*2.1. Study Population*

All DCM patients consecutively enrolled in the Heart Muscle Disease Registry of Trieste between 1 January 1990 and 31 December 2015 and, with available data at 24-month follow up, were retrospectively analysed.

DCM was defined as an impairment of the Left Ventricular Ejection Fraction (LVEF) to < 50% and a left ventricular dilation in the absence of: a history of significant hypertension, obstruction > 50% of a major coronary artery branch, excessive alcohol intake, chemotherapy, an advanced systemic disease affecting short-term prognosis, pericardial diseases, congenital heart diseases, pulmonal, persistent supraventricular tachyarrhythmias, and active myocarditis [1,6].

The presence of a significant coronary artery obstruction was carefully excluded by a coronary artery angiography or, in case of a low likelihood of coronary artery disease, by coronary computed tomography scan.

All patients were on optimal medical treatment, receiving the highest tolerated doses of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers and beta-blockers unless contraindicated [9]. Furthermore, implanted cardioverter defibrillators (ICDs) and cardiac resynchronization therapy (CRT) have been systematically introduced respectively since 1998 and 2005, according to international guidelines [10].

A structured outpatient follow-up, comprehensive of clinical evaluation, a 12-lead ECG, and two-dimensional echocardiography were performed at regularly scheduled time points until 24 months from enrolment (i.e., first evaluation at our Department) and then yearly or every other year afterwards according to specific clinical needs.

The institutional ethics board approved the study. The investigation complied with the Declaration of Helsinki.
