Gender-related differences in left ventricular chamber function.

Abstract

While women have lower rates of atherosclerotic disease than men, they are more likely to suffer cardiac failure following infarction or cardiac surgery, despite typically having a greater left ventricular (LV) ejection fraction. We hypothesised that gender differences in systolic chamber function and ventriculo-vascular coupling may contribute to these clinical findings. LV chamber function was determined in a cohort of 30 patients (16 women) aged 48-75 years with normal LV function using pressure-volume loops obtained by simultaneous conductance catheter volumetry and micromanometer pressure. End-systolic and end-diastolic pressure volume (ESPVR, EDPVR) and preload recruitable stroke work relations (PRSWR) were derived. Results were analysed according to gender, and the effects of body size and chamber dimensions were examined. The groups were closely matched for age (60+/-6 vs. 60+/-8 years) and co-morbid conditions. Women had higher end-systolic blood pressure (139.7+/-21.1 vs. 123.6+/-12.6 mmHg, P=0.001), and smaller LV cavity volume (end-diastolic volume 96.4+/-30.6 vs. 139+/-30.7 ml, P=0.001). Women had significantly higher LV end-systolic elastance (Ees, 2.65+/-0.10 vs. 1.96+/-0.09 mmHg ml(-1), P<0.002), arterial elastance (2.41+/-1.13 vs. 1.54+/-0.55 mmHg ml(-1), P=0.01) and lower passive LV diastolic compliance (slope EDPVR, 6.12+/-0.37 vs. 10.0+/-0.50 ml mmHg(-1), P<0.001). While there was a strong relationship between end-systolic elastance and chamber volume (r=0.69, P<0.001), gender differences in chamber function all persisted after indexing to body size. Higher LV systolic function in women was also shown in PRSWR analysis (slope, M(SW); 101.4+/-3.8 vs. 90.4+/-2.8 mmHg, P<0.05), which is independent of chamber size. After normalising volumes to resting diastolic volume, the greater systolic and diastolic elastance in women was accounted for. The ratio of end-systolic to arterial elastance, a measure of ventriculo-vascular coupling, was similar in women and men (1.19+/-0.40 vs. 1.54+/-0.30, respectively, P=0.23). This study demonstrates greater systolic chamber function and lower diastolic compliance in women. Within the range of chamber dimensions seen in patients with normal LV function, a strong relationship was found between cardiac size and end-systolic elastance. While these differences were not accounted for by indexing to body size, the greater ventricular elastance in women was removed after normalising to chamber size. Despite differences in resting ventricular elastance, appropriate ventriculo-vascular coupling was maintained in both genders as the greater end-systolic elastance in women was matched by similarly elevated arterial elastance.