EXPERIMENTAL AND NUMERICALLY MODELED EFFECTS OF ALTERED LOADING CONDITIONS ON PULMONARY VENOUS FLOW AND LEFT ATRIAL PRESSURE IN PATIENTS WITH MITRAL REGURGITATION

Pulmonary venous flow measured by pulsed-wave Doppler transesophageal echocardiography reflects the effects of mitral regurgitation on left atrial pressure contour. To assess the relationship between pulmonary venous flow and left atrial pressure in patients with mitral regurgita tion under altered loading conditions, we studied 25 patients with 3or 4+ mitral regurgitation and a control group by measuring pulmonary venous flow with transesophageal echocardiography and left atrial pres sures after administering saline solution (n = 6), nitroglycerin (n = 6), phenylephrine (n = 6), or nitroprusside (n = 7). After administrat ion, the left atrial pressure v wave increased in the group given phen ylephrine, concomitant with an increased diastolic flow. In contrast, the left atrial pressure v wave decreased in the group given nitroglyc erin, concomitant with a decreased diastolic flow. Changes in diastoli c flow were closely related to changes in the left atrial pressure v w ave under all loading conditions (r = 0.91; p < 0.0001). Numeric model ing of left atrial pressure and pulmonary venous diastolic flow corrob orated the experimental findings. We conclude that changes in pulmonar y venous diastolic flow are closely related to changes in the left atr ial pressure v wave in mitral regurgitation, under altered loading con ditions.