DETERMINANTS OF STROKE VOLUME AND SYSTOLIC AND DIASTOLIC AORTIC

We investigated how parameters describing the heart and the arterial s ystem contribute to the systolic and diastolic pressures (P-s and P-d, respectively) and stroke volume (SV). We have described the heart by the varying-elastance model with six parameters and the systemic arter ial tree by the three-element windkessel model, leading to a total of nine parameters. Application of dimensional analysis led to a total of six dimensionless parameters describing dimensionless P-s and P-d, i. e., pressures with respect to venous pressure (P-s/P-v and P-d/P-v). S V was normalized with respect to unloaded ventricular volume (V-d). Se nsitivity analysis showed that P-s/P-v, P-d/P-v, and SV/V-d could be a ccurately described by four, three, and three dimensionless parameters , respectively. With this limited number of parameters, it was then po ssible to obtain empirical analytical expressions for P-s/P-v, P-d/P-v , and SV/V-d. The analytic predictions were tested against the model v alues and found to be as follows: P-s predicted = (1.0007 +/- 0.0062) P-s, r = 0.987; P-d predicted = (1.016 +/- 0.0085) P-d, r = 0.992; and SV predicted = (0.9987 +/- 0.0028) SV, r = 0.996. We conclude that ao rtic P-s, P-d, and SV can be accurately described by a Limited number of parameters and that, for any condition of the heart and the arteria l system, P-s, P-d, and SV can be presented in analytical form.