Interobserver agreement in the electrocardiographic diagnosis of acute myocardial infarction in patients with left bundle branch block

Study objective: To determine the interobserver agreement between cardiolog ists and emergency physicians in the ECG diagnosis of acute myocardial infa rction (AMI) in patients with left bundle branch block (LBBB) using the ECG algorithm previously described by Sgarbossa et al. Methods: Using the Sgarbossa ECG algorithm, 4 cardiologists and 4 emergency physicians independently interpreted a test set of 224 ECGs with LBBB, of which 100 ECGs were from patients with an evolving AMI. A subset of 25 ECGs was reinterpreted by each reader to test intraobserver agreement for AMI a s well as interobserver agreement for the degree of ST-segment deviation. A greement rates for AMI were estimated using the kappa statistic. In additio n, the sensitivity and specificity for diagnosing AMI were determined for e ach reader, using the Global Utilization of Streptokinase and Tissue Plasmi nogen Activator for Occluded Coronary Arteries (GUSTO I) enzyme criteria fo r AMI as the gold standard. The study was conducted at 3 university-affilia ted medical centers. The test set contained ECGs from 100 patients enrolled in the GUSTO I trial with LBBB on their initial ECG and an evolving AMI co nfirmed by serum cardiac enzyme changes, and 124 control patients from the Duke Databank for Cardiovascular Disease who had stable, angiographically d ocumented coronary artery disease and LBBB. Results: There was excellent interobserver agreement (kappa =0.81, 95% conf idence interval [CI] 0.80 to 0.83) between cardiologists and emergency phys icians for diagnosing AMI. Intraobserver agreement KC values for AMI diagno sis by cardiologists and emergency physicians were 0.81 (95% CI 0.67 to 0.9 4) and 0.71 (95% CI 0.54 to 0.89). The median sensitivity for diagnosing AM I by cardiologists and emergency physicians was 73% (range 66% to 80%) vers us 67% (range 61% to 75%); median specificity was 98% (range 97% to 99%) ve rsus 99% (range 98% to 99%). Spearman rank correlation coefficients for the degree of ST-segment deviation in all 12 leads was 0.86 (95% CI 0.85 to 0. 87) among all readers. Conclusion: There is excellent interobserver agreement between cardiologist s and emergency physicians for diagnosing AMI when applying the Sgarbossa E CG algorithm to patients with LBBB. Emergency physicians should be able to reliably use this algorithm when evaluating patients.