VO2) may misclassify heart transplant candidates. Direct hemodynamic measurement is crucial for accurate assessment of cardiac dysfunction severity in these patients.
Area of Science:
- Cardiology
- Exercise Physiology
- Transplant Medicine
Background:
- Cardiopulmonary exercise testing (CPET) is used for heart transplant candidate selection based on peak exercise oxygen consumption (VO2).
- Low peak exercise VO2 is assumed to indicate severe hemodynamic dysfunction and poor prognosis.
- Non-cardiac factors like muscle deconditioning can influence exercise capacity, potentially leading to overestimation of cardiac dysfunction severity.
Purpose of the Study:
- To determine the frequency with which peak exercise oxygen consumption (VO2) misclassifies cardiac dysfunction severity in potential heart transplant candidates.
- To evaluate the reliability of peak exercise VO2 as a sole indicator for heart transplant candidacy.
Main Methods:
- Maximal treadmill exercise testing was performed on 64 potential heart transplant candidates with ejection fraction < 35% and reduced peak exercise VO2.
- Hemodynamic (cardiac output, pulmonary wedge pressure) and respiratory responses were measured during exercise.
- Patients were categorized based on exercise-induced hemodynamic responses and pulmonary wedge pressure.
Main Results:
- 44% of patients showed severe hemodynamic dysfunction (reduced cardiac output, elevated pulmonary wedge pressure).
- 36% showed moderate dysfunction (normal cardiac output, elevated pulmonary wedge pressure).
- 20% showed mild dysfunction (normal cardiac output, normal pulmonary wedge pressure).
- Despite differing hemodynamic severities, peak exercise VO2 levels were similar across groups.
- A peak exercise VO2 < 14 ml/min per kg was observed in 18 patients with normal cardiac output, while 7 with severe dysfunction had VO2 > 14 ml/min per kg.
Conclusions:
- Over 50% of potential heart transplant candidates with reduced peak exercise VO2 exhibit only mild or moderate hemodynamic dysfunction.
- Peak exercise VO2 alone is insufficient for accurately assessing cardiac dysfunction severity in heart transplant candidates.
- Direct measurement of hemodynamic responses during exercise is essential for confirming severe circulatory dysfunction before transplantation.