The histological effects of cryocoagulation on the myocardium and coronary arteries.

The effects of epicardial and endocardial cryolesions were histologically studied in 29 dogs. To produce epicardial lesions, hypothermic exposure was applied at -60 degrees C for 3 minutes, over or adjacent to the left anterior descending coronary artery. To produce endocardial lesions, exposure was applied at -60 degrees C for 2 minutes, using the inflow occlusion technique over the ventricular septum. The dogs were killed 30 minutes to 6 months later. The cryolesions were sharply demarcated from the surrounding tissues and showed similar healing processes. The lesions showed no tendency to form aneurysms or rupture, although moderate intimal thickening of the coronary artery subjacent to the probe was observed. Our results indicate that cryocoagulation may greatly contribute to the surgical treatment of cardiac arrhythmias.