Improved estimation of cardiac power output by including pulsatile power

Sex differences in left ventricular stroke work and cardiac power output per unit myocardium relate to blood pressure in apparently healthy adults

BACKGROUND

Left ventricular stroke work per unit myocardium (LVSWM) and cardiac power output per unit myocardium (CPOM) are important measures of myocardial workload. The sex differences in the myocardial workload and its correlation with blood pressure remain largely unclear.

OBJECTIVES

The purpose of this study is to investigate the sex differences in LVSWM and CPOM, and to relate them to blood pressure in a cohort of apparently healthy adults.

METHODS

The LVSWM and CPOM were estimated in 596 age- and heart rate-matched apparently healthy adults (298 men) using transthoracic echocardiography combined with cuff-measured brachial blood pressure. The data were compared between sexes, and the sex differences in LVSWM and CPOM were related to blood pressure.

RESULTS

After adjustment for the blood pressure, the LVSWM and CPOM were higher in women than in men [75.0 (73.7-76.4) vs 64.9 (63.5-66.2) cJ/100g for LVSWM, and 912.4 (894.1-930.6) vs 780.2 (762.0-798.5) milliwatt/100g for CPOM, respectively; all P<0.001]. After adjustment for the LVSWM and CPOM, the mean systolic and diastolic blood pressure were 7.4 mm Hg and 5.2 mm Hg higher in men than in women, respectively (all P<0.001).

CONCLUSIONS

For any given blood pressure, the workload per unit myocardium is higher in apparently healthy women than in their male counterparts. A sex-specific definition of normal blood pressure with a relatively lower threshold for women can minimize the sex differences in the myocardial workload, which might reduce the potentially comparatively higher risk of heart failure in women.

Noninvasive Assessment of Sex Differences in Arterial Load in Healthy Adults

Background

Women have higher risk of heart failure than their male counterparts. Although the mechanical inefficiency of myocardium against an excessive afterload is an important reason of heart failure, little attention has been paid to the sex differences in arterial load and its clinical relevance.

Results

The effective arterial elastance index (EaI), total arterial compliance index (TACI), and systemic vascular resistance index (SVRI) were determined using transthoracic echocardiography combined with cuff-measured brachial blood pressure in 460 healthy adults (230 men). The sex differences in these arterial load indexes were analyzed. No statistical difference was found in the age, heart rate, and stroke volume index (all P < 0.05). After adjustment for the cuff-measured blood pressure; the estimated marginal means (95% CIs) of the EaI was higher in women than in men [0.972 (0.952–0.991) vs 0.743 (0.724–0.763) mmHg m2/mL, P < 0.001], the TACI was lower in women than in men [0.924 (0.905–0.944) vs 1.055 (1.036–1.075) mL/mm Hg m2, P < 0.001], and no statistical difference was found in the SVRI between sexes (P > 0.05).

Conclusions

For any given cuff-measured blood pressure, greater integrated and pulsatile arterial load are imposed on left ventricle in women than in men, which is a piece of evidence that women have higher risk of heart failure than their counterparts.