Retrograde continuous warm blood cardioplegia

he concept of retrograde continuous warm blood T cardioplegia is truly a different approach to myocardial preservation deserving of our consideration. In analyzing the pros and cons of this methodology, it is first appropriate to discuss the retrograde route of cardioplegic administration, which has in recent years become increasingly popular. Coronary sinus cardioplegia is an approach based largely on an understanding of coronary venous and arterial anatomy. This was reviewed in some detail by Hochberg and Austen in 1980 [l]. Their analysis explains quite simply how the coronary venous drainage patterns can be divided into two systems: the "greater system" incorporates the myocardial arterioles draining into capillaries and subsequently into the coronary venous system, emptying into the great and middle veins, the coronary sinus and right atrium. Approximately 73% of venous drainage in the heart occurs through this system. Hochberg and Austen [l] have also defined a "lesser system" that drains approximately 27% of the coronary arterial blood through a deep venous circulation that drains directly into the cardiac chambers. These have been termed the arteriosinusoidal and thebesian vessels. Thebesian channels drain into the right ventricle whereas the arteriosinusoidal vessels drain primarily into the left ventricle. Thus, in an antegrade direction, approximately 27% of coronary arterial blood bypasses the normal venous drainage system and enters the ventricular chambers directly through either thebesian or arteriosinusoidal channels. Partington and associates [2] have more recently reported on microsphere studies that clearly define how retrograde perfusion at 50 mm Hg of blood cardioplegia through the coronary sinus distributes into myocardial tissue in regions of both open and occluded coronary arteries. These authors reported that in the arrested heart, total cardiac nutritive retrograde flow averaged 70% (2 4%) of the delivered flow when the coronary arteries were patent and fell to 61% (k 6%) when the left anterior descending artery was occluded. Conversely, they found that 30% (2 4%) and 39% (k 6%) of the injected microspheres bypassed the myocardial capillary bed with all vessels open and the left anterior descending artery occluded. The only criticism that can be leveled against this very carefully performed study relates to the fact that it was done in dogs, and there are undoubtedly species Address reprint requests to Dr Engelman, Baystate Medical Center, 759 Chestnut St, Springfield, MA 01107. differences in coronary venous anatomy. One is clearly struck by the correlation between the 73% figure for the greater venous drainage system as described by Hochberg and Austen [l] and the 70% nutritive retrograde perfusion as described by Partington and co-workers in the arrested canine heart [2]. One must remember that there is a natural advantage of retrograde cardioplegia in its ability to bypass obstructed coronary arteries, providing distal myocardial preservation. A concern about retrograde preservation deals with the possibility of inadequate preservation of the right ventricle, a subject well discussed by Menasche and associates [3]. In their report, pathological studies, presumably in humans, have shown that veins draining the right ventricle and posterior part of the interventricular septum can drain into the more distal portion of the coronary sinus, as close as 0.5 cm from its termination in the right atrium, and thus be subject to occlusion by a balloon placed within the coronary sinus, preventing retrograde perfusion of these venous channels. This is consistent with the