Abstract 2821: Does End-systolic Stress Adequately Reflect Time-varying Left Ventricular Wall And Fiber Stress in Hypertension?: Influence Of The Components Of Arterial Pulsatile Load
Pulsatile hemodynamic abnormalities are key determinants of left ventricular (LV) afterload, which is commonly assessed by end-systolic wall and fiber stress. These important indices of afterload are highly sensitive to cavity size and wall thickness. Since cavity size, pressure and wall thickness all change markedly throughout systole, end-systolic stress may not adequately describe the contribution of different components of arterial load to time-varying stress, since these arterial components also vary markedly throughout systole. We studied 25 hypertensive adults (mean age: 58 yrs; 44% male). Central pressure (carotid tonometry) and flow (Doppler echocardiography) were measured simultaneously and the pressure wave was decomposed into its forward (Pf) and reflected (backward, Pb) components. Speckle-tracking echocardiography was used to measure instantaneous LV cavity and wall areas during systole, which were used to compute time-varying fiber (Arts method) and meridional wall (Janz method) stress. Peak fiber and wall stress values were, on average, 1.87- and 2.19-fold higher than end-systolic values, respectively. Peak fiber and wall stress occurred in early systole (97±7 and 81±4 msec after the onset of ejection, respectively), before important contributions of Pb to central pressure. Although end-systolic stress predicted a large proportion of the variability in peak fiber (76%; p<0.0001) and wall (80%; p<0.0001) stress, the ratio of peak/end-systolic stress decreased with increasing Pb/Pf amplitude ratio (fiber stress: R=−0.59, p=0.001; wall stress: R=−0.50; p=0.01). Similarly, the ratio of mean systolic/end-systolic stress decreased with increasing Pb/Pf amplitude ratio (fiber stress: R=−0.58, p=0.002; wall stress: R=−0.51; p=0.007). Adjustment for systemic vascular resistance did not affect these results. The relationship between end-systolic and time-varying LV fiber and wall stress is strongly biased by wave reflections. End-systolic stress does not adequately reflect the contribution of different components of arterial load on time-varying stress, which should be assessed with the combination of arterial tonometry and contemporary echocardiographic techniques.