IDENTIFYING FALSE-POSITIVE ST-ELEVATION MYOCARDIAL INFARCTION IN EMERGENCY DEPARTMENT PATIENTS

Background: In a push to treat ST-elevation myocardial infarction (STEMI) patients with primary percutaneous coronary intervention (PCI) within 90 min of door-to-balloon time, emergency cardiac catheterization laboratory activation protocols bypass routine clinical assessments, raising the possibility of more frequent catheterizations in patients with no culprit coronary lesion. Objective: To determine the incidence, predictors, and prognosis of false-positive STEMI. Methods: We followed a prospective cohort of patients diagnosed with STEMI by usual criteria receiving emergency cardiac catheterization with intention of primary PCI between January 2005 and December 2007 at a tertiary care center. False-positive STEMI was defined as absence of a clear culprit lesion on coronary angiography. Results: Of 489 patients who received emergency cardiac catheterization indicated for STEMI, 54 (11.0%, 95% confidence interval [CI] 8.3-13.8) had no culprit lesion on coronary angiography. Independent predictors of false-positive STEMI were absence of chest pain (odds ratio [OR] 18.2, 95% CI 3.7-90.1), no reciprocal ST-segment changes (OR 11.8, 95% CI 5.14-27.3), fewer than three cardiovascular risk factors (OR 9.79, 95% CI 4.0-23.8), and symptom duration longer than 6 h (OR 9.2, 95% CI 3.6-23.7); all p < 0.001. Using predictors, we modeled a risk score that achieved 88% (95% CI 81-94%) accuracy in identifying patients with negative coronary angiography. Among the false-positive STEMI patients, 48.1% had other serious diagnoses related to their electrocardiographic findings. Conclusion: When the diagnosis of STEMI is in doubt, clinicians may use predictors to quickly reassess the likelihood of an alternative diagnosis. (C) 2012 Elsevier Inc.