ECG criteria in diagnosis of acute myocardial infarction in the presence of left bundle branch block

Background: The diagnosis of acute myocardial infarction in the presence of left bundle branch block is difficult. Recently a diagnostic ECG scoring system was suggested, showing good diagnostic abilities. This scoring system has never been tested in a prospective manner; we have done so and investigated if it might bear prognostic information. Methods: A prospective multi-centre study. Consecutive patients with left bundle branch block and suspicion of acute myocardial infarction, admitted to 14 Swedish coronary care units. Recruitment from March 1996 to December 1997. ECG registered on admission and after 12–24 h. Results: One hundred and fifty-eight patients were included, mean age 74.9 years. Seventy-six patients (48%) had an acute myocardial infarction. The proposed cut-off total score of ≥3 of the ECG scoring system for the diagnosis of acute myocardial infarction had a sensitivity of 17.1% (95% CI 8.6–25.6%) and specificity of 94.0% (95% CI 88.9–99.1%). Clinical judgement of acute myocardial infarction resulted in a sensitivity of 15.8% (95% CI 7.6–24%) and specificity of 96.0% (CI 92.3–100%). No difference was seen in 3-month or 1-year survival between those with total ECG score ≥3 versus total score <3. Conclusion: The diagnostic abilities of the proposed ECG criteria are low and not better than the clinical judgement. The criteria are therefore not suitable for screening patients with suspicion of acute myocardial infarction in the presence of left bundle branch block, nor do they seem to identify high risk patients.