Declining rates of out-of-hospital-cardiac arrest among individuals with ischemic heart disease

Abstract Background Declining cardiovascular mortality rates have been well-documented, yet temporal trends of out-of-hospital cardiac arrest (OHCA) in patients with ischemic heart disease (IHD) remain unclear. We provide contemporary nationwide estimates of the incidence of OHCA in patients with IHD aged 40–80 from 2016–2022, asses temporal trends, and correlate OHCA trends to changes in out-of-hospital cardiac arrest (OHCA) patterns and diagnostic rates of cardiovascular diseases (CVD) Methods All individuals aged 40–80 living in Denmark from 2016–2022 were included. Information on prior medical history, OHCA characteristics, diagnostic rates of CVD, and ICD implantations were captured from nationwide administrative registries. Annual incidence rates (IR) of OHCA were calculated, and temporal trends in OHCA IR were computed as percentage change annualized (PCA). Trends in OHCA characteristics, diagnostic rates of CVD. Results During the 7-year study period, 230 100 individuals with IHD were identified (1 mill. person-years PY), of which 3 499 (1.5%) experienced an OHCA (median age 72 years, 76% male sex). The overall IR of OHCA among IHD patients was 336.86 per 100 000 PY (95%CI 325.82 – 348.15) and declined by 2.15% (95%CI 2.08 – 2.23) annually, corresponding to a 14.13% (95%CI 13.66 – 14.61) reduction during the study. Among individuals without IHD, the OHCA IR rate was 95.30 per 100 000 PY (95%CI 93.92 – 96.70) with an annual decline of 0.31% (95%CI 0.29 – 0.34). We observed no differences in the temporal decline of OHCA IR between sex (difference 0.57%, p = 0.94) or age groups (40-60 vs 61-80 years, dilfference 0.21, p = 0.94). 30-day survival after OHCA was stable at 18% (p for trend 0.82), however the relative risk of bystander CPR increased by 10% (95%CI 1.01-1.20), of shockable rhythm by 24% (95%CI 1.02-1.50) and of early defibrillation by 55% (95%CI 1.07-2.26). Diagnostic rates of CVD in the background population increased throughout the study period (p for trend 0.008), however IR of IHD declined significantly (p for trend 0.003) and the incidence of myocardial infarction was unchanged (p for trend 0.21). Conclusions Individuals with IHD aged 40–80 had a 3-fold higher OHCA incidence compared to non-IHD, but displayed significantly greater decline in OHCA rates from 2016–2022. The decline was paralleled by lower incidence rates of IHD in the background population. However, rated of MI were stable and despite improving rates of bystander CPR and early defibrillation, survival among OHCA patients with IHD did not improve.