Effects of gender on peak oxygen consumption and the timing of cardiac transplantation

Abstract

Objectives: This study examines the gender effects on peak exercise oxygen consumption (VO2) and survival in heart failure (HF) patients and their implications for cardiac transplantation.

Background: The predictive value of peak VO2 in women HF patients is poorly established but is one of the indicators used to optimally time cardiac transplantation in women.

Methods: A total of 594 ambulatory HF patients (mean age 52 +/- 12 years, 28% women, mean left ventricular ejection fraction 26 +/- 12%, 73% on beta-blocker) underwent symptom-limited exercise tests with breath-by-breath expired gas analyses using ramped treadmill protocols. Kaplan-Meier survival curves were generated for each gender and compared using log-rank tests.

Results: Women had a significantly lower peak VO2 than men (14.0 +/- 4.9 ml/kg/min vs. 16.6 +/- 7.1 ml/kg/min; p < 0.0001), despite being younger (48.9 +/- 11.5 years vs. 53.2 +/- 12.4 years; p < 0.0001) and having a higher left ventricular ejection fraction (29 +/- 13% vs. 25 +/- 11%; p < 0.0003). However, the one-year transplant-free survival was significantly lower for men than for women (81% vs. 94%, p < 0.0001), a finding seen across each Weber class. Cox regression analyses confirmed the protective effects of female gender on transplant-free survival when controlling for peak VO2, age, race, beta-blocker use, and type of cardiomyopathy. The peak VO2 associated with 85% one-year transplant-free survival was significantly higher in men than in women (11.5 vs. 10.0 ml/kg/min).

Conclusions: Women had a significantly lower peak Vo(2) than men, but had better survival at all levels of exercise capacity. The current practice of uniform application of peak VO2 as an aid to determine cardiac transplantation timing should be re-examined.