Experimental Right Atrial Ischemia and Its Response to Stimulation with Dobutamine.

In order to analyze the repercussion of experimental isolated selected right atrial ischemia on the hemodynamics of both ventricles, we investigated the response of atrial myocardium with administration of dobutamine and evaluated the utility of transesophageal echocardiography (TEE) with Doppler in the examination of alterations produced by atrial ischemia. Ten dogs were studied with normal, diminished, and increased cardiac output with ligation of the visible atrial branches of the right coronary artery. Right atrial wall movement and peak A wave velocity of tricuspid flow registered by TEE decreased (P < 0.05). The amplitude of the right atrial A wave decreased in hemodynamic recordings (P < 0.05). No significant modifications occurred in right ventricular wall movement nor in pressures registered in right or left ventricles or cardiac output. Seventy-five minutes after atrial ischemia was induced dobutamine was administered. In dogs with incomplete ligations of atrial circulation, right atrial wall movement improved (P < 0.001), and the amplitude of the peak A wave velocity of tricuspid flow increased. In dogs with complete coronary ligation, administration of the medication produced no improvement of these variables. The findings indicate that it is possible to produce selective right atrial ischemia manifested by diminished wall movement, a diminished atrial component of tricuspid flow in TEE, and decreased amplitude of the A wave in atrial pressure recordings. The localized hemodynamic changes produced by right atrial ischemia are not related to variations in venous return when right ventricular function is normal. Apparently isolated right atrial damage from ischemia does not affect ventricular function if these remain healthy. The recuperation of atrial contractility can be demonstrated with dobutamine. Transesophageal echocardiography is a very useful technique for studying right atrial ischemia and infarction.