Electrocardiographic Findings in Patients with Acute Coronary Syndrome Presenting with Out-of-Hospital Cardiac Arrest

We sought to characterize presenting electrocardiographic findings in patients with acute coronary syndromes (ACS) and out-of-hospital cardiac arrest (OHCA). In the Global Registry of Acute Coronary Events (GRACE) and Canadian ACS Registry I, we examined presenting and 24-48 hour follow-up ECGs of ACS patients who survived to hospital admission, stratified by presentation with OHCA. We assessed the prevalence of ST-segment deviation and bundle branch blocks and their association with in-hospital and 6-month mortality amongst those with OHCA. 215 (1.8%) of 12,040 ACS patients survived to hospital admission following OHCA. Those with OHCA had higher presenting rates of ST-segment elevation, ST-segment depression, T wave inversion, precordial Q waves, left bundle branch block (LBBB), and right bundle branch block (RBBB) than those without. Among patients with OHCA, those with ST-segment elevation had significantly lower in-hospital mortality (20.9% vs. 33.0%, p=0.044) and a trend toward lower 6-month mortality (27% vs. 39%, p=0.060) compared to those without ST-segment elevation. Conversely, among OCHA patients, LBBB was associated with significantly higher in-hospital and 6-month mortality rates (58% vs. 22%, p<0.001 and 65% vs. 28%, p<0.001 respectively). ST-segment depression and RBBB were not associated with either outcome. 63% of bundle branch blocks (RBBB or LBBB) on the presenting ECG resolved by 24-48 hours. In conclusion, compared with ACS patients without cardiac arrest, those with OHCA had higher rates of ST-segment elevation, LBBB and RBBB on admission. Among OHCA patients, ST-segment elevation was associated with lower in-hospital mortality, while LBBB was associated with higher in-hospital and 6-month mortality.