Quantitation of Mitral Regurgitation by Constant Infusion of Xenon-133

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Abstract
A method for the accurate quantitation of mitral regurgitation in man was described and tested in 23 patients. The technique involves a constant infusion of xenon-133 into the left ventricle for 2 minutes. Left atrial and arterial samples must be withdrawn after constant concentration is achieved and before recirculation reaches high values. It was shown that concentration of indicator at both sample sites was constant by 60 seconds from the onset of infusion and that at 60 and 120 seconds left atrial concentration would rise on the average to 2.3 and 4.3% arterial concentration, respectively, as a result of recirculation. It could be demonstrated by altering the left atrial sample site that error due to incomplete mixing in the left atrium might average 2% and would be unlikely to exceed 7%. Values for cardiac output and regurgitant flow and regurgitant fraction, measured between 60 and 120 seconds, were relatively constant in any one patient. Regurgitant fraction varied from 1 to 84% of blood leaving the left ventricle in systole in different patients and there was good correlation with clinical and angiocardiographic estimates of severity of regurgitation.