Post-Reperfusion Lymphopenia and Microvascular Obstruction in ST-Segment Elevation Acute Myocardial Infarction

Introduction and objectives. The presence of microvascular obstruction after ST-segment elevation acute myocardial infarction is associated with a poor outcome. The pathophysiology of this process has not been fully defined. The aim of this study was to investigate the relationship between post-reperfusion lymphopenia and microvascular obstruction. Methods. This prospective study involved 212 patients with a first ST-segment elevation acute myocardial infarction who underwent reperfusion with thrombolytic agents or primary angioplasty and who had an open infarct-related artery. Serial measurements of lymphocyte, neutrophil and monocyte counts were taken. Cardiac magnetic resonance was used to detect microvascular obstruction during the first week after the infarction. Imaging was repeated 6 months after infarction. Results. Microvascular obstruction was observed in 67 patients (32%). A post-reperfusion lymphocyte count <1800 cells/ml was associated with a higher risk of microvascular obstruction (44% versus 20%; P<.001) as well as with a low left ventricular ejection fraction and large left ventricular volumes (P<.05). After adjustment for baseline characteristics, ECG findings, necrosis marker levels and angiographic variables, multivariate analysis showed that a post-reperfusion lymphocyte count <1800 cells/ml was independently associated with an increased risk of microvascular obstruction (odds ratio=3.2; 95% confidence interval 1.6-6.3; P<.001). Conclusions. In ST-segment elevation myocardial infarction, post-reperfusion lymphopenia is an early and powerful predictor of the presence of microvascular obstruction. The pathophysiological and therapeutic implications of this association require further study.