Prognostic impact of myocarditis as aetiology compared with dilated cardiomyopathy and ischaemic heart disease in heart failure

Abstract Background A subgroup of myocarditis can lead to heart failure. However, whether prognosis of myocarditis-induced heart failure differs from other heart failure remains largely unknown. Aim This study aimed to investigate the prognostic impact of myocarditis induced heart failure compared with heart failure with dilated cardiomyopathy and ischaemic heart disease as causes respectively in the overall population and a propensity score-matched cohort, based on patient-level data from the Swedish Heart Failure Registry (SwedeHF). Methods Patients with heart failure (HF) were enrolled from the SwedeHF (2003-2020) linked with the National Patient Register, and the Swedish Cause of Death Register. Endpoints were all-cause mortality, cardiovascular death, and hospital re-admissions, followed up from the index date until censoring or event. Results Of 54416 patients identified through the SwedeHF with HF, 418 hade myocarditis as aetiology (MC-HF), 6,871 with dilated cardiomyopathy (DCM-HF) and 47127 with ischemic heart diseases (IHD-HF). In general patients with MC-HF have shorter disease duration and less comorbidities compared with DCM-HF and IHD-HF, but older than DCM-HF and younger than IHD-HF. Compared with DCM-HF, MC-HF are associated with 29% higher risk for all cause mortality [(1.29 (1.07 - 1.55), p=0.0079] and 40% higher risk for cardiovascular death [ 1.40 (1.09 - 1.80), p=0.0088], and 19 % higher risk for heart failure rehospitalization [1.19 (1.03 - 1.37), p=0.018] and even higher risk by censoring within one-year . However, compared with IHD-HF, patients with MC-HF have similar risk for all cause mortality [0.95 (0.80 - 1.13), p=0.54], cardiovascular death [0.95 (0.75 - 1.20), p=0.65], and heart failure rehospitalization [0.93 (0.81 - 1.06), p=0.29]. Similar results were obtained from a propensity 1:2 matched cohort. No significant interactions were found regardless of age (< and < 70 years) , sex, LVEF (≥50%, 40-49%, 30-39% and < 30%) for all cause mortality comparing MC-HF vs DCM-HF, and MC-HF vs IHD-HF. Conclusion Patients with myocarditis-induced heart failure have worse outcome than heart failure due to dilated cardiomyopathy, with even higher risk during one year. This finding highlights the importance of early and more effective customized management of patients with myocarditis in particular those with high risk to develope heart failure.