Oxygen Consumption at Anaerobic Threshold Predicts Cardiac Events After Heart Transplantation

The ventilatory efficiency and functional capacity measured by the cardiopulmonary exercise test (CPET) have been used as important prognostic variables in congestive heart failure. This study sought to identify whether these predictors before heart transplantation (HTX) play a key role in predicting adverse events in patients with heart failure after HTX.

This was a retrospective cohort study design. HTX recipients were included for analysis. Ventilation to carbon dioxide production slope (VE/VCO₂ slope) and oxygen consumption (VO₂) during exercise were collected by CPET, which represented ventilator efficiency and functional capacity respectively. Cardiac-related events 2 years after HTX were recorded by chart review. We divided patients into 2 groups based on VE/VCO₂ slope = 34, peak VO₂ = 14 mL/kg/min and VO₂ at aerobic threshold (AT) = 11 mL/kg/min. Kaplan-Meier survival curves was used to represent the events rate between groups and Log rank test was used to test significance.

A total of 87 patients after HTX were included. Mean (SD) age was 48 (11) years and 73 were male; 28 subjects suffered from events, and 76 cardiac events were recorded. The mean (SD) data of peak VO₂, VO₂ at AT, and VE/VCO₂ slope analyzed from CPET were 17.8 (5.6) mL/kg/min, 15.4 (4.4) mL/kg/min, and 33.1 (8.2) mL/kg/min, respectively. Lower VO₂ at AT contributed to increase events rate (P < .05).

Aerobic capacity may better predict 2-year cardiac events in patients after HTX. Strategies to improve aerobic capacity should be focused on in the cohort.