Clinical features and determinants of VO2peak in de novo heart transplant recipients

ARTICLE HIGHLIGHTS

Research background

Peak oxygen consumption (VO_2peak) is reduced after heart transplant (HTx). Both peripheral and central factors are determinants of the reduced VO_2peak in maintenance HTx recipients, but there are still few studies among de novo HTx patients. A higher VO_2peak is associated with better prognosis after HTx, and knowledge about predictors for VO_2peak in de novo HTx is important for the rehabilitation process. A cardiopulmonary exercise test (CPET) is the gold standard for measuring VO_2peak and should be performed as a routine test early after HTx.

Research motivation

More knowledge about predictors for VO_2peak in de novo HTx patients may contribute to a better understanding of the reduced exercise capacity early after HTx. Individualized exercise prescriptions are very important after HTx, and a CPET early after HTx will guide both clinicians and physiotherapists in this vulnerable phase of the rehabilitation process.

Research objectives

The aim of this study was to investigate determinants of early VO_2peak and exercise capacity in a cohort of de novo HTx recipients.

Research methods

This study used baseline data from an ongoing randomized controlled trial investigating high-intensity interval training compared to moderate continuous exercise training among de novo HTx recipients, the HITTS study. A cross sectional analysis was performed on the baseline data from the 81 patients included in the study, and all baseline tests were performed an average of 11 wk after surgery. The primary endpoint was VO_2peak measured by CPET. Secondary endpoints were lung function, maximum muscle strength and muscular exercise capacity, bioelectrical impedance analysis, echocardiography, blood samples and health-related quality of life.

Research results

The main findings in this study were that de novo HTx patients display reduced exercise capacity compared to a general population, but comparable with maintenance HTx recipients. This de novo HTx cohort demonstrated a median VO_2peak level of 19.4 mL/kg per min at 11 ± 1.8 wk post-HTx. Maximal exercise capacity was determined by both central (O₂ pulse and HR_reserve) and peripheral factors (muscular exercise capacity). The CPET tests were performed without any serious adverse events mean 11 wk after HTx. This is a cross-sectional study, and no causal relationships should be drawn from such a study design. We present only associations between VO_2peak and different possible determinants.

Research conclusions

In this de novo HTx cohort, the age-predicted mean VO_{2 peak} value was 56% of age-expected values, which is comparable to previously reported values in maintenance HTx. Predictors for VO_2peak in de novo HTx recipients seem to be of both central and peripheral origin.

Research perspectives

A CPET and determination of muscular exercise capacity provide important information for patient motivation, rehabilitation and prognosis and thus, measurements for physical function should be considered as routine examinations early after HTx.