MYOCARDIAL DISTRIBUTION OF RETROGRADE CARDIOPLEGIC SOLUTION ASSESSED BY MYOCARDIAL THALLIUM-201 UPTAKE

Perfusion of the right ventricular myocardium with retrograde infusion of cardioplegic solution through the coronary sinus has been reported to be less than optimal. To study left and right ventricular perfusio n during retrograde and antegrade coronary sinus cardioplegia, we adde d 0.5 mCi of thallium 201 to 500 ml of hyperkaliemic crystalloid cardi oplegic solution injected retrogradely into the coronary sinus at low perfusion pressure (20 to 40 mm Hg) in 14 dogs and antegradely in the ascending aorta in seven dogs. The cardioplegic solution was cold (4 d egrees C) in eight animals perfused retrogradely and warm (21 degrees C) in 13 animals. After aortic crossclamping, the ascending aorta and the left and right ventricles were vented and cardioplegic solution wa s injected retrogradely into the coronary sinus. Antegrade injections were performed after aortic crossclamping and venting of the left and right ventricles and of the left and right atrium. After cardioplegic arrest, the heart was harvested, fixed, and scanned with a gamma camer a. With cold retrograde cardioplegia, 82% +/- 5% of the injected thall ium 201 activity was identified in the myocardium-71% +/- 9% for warm retrograde perfusion and 80% +/- 3% for antegrade perfusion (p > 0.05) . Focal areas of hypoactivity in the septum and in the right ventricul ar free wall were present at scintigraphic imaging in all animals rece iving retrograde perfusion. In conclusion, most thallium 201 activity of cardioplegic solution injected retrogradely in the coronary sinus w as identified in the myocardium, but focal areas of hypoactivity in th e septum and in the right ventricular free wall were present, indicati ng uneven distribution. Temperature of the crystalloid solution had no effect on the myocardial distribution of the thallium 201 radiotracer in the myocardium.