FURTHER OBSERVATIONS ON EXPERIMENTAL AORTIC INSUFFICIENCY

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Abstract
The changes in ventricular areas before and after production of an experimental aortic insufficiency were [in a large number of experiments on 10 dogs] studied at constant heart rates, for the purpose of evaluating the percentile regurgitation. Successive photographs of the exposed heart, properly suspended in the pericardium, were taken at intervals of 0.031 sec. by means of a moving picture camera. Each photograph was subsequently projected, its outline drawn and the area measured. The values so obtained were plotted as curves and related to simultaneous records of aortic pressures and anteroposterior movements of the left ventricle. The advantages of the method and the precautions necessary in its employment are analyzed in detail. The curves of outline changes during systole and diastole resemble volume curves in their general characteristics, but do not permit us to draw direct conclusions as to the degree to which the stroke of the left ventricle increases during aortic insufficiency. This is accomplished by applying Skavlem''s formula, determining the increase in output and adding this to 1/2 the output of the 2 ventricles. By taking the left ventricular discharge, so determined, as a base, the percentile increase in stroke volume is easily calculated. The results show that during aortic insufficiency the diastolic size is larger and the left ventricular discharge is increased from 16-58% in different experiments, on an average 36.4%. Factors other than heart rate and size of leak are responsible for the variations. In the discussion it is pointed out (a) that changes in heart size without data concerning the stroke volumes of the left ventricle are of no value in determining the percentile regurgitation, but (b) that the percentile changes in stroke volume of the left ventricle give by inference a fair estimate of the percentile regurgitation. The conclusion is reached that approximately 1/3 of the discharge during systole regurgitates through insufficient valves during diastole.[long dash]Authors'' summary.

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