Mitral incompetence complicating acute myocardial infarction.

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Abstract
The occurrence and clinical characteristics of mitral incompetence developing in connection with acute myocardial infarction were studied in 195 patients consecutively admitted to hospital. Apical systolic murmurs consistent with mitral incompetence developed during the hospital stay of 107 patients. The murmur usually appeared within 5 days of the estimated onset of the infarction. in 2/3 of the patients the murmur was faint (grade 1-2), easily escaping detection if not particularly searched for. The character of the murmur was most often high frequency and pansystolic, but many times it changed later to a harsher ejection type of murmur. in this study in patients developing the acute mitral systolic murmur, no difference was found between the incidence of anterior and inferoposterior infarction as judged by ecg. Necropsy revealed a large macroscopical necrosis in one or both papillary muscles in 15 of the 18 patients with clinically observed mitral incompetence. in the hearts of 10 patients without a murmur there was no significant macroscopical necrosis in the papillary muscles; all hearts were involved by an anterior infarction in this group. The common occurrence and characteristics of the systolic murmur of mitral incompetence in acute myocardial infarction are discussed with reference to the pathophysiology of acute ischemic heart disease.