Abstract 14012: The Importance of Right Bundle Branch Block in Suspected ST-Elevation Myocardial Infarction is Independent of ST-T Deviations

Abstract

Background: In patients with suspected acute coronary syndrome (ACS) and bundle branch block (BBB) an emergent invasive strategy is recommended. While left bundle branch block (LBBB) is a well-known high-risk feature in patients with acute myocardial infarction, data supporting this strategy for right bundle branch block (RBBB) are scarce. Hypothesis: RBBB poses a high-risk feature in suspected ST-elevation myocardial infarction (STEMI). Methods: 2,139 patients with suspected STEMI were triaged to acute coronary angiography based on a prehospital, tele-transmitted digital 12-lead ECG. All discharge diagnoses were independently adjudicated. Sensitivity and specificity for STEMI-ECG-criteria were compared in RBBB and non-BBB patients. Adjusted hazard ratios for 1-year overall mortality were computed. Results: STEMI was adjudicated in 1,832/2,139 (85.6%) of all patients and in 102/117 (87.2%) of RBBB patients. ST-segment deviation followed typical patterns in most RBBB patients (n=36 for anterior, n=49 for inferior and n=15 for lateral STEMI) and among these a final diagnosis of STEMI was adjudicated in 88. Out of 17 patients without significant ST-changes, 14 (82%) were adjudicated as STEMI. Diagnostic accuracy of STEMI-criteria was comparable in RBBB and non-RBBB patients for anterior (sensitivity: 51.1% vs 59.1%, p=0.14; specificity: 66.7% vs 52.1%, p=0.33) and inferior STEMI (sensitivity: 35.2% vs 36.6%, p=0.80; specificity: 58.3% vs 49.5%, p=0.55). There was a statistical difference for lateral STEMI (sensitivity: 14.8% vs 4.4%, p=0.001; specificity: 75.0% vs 98.4%, p=0.001). Patients with RBBB had significantly higher1-year mortality compared to non-BBB patients. Adjusted hazard ratio for 1-year mortality comparing RBBB to non-BBB patients was 2.3% (95% CI 1.25-4.21, p=0.007). Conclusion: ECG-criteria for the detection of STEMI show comparable diagnostic accuracy in RBBB and non-BBB patients. However, STEMI was frequently present in RBBB patients not fulfilling diagnostic ECG-criteria. In addition, RBBB-patients showed poorer outcome after 1 year. Our data therefore reinforce current guidelines in designating ACS patients with RBBB, independent of ST-T deviations, high-risk and candidates for acute invasive evaluation.