Late systolic pressure augmentation in the ascending aorta significantly prolonged the rate of isovolumic left ventricular pressure decline, with Tau increasing proportionally to the augmentation index (r=0.64, p<0.001).
Does altering loading patterns with angiotensin and nitroglycerin affect the rate of isovolumic left ventricular pressure decline in humans?
Late systolic pressure augmentation in the ascending aorta is an important factor that prolongs the rate of isovolumic left ventricular pressure decline in humans.
Effect estimate: r=0.64
Absolute Event Rate: 54% vs 49%
p-value: p=<0.001
This clinical investigation was designed to determine the effect of changes in loading patterns on left ventricular (LV) relaxation when heart rate was maintained constant. Not only were changes noted in total load or time in which load is changed, but also the contour of the ascending aortic systolic pressure wave. Twenty patients were studied. LV and ascending aortic pressure were measured by a multisensor catheter under baseline conditions (C) and after an intravenous injection of 2.5 microg angiotensin (A) and sublingual administration of 0.3 mg nitroglycerin (N). A bipolar pacing catheter was placed in the right atrium to maintain a constant heart rate throughout the protocol. The augmentation index (AI), which characterizes the contour of the ascending aortic systolic pressure wave, was defined as the ratio of the height of the late systolic shoulder/peak to that of the early systolic shoulder/peak in the pulse. The rate of isovolumic LV pressure decline was calculated as a time constant (Tau). Ascending aortic systolic pressures (mmHg) were 127+/-29 (C), 158+/-20 (A) and 109+/-15 (N). AI were 1.61+/-1.14 (C), 2.08+/-1.11 (A) and 1.27+/-1.14 (N). Tau values (msec) were 49+/-4 (C), 54+/-4 (A) and 45+/-5 (N). Tau was prolonged proportionally with increasing AI (p<0.001, r=0.64). It was concluded that late systolic pressure augmentation in the ascending aorta is one important factor that influences the rate of isovolumic left ventricular pressure decline in humans.
Iketani et al. (1998) studied Patients undergoing diagnostic cardiac catheterization (n=20). Angiotensin and nitroglycerin administration vs. Baseline conditions was evaluated on Rate of isovolumic left ventricular pressure decline (Tau) (r=0.64, p=<0.001). Late systolic pressure augmentation in the ascending aorta significantly prolonged the rate of isovolumic left ventricular pressure decline, with Tau increasing proportionally to the augmentation index (r=0.64, p<0.001).