We aimed to verify whether slow heart rate (HR) is associated with neurologic outcome and the factors that can contribute to the development of bradycardia in out-of-hospital cardiac arrest (OHCA) survivors who underwent targeted temperature management (TTM). We extracted the data of comatose adult OHCA survivors who underwent TTM between October 2015 and December 2018 from the prospective multicenter registry. Data on HR recorded every 6 hours within 72 hours after return of spontaneous circulation and calculated minimal, mean, and maximal HR and time to the lowest HR were obtained. HR <50 bpm was defined as bradycardia. The primary outcome was a 6-month neurologic outcome based on Pittsburgh-Glasgow Cerebral Performance Category Scale. Of the 814 included patients, 508 (62.4%) had poor neurologic outcome and 197 (24.2%) had bradycardia. Bradycardia (odds ratio [OR], 0.574; 95% confidence interval [CI], 0.362-0.192), minimal HR (OR, 1.023; 95% CI, 1.008-1.037), and mean HR (OR, 1.016; 95% CI, 1.002-1.030) were independently associated with poor neurologic outcome, but not maximal HR and time to the lowest HR. Preexisting arrhythmia (OR, 2.067; 95% CI, 1.037-4.118), renal disease (OR, 2.028; 95% CI, 1.153-3.567), cardiac etiology (OR, 1.526; 95% CI, 1.045-2.228), downtime (OR, 0.985; 95% CI, 0.974-0.996), and serum lactate levels (OR, 0.936; 95% CI, 0.900-0.974) were independently associated with bradycardia. Bradycardia and decreased mean and minimal HR were independently associated with good neurologic outcomes. Bradycardia was associated with preexisting arrhythmia, renal disease, cardiac etiology, shorter downtime, and lower serum lactate level.
Keywords: bradycardia; heart rate; hypothermia; induced; out-of-hospital cardiac arrest; outcome.