Study definitions 
  1. ICM was defined as those patients with impaired LVEF in whom there was a history of MI, evidence of prior MI in form of q-waves in ECG or regional wall motion abnormalities in echocardiogram or\(\geq\) 70% coronary artery stenosis in one of the major epicardial vessels in a diagnostic coronary angiogram (CAG) or coronary revascularisation based on results of functional testing.11
  2. NICM  was defined as those patients with depressed LV systolic function in whom moderate to severe CAD (\(\geq\) 50% stenosis in one of the epicardial arteries) was ruled out by a CAG and with no history suggestive of MI. After corroborative evidence from electrocardiography, echocardiography, cardiac MRI, PET scan and genomic assessment, the aetiopathogenesis of NICM was assigned and included the following; post-myocarditis sequelae, arrhythmogenic right ventricular cardiomyopathy, sarcoidosis, hypertrophic cardiomyopathy, infiltrative cardiomyopathy (amyloidosis, hemochromatosis), non-compaction (dilated and low LVEF associated with features of non-compaction documented by echocardiogram or cardiac MRI), valvular heart disease (severe valvular stenosis/ regurgitation leading to dilatation of heart and low LVEF), alcohol-related (documented alcohol abuse or dependence leading to deterioration in LVEF), congenital heart disease (including post-operative patients with persisting heart defects or new onset valvular diseases), tachy-cardiomyopathy, and chemotherapy-related cardiomyopathy. Patients with no known aetiology other than those stated above, but with LVEF ≤35% were classified as idiopathic dilated cardiomyopathy (DCM).
  3. The term mixed CMP was used in this study to categorise patients with dilated cardiomyopathy, a documented non-ischemic aetiology along with moderate CAD (\(\geq\) 50% and < 70% stenosis). The following distribution of CAD was included: single epicardial vessel involving proximal left anterior descending artery (LAD) or proximal dominant left circumflex (LCX) or proximal dominant right coronary artery (RCA); double or triple vessel involvement; 30-50% stenosis involving the left main coronary artery.
  4. Minimum cycle length of VT was calculated based on the least measured near-field EGM intervals in the available intracardiac traces. The average of first 10 intervals was considered in case of unstable intervals. Additional study definitions are incorporated in the supplement.