When does ST depression predict coronary occlusion after an out-of-hospital cardiac arrest?

Following an out-of-hospital cardiac arrest (OHCA), guidelines support immediate coronary angiography for acute ST-segment elevation (STE), although no such recommendations exist for ST-segment depression (STD). In registry studies, immediate coronary angiography has been associated with improved survival, irrespective of ST-segment elevation. We performed a retrospective analysis of patients presenting with OHCA in the BC Lower Mainland, between November 2009 and December 2011. Patients were identified using the Resuscitation Outcomes Consortium Cardiac Arrest Registry. Demographics, clinical history, presenting rhythm, survival, and neurological outcomes were abstracted. The post-resuscitation ECG was interpreted for ST-segment changes (defined as >0.1mV in 2 contiguous leads). Angiographic reports were reviewed for coronary occlusion (stenosis 99% or greater) and obstructive coronary disease (stenosis 70% or greater, or left main stenosis 50% or greater). Our cohort of n=226 pts had a mean age of 64±17y (74% male). The presenting rhythm was ventricular tachycardia/fibrillation (VT/VF; n=114, 50%), pulseless electrical activity (n=43, 19%), asystole (n=41, 18%), and unspecified (n=28, 12%). The post-resuscitation ECG demonstrated STE in 72 patients (31%), STD in 60 patients (26%) and no ST abnormality in 94 patients (42%). Coronary angiography was performed in 94 patients (41%). Coronary occlusion was present in 54 patients (24%) and obstructive coronary disease in 74 patients (33%). Patients presenting with VT/VF were more likely to have STE or STD on the post-resuscitation ECG (OR 2.66), and subsequently more likely to have occlusion on angiography (OR 9.80). After excluding patients with STE, VT/VF remained associated with occlusion (OR 1.63). STD was strongly associated with occlusion (OR 4.20) and obstructive coronary disease (OR 4.67). The degree of STD (i.e. 0-1mm, 1-2mm, 2-3mm, >3mm) was moderately predictive for occlusion (C-statistic 0.72). Patients with STD of >3mm were most likely to have an occlusion (40% sensitivity, 97% specificity). Survival to discharge occurred in 40% with a mean cerebral performance category (CPC) scale of 1.3±1.9. Patients receiving angiography were more likely to survive until discharge (OR 12.72) and have a favorable neurological outcome (OR 11.11). In patients without STE after OHCA, a VT/VF cardiac arrest was associated with occlusion on coronary angiography. The presence and degree of STD was strongly associated with occlusion, with STD of >3mm demonstrating high likelihood (specificity) for coronary occlusion. Although various factors can affect STD post-OHCA, significant STD greatly increases the likelihood of occlusion on coronary angiography, and coronary angiography may improve survival and neurological outcomes.