[Experimental study on myocardial protection by means of retrograde coronary sinus cooling perfusion (RCSP) during aorto-coronary bypass surgery].

Cold chemical cardioplegia by the antegrade method is a useful, widely employed procedure for protecting the myocardium in aorto-coronary by pass surgery. Perfusion of a cardioplegic solution into the ischemic area is, however, insufficient in the presence of a severe lesion in the coronary artery, leading to postoperative cardiac hypofunction. We performed an experimental study using RCSP, which lessens this problem, in the excised dog heart. Hearts excised from 20 dogs were assigned to normal coronary artery groups (group I consisting of the hearts from 5 dogs and a perfusion solution temperature of 20 degrees C, group II consisting of the hearts from 5 dogs and a temperature of 30 degrees C) and blocked coronary artery groups (group III consisting of the hearts from 5 dogs and a temperature of 20 degrees C, group IV consisting of the hearts from 5 dogs and a temperature of 30 degrees C). RCSP was undertaken for two hours with a new modified Krebs solution. Hemodynamic and myocardial metabolic parameters during a given work load under fixed conditions and heart beat after reopening of the blood flow using our original function circuit were compared between the experimental groups and a control group (consisting of normal hearts studied immediately after excision from 5 dogs not given myocardial protection). In the group with normal coronary arteries, LVW and LV dp/dt were better in group I than in group II throughout the course; these values were significantly lower in group II than in the control group, but there was no significant difference between group I and the control group. These parameters were also improved in group III (with blocked coronary arteries), but there was no significant difference in improvement between group III and the control group 60 minutes after reperfusion. In group IV, on the other hand, improvement was poor. The myocardial metabolic parameters also showed approximately the same results. These results suggested that RCSP with the new modified Krebs' solution at perfusion temperature of 20 degrees C afforded effective protection of the myocardium for two hours. From the fact that a favorable protective effect of the myocardium was obtained in group III, as in group I, RCSP was considered to provide a useful procedure for protection of the myocardium in aorto-coronary bypass for severe or wide-ranging coronary artery diseases.