Study definitions
- 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
- 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).
- 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.
- 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.