Low compliance rather than high reflection of arterial system decreases stroke volume in arteriosclerosis: a...

Although various investigators have suggested that the left ventricles of aged subjects suffer from high-frequency reflection, arterial reflection is larger in the low-frequency range because of a larger impedance mismatch. It has not been quantified whether high-frequency reflection rather than low-frequency reflection has larger deleterious effects on stroke volume. We used a computer simulation method to evaluate how increases in high- and low-frequency arterial reflections associated with age-related arterial sclerosis affect left ventricular (LV) pump function. Low-frequency reflections derive principally from the total arterial compliance, and high-frequency reflections result from impedance fluctuations in the high-frequency range. We numerically coupled a time-varying elastance LV model with a variety of arterial impedances to quantitatively evaluate the effects of low- and high-frequency reflections on LV pump performance. When we simultaneously increased low- and high-frequency reflections to levels of sclerotic impedance (type A in Murgo et al., Circulation 62: 105-116, 1980), stroke volume decreased by 4.4%. Further increases of the reflections up to 8 times of the type A impedance lowered stroke volume by 15.9%. This trend was clearly seen with selective increases in low-frequency reflections (3.5 and 20.2% decrease in stroke volume, respectively), but not with those in high-frequency reflections (1.0% decrease and 0.9% increase in stroke volume, respectively). Thus we conclude that the detrimental effect of increases in arterial reflections associated with arterial sclerosis on stroke volume is mild and mainly attributable to decreased compliance rather than to increased high-frequency reflections.