Role of Cardiac Magnetic Resonance Imaging in Patients with Idiopathic Ventricular Arrhythmias

Ventricular Arrhythmias (VAs) may present with a wide spectrum of clinical manifesta-tions ranging from mildly symptomatic frequent premature ventricular contractions to life-threatening events such as sustained ventricular tachycardia, ventricular fibrillation and sudden cardiac death. Myocardial scar plays a central role in the genesis and maintenance of re-entrant arrhythmias which are commonly associated with Structural Heart Diseases (SHD) such as ischemic heart disease, healed myocarditis and non-ischemic cardiomyopathies. However, the arrhythmogenic substrate may remain unclear in up to 50% of the cases after a routine diagnostic workup, comprehensive of 12-lead surface ECG, transthoracic echocardiography and coronary angiography/computed tomography. Whenever any abnormality cannot be identified, VAs are referred as to “idiopathic”. In the last dec-ade, Cardiac Magnetic Resonance (CMR) imaging has acquired a growing role in the identification and characterization of myocardial arrhythmogenic substrate, not only being able to accurately and re-producibly quantify biventricular function, but, more importantly, providing information about the presence of myocardial structural abnormalities such as myocardial fatty replacement, myocardial oe-dema, and necrosis/ fibrosis, which may otherwise remain unrecognized. Moreover, CMR has recent-ly demonstrated to be of great value in guiding interventional treatments, such as radiofrequency abla-tion, by reliably identifying VA sites of origin and improving long-term outcomes. In the present manuscript, we review the available data regarding the utility of CMR in the workup of apparently “idiopathic” VAs with a special focus on its prognostic relevance and its application in planning and guiding interventional treatments.