THE PATHOGENESIS OF INFARCTION OF THE RIGHT VENTRICLE

Abstract

In myocardial infarction it is rare for the right ventricle to be predominantly affected. The relative incidence of infarction of this ventricle in two large series has been shown to be 1-7 per cent (Bean, 1938) and 3 per cent (Wartman, 1948) respectively. In the average human heart the entire right ventricle with the exception of the left third of the anterior wall is supplied by the right coronary artery (Gross, 1921). However, the uncommon occurrence of right ventricular infarction bears no relationship to the frequency with which this artery is occluded. Schlesinger and Zohl (1941) showed from their perfusion studies of human hearts at necropsy that the right coronary artery was occluded in 34 per cent of all main stem occlusions. In comparison, the corresponding figures for the anterior descending and circumflex branches of the left coronary artery were 39 per cent and 27 per cent respectively. Blumgart et al. (1940) have suggested that the right ventricular Thebesian system accounts for the immunity of this ventricle to infarction. Wood (1956) on the other hand, has asserted that it is protected through being supplied by the two biggest coronary arteries and because it offers less resistance to systolic coronary flow than the left ventricle. In this communication, the pathological and clinical features of eleven new cases of right ventri-cular infarction are presented; this constitutes the largest series of cases of this kind that has so far been published. In addition, nine examples previously reported are reviewed and the main aetiological factors that emerge are discussed in relation to the results of recently reported physiological experiments. The clinical data and the gross pathological findings in the eleven new cases were obtained from the records in this Institute. The histological material was available from each case and was personally reviewed using the criteria laid down by Mallory (1939) for estimating the age of an infarct. For comparison, the corresponding gross pathological features in a consecutive series of 100 cases of left ventricular infarction investigated in this Institute were also assembled. GROSS PATHOLOGICAL FEATURES OF RIGHT VENTRICULAR INFARCTION Of the eleven cases here described only one was a woman. A similar sex distribution is found in those cases previously described in which two out of the eight cases where the sex was given were woman [Sanders, 1930; Sprague and Orgain, 1935, two cases; Feil et al., 1938; Weinberg and Katz, 1941; Roberts and Loube, 1947; Case 34442 (M.G.H.) 1948, and Zaus and Kearns, 1952]. In this series (Table I) the mean age for the eleven cases was 65 5 years, but the range was wide, being 40-84 years. In ten hearts in which the relative thickness of the ventricular wall was described, left ventricular hypertrophy was present in six and in four of these there was also right ventricular hypertrophy. The right coronary artery was occluded by a. recent thrombus in nine hearts and by an old organized lesion in one other. In those hearts with recent occlusions of the right coronary artery there were five in which additional old occlusions were found; of the left anterior descending coronary artery in four and of the left circumflex artery in the fifth. One heart in this series 545