Clinical features and determinants of VO

To study exercise capacity and determinants of early peak oxygen consumption (VO2peak) in a cohort of de novo heart transplant (HTx) recipients.

To determine possible central (chronotropic responses, cardiopulmonary and hemodynamic function) and peripheral factors (muscular exercise capacity and body composition) predictive of VO2peak, 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 VO2peak and VE/VCO2 slope. Additional measures included muscle strength testing, bioelectrical impedance analysis, echocardiography, blood sampling and health-related quality of life. Based on the VO2peak (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 VO2peak (L/min) as the dependent variable.

The mean ± standard deviation (SD) age of the total study population was 49 ± 13 years, and 73% were men. This de novo HTx cohort demonstrated a median VO2peak 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, O2 pulse, peak heart rate and heart rate reserve, while the VE/VCO2 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, O2 pulse, heart rate reserve, muscular exercise capacity, body mass index, gender and age accounted for 84% of the variance in VO2peak (L/min). There were no minor or major serious adverse events during the CPET.

Although there is great individual variance among de novo HTx recipients, early VO2peak measures appear to be influenced by both central and peripheral factors.