Abstract
In the preceding paper it was shown that the stroke output of the heart may be measured accurately by calculation from the diastolic and systolic areas traced on a roentgenkymogram. Actually, this is a measure of the amount of blood expelled from the heart; in the subject with normal valves it equals the net amount of blood circulated by the stroke. In the patient with aortic or mitral regurgitation, however, we should expect that such equality would not hold and the amount of blood circulated would be less than the amount expelled from the heart by the amount of regurgitation.
The net amount of blood circulated may be measured by the acetylene-rebreathing method. We have found it possible to make what are essentially simultaneous roentgenkymograms and acetylene cardiac output determinations. Comparison of the two results with this procedure should give an absolute quantitative measure of the extent of the back leakage (or the efficiency) of the mitral and aortic valves.
The equation we have developed for the calculation of stroke volume gives, by definition, an average efficiency of the valves of 100% when subjects with normal valves are studied in this way with the two procedures used simultaneously. We have applied this procedure to a series of cases of aortic, mitral, and double aortic and mitral regurgitation and invariably have obtained results which differ from the normal subjects in the expected way.
The subjects were selected on the basis of a clearly defined clinical condition and ability to cooperate in the acetylene rebreathing. None of the subjects was decompensated, though several were on the verge of decompensation or had been decompensated at some time. The clinical evaluation of the lesions in the various patients differentiated 3 groups: (1) minimal leaks, (2) moderate leaks, (3) severe leaks.
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