Should the electrocardiogram be used to guide therapy for patients with left bundle-branch block and suspected myocardial infarction?

Context Recently, an algorithm based on the electrocardiogram (ECG) was rep orted to predict myocardial infarction (MI) in patients with left bundle-br anch block (LBBB), but the clinical impact of this testing strategy is unkn own. Objective To determine the diagnostic test characteristics and clinical uti lity of this ECC algorithm for patients with suspected MI. Design Retrospective cohort study to which an algorithm was applied, follow ed by decision analysis regarding thrombolysis made with or without the alg orithm. Setting University emergency department, 1994 through 1997. Patients Eighty-three patients with LBBB who presented 103 times with sympt oms suggestive of MI. Main Outcome Measures Myocardial infarction determined by serial cardiac en zyme 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 indi cated positive findings in only 3% of presentations and had a sensitivity o f 10% (95% confidence interval, 2%-26%). The decision analysis showed that among 1000 patients with LBBB and chest pain, 929 would survive without maj or stroke if all received thrombolysis compared with 918 if the ECC algorit hm was used as a screening test. Conclusions The ECG is a poor predictor of MI in a community-based cohort o f patients with LBBB and acute cardiopulmonary symptoms. Acute thrombolytic therapy should be considered for all patients with LBBB who have symptoms consistent with MI.