Studies Made by Simulating Systole at Necropsy. IX. A Test of the Aortic Compression Chamber Hypothesis and of Two Stroke Volume Methods Based Upon It

¹ From the Department of Therapeutic Research, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania

Data secured by simulating systole at necropsy have been used to assess two methods of estimating cardiac stroke volume, that of Wezler and Böger, and that of Broemser and Ranke. The correlation between estimates made by each of these methods and the true stroke volumes is highly significant. One is not significantly better than the other. Neither method is highly accurate. Both detect changes in stroke volumes in individuals much better than differences in stroke volume between individuals. In our most arteriosclerotic subject the Wezler and Böger method gives results which are too high; in the remaining subjects the method works much better. The hypothesis of the aortic compression chamber, on which these methods are based, has been examined in two ways. First, when accurate measurements of the aorta, made at necropsy after our experiments had been completed, were substituted for the indirect estimates of aortic size usually employed, the accuracy of the estimates of stroke volume was diminished. Second, when those parts of the equations representing the dimensions of the compression chamber were removed from both formulae, estimates made from the remaining part, common to both formulae, correlate with the true stroke volumes better than before. Therefore, our data do not support the compression chamber hypothesis, in accordance with which these methods were designed.