Total arterial compliance estimated by stroke volume-to-aortic pulse pressure ratio in humans

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Abstract
On the basis of the windkessel model, the stroke volume-to-aortic pulse pressure ratio (SV/PP) has been proposed as an estimate of total arterial compliance, but recent studies have questioned this approximation. Aortic pressure was obtained at rest in 31 adults undergoing cardiac catheterization (47 ± 14 yr): controls (n = 7), patients with dilated cardiomyopathy (n = 10), and patients with other cardiac diseases (n = 14). We calculated PP, mean aortic pressure (MAoP), heart period (T), SV (thermodilution cardiac output/heart rate), total peripheral resistance (R), total arterial compliance estimated by area method (Carea), and the time constant of aortic pressure decay in diastole (RCarea). In the overall population (n = 31), there was no significant difference between SV/PP andCarea. SV/PP was linearly related toCarea (SV/PP = 0.99Carea + 0.05;r = 0.98;P < 0.001); the slope and intercept did not differ from unity and zero, respectively. Similar results were obtained in the three subgroups. These results implied that PP/MAoP andT/RCareawere proportionally related (T/RCarea= 1.18PP/MAoP − 0.07; r = 0.96;P < 0.001). We conclude that for humans at rest 1) SV/PP gave a reliable estimate ofCarea, and2)T normalized by the time constant of aortic pressure decay in diastole was proportionally related to PP/MAoP. This last relationship could be considered an aspect of the coupling between the left ventricle and its load.