Pulmonary Embolism: A Precipitating Factor of Acute Coronary Insufficiency

A clinical and pathological study of 40 necropsied cases of massive pulmonary embolism indicates that acute coronary insufficiency plays as large a part as does cor pulmonale in the cardiac sequellae of embolism. Electrocardiographic changes attributable to coronary insufficiency occurred more often than the classical cor pulmonale pattern. They were more common in older patients with antecedent coronary sclerosis and cardiac enlargement whereas the classical cor pulmonale pattern occurred most often in patients with normal coronary arteries and heart size. Focal subendocardial infarction of the left ventricle, in the absence of acute coronary occlusion, was found postmortem in nine cases. This resulted from coronary insufficiency precipitated by the pulmonary embolism, in patients with antecedent coronary disease and cardiac hypertrophy who had sustained recurrent emboli. The various precipitating factors of coronary insufficiency following pulmonary embolism were evaluated. These were anoxemia, shock, right ventricular strain, and reflex coronary vasoconstriction. Of these, shock associated with diminished cardiac output and coronary blood flow was considered the most important. It can be concluded that acute coronary insufficiency may be the predominant factor underlying the electrocardiographic changes and myocardial involvement in pulmonary embolism, even when right ventricular strain exists.