Magnetic resonance imaging assessment of ventricular remodeling after myocardial infarction in the rabbit

We studied 3‐D depictions of myocardial microstructure to determine the structure‐function relationship in the post‐infarcted myocardium. Heart ischemia was induced by ligating the left circumflex coronary artery using 6‐0 prolene suture. Sham controls had only thoracotomy performed. Cardiac MR imaging was conducted on a Siemens 3T scanner with pulse oximetry‐gated cine acquisition to provide a complete display of the heart cycle. The rabbit was anesthetized under 1.5% isoflurane ventilation, and ultrafast techniques made breath hold 3‐D coverage in different cardiac axes feasible. MR viability imaging was approached after IV injection of 0.6 ml gadolinium (0.32 mmol/Kg) to assess the damage of myocardial infarction. Data (n≥6) are presented as mean±SEM and analyzed by ANOVA. Myocardial late enhancement delineated 25±3% myocardial scar tissue with wall thinness and limited wall motion. End‐systolic (2.3±0.3) and end‐diastolic (4.2±0.4) volumes (ml) in ligated rabbits were increased (p<0.05) when compared to normal (1.1±0.1, 2.98±0.2, respectively) and sham (1.1±0.1, 2.8±0.2, respectively). Ejection fraction (%) in ligated rabbits (45.9±1.3) was decreased (p<0.05) when compared to normal (62.4±1.2) and sham control (59.8±1.8). These MR imaging techniques, including characterization of myocardial scar tissue, offer a valuable method for assessing treatments that is underway.