Abstract 399: Infarct Healing is a Dynamic Process Following Acute Myocardial Infarction
Introduction: The role of infarct size on ventricular remodeling in heart failure after an acute ST-segment elevation myocardial infarction (STEMI) is well recognized. It has been shown that infarct size, as determined by cardiac magnetic resonance imaging (CMR), decreases over time. It is unknown how quickly infarct healing occurs, how long the process continues, and what effect initial infarct size has on healing potential.
Hypothesis: We hypothesize that the majority of infarct healing occurs within 3 months of the initial event but continues at a slower rate up to a year.
Methods: A total of 52 patients were prospectively enrolled after reperfusion for an acute STEMI. Patients were included if they fulfilled the criteria of documented STEMI with chest pain >30 minutes, >1.0 mm ST elevation in two contiguous leads, and elevated CK-MB. Patients underwent a CMR evaluation within 1 week, 3 months, and 12 months of the STEMI.
Results: Average infarct sizes for the 52 patients in the acute setting, at 3 months, and at 12 months were 25±18 g, 17±13 g, and 15±12 g, respectively. Patients were stratified based on infarct size (small, medium, and large) with larger infarcts having the greatest absolute decrease in mass at 3 and 12 months, as seen in table 1⇓. The percent reduction of infarct mass was independent of infarct size and almost identical at 12 months across categories. An ANOVA analysis found a statistically significant difference (p = 0.02) in the healing over the first 3 months after the initial insult. There was a trend towards ongoing healing between 3 and 12 months that was not statistically significant (p = 0.38).
Conclusions: In conclusion, infarct healing continues after 3 months, demonstrating that there are other factors than just acute changes such as edema and partial volume effects. Given the dynamic process of infarct healing through the first year after STEMI, infarct sizes must be uniformly measured within the same time frame for decisions based on infarct sizes to be made.