Mitral insufficiency following experimental papillary muscle infarction

Nineteen dogs which survived occlusion of the left circumflex coronary artery with infarction and scarring of the posterior papillary muscle and adjacent left ventricle were studied by cineangiography 260 to 341 days after occlusion. Development of slight to moderate mitral-valve regurgitation was observed in 4 of the 19. Angiograms showed varying degrees of stiffness and rigidity of the posterior lateral wall of the left ventricle. There was no indication of heart failure. Autopsy studies revealed a dense fibrous scar involving 50 to 100 per cent of the posterior papillary muscle and varying portions of the adjacent left ventricular wall, with no involvement of the mitral-valve leaflets or chordae tendineae. The combination of a papillary muscle and left ventricular wall scar acted together to produce mitral-valve regurgitation in 4 of 19 animals.