CLINICAL RESEARCH: HEART FAILURE
Effects of Gender on Peak Oxygen Consumption and the Timing of Cardiac Transplantation
Sammy Elmariah, MD*,
Lee R. Goldberg, MD, MPH, FACC*,
Michael T. Allen, EMT-P* and
Andrew Kao, MD, FACC ,*
* Department of Medicine, Cardiovascular Division, Heart Failure and Cardiac Transplant Program, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
Cardiovascular Consultants, Mid-America Heart Institute, Kansas City, Missouri
Manuscript received May 18, 2005;
revised manuscript received November 21, 2005,
accepted November 28, 2005.
* Reprint requests and correspondence: Dr. Andrew Kao, Cardiovascular Consultants, PC, 4330 Wornall Road, Suite 2000, Kansas City, Missouri 64111. (Email: akao{at}cc-pc.com).
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 VO2 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.
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Abbreviations and Acronyms
| | HF = heart failure | | LVEF = left ventricular ejection fraction | | OHT = orthotopic heart transplant | | RER = respiratory exchange ratio | | VO2 = oxygen consumption |
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