Incidence, Analysis and Risk of Out-of-Hospital Cardiac Arrest in Individuals with Non-Ischaemic Dilated Cardiomyopathy

Background The incidence, risk and resuscitation characteristics of out-of-hospital-cardiac-arrest (OHCA) in the non-ischaemic dilated cardiomyopathy (NIDCM) population have not been analysed before in an unselected nationwide population, and could provide insight into risk stratification and prevention of sudden cardiac death in this unique heart failure cohort. Methods We conducted an observational, register-based study with cohort and nested case-control analyses using Denmark’s healthcare registers between June 1, 2001 to December 31, 2022. DCM was classified as non-ischaemic using validated methods combined with exclusion of other causes of ischaemia or abnormal loading conditions. Incidence rates and hazard ratios were calculated in the general population. Absolute risk was determined using the Aalen-Johansen estimator in an exposure-matched cohort including incident NIDCM patients and matched controls. Resuscitation characteristics were determined in a nested case-control study. Results The incident rate of OHCA was approximately 12 times higher in NIDCM patients compared with the general population (incidence rate 532 vs 45 per 100,000 person years). The 5 and 10-year risk of OHCA for male de novo NIDCM patients was 2% and 3.4% respectively (vs 0.6% and 1.1% for non-NIDCM) and 1.4% and 2.1% for female de novo NIDCM patients (vs 0.4 and 0.5% for non-NIDCM). NIDCM OHCAs had higher rates of initial shockable rhythm than non-NIDCM OHCAs (48.5% vs 22.3%, p<0.001) but no significant differences in 30 day and 1 year mortality (79% vs 84% and 82% vs 84, respectively). Conclusion The Danish NIDCM population has a significantly increased incidence of OHCA compared to the general population but a comparable mortality despite multiple positive resuscitation characteristics.