Heart Rate and Mortality After Resuscitation in Patients With Out-of-Hospital Cardiac Arrest　― Insights From the SOS-KANTO Registry

Background: Heart rate (HR) predicts outcomes in patients with acute coronary syndrome (ACS), whereas the impact of HR on outcomes after out-of-hospital cardiac arrest (OHCA) remains unclear. This study aimed to investigate the impact of HR after resuscitation on outcomes after OHCA and whether the impact differs with OHCA etiology.Methods and Results: Of 16,452 patients suffering from OHCA, this study analyzed 741 adults for whom HR after resuscitation was recorded by 12-lead electrocardiogram upon hospital arrival. Etiology of OHCA was categorized into 3 groups: ACS, non-ACS, and non-cardiac. Patients in each etiology group were further divided into tachycardia (>100 beats/min) and non-tachycardia (≤100 beats/min). The impact of HR on outcomes was evaluated in each group. Among the 741 patients, the mean age was 67.6 years and 497 (67.1%) patients were male. The primary outcome – 3-month all-cause mortality – was observed in 55.8% of patients. Tachycardia after resuscitation in patients with ACS was significantly associated with higher all-cause mortality at 3 months (P=0.002), but there was no significant association between tachycardia and mortality in non-ACS and non-cardiac etiology patients. In a multivariate analysis model, the incidence of tachycardia after resuscitation independently predicted higher 3-month all-cause mortality in OHCA patients with ACS (hazard ratio: 2.17 [95% confidence interval: 1.05–4.48], P=0.04).Conclusions: Increased HR after resuscitation was associated with higher mortality only in patients with ACS.