Stress troubles women’s hearts

By Eleanor McDermid

Women experience more myocardial stress than men, regardless of arterial hemodynamic function and cardiac geometry and output, research shows.

This "suggests a less efficient myocardial-arterial coupling in women compared with men," say Julio Chirinos (University of Pennsylvania, Philadelphia, USA) and colleagues.

They add that the findings are "novel" and may help to explain why women are more likely than men to develop heart failure. But they note that this study involves a middle-aged population (average age 45 years), so the findings should be replicated in older people who are at greater risk for heart failure.

Peak stress was 534 kdyne/cm² in 551 women versus 507 kdyne/cm² in 663 men, as was end-systolic stress, at 335 versus 320 kdyne/cm², the team reports in Hypertension. Also, the ejection-phase stress-time integral (ie, stress throughout the ejection phase) was higher in women than men, at 157 versus 142 kdyne/cm² per second.

These differences were independent of multiple arterial properties, plus stroke volume, heart rate, and end-diastolic left ventricle geometry.

The researchers assessed myocardial stress throughout the ejection phase, as opposed to just at specific timepoints, to allow for changes in variables such as wall thickness, cavity size, and ventricular pressure during systole.

They found that peak myocardial stress rose in line with systemic vascular resistance and aortic characteristic impedance. This large impact of the microvasculature and the aortic root fits with the team's previous work showing that peak myocardial stress occurs during early systole, corresponding with the first systolic pressure peak, and is therefore heavily influenced by ascending aortic wall stiffness and aortic size.

This also explains why wave reflections did not affect peak stress, say the researchers, as these come into play later in systole.

End-systolic wall stress rose in line with systemic vascular resistance and reflection magnitude, and the ejection-phase stress-time integral rose with increasing systemic vascular resistance, and fell with increasing total arterial compliance and faster return of wave reflections.

Wave reflections are thought to influence risk for left ventricular hypertrophy and dysfunction. Combined with the current findings, this suggests that "the loading sequence may be more important than absolute stress levels, per se," say Chirinos et al. "Although we found absolute wall stress to be low in late systole, the myocardium may be particularly vulnerable to even small wall stress increases during this period of time."

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