Gender and the Heart. Sex-Specific Differences in the Normal Myocardial Anatomy and Physiology

This chapter reviews the differences between men and women's normal cardiac physiology and describes some differences in their unique experiences with common diseases of the cardiovascular system. As a consequence of their smaller body size compared with that of men, women's hearts are generally smaller than that of their male counterparts. Contrary to popular assumption, though, there is wide variability in the size of coronary arteries; the Coronary Artery Surgery Study (CASS) reported that the coronaries are not always smaller in women than in men and that most are entirely suitable for bypass grafting. Vascular function is different in the two sexes, in part due to hormone-dependent gender differences. Premenopausal women have lower blood pressure than same-aged men; it rises after the menopause. Long-term estrogen administration improves vasodilation in men but does not lower blood pressure in postmenopausal women. Estrogen titers in men are lower than those of women, but are physiologically relevant; aromatase inhibitors disrupt normal vascular relaxation in males. Conversion of testosterone to estrogen by aromatase inhibitors is essential to physiologic vascular function in men. Moreover, there are clearly differences in cardiac chamber size between the sexes, which are largely but not completely explained by differences in body size and become established at puberty.