AIMS: Cardiac resynchronization therapy (CRT) improves outcomes in heart failure (HF) but may be underutilized. The reasons are unknown.

METHODS AND RESULTS: We linked the Swedish Heart Failure Registry to national registries with ICD-10 (International Classification of Diseases-10th Revision) co-morbidity diagnoses and demographic and socio-economic data. In patients with EF ≤39% and NYHA II-IV, we assessed prevalence of CRT indication and CRT use. In those with CRT indication, we assessed the association between 37 potential baseline covariates and CRT non-use using multivariable generalized estimating equation (GEE) models. Of 12 807 patients (mean age 71 ± 12 years, 28% female), 841 (7%) had CRT, 3094 (24%) had an indication for but non-use of CRT, and 8872 (69%) had no indication. Important variables independently associated with CRT non-use were: HF duration <6 months [risk ratio (RR) 1.21, 95% confidence interval (CI) 1.17-1.24]; non-cardiology planned follow-up (RR 1.14, 95% CI 1.09-1.18); age >75 years (RR 1.13, 95% CI 1.09-1.18); non-cardiology care at baseline (RR 1.10, 95% CI 1.07-1.14); small-town non-university centre (RR 1.08, 95% CI 1.05-1.12); female sex (RR 1.07 95% CI 1.03-1.10) (all P < 0.05); as was absence of AF, living alone; psychiatric diagnosis; smoking; and non-use of HF drugs. Education, income, cancer, or HF characteristics were not independently associated with CRT non-use.

CONCLUSION: In this population-wide HF registry, CRT was underutilized. Non-use was associated mostly with demographic and organizational, but not clinical or socio-economic factors. This calls for programmes to raise awareness of CRT indications and improve access and referrals to cardiology specialists.