CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Sammy Elmariah, MD,
Lee R. Goldberg, MD, MPH, FACC,
Michael T. Allen, EMT-P and
Andrew Kao, MD, FACC*
* Cardiovascular Consultants, PA, 4330 Wornall Road, Suite 2000, Kansas City, Missouri 64111 (Email: akao{at}cc-pc.com).
We appreciate the letter by Dr. Lavie and colleagues in reference to our report on the effects of gender on the prognostic value of peak oxygen consumption (VO
2) in heart failure (HF) patients (1). Lavie and colleagues present an interesting theory that the superior survival in female HF patients may be due to their higher body fat content. Although a plausible assumption at first glance, we controlled for several important variables in our study population to account for body fat composition. First, body mass index (BMI), a reliable surrogate for body fat content (2), was equivalent between genders in our study. Regardless of this, to address Lavie’s concerns, we reanalyzed our data to correct for body composition. As skin-fold measurements were not performed on our patients, we adjusted peak VO
2 values to "ideal body weight," as calculated using the Wasserman formulae (3). We found that the gender difference in peak VO
2 persisted: peak VO
2/ideal body weight = 16.5 ± 5.7 ml/kg/min in women and 18.7 ± 7.9 ml/kg/min in men (p < 0.002). Thus, higher percent body fat does not explain the lower peak VO
2 or improved survival in female HF patients.
Although Dr. Lavie and colleagues speculate that the difference in body fat composition accounts for the gender differences in exercise capacity in HF patients, it is clear that the mechanisms for gender differences are much more complex. For example, myocardium responds differently between the genders to stresses such as increased afterload (4–6), and data suggest that this may be due to hormonal influences on regulation of vasculature and myocardial responses (6,7). Additionally, sudden cardiac death, which accounts for approximately 40% of HF deaths, occurs less frequently in women, potentially explaining their prolonged survival (8). Given the complex HF pathophysiology, multiple factors are likely responsible for the observed gender difference beyond just body fat composition. We hope our study will encourage additional research into the mechanism of gender differences in HF so that the best treatment decisions can be made and the best therapies can be applied to all patients.
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References
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- Elmariah S, Goldberg LR, Allen MT, Kao A. Effects of gender on peak oxygen consumption and the timing of cardiac transplantation J Am Coll Cardiol 2006;47:2237-2242.[Abstract/Free Full Text]
- Garrow JS, Webster J. Quetelet’s index (W/H2) as a measure of fatness Int J Obes 1985;9:147-153.[ISI][Medline]
- Wasserman K, Hansen JE, Sue DY, Stringer WW, Whipp BJ. Principles of exercise testing and interpretation, including pathophysiology and clinical applications. Philadelphia, PA: Lippincott Williams & Wilkins; 1999. pp. 148.[Free Full Text]
- Carroll JD, Carroll EP, Feldman T, et al. Sex-associated differences in left ventricular function in aortic stenosis of the elderly Circulation 1992;86:1099-1107.[CrossRef][ISI][Medline]
- Topol EJ, Traill TA, Fortuin NJ. Hypertensive hypertrophic cardiomyopathy of the elderly N Engl J Med 1985;312:277-283.[Abstract]
- Schaible TF, Malhotra A, Ciambrone G, Scheuer J. The effects of gonadectomy on left ventricular function and cardiac contractile proteins in male and female rats Circ Res 1984;54:38-49.[Abstract/Free Full Text]
- Dubey RK, Oparil S, Imthurn B, Jackson EK. Sex hormones and hypertension Cardiovasc Res 2002;53:688-708.[Abstract/Free Full Text]
- Lund LH, Mancini D. Heart failure in women Med Clin N Am 2004;88:1321-1345.[CrossRef][ISI][Medline]
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References