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The coronary arteries were examined in 60 specimens from patients with mitral stenosis. In three, localized obstruction was nonatherosclerotic in nature (in one, arterial dysplasia; in two, embolic). In 18 of the remaining 57 cases (31.5%), significantly obstructive atherosclerosis in one or more segments of the coronary arterial system was found. This represented 46% of the males and 27% of the females. The incidence of involvement of three or more arteries by significantly obstructive atherosclerosis was 39%, while in a cited series of subjects with angina pectoris three or more vessels were involved in 79% of the cases. It may be concluded that, on the average, the distribution of lesions in patients with mitral stenosis and significant coronary atherosclerosis is less wide than in subjects with clinical coronary disease.

Histologic examination of coronary arteries reveals many features of pertinence. In infants, a new layer, the musculo-elastic layer, develops focally associated with thickening of the intima. Later in life, distinction of this normal process from pathologic states may be difficult. In cross sections, two types of lesions are seen: one purely fibrous and the other, a pairing of lipid pools and walling fibrous tissue (the “parite”). Lipid may be seen in phagocytes, as pools and in collagen, the latter, whether part of a fibrous lesion or part of a parite. Lipid collagen may be termed “collipid.” In established atherosclerosis, an episodic character to the development of atherosclerosis is strongly supported. Intimal hemorrhages rarely narrow the lumen but may underlie formation of thrombi. Calcification in atheromas is a sign of age of the lesion, but by itself has no direct bearing on the severity of luminal obstruction by the atheroma. The location and the shape of the arterial lumen in segments with severe sclerosis varies. The lumen may be central or eccentric. In about one-quarter of obstructed segments, the lumen is eccentric and slit-like. This is perhaps the basis for a false-negative arteriographic reading. Study of the distribution of atheromatous lesions indicates that the segment of the right coronary artery between the marginal and posterior descending arteries is the most commonly involved of all segments in the conorary tree. Second to this site is the proximal half of the anterior descending coronary artery.

The histologic changes in the coronary arteries in full-term fetuses, infants, and children of 211 consecutive necropsy specimens from Ashkenazy, Yemenite, and Bedouin groups were studied, excluding cardiac deaths. The developmental structural pattern of the coronary arteries is similar in the three ethnic groups. Differences in the intensity and quantity of the structural findings between the sexes and among various ethnic groups are found in early life. The intimal tissue in the Ashkenazy male develops in an eccentric form, has more collagen tissue components, and is more highly developed than in the Ashkenazy female. Structural findings in the internal elastic membrane and the elastic fibers of the intima are less apparent in the Bedouin group, particularly in the female, than in the Ashkenazy and Yemenite groups. Statistical analysis of the quantitative data showed the intima and musculo-elastic layers to be more developed in the Ashkenazy male than in the Yemenite and Bedouin males. However, Ashkenazy males clearly have more intima and musculo-elastic tissue than do the Ashkenazy females. This was not true for Yemenites and was found in only one of three age groups among Bedouins. The relationship between the structural findings in coronary arteries of children under 10 years and the reported prevalence of coronary heart disease in the corresponding adult population in these three different ethnic groups has been pointed out.

This 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 3½ 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 intimal fibrous proliferative lesion appears primarily to be a response to arterial pressure within the segment of vein. Obstructive atherosclerosis in the artery beyond the anastomosis with the graft may favor the development of the intimal lesion. The intimal lesion may progress rapidly according to the data in one of the cases. In this, patency of the graft demonstrated angiographically 3½ months after the operation was followed by near-complete occlusion of the lumen by the proliferative lesion 3 weeks following demonstration of patency.

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.

Three commercial vessel dilators and a dilator of an improved design were tested during percutaneous catheterization in 16 mongrel dogs to evaluate arterial damage produced with their use. The results indicate that, although all dilators often produce arterial damage, the improved design produced much less damage. In addition, lesions were less severe overall. The dilator has been safely and successfully used in patients for percutaneous vessel catheterization for the past 30 years at the authors' institution.