Measurement of mitral regurgitation in man from simultaneous atrial and arterial dilution curves after ventricular injection.

THE MOST DIRECT APPROACH to measurement of the volume of blood regurgitating across an insufficient mitral valve consists of the injection of indicator into the left ventricle and simultaneous sampling of blood from the left atrium and from the aorta or one of its branches. If mixing is complete in the left ventricle, the distribution of indicator to upstream and downstream collection sites is a function of the volumes of blood flowing in these directions. This principle has been used in experimental animals and in man by a number of investigators.1-5 Their data demonstrate a relationship between the calculated values of regurgitant flow and the clinical or surgical estimates of the severity of insufficiency. The studies referred to, however, involve only 33 patients with clinical mitral disease. Fewer than half of these had any appreciable regurgitation as judged by clinical, surgical, and physiologic criteria. Figures for actual backflow in liters per minute are provided only in one preliminary report3 of a small series. In 20 of the cases,4 the essential dilution curves were not obtained simultaneously. In