Duration of Ischemia Is a Major Determinant of Transmurality and Severe Microvascular Obstruction After Primary Angioplasty

OBJECTIVES: This study sought to assess the relationship between duration of ischemia and both myocardial transmural necrosis (TN) and severe microvascular obstruction (SMO), by contrast-enhanced magnetic resonance (CE-MR), in patients with acute myocardial infarction (AMI) treated with angioplasty (PCI), and to estimate the risk of TN and SMO with the duration of ischemia. BACKGROUND: The impact of ischemic time on myocardial and microvascular injury is not well characterized in people. METHODS: We performed CE-MR in 77 patients with first AMI, 5 +/- 3 days after successful PCI. The AMI was labeled as transmural if hyperenhancement at CE-MR was extended to > or =75% of the thickness in two or more ventricular segments. The SMO was identified as areas of late hypoenhancement surrounded by hyperenhanced tissue. The relationship between ischemic time and CE-MR evidence of SMO or TN was evaluated by logistic regression. RESULTS: Thirteen patients were excluded because of preprocedural Thrombolysis In Myocardial Infarction (TIMI) flow grade 3 of the infarct-related artery. For the remaining 64 patients, the mean time to treatment was 190 +/- 110 min, 45 (65%) patients had TN and 23 (39%) had SMO. Mean pain to balloon time was 90 +/- 40 min, 110 +/- 107 min, and 137 +/- 97 min in patients without TN and SMO, with TN but without SMO, or with both TN and SMO, respectively (p = 0.001). Multivariate analysis showed that time delay was significantly associated both with TN (odds ratio per 30 min, 1.37, p = 0.032), and SMO (odds ratio per 30 min, 1.21; p = 0.021). CONCLUSIONS: In AMI patients with impaired coronary perfusion undergoing PCI, the risk of TN and SMO increases with the duration of the ischemic time.