Myocardial abnormalities underlying persistent ST-segment elevation after anterior myocardial infarction

OBJECTIVES: Persistence of ST-segment elevation after myocardial infarction has been ascribed to left ventricular aneurysm development. However, its pathophysiological basis is still undefined. This study sought to evaluate myocardial structural and functional abnormalities underlying persistent ST-segment elevation, using contrast-enhanced magnetic resonance imaging. METHODS: Forty patients treated with primary angioplasty for a first anterior myocardial infarction underwent contrast-enhanced magnetic resonance imaging. Persistent ST-segment elevation was defined as ST-segment elevation of at least 2 mm in two or more leads on predischarge electrocardiogram. The presence and extent of myocardial necrosis and persistent microvascular damage, as well as wall motion abnormalities, were assessed by contrast-enhanced magnetic resonance imaging. RESULTS: At contrast-enhanced magnetic resonance imaging, patients with persistent ST-segment elevation had higher infarct size index (P=0.02) and showed transmural necrosis (P=0.03) and persistent microvascular damage (P=0.003) more often. Left ventricular aneurysm was seen more frequently in patients with ST-segment elevation (P=0.08). In a multivariate model, persistent microvascular damage was the only independent predictor of persistent ST-segment elevation (odds ratio 3.13, confidence interval 1.21-8.10, P=0.01). CONCLUSION: Persistent ST-segment elevation after anterior myocardial infarction is related to a larger extent of transmural necrosis and persistent microvascular damage as assessed by contrast-enhanced magnetic resonance imaging. However, the presence of microvascular damage seems to be the most powerful determinant of persistent ST-segment elevation.