Corresponding author:
Rajeev Kumar Pathak, MBBS, PhD
Cardiac Electrophysiology Unit, Department of Cardiology
Canberra Hospital, Australian National University
Yamba Drive, Garran, ACT, 2605
Tel: +61 2 6174 8723; Fax: +61 2 6244 4964
E-mail: rajeev.pathak@canberraheartrhythm.com.au
Twitter handle: @drrpathak
Acknowledgments:  Dr Sanders is supported by a Practitioner Fellowship from the National Health and Medical Research Council of Australia and by the National Heart Foundation of Australia.
Conflict of Interest Disclosures:  Dr Sanders reports having served on the advisory board of Medtronic, Abbott Medical, Boston Scientific, CathRx and PaceMate. Dr Sanders reports that the University of Adelaide has received on his behalf lecture and/or consulting fees from Medtronic, Abbott Medical, and Boston Scientific. Dr Sanders reports that the University of Adelaide has received on his behalf research funding from Medtronic, Abbott Medical, Boston Scientific, BD, and Microport. All other authors have no disclosures.  Dr Pathak reports having served on the advisory board of Medtronic, Abbott Medical, Boston Scientific. Dr Pathak reports that Canberra Heart Rhythm Foundation has received on his behalf lecture and/or consulting fees from Medtronic, Abbott Medical, Boston Scientific and Biotronik. Dr Pathak reports that Canberra Heart Rhythm Foundation has received on his behalf research funding from Medtronic, Abbott Medical, Boston Scientific, and Biotronik.ABSTRACT
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.
Key words: Ischemic cardiomyopathy; Nonischemic cardiomyopathy; Mixed cardiomyopathy; Implantable-cardioverter defibrillator; Device shocks; Mortality