In a nationwide cohort of primary (PP‐ICD) and secondary prevention (SP‐ICD) implantable cardioverter defibrillator (ICD) patients, we aimed to investigate the association between co‐morbidity burden and risk of appropriate ICD therapy and mortality.

We identified all patients >18 years, implanted with first‐time PP‐ICD (n = 1873) or SP‐ICD (n = 2461) in Denmark from 2007 to 2012. Co‐morbidity was identified in administrative registers of hospitalization and drug prescription from pharmacies. Co‐morbidity burden was defined as the number of pre‐existing non‐ICD indication‐related co‐morbidities including atrial fibrillation, diabetes, chronic obstructive pulmonary disease, chronic renal disease, liver disease, cancer, chronic psychiatric disease, and peripheral and/or cerebrovascular disease, and divided into four groups (co‐morbidity burden 0, 1, 2, and ≥3). Through Cox models, we assessed the impact of co‐morbidity burden on appropriate ICD therapy and mortality. Increasing co‐morbidity burden was not associated with increased risk of appropriate therapy, irrespective of implant indication [all hazard ratios (HRs) 1.0–1.4, P = NS]. Using no co‐morbidities as reference, increasing co‐morbidity burden was associated with increased mortality risk in PP‐ICD patients (co‐morbidity burden 1, HR 2.1; comorbidity burden 2, HR 3.7; co‐morbidity burden ≥3, HR 6.6) (all P < 0.001) and SP‐ICD patients (co‐morbidity burden 1, HR 2.2; co‐morbidity burden 2, HR 3.8; co‐morbidity burden ≥3, HR 5.8). With increasing co‐morbidity burden, an increasing frequency of patients died without having utilized their device, with 72% PP‐ICD and 45% SP‐ICD patients with co‐morbidity burden ≥3 dying without prior appropriate ICD therapy.

Increasing co‐morbidity burden was not associated with increased risk of appropriate ICD therapy. With increasing co‐morbidity burden, mortality increased, and a higher proportion of patients died, without ever having utilized their device.