Characteristics of the Phenotype of Mixed Cardiomyopathy in Patients with Implantable Cardioverter-Defibrillators

Introduction: The prognosis of mixed cardiomyopathy (CMP) in patients with implanted cardioverter-defibrillators (ICDs) has not been investigated. We aim to study the demographic, clinical, device therapies and survival characteristics of mixed CMP in a cohort of patients implanted with a defibrillator. Methods: : The term mixed CMP was used to categorise patients with impaired left ventricular ejection fraction attributed to documented non-ischemic triggers with concomitant moderate coronary artery disease. This is a single center observational cohort of 526 patients with a mean follow-up 8.7±3.5 years. Results: : There were 42.5% patients with ischemic cardiomyopathy (ICM), 26.9% with non-ischemic cardiomyopathy (NICM) and 30.6% with mixed CMP. Mixed CMP, compared to NICM, was associated with higher mean age (69.1±9.6 years), atrial fibrillation (55.3%) and greater incidence of comorbidities. The proportion of patients with mixed CMP receiving device shocks was 23.6% compared to 18.4% in NICM and 27% in ICM. The VT cycle length recorded in mixed CMP (281.6 ± 43.1ms) was comparable with ICM (282.5 ± 44ms; p=0.9) and lesser than NICM (297.7 ± 48.7ms; p=0.1). All-cause mortality in mixed CMP (21.1%) was similar to ICM (20.1%; p=0.8) and higher than NICM (15.6%; p=0.2). Kaplan-Meier curves revealed hazards of 1.57 (95% CI: 0.91, 2.68) for mixed CMP compared to NICM. Conclusion: In a cohort of patients with ICD, the group with mixed CMP represent a phenotype predominantly comprised of elderly with higher incidence of comorbidities. Mixed CMP resembles ICM in terms of number of device shocks and VT cycle length. Long-term prognosis of patients with mixed CMP is worse than NICM and similar to ICM.