All-cause mortality and incidence of appropriate therapy from a primary preventive implantable cardioverter defibrillator in patients with non-ischemic dilated cardiomyopathy

The DANISH study published in 2016 indicated limited benefit of primary prevention implantable cardioverter-defibrillator (ICD) in patients with non-ischemic dilated cardiomyopathy (niDCM). We aimed to investigate the long-term outcome and incidence of ICD therapy in patients with niDCM implanted on primary prevention indication during 2014-2022.

A total of 116 patients with niDCM were prospectively included for primary prevention ICD implantation between 2014 and 2022 in the multicenter IMPROVE study (clinical trials NCT02286908). All patients were examined with electrocardiogram, echocardiography and blood sampling at inclusion. The primary outcome was all-cause mortality, and the secondary outcome was appropriate ICD therapy. Outcomes were compared in patients included from 2014 to end of 2016 (DCM2014-16, n=49) and from 2017-2022 (DCM2017-22, n=67).

At inclusion, patients in DCM2017-22 were younger (54 years [interquartile range (IQR) 44-68] vs. 64 years [IQR 55-70], p=0.001), had higher left ventricular ejection fraction (LVEF) (33% [IQR 25-38] vs. 24% [IQR 21-31], p<0.001) and less frequently received cardiac-resynchronization therapy defibrillator (6% vs. 29%, p=0.001) compared to DCM2014-16. Over a median 4.4-year follow-up, the all-cause mortality was 14%, of which 10% occurred in the DCM2017-22 patients (2.6 events/100 person-years), and 18% in the DCM2014-16 patients (4.0 events/100 person-years), p=0.38. There was no difference in appropriate ICD therapy between the two groups (p=0.90).

Patients receiving primary prevention ICD for niDCM after publication of the DANISH study were younger with higher LVEF, indicating a change in clinical practice after the publication. Despite this, there was no significant reduction in all-cause mortality or difference in appropriate ICD therapies. Unchanged mortality and event-rates may indicate the correct identification of high-risk patients.