Very Early Left Ventricular Remodeling After Experimental Induced Myocardial Infarction

PurposeThe classical definition of left ventricular remodeling(LVRM) is the changes in shape and size of the entire left ventricle after acute myocardial infarction(AMI). Many investigators have shown that left ventricular remodeling is related to clinical outcomes, including mortality, that represent the natural history of the heart failure symdrome in the post myocardial infarction process. The aim of this study was to observe the very early left ventricular (LV) remodeling in a dog model after myocardial infarction and the protective role of Captopril and Metoprolol. MethodsLeft ventricular remodeling investigation was performed with ^99mTc-sestamibi myocardial SPECT imaging.Experimental subjects: 37 healthy mongrel dogs (12-25kg, l-3y.o) of either sex were divided into four groups randomizedly. They were studied under general anesthesia(sodium pentobarbital, 30mg/kg). In group 1 (G1 n=5) the heart was exposed and closed with nothing done to the coronary arteries. The left anterior descending (LAD) coronary artery was exposed and ligated between the first and second diagonal branches in group 2 (G2 n=16). Group 3 (G3 n=8) was given Captopril and group 4 (G4 n=8) was given Metoprolol (G4) 3 days before the LAD were ligated. ^99mTc-sestamibi myocardial perfusion imaging was performed before and after surgery in all dogs. Each dog served as its own control, and was scanned with SPECT at 48-72 hours before surgery and (14-48) minutes post-operatively. Quantitative Gated SPECT software was used for calculating EDV, ESV and EF. Qualitative analysis was used to assess shape, size and wall motion of the left ventricle. ^99mTc-MIBI myocardial perfusion imagingStatic ^99mTc-MIBI myocardial imaging was taken with ADAC Vertex Dual-head SPECT. ^99mTc-MIBI kit was manufactured in Syncor,China. The auto-control of each dog was performed by ^99mTc-MIBI myocardial imaging at 48-72 hours before ligated. Acquisition techniques for Gated SPECT:ECG synchronized data collection R wave trigger, 8 Frames/Cardiac cycle. Images were gathered by rotating the detectors for 180 degrees at 6 degrees per frame. Each frame took 35-40 seconds. The dog position: supine. The images of each acquisition were recorded until 3 hours after LAD coronary artery was ligated.SPECT reconstruction parameters:Filter:Butterworth:cutoff 0.5 and order 6: filtered back projection.Images:short axis,horizontal and vertical long axis.