Early Risk Stratification of Patients After Successfully Resuscitated Out-of-Hospital Cardiac Arrest Without ST-Segment Elevation-The Angiography After Out-of-Hospital Cardiac Arrest Without ST-Segment Elevation (TOMAHAWK) Risk Score

OBJECTIVES: Existing scores for risk stratification after out-of-hospital cardiac arrest (OHCA) are either medically outdated, limited to registry data, small cohorts, and certain healthcare systems only, or include rather complex calculations. The objective of this study was to develop an easy-to-use risk prediction score for short-term mortality in patients with successfully resuscitated OHCA without ST-segment elevation on the post-resuscitation electrocardiogram, derived from the Angiography after Out-of-Hospital Cardiac Arrest without ST-Segment Elevation (TOMAHAWK) trial. The risk score was externally validated in the Coronary Angiography after Cardiac Arrest Trial (COACT) cohort (shockable arrest rhythms only) and additional hospitals from Berlin, Germany (shockable and nonshockable arrest rhythms).

DESIGN: Predefined subanalysis of the TOMAHAWK trial.

SETTING: Development and external validation across 52 centers in three countries.

PATIENTS: Adult patients with successfully resuscitated OHCA and no ST-segment elevations.

INTERVENTIONS: Utilization of the TOMAHAWK risk score upon hospital admission.

MEASUREMENTS AND MAIN RESULTS: The risk score was developed using a backward stepwise regression analysis. Between one and four points were attributed to each variable in the risk score, resulting in a score with three risk categories for 30-day mortality: low (0-2), intermediate (3-6), and high (7-10). Five variables emerged as independent predictors for 30-day mortality and were used as risk score parameters: age of 72 years old or older, known diabetes, unshockable initial electrocardiogram rhythm, time until return of spontaneous circulation greater than or equal to 23 minutes, and admission arterial lactate level greater than or equal to 8 mmol/L. The 30-day mortality rates for each risk category were 23.6%, 68.8%, and 86.2%, respectively (p < 0.001) with a good discrimination at an area under the curve of 0.82. External validation in the COACT and Berlin cohorts showed short-term mortality rates of 23.1% and 20.4% (score 0-2), 44.8% and 48.1% (score 3-6), and 78.9% and 73.3% (score 7-10), respectively (each p < 0.001).

CONCLUSIONS: The TOMAHAWK risk score can be easily calculated in daily clinical practice and strongly correlated with mortality in patients with successfully resuscitated OHCA without ST-segment elevation on post-resuscitation electrocardiogram.