THE LEFT ATRIAL VOLUME CURVE CAN BE ASSESSED FROM PULMONARY VEIN AND MITRAL-VALVE VELOCITY TRACINGS

After instantaneous left atrial volume was defined as the net differen ce between the forward-flowing blood from the lungs and the blood flow ing through the mitral valve, we constructed the left atrial volume cu rve by sampling the Doppler mitral valve and the right upper pulmonary vein velocity from an apical four-chamber view in eight normal subjec ts and 11 patients with heart disease. The instantaneous mitral valve flow was estimated as mitral valve velocity X annular area (derived fr om the same view), whereas the pulmonary venous flow was obtained as r ight upper pulmonary vein velocity X pulmonary vein area, where pulmon ary vein area = mitral valve velocity integral x mitral valve area) di vided by pulmonary vein velocity integral. The left atrial volume curv e can then be derived as: (instantaneous pulmonary venous flow - mitr al valve flow) + left atrial volume assessed at end diastole by two-di mensional echocardiography. Biplane angiographic left atrial volume c urves, available in four of 11 patients, compared morphologically very closely with the noninvasive curves, whereas the correlation coeffici ent for maximum (end-systolic) and filling (maximum minus minimum) lef t atrial volumes obtained from the Doppler-derived curve and the corre sponding two-dimensional echocardiographic estimates was 0.95 (p < 0.0 01, standard error of the estimate = 11.9 ml), the dispersion of the d ata increased with decreasing volumes. These data demonstrate that com bined Doppler mitral valve and pulmonary vein velocities can be used t o construct the left atrial volume curve in human beings. The approach described, besides providing a tool for further noninvasive evaluatio n of the left atrial function, offers the opportunity for relating the continuous pulmonary venous flow to the intermittent filling of the v entricle through the mitral orifice in diastole, underlining the compl ex role that the left atrial cavity plays in this process.