012 ST-segment resolution following primary percutaneous coronary intervention for STEMI: relationship with infarct size and microvascular obstruction assessed by MRI

Abstract

Cardiac magnetic resonance imaging (MRI) is the gold standard to quantify the infarct size and the extend of microvascular obstruction in ST-elevation myocardial infarction (STEMI). ST-segment resolution (STR) after primary percutaneous intervention (PCI) is currently used to assess the reperfusion quality in the acute phase myocardial infarction. The relation between STR and microvascular obstruction evaluated by MRI is unknown. The aim of this study was to determine the relationship between the ST-segment resolution, the infarct size and the extend of microvascular obstruction. 41 patients undergoing primary PCI for STEMI within 6 hours of symptom onset were prospectively included. ST-segment resolution was evaluated one hour after reperfusion. MRI was performed in all patients. Complete STR was defined as a STR>70%. Mean age of the patients was 54 ± 12 yo, 85 waer males. The percent of infarct size was 18,6 ±16% of the left ventricular volume. Microvascular obstruction was present in 68% of patients. Mean STR was 59 ± 39% and 14 patients (34%) presented complete STR. A large infarct size (> 75 th percentile) was associated with anterior localisation and left descending artery obstruction. STR significantly correlated with infarct size measured by MRI (r=-0,38 p=0,026). Incomplete STR (<70%) predicted large infarct size with a sensitivity of 78%, a specificity of 42% and high degree of microvascular obstruction with sensitivity of 80% and specificity of 45%. STR one hour after primary PCI is associated with the level of infarct size and microvascular obstruction in STEMI patients. Incomplete STR after PCI is a strong prognostic marker of large infarct size and high degree of micro vascular obstruction.