Measurement of Mitral Regurgitation in Man from Simultaneous Atrial and Arterial Dilution Curves after Ventricular Injection

Abstract

Measurements of forward and regurgitant flow were obtained in 16 patients with rheumatic disease of the mitral valve by means of simultaneous systemic arterial and left atrial dilution curves after injection of Evans-blue dye into the left ventricle. The results indicate that satisfactory measurements of forward flow may be obtained with injections into the left ventricle and that the calculated regurgitant flow has a good correlation with the severity of mitral insufficiency, as estimated clinically and surgically. The mean and range of regurgitant flow, expressed as a per cent of estimated total left ventricular output, for patients with pure mitral stenosis, predominant stenosis with mild to moderate insufficiency, and predominant or pure insufficiency, were 6 per cent (0 to 11), 21 per cent (8 to 39), and 58 per cent (28 to 82), respectively. Eight studies in six patients, however, gave results that were either mathematically absurd, physiologically incredible, in conflict with diagnostic evidence, or otherwise suspect. Moreover, in the seven patients in whom satisfactory duplicate studies were obtained, the reproducibility of results was poor: the mean absolute difference in successive measurements was 17 per cent of total left ventricular output and the coefficient of variation was 23 per cent of an observation. It is suggested that the principal source of error lies in unrepresentative sampling from the left atrium in the presence of incomplete mixing of indicator with blood in the cardiac chambers. In some patients, an additional and possibly appreciable error may arise from the existence of an enhanced pulmonary collateral blood flow, which provides an alternative short pathway from the left ventricle to the left atrium. It is concluded that, with conventional sampling technics, this theoretically sound approach is too capricious to be a dependable quantitative method.