Clinical symptoms and myocardial infarction in left bundle branch block patients.

In patients with left bundle branch block (LBBB) and acute chest pain, the association between the clinical presentation and the diagnosis of myocardial infarction has not been investigated. We sought to identify features in the clinical history of patients with LBBB and acute cardiopulmonary symptoms that predict myocardial infarction among candidates for reperfusion therapy. We retrospectively studied a consecutive cohort of 75 patients (94 presentations) who presented to a university emergency department from 1994 to 1997 with LBBB on initial electrocardiogram (ECG) and acute chest pain of >/=20 min duration or acute pulmonary edema. Among the 94 presentations meeting criteria for the cohort, 26 (28%) had confirmed myocardial infarction. Coronary heart disease risk factors, past cardiac history, prior LBBB on the ECG, and presenting symptoms did not predict whether patients were having myocardial infarction. The clinical history was not effective at distinguishing LBBB patients with myocardial infarction among patients who appeared to be candidates for acute reperfusion therapy.

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 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.