The pathogenesis of papillary muscle rupture complicating myocardial infarction: hemorrhage accompanying contraction band necrosis.

Although frank rupture of the papillary muscle complicating myocardial infarction is gaining widespread interest as its incidence continues to rise, the mechanism of rupture remains unclear. Of all patients who died with myocardial infarction and who came to autopsy at this institution over the past 21 years, 13 were found to have papillary muscle rupture. Twelve of these 13 had severe contraction band necrosis with interstitial hemorrhage in the areas surrounding the site of rupture. The hemorrhages infiltrated the interstitium and appeared to have dissected both longitudinally and transversely through the myocardium. In contrast, those patients with papillary muscle infarction without rupture were found to have coagulation necrosis. These findings suggest that the interstitial hemorrhages occurring with contraction band necrosis may act as dissecting masses of blood, thereby causing the rupture.