Prevention of ischemic mitral regurgitation does not influence the outcome of remodeling after posterolateral myocardial infarction.
OBJECTIVE
This study was designed to test the hypothesis that ischemic mitral regurgitation (IMR) results from, but does not influence, the progression of left ventricular (LV) remodeling after posterolateral infarction.


BACKGROUND
Surgical correction of chronic IMR is being increasingly recommended.


METHODS
Three groups of sheep had coronary snares placed around the second and third obtuse marginal coronary arteries. Occlusion of these vessels in the control group resulted in progressive IMR over eight weeks. In a second group, Merseline mesh was fitted to cover the exposed LV before infarction. In a third group, a ring annuloplasty was placed before infarction to prevent IMR. Remodeling and degree of IMR were assessed with echocardiography at baseline and at 30 min and two, five, and eight weeks after infarction.


RESULTS
Eight weeks after infarction, mean IMR grade was significantly higher in control animals than mesh and annuloplasty animals. At eight weeks, LV end-systolic volume and end-systolic muscle-to-cavity-area ratio (ESMCAR) were significantly better in mesh-treated sheep than in control sheep; also, at eight weeks, ESMCAR and akinetic segment length were significantly better in mesh-treated sheep than in annuloplasty sheep. Ejection fraction was significantly higher in the mesh than the annuloplasty group. There was no significant difference in any measure of remodeling between the annuloplasty and control groups.


CONCLUSIONS
Prophylactic ventricular restraint reduces infarct expansion, attenuates adverse remodeling, and reduces IMR severity. Prevention of IMR by prophylactic ring annuloplasty does not influence remodeling. Ischemic mitral regurgitation is a consequence, not a cause, of postinfarction remodeling; infarct expansion is the more important therapeutic target.
Guy
T Sloane
TS
Harrison Department of Surgical Research, University of Pennsylvania School of Medicine, 3400 Spruce Street, Philadelphia, PA 19104, USA.
Moainie
Sina L
SL
Gorman
Joseph H
JH
Jackson
Benjamin M
BM
Plappert
Theodore
T
Enomoto
Yoshiharu
Y
St  John-Sutton
Martin G
MG
Edmunds
L Henry
LH
Gorman
Robert C
RC
D000818:Animals; D006348:Cardiac Surgical Procedures / Q000379:methods; D006439:Hemodynamics; D008297:Male; D008944:Mitral Valve Insufficiency / Q000209:etiology* / Q000517:prevention & control; D023421:Models, Animal; D009203:Myocardial Infarction / Q000150:complications / Q000503:physiopathology* / Q000601:surgery; D017202:Myocardial Ischemia / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D012756:Sheep; D020257:Ventricular Remodeling / Q000502:physiology*