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 inve stigated the response of atrial myocardium with administration. of dob utamine and evaluated the utility of transesophageal echocardiography (TEE) with Doppler in the examination of alterations produced by atria l ischemia. Ten dogs were studied with normal, diminished, and increas ed cardiac output with Ligation of the visible atrial branches of the right coronary artery. Right atrial wall movement and peak A wave velo city of tricuspid flow registered by TEE decreased (P < 0.05). The amp litude 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 ventricle s or cardiac output. Seventy-five minutes after atrial ischemia was in duced 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 increa sed. In dogs with complete coronary ligation, administration of the me dication produced no improvement of these variables. The findings indi cate that it is possible to produce selective right atrial ischemia ma nifested by diminished wall movement, a diminished atrial component of tricuspid flow in TEE, and decreased amplitude of the A wave in, atri al pressure recordings. The localized hemodynamic changes produced by right atrial ischemia are not related to variations in venous return w hen right ventricular function is normal. Apparently isolated right at rial damage from ischemia does not affect ventricular function if thes e remain healthy. The recuperation of atrial contractility can be demo nstrated with dobutamine. Transesophageal echocardiography is a very u seful technique for studying right atrial ischemia and infarction.