Demographic and clinical characteristics (Table 1)
The mean age of patients with mixed CMP (69.1±9.6 years) was higher compared to both ICM (66.3±10.9 years; p=0.008) and NICM (54.4±14.5 years; p<0.001). The mean LVEF in patients with mixed CMP (32.9±8.6 %) was comparable to patients with ICM (32.7±8.3%; p=0.8) and lower compared to patients with NICM (40.9±14.2%; p<0.001). The proportion of male gender was 82% in mixed CMP, 92% in ICM and 66.7% in NICM. Patients with mixed CMP, in comparison with ICM, had lesser proportions of diabetes mellitus (33.5% vs 44.8%; p=0.03), higher proportions of alcohol abuse (22.4% vs 8%; p<0.001) and malignancy (30.4% vs 2.7%; p<0.001), and comparable proportions of hypertension, chronic lung diseases and chronic kidney diseases. (Table 1; Supplemental Table 1 ). Patients with mixed CMP, in comparison with NICM, had higher proportions of diabetes mellitus (33.5% vs 13.5%; p<0.001), systemic hypertension (62.1% vs 36.2%; p<0.001), chronic lung disease (13% vs 2.1%; p<0.001), chronic kidney disease (22.4% vs 7.1%; p<0.001), malignancy (30.4% vs 11.3%; p<0.001) and comparable proportions of alcohol abuse (22.4% vs 17%; p=0.2).
The distribution of moderate CAD in patients with mixed CMP was LM/LAD (22.4%), LCX/RCA (1.8%), double vessel disease (56.6%) and triple vessel disease (18.6%). Coexisting nonischemic aetiologies in the patients of mixed CMP were post myocarditis sequelae (32.9%), chemotherapy-related (24.2%), tachycardiomyopathy (19.3%), alcohol-related (16.1%) and hypertrophic cardiomyopathy (7.5%). The nonischemic aetiologies in the patients of NICM were idiopathic (23%), ARVC (11%), restrictive CMP (22.7%), valvular heart diseases (12.8%), inflammatory (10.6%), chemotherapy-related (5%), tachycardiomyopathy (6.4%), alcohol-related (7.1%) and congenital heart diseases (1.4%).
The proportion of patients receiving ICD for secondary prevention in mixed CMP was 44.1% compared to 56.3% in ICM (p=0.02) and 38.3% in NICM (p=0.3). While history of sudden cardiac arrest was comparable amongst all the 3 groups (23.6% in mixed CMP, 20.5% in ICM and 16.3% in NICM), incidence of atrial fibrillation was higher in mixed CMP (55.3%) compared to ICM (28.6%; p<0.001) and NICM (30.5%; p<0.001). While usage of beta blockers was comparable amongst all 3 groups (>95%), amiodarone usage was highest in ICM (38%). With respect to the distribution of type of ICD implant, patients with mixed CMP had higher proportions of CRT-d (29.2%) compared to patients with ICM (18.4%; p=0.04) and NICM (18.4%; p=0.03).