Papillary muscle infarction was produced in 16 mongrel dogs by placing sutures around the base of one of the papillary muscles. In addition, patchy infarction of the adjacent left ventricular wall was produced by placing an Ameroid constrictor around the appropriate coronary artery. Mitral insufficiency developed in 14 of these animals; it was severe in four and mild to moderate in ten. Mitral insufficiency was not produced by isolated infarction of a papillary muscle or by isolated infarction of the left ventricular wall. It is concluded that papillary muscle infarction alone does not lead to mitral regurgitation, but that papillary; muscle dysfunction acts in concert with left ventricular wall dyskinesia or dilatation to produce mitral valve incompetency.

We compared patients with variant angina (ST-segment elevation during pain) who had normal or near normal coronary arteriograms (Group 1) with 20 in whom variant angina occurred in the presence of obstructive coronary lesions (Group 2). A long history of nonexertional angina without angina of effort or previous infarction was the rule in Group 1, whereas recent-onset unstable angina preceded by effort angina and infarction predominated in Group 2 (P less than 0.001). Normal electrocardiograms at rest, with ischemic ST-segment elevation in the inferior leads, and ischemia-induced heart block and bradycardia, characterized Group 1, whereas abnormal electrocardiograms, ischemic involvement or fibrillation were more common in Group 2 (P less than 0.001). Variant angina with normal coronary arteriogram generally has a benign course and is probably unrelated to atherosclerosis.

Emergency coronary arteriography and aortocoronary bypass were successfully performed in three patients with preinfarction angina. Four patients with impending extension of a recent infarction died during or after aortocoronary bypass surgery. Aortocoronary bypass may improve angina and prevent infarction in selected instances of preinfarction angina. In patients with recent infarction and impending extension the risk of surgery appears to be prohibitively high.