Severity of ischemic heart disease and presenting rhythm in patients with out-of-hospital cardiac arrest

INTRODUCTION: Ischemic heart disease (IHD) is associated with a shockable rhythm in out-of-hospital cardiac arrest (OHCA). However, the impact of IHD severity on first recorded rhythm is unknown. We hypothesized that the strength of the association between IHD and shockable rhythm increases with increasing IHD severity.

METHODS: OHCA patients were identified in the Danish Cardiac Arrest Registry (2001-2014). Population-based registries were used to identify chronic diseases, drug prescriptions and cardiac procedures such as coronary angiography (CAG), percutaneous coronary intervention (PCI), and coronary artery bypass grafting (CABG). Severity of IHD was categorized as 1) No diagnosis of IHD, 2) IHD without previous CAG, PCI or CABG, 3) IHD with CAG, 4) IHD with PCI, and 5) IHD with CABG. Adjusted odds ratios (ORs) for a shockable rhythm was computed using multivariable logistic regression.

RESULTS: Of 34,749 patients with OHCA, 6325 (18.2%) patients had a diagnosis of IHD. The prevalence of a shockable rhythm was higher for patients with a previous diagnosis of IHD (25.6%) and for those with previous CAG (33.3%), PCI (36.4%) or CABG (34.0%) when compared to patients without IHD (21.2%). IHD was associated with shockable rhythm (OR = 1.69, 95%CI 1.55-1.85) when compared to patients without IHD. The association with shockable rhythm was higher for patients with a history of CAG (OR = 1.92, 95%CI 1.67-2.20) and PCI (OR = 1.93, 95%CI 1.67-2.23), but similar in patients with CABG (OR = 1.69, 95%CI 1.37-2.10).

CONCLUSION: IHD was associated with a shockable rhythm, with a moderate increase in the association in patients with a CAG or PCI procedure.