Aims Patients with heart failure and low income have a high mortality risk. We examined whether lower survival among low-income patients with heart failure could be explained by different use of beta-blockers, renin-angiotensin system inhibitors (RASi), and implanted devices compared with high-income patients.

Methods and results We linked Danish national registries to identify patients with new-onset heart failure between 2005 and 2016. A total of 18 308 patients was included in the main analysis. We collected information on medical treatment and device therapy after discharge. We investigated the remaining income disparity if everybody had the same probability of treatment as the high-income patients. We used causal mediation analysis to examine to what extent treatment differences mediate the association between income and 1-year mortality in strata defined by sex and cohabitation status. If low-income patients had the same probability of initiating beta-blockers and RASi treatment as high-income patients, low-income men who lived alone would increase initiation of treatment by 12.4% (CI: 10.0% to 14.9%) and as a result reduce their absolute 1-year mortality by 1.0% (CI: -1.4% to -0.5%). If low-income patients had the same probability of not having breaks in medical treatment and getting device therapy, as high-income patients, low-income patients would increase the probability of not having breaks in treatment between 1.8% and 5.8% and increase the probability of getting device therapy between 1.0% and 3.8%, across strata of sex and cohabitation status.

Conclusion Lower rates of treatment initiation appear to mediate the poorer survival seen among patients with heart failure and low income, but only in males living alone.