Mitral regurgitation augments post-myocardial infarction remodeling failure of hypertrophic compensation

• Published in: Journal of the American College of Cardiology Vol. 51; no. 4; pp. 476 - 486
• Main Authors: Beeri, Ronen, Yosefy, Chaim, Guerrero, J Luis, Nesta, Francesca, Abedat, Suzan, Chaput, Miguel, del Monte, Federica, Handschumacher, Mark D, Stroud, Robert, Sullivan, Suzanne, Pugatsch, Thea, Gilon, Dan, Vlahakes, Gus J, Spinale, Francis G, Hajjar, Roger J, Levine, Robert A
• Format: Journal Article
• Language: English
• Published: United States Elsevier Limited 29.01.2008
• Subjects: Animals; Calcium - metabolism; Cardiology; Coronary vessels; Disease Models, Animal; Echocardiography, Three-Dimensional; Heart attacks; Hypertrophy - etiology; Hypertrophy - metabolism; Hypertrophy - pathology; Intracellular Signaling Peptides and Proteins - metabolism; Matrix Metalloproteinases - metabolism; Mitral Valve Insufficiency - etiology; Mitral Valve Insufficiency - metabolism; Mitral Valve Insufficiency - pathology; Muscle Cells - pathology; Myocardial Infarction - complications; Myocardial Infarction - metabolism; Myocardial Infarction - pathology; Sheep; Stroke Volume; Studies; Ventricular Function, Left; Ventricular Remodeling
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/j.jacc.2007.07.093

We examined whether mitral regurgitation (MR) augments post-myocardial infarction (MI) remodeling. MR doubles mortality after MI, but its additive contribution to left ventricular (LV) remodeling is debated and has not been addressed in a controlled fashion. Apical MIs were created in 12 sheep, and 6 had an LV-to-left atrial shunt implanted, consistently producing regurgitant fractions of approximately 30%. The groups were compared at baseline, 1, and 3 months. Left ventricular end-systolic volume progressively increased by 190% with MR versus 90% without MR (p < 0.02). Pre-load-recruitable stroke work declined by 82 +/- 13% versus 25 +/- 16% (p < 0.01) with MR, with decreased remote-zone sarcoplasmic reticulum Ca(2+)-ATPase levels (0.56 +/- 0.03 vs. 0.76 +/- 0.02, p < 0.001), and decreased isolated myocyte contractility. In remote zones, pro-hypertrophic Akt and gp130 were upregulated in both groups at 1 month, but significantly lower and below baseline in the MR group at 3 months. Pro-apoptotic caspase 3 remained high in both groups. Matrix metalloproteinase (MMP)-13 and membrane-type MMP-1 were increased in remote zones of MR versus infarct-only animals at 1 month, then fell below baseline. The MMP tissue inhibitors rose from baseline to 3 months in all animals, rising higher in the MI + MR-group border zone. In this controlled model, moderate MR worsens post-MI remodeling, with reduced contractility. Pro-hypertrophic pathways are initially upregulated but subsequently fall below infarct-only levels and baseline; with sustained caspase 3 elevation, transformation to a failure phenotype occurs. Extracellular matrix turnover increases in MR animals. Therefore, MR can precipitate an earlier onset of dilated heart failure.