Electrocardiographic Criteria for ST-Elevation Myocardial Infarction in Patients With Left Ventricular Hypertrophy

Patients with electrocardiographic (ECG) left ventricular hypertrophy (LVH) have repolarization abnormalities of the ST segment that may be confused with an ischemic current of injury. We analyzed the ACTIVATE-SF database, a registry of consecutive emergency department ST-segment elevation (STE) myocardial infarction diagnoses from 2 medical centers. Univariate analysis was performed to identify ECG variables associated with presence of an angiographic culprit lesion. Recursive partitioning was then applied to identify a clinical decision-making rule that maximizes sensitivity and specificity for presence of an angiographic culprit lesion. Seventy-nine patients with ECG LVH underwent emergency cardiac catheterization for primary angioplasty. Patients with a culprit lesion had greater magnitude of STE (3.0 ± 1.8 vs 1.9 ± 1.0 mm, p = 0.005), more leads with STE (3.1 ± 1.6 vs 2.0 ± 1.8 leads, p = 0.002), and a greater ratio of STE to R-S–wave magnitude (median 25% vs 9.2%, p = 0.003). Univariate application of ECG criteria had limited sensitivity and a high false-positive rate for identifying patients with an angiographic culprit lesion. In patients with anterior territory STE, using a ratio of ST segment to R-S–wave magnitude ≥25% as a diagnostic criteria for STE myocardial infarction significantly improved specificity for an angiographic culprit lesion without decreasing sensitivity (c-statistic 0.82), with a net reclassification improvement of 37%. In conclusion, application of an ST segment to R-S–wave magnitude ≥25% rule may augment current criteria for determining which patients with ECG LVH should undergo primary angioplasty.