Clinical features and determinants of VO in heart transplant recipients.

Aim: To study exercise capacity and determinants of early peak oxygen consumption (VO) in a cohort of heart transplant (HTx) recipients.

Methods: To determine possible central (chronotropic responses, cardiopulmonary and hemodynamic function) and peripheral factors (muscular exercise capacity and body composition) predictive of VO, a number of different measurements and tests were performed, as follows: Cardiopulmonary exercise testing (CPET) was performed mean 11 wk after surgery in 81 HTx recipients > 18 years and was measured with breath by breath gas exchange on a treadmill or bicycle ergometer. Metabolic/respiratory measures include VO and VE/VCO slope. Additional measures included muscle strength testing, bioelectrical impedance analysis, echocardiography, blood sampling and health-related quality of life. Based on the VO (mL/kg per minute) median value, the study population was divided into two groups defined as a low-capacity group and a high-capacity group. Potential predictors were analyzed using multiple regression analysis with VO (L/min) as the dependent variable.

Results: The mean ± standard deviation (SD) age of the total study population was 49 ± 13 years, and 73% were men. This HTx cohort demonstrated a median VO level of 19.4 mL/kg per min at 11 ± 1.8 wk post-HTx. As compared with the high-capacity group, the low-capacity group exercised for a shorter time, had lower maximal ventilation, O pulse, peak heart rate and heart rate reserve, while the VE/VCO slope was higher. The low-capacity group had less muscle strength and muscular exercise capacity in comparison with the high-capacity group. In order of importance, O pulse, heart rate reserve, muscular exercise capacity, body mass index, gender and age accounted for 84% of the variance in VO (L/min). There were no minor or major serious adverse events during the CPET.

Conclusion: Although there is great individual variance among HTx recipients, early VO measures appear to be influenced by both central and peripheral factors.