Abstract Body: Introduction:
Head-to-pelvis “sudden death computed tomography” angiography (SDCT) has a high diagnostic yield to identify causes and complications of out-of-hospital cardiac arrest (OHCA). The differences in yields of non-contrast head CT (H-CT) and pulmonary embolism chest CT (CT PE) angiography alone or in combination is not clear.

Methods:
Our prospective observational cohort enrolled patients that survived OHCA resuscitation and had a SDCT (H-CT, ECG-gated chest CT, and non-ECG gated venous phase abdomen/pelvis CT) within 6 hours of arrival (December 2015 – February 2018). For this sub-study, we assessed the same scans for diagnoses obtainable from routine H-CT and CT PE axial coverage alone, excluding any added (SDCT) findings from ECG-gating and abdomen/pelvis assessment. The primary outcome was the difference in diagnostic yield of time-critical and non-time-critical diagnoses by CT PE with or without H-CT compared to SDCT.

Results:
SDCT identified 86 time-critical diagnoses in 104 enrolled patients, including 39 pneumonias (45% of diagnoses), 13 myocardial infarctions [MI] (15%), 8 pulmonary embolisms (9%), 8 pneumothoraces (9%), 8 abdominal catastrophes (9%), 3 intracranial hemorrhages (3%), and 1 vascular access hemorrhage (1%) [Table]. CT PE alone identified 61 of the 86 time-critical diagnoses (71%), missing 25 diagnoses (29%) compared to SDCT. Missing diagnoses included MI (13/13), abdominal catastrophe (8/8), and active vascular access hemorrhage (1/1). H-CT diagnosed all 3 intracranial hemorrhages. Of the 208 non-time-critical diagnoses identified by SDCT, CT PE identified 183 non-time critical diagnoses (88%), missing 25 diagnoses (12%). H-CT did not identify any non-time-critical diagnoses.

Conclusions:
CT PE imaging with H-CT identifies a majority—but not all—time-critical and non-time-critical diagnoses in OHCA patients, mainly failing to capture coronary and intra-abdominal pathologies. SDCT, which includes ECG-gated chest CT and abdomen/pelvis CT, improves total diagnostic yield, but its incremental utility requires further study.