Mitral regurgitation augments post-myocardial infarction remodeling failure of hypertrophic compensation.
OBJECTIVE
We examined whether mitral regurgitation (MR) augments post-myocardial infarction (MI) remodeling.


BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Beeri
Ronen
R
Cardiac Ultrasound Laboratory, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA.
Yosefy
Chaim
C
Guerrero
J Luis
JL
Nesta
Francesca
F
Abedat
Suzan
S
Chaput
Miguel
M
del Monte
Federica
F
Handschumacher
Mark D
MD
Stroud
Robert
R
Sullivan
Suzanne
S
Pugatsch
Thea
T
Gilon
Dan
D
Vlahakes
Gus J
GJ
Spinale
Francis G
FG
Hajjar
Roger J
RJ
Levine
Robert A
RA
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004195:Disease Models, Animal; D019560:Echocardiography, Three-Dimensional; D006984:Hypertrophy / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D020782:Matrix Metalloproteinases / Q000378:metabolism; D008944:Mitral Valve Insufficiency / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D032342:Muscle Cells / Q000473:pathology; D009203:Myocardial Infarction / Q000150:complications* / Q000378:metabolism / Q000473:pathology; D012756:Sheep; D013318:Stroke Volume; D016277:Ventricular Function, Left; D020257:Ventricular Remodeling
D047908:Intracellular Signaling Peptides and Proteins; D020782:Matrix Metalloproteinases; D002118:Calcium