Concealed Myocardial Abnormalities by Cardiac Magnetic Resonance Imaging in Idiopathic VT

Idiopathic Ventricular arrhythmia (VAs) refers to VAs that occur in the absence of clinically apparent structural heart disease. The outflow tracts (OTs) are the most common origin of idiopathic VT and PVCs, accounting for approximately 10% of all patients referred for evaluation of VT with the RVOT being the origin of about 70-80% of these arrhythmias. Studies have shown that increased PVC burden was associated with reduced LV function, a higher incidence of heart failure, and a higher risk of death. The diagnosis, prognostication and treatment of patients with VAs are challenging. A routine diagnostic workup that includes transthoracic echocardiography and an assessment for the presence of coronary artery disease (CAD) as recommended by current clinical guidelines cannot recognize focal structural abnormalities or underlying structural heart disease (SHD) in a substantial proportion of patients. Cardiac magnetic resonance (CMR) provides an excellent assessment of cardiac morphology and function and enables a detailed myocardial tissue characterization with a high degree of precision. CMR is widely regarded as the gold standard for identifying structural arrhythmogenic substrates in patients with VAs and normal echocardiography. More importantly, myocardial structural abnormalities detected on CMR in patients with idiopathic VAs are associated with an increased risk of arrhythmic events and worse clinical outcomes. However, little is known regarding the added value of CMR including feature-tracking strain CMR (FT-CMR) in identifying underlying myocardial abnormalities and biventricular dysfunction in a relatively 'healthy' population of patients with VAs and normal echocardiography.