A new theory of the mechanism of percutaneous arterial angioplasty is advanced. For this study, abdominal aortas and coronary, renal, superior mesenteric, and iliac arteries were obtained from cadavers. In addition, the iliac arteries of dogs were dilated and studied. No evidence of significant compression or redistribution of plaques could be found, supporting the theory that atheromatous material is incompressible. Cracking of the intima and separation of it from the media were histologically demonstrated following angioplasty. It is proposed that the stretched media distends following dilatation, carrying with the intima and atheromatous material. Once the media is freed from the encasing effect of the intima, it adapts to the circulatory needs of the body. Beyond a certain point, the arterial widening becomes permanent, due to an overstretching of the muscle fibers, which is demonstrated by a corkscrew deformity of the muscle cell nuclei.

Two cases are described of sudden death resulting from rupture of small chronic false aneurysm of the left ventricle with secondary hemopericardium. The cases support the point that rupture of chronic false left ventricular aneurysm tends to occur. This appears to be contrary to the potential for chronic true aneurysms of the left ventricle which tend not to rupture. Rupture of true left ventriuclar aneurysm in its deveoping stahe may, however, occur.

Correlative studies were carried out on the coronary arteriograms made during diagnostic procedures and on the specimens obtained at necropsy in 10 cases of coronary heart disease. Of the 134 segments of coronary arteries available for both studies, 44 (33%) were given false-negative arteriographic diagnosis of obstructive atherosclerosis.Factors which may underlie this discrepancy include (1) radiographic technic, (2) projection used, (3) a slitlike lumen adjacent to the atheroma, (4) comparison of severely obstructed segments involved but less severely obstructed, and (5) misinterpretation from the specimen of obstruction present in life.

SUMMARYThis is a pathologic study of segments of saphenous vein used as a graft between the aorta and a coronary artery in the surgical treatment of coronary atherosclerosis. Except for an occasional case with thrombotic occlusion of the graft, no lesions were observed in grafts which had been in place for less than 1 month. In each of two grafts in place for 1 month, mild fibrous thickening of the intima was present. Eight grafts which had been in place for 32 months or longer consistently showed lesions, either organized thrombi (two grafts) or intimal fibrotic proliferative lesion (six grafts). In this group, five of the six grafts with intimal fibrous proliferation showed near or complete occlusion of the lumen.The