Background
Late systolic load has been shown to cause diastolic dysfunction in animal models. Whereas the systolic loading sequence of the ventricular myocardium likely affects its coupling with the left atrium (LA), this issue has not been investigated in humans. We aimed to assess the relationship between the myocardial loading sequence and LA function in human hypertension.
Methods and Results
We studied 260 subjects with hypertension and 19 normotensive age- and sex-matched controls. Time-resolved central pressure and LV geometry were measured with carotid tonometry and cardiac MRI, respectively, for computation of time-resolved ejection-phase myocardial wall stress (MWS). The ratio of late/early ejection-phase MWS time-integrals was computed as an index of late systolic myocardial load. Atrial mechanics were measured with cine-SSFP MRI using feature-tracking algorithms. Compared to normotensive controls, hypertensive participants demonstrated increased late/early ejection-phase MWS and reduced LA function. Greater levels of late/early ejection-phase MWS were associated with reduced LA conduit, reservoir and booster pump LA function. In models that included early and late ejection-phase MWS as independent correlates of LA function, late-systolic MWS was associated with lower, whereas early-systolic MWS was associated with greater LA function, indicating an effect of the relative loading sequence (late vs. early MWS) on LA function. These relationships persisted after adjustment for multiple potential confounders.
Conclusions
A myocardial loading sequence characterized by prominent late systolic MWS was independently associated with atrial dysfunction. In the context of available experimental data, our findings support the deleterious effects on late systolic loading on ventricular-atrial coupling.
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