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Original Contribution
February 24, 1999

Should the Electrocardiogram Be Used to Guide Therapy for Patients With Left Bundle-Branch Block and Suspected Myocardial Infarction?

Author Affiliations

Author Affiliations: General Internal Medicine Section, Veterans Affairs Medical Center (Drs Shlipak, Lyons, Go, and Browner), and the Divisions of General Internal Medicine (Drs Shlipak, Lyons, Go, and Browner), Geriatrics (Dr Lyons), and Cardiology (Drs Chou and Evans), Department of Medicine, and the Department of Epidemiology and Biostatistics (Dr Browner), University of California, San Francisco; and the Division of Research, Kaiser Permanente Medical Care Program—Northern California, Oakland (Dr Go).

JAMA. 1999;281(8):714-719. doi:10.1001/jama.281.8.714

Context Recently, an algorithm based on the electrocardiogram (ECG) was reported to predict myocardial infarction (MI) in patients with left bundle-branch block (LBBB), but the clinical impact of this testing strategy is unknown.

Objective To determine the diagnostic test characteristics and clinical utility of this ECG algorithm for patients with suspected MI.

Design Retrospective cohort study to which an algorithm was applied, followed by decision analysis regarding thrombolysis made with or without the algorithm.

Setting University emergency department, 1994 through 1997.

Patients Eighty-three patients with LBBB who presented 103 times with symptoms suggestive of MI.

Main Outcome Measures Myocardial infarction determined by serial cardiac enzyme analyses and stroke-free survival.

Results Of 9 ECG findings assessed, none effectively distinguished the 30% of patients with MI from those with other diagnoses. The ECG algorithm indicated positive findings in only 3% of presentations and had a sensitivity of 10% (95% confidence interval, 2%-26%). The decision analysis showed that among 1000 patients with LBBB and chest pain, 929 would survive without major stroke if all received thrombolysis compared with 918 if the ECG algorithm was used as a screening test.

Conclusions The ECG is a poor predictor of MI in a community-based cohort of patients with LBBB and acute cardiopulmonary symptoms. Acute thrombolytic therapy should be considered for all patients with LBBB who have symptoms consistent with MI.