[Mitral insufficiency, excluding ruptured papillary muscles, in the acute phase of posterior primary infarction. Anatomical study].
Mitral regurgitation (MR) was demonstrated by water testing valve closure in 23 out 46 cases of patients dying in the 8 days following primary posterior wall infarction due to occlusion of the right coronary or left circumflex arteries (normal valves and chordae; no chronic fibrosis of the papillary muscle). MR was less common with right coronary artery occlusion (14 out of 32; 44%) than with left circumflex occlusion (9 out of 14; 64%). Two anatomical conditions seem to be necessary (all cases but one) for MR to occur: ischaemic necrosis of all or nearly all of the posterior papillary muscle and its base of implantation on the posterior wall. These valvular leaks are usually mild (papillary muscle rupture was excluded) and do not seem to play a major role in the haemodynamic deterioration of these patients, the majority of whom die of irreducible cardiac failure caused by extensive myocardial destruction. The mechanism of the majority of these MR was systolic eversion of the posterior part of the posterior leaflet in the left atrium (6 cases) of the posterior juxtacommissural part of both leaflets (13 cases), of the posterior part of the anterior leaflet (3 cases). Ischaemic destruction of the posterior papillary muscular system and its base of mural implantation (anatomical criteria that we retained) correlated with the occluded artery.