Electrocardiographic evaluation of microvascular dysfunction in acute myocardial infarction and its prognosis

Abstract

Introduction: Percutaneous coronary intervention (PCI) is the main treatment in patients with acute myocardial infarction with persistent ST elevation (STEMI). However, despite the successful permeability of the epicardial vessel, perfusion of the distal coronary microvasculature is not always restored. The diagnosis of coronary microvascular dysfunction (CMD) by electrocardiogram (ECG) can contribute in a non-invasive quick way to the identification of a population at higher risk, with a larger infarct size (IS) and a worse prognosis. Objectives: To relate CMD identified as the lack of downsloping ST segment in patients with STEMI, with an IS measured by Gated-SPECT and in-hospital prognosis. Material and Methods: Patients with STEMI and successful PCI were analyzed. The percentage of downsloping ST segment (in millimeters) between the ECGs before and after reperfusion was calculated, dividing them into two groups: greater than 50% and less than 50%. Baseline characteristics, IS measured by GatedSPECT were compared, and in-hospital events, death, heart failure, and combined events were evaluated. Results: There were 481 patients included: 62% (n = 298) with a downsloping ST segment greater than 50% (G >50%), and 38% (n = 183) less than 50% (G <50%). No differences in age (60 ± 11 years) or percentage of diabetics (18%) were found. Those with G >50% had better time to reperfusion (180 min [120-260] vs 198 min [29-360]; p: 0.03), higher ejection fraction (50% [45-60] vs 46% [40-55]; p: 0.0001) and lower IS measured by Gated-SPECT (10% [2-20] vs 22% [12-32]; p: 0.0001). In G <50%, higher mortality was observed (9% vs. 1% vs.; p: 0.0001), heart failure (34% vs. 15% vs.; p: 0.0001), and combined event rate (36% vs. 15% vs; p: 0.0001). Multivariate logistic regression analysis identified as independent predictors of death and heart failure the following: anterior STEMI (OR: 2.6; 95% CI: 1.3-5.2; P: 0.009) and IS by Gated-SPECT (OR: 1.05; 95% CI: 1.02-1.08; p: 0.0001). Conclusion: ECG proved to be a quick and effective tool to assess CMD after PCI, being able to differentiate two subgroups with different IS and in-hospital evolution.