Gender Differences in Cardiac Structure and Function

GENDER DIFFERENCES IN CARDIAC STRUCTURE AND FUNCTION

Compared with a man’s heart, a woman’s heart tends to be smaller. It weighs less and has smaller coronary arteries. These structural differences have significant implications. Because the coronary ar-teries of a woman are smaller, they occlude from atherosclerosis more easily, making procedures such as cardiac catheterization and angioplasty technically more difficult, with a higher incidence of postprocedure complications. In addition, the resting rate, stroke volume, and ejection fraction of a woman’s heart are higher than those of a man’s, and the conduction time of an electrical impulse coursing from the SA node through the AV node to the Purkinje fibers is briefer.

Another significant difference between the genders is the phys-iologic effects of estrogen on the cardiovascular system. Two im-portant effects of estrogen, regulation of vasomotor tone and of response to vascular injury, may be the mechanisms that protect women against the development of atherosclerosis. An addi-tional, potentially beneficial effect of estrogen is its action on the liver, which results in improved lipid profiles. On the other hand, less favorable effects of estrogen include an increase in coagulation proteins and a decrease in fibrinolytic protein, which enhance the risk of thrombus formation. Progesterone also has vascular effects, but its role in the development of CVD is unclear at this time. Ben-eficial effects of estrogen disappear after menopause, as evidenced by the increased incidence of CVD in this population. However, because of health risks associated with hormone replacement ther-apy, the American Heart Association does not recommend its use as a primary or secondary prevention intervention for CVD (Mosca et al., 2001; Roussouw et al., 2002).