[Effects of cardioplegic solutions on coronary and myocardial ultrastructure. Preliminary note].

Ultrastructural changes of the myocardium and the coronary arterial endothelium were studied following cold perfusion with two different cardioplegic solutions (CPS) (the University of Alabama and the St. Thomas Hospital solutions), and with Krebs' solution as a control (CS). Guinea pig heart-lung preparations (HLP) were subjected to cardiac arrest by perfusion under CPS or CS (4 ml/Kg/min. X 4 min.). The duration of the cardiac arrest was 60 minutes, and additional amounts of cold solution were perfused after the first 30 minutes. In a second experimental group, HLP were reperfused with blood following 60 minutes of cardioplegic arrest, and maintained under full activity for the next 30 minutes. At the end of the study, specimens of coronary artery and myocardium were obtained and observed by Scanning (SEM) and Trasmission (TEM) electron microscopy. All the specimens were compared with additional specimens obtained from control hearts not subjected to cardiac arrest. The myocardial ultrastructure of hearts arrested with CPS was well preserved, whereas severe myocardial damage, consisting in the absence of glycogen granules, intracellular edema and myofibrillar contraction, was following CS-induced cardiac arrest. In contrast, perfusion with the St. Thomas CPS produced severe vascular damage, characterized by interruption of the endothelial layer, and bulging of endothelial cells into the lumen; no vascular changes were observed following cardiac arrest with CS or Alabama CPS. We conclude that the damage to the coronary arterial endothelium is not related to cardiac arrest, or to perfusion with cristalloid solution, or to myocardial damage, but appears to depend on the composition of the CPS.