Impact of white blood cell count on myocardial salvage, infarct size, and clinical outcomes in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction: a magnetic resonance imaging study.

We sought to determine the relationship between white blood cell count (WBCc) and infarct size assessed by cardiovascular magnetic resonance imaging (CMR) in patients undergoing primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (STEMI). In 198 patients undergoing primary PCI for STEMI, WBCc was measured upon arrival and CMR was performed a median of 7 days after the index event. Infarct size was measured on delayed enhancement imaging and the area at risk (AAR) was quantified on T2-weighted images. Baseline characteristics were not significantly different between the high WBCc group (>11,000/mm(3), n = 91) and low WBCc group (≤11,000/mm(3), n = 107). The median infarct size was larger in the high WBCc group than in the low WBCc group [22.0% (16.7-33.9) vs. 14.7% (8.5-24.7), p < 0.01]. Compared with the low WBCc group, the high WBCc group had a greater extent of AAR and a smaller myocardial salvage index [MSI = (AAR-infarct size)/AAR × 100]. The major adverse cardiovascular events (MACE) including cardiac death, nonfatal reinfarction, and rehospitalization for congestive heart failure at 12-month occurred more frequently in the high WBCc group (12.1 vs. 0.9%, p < 0.01). In multivariate analysis, high WBCc significantly increased the risk of a large infarct (OR 3.04 95% CI 1.65-5.61, p < 0.01), a low MSI (OR 2.08, 95% CI 1.13-3.86, p = 0.02), and 1-year MACE (OR 16.0, 95% CI 1.89-134.5, p = 0.01). In patients undergoing primary PCI for STEMI, an elevated baseline WBCc is associated with less salvaged myocardium, larger infarct size and poorer clinical outcomes.