[Effect of acute myocardial ischemia on pulmonary venous flow pattern. Experimental study with transesophageal...

Pulmonary venous flow (PVF) has been analyzed by Doppler echocardiography in various cardiopathies, but up to now no studies of its behavior in acute myocardial ischemia have been reported. The purpose of this study is to describe the changes observed in the normal pattern of PVF with myocardial ischemia in an experimental model. Thoracotomy and pericardiectomy with exposure of the heart were performed on 19 mongrel dogs, weighing between 18 and 25 kg anesthetized with intravenous sodium pentobarbital. Pulmonary venous and mitral flows were analyzed by transesophageal echocardiography with pulsed Doppler and simultaneous recording of intracavitary pressures in left atrium (LA) and left ventricle (LV) before and after 30 minutes of partial occlusion of the middle portion of the anterior descending coronary artery distal to the first diagonal branch. The variables examined included maximal velocities and time-velocity integrals of antegrade systolic(s) and diastolic (D) PVF, mitral rapid filling flow (E) and left ventricular isovolumic relaxation time (LVIRT). The pressures directly measured were mean left atrial pressure (MLAP), systolic and diastolic pressures of the LV. Results included a decrease in peak velocities and time-velocity integrals of PVF (S and D) with myocardial ischemia, S velocity from 70.1 +/- 14.8 to 49.5 +/- 13.8 cm/sec (p < 0.001) and D from 41.4 +/- 16.5 to 29.5 +/- 11.4 cm/sec (p = 0.001), with an increase in LVIRT from 65.8 +/- 8.6 to 76.0 +/- 12.6 msec (p < 0.006) and elevation of the mean pressure of the LA from 4.3 +/- 1.0 to 6.4 +/- 1.5 mmHg (p < 0.001). This findings suggest that acute myocardial ischemia alters the normal pattern of PVF, producing a significant decrease in peak velocities and time-velocity integrals of antegrade systolic and diastolic flows as well as an increase in LVIRT and MLAP, which taken together may reflect altered diastolic function of the LV.