THE EFFECTS OF DISTAL CORONARY EMBOLIZATION ON INFARCT SIZE AND CARDIAC REMODELING IN A PORCINE ACUTE MYOCARDIAL INFARCTION MODEL

Distal coronary embolization (DCE) occurs frequently during percutaneous interventions for acute myocardial infarction (AMI) and can alter coronary flow. The significance of DCE on infarct size and myocardial function remains unsettled. The objective of this study was to evaluate the effects of DCE sufficient to cause no reflow (NR) on infarct size, cardiac function and ventricular remodeling in a porcine AMI model. Female Yorkshire pigs underwent 60 min balloon occlusion of the left anterior descending coronary artery followed by reperfusion and injection of either microthrombi sufficient to cause NR (DCE), or saline (control). Animals were sacrificed at 3 d (n=20) or 6 wk (n=20) post AMI. Cardiac magnetic resonance (CMR) imaging, serum troponin I, and cardiac gelatinase (MMP) and survival kinase (Akt) activities were assessed. At 3 d, DCE resulted in increased infarct size (CMR: 18.8 ± 5.8% vs. 14.5 ± 4.4%vs, p=0.04; serum troponin-I: 13.3 ± 9.4 vs. 6.9 ± 2.7 ng/uL, p<0.05). MMP-2 activity levels of infarcted myocardial tissue were higher in DCE animals compared to controls (active-MMP2: 0.81 ± 0.08 vs. 0.49 ± 0.12, p=0.002). DCE infarct samples also had reduced activation of Akt compared to controls (0.06 ± 0.07 versus 0.26 ± 0.12, p=0.02). At 6 wk, there were no differences in infarct size, ventricular volume or cardiac function between the two groups, although infarct transmurality (70 ± 10% vs. 57 ± 15%, p<0.04) and ventricular thinning (% change in thickness: -25.6% ± 21.1% vs. 0.7% ± 26.8%, p=0.03) were significantly increased in the DCE group. DCE increased early infarct size and MMP-2 activity with reduced Akt activation, without affecting late infarct size, ejection fraction or ventricular volumes. The significance of late remodelling changes (ventricular thinning and transmurality) following DCE merits further study.