[Right ventricular function in retrograde cardioplegia for myocardial protection--an experimental study]

Anterior cardiac veins which are the main drainage vessels of the right ventricle drain directly into the right atrium. Therefore, the right ventricular wall may not be perfused effectively during open heart surgery by the use of retrograde cardioplegic method resulting in postoperative right ventricular dysfunction. Seventeen mongrel dogs were subjected to this study and were placed on cardiopulmonary bypass using a conventional heart-lung machine. Total aortic cross-clamping time was 60 minutes in all dogs. In Group I (n = 6), 4 degrees C St. Thomas' Hospital solution (15 ml/kg body weight) was injected into the aortic root by the use of a syringe. Cardioplegic solution was replenished every 20 minutes with a half of the initial dose (7.5 ml/kg body weight). Group II (n = 6) were the dogs with the retrograde cardioplegia in which 4 degrees C St. Thomas' Hospital solution (15 ml/kg body weight) was given retrogradely from the coronary sinus by the drip method at the height of 60 cm, and the replenishing dose and interval of cardioplegia were the same as Group I. Group III (n = 5) was the dogs treated with retrograde cardioplegia identical to Group II and the combined use of topical cooling with ice-slush. The hearts were resuscitated after 60 minutes of aortic cross-clamping. Right ventricular functions such as cardiac output, right atrial pressure, right ventricular end-diastolic pressure, right ventricular max dp/dt, and shortening fraction of the right ventricle were measured 15, 30, 45, and 60 minutes after cardiac resuscitation respectively. In Group II, right atrial pressure was significantly elevated from the control value 15 and 30 minutes after cardiac resuscitation. On the other hand, all indices of right ventricular functions in Group III showed insignificant changes. The present experimental study demonstrated the retrograde cardioplegic method could produce right ventricular perfusion resulting in right ventricular dysfunction early after cardiac resuscitation. This deleterious effect however could be prevented by the combined use of topical cooling of the right ventricle with ice-slush.