Identifying false-positive ST-elevation myocardial infarction in emergency department patients

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.

To determine the incidence, predictors, and prognosis of false-positive STEMI.

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.

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 6h (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.

When the diagnosis of STEMI is in doubt, clinicians may use predictors to quickly reassess the likelihood of an alternative diagnosis.