Reappraisal of cardiac magnetic resonance imaging in idiopathic outflow tract arrhythmias.
Academic Article
Overview
abstract
INTRODUCTION: Because of prognostic and therapeutic implications, the distinction between idiopathic right ventricular (RV) outflow tract (iRVOT) and arrhythmogenic RV cardiomyopathy (ARVC) is clinically important. Over the last 2 decades multiple reports have identified RV abnormalities using CMR in patients with idiopathic VT, suggesting a link between these arrhythmias and ARVC. The purpose of this study was to assess for structural abnormalities in patients with iRVOT tachycardia using contemporary cardiac magnetic resonance (CMR) imaging. METHODS AND RESULTS: CMR was performed in 46 patients with iRVOT tachycardia and 16 normal controls, with quantitative evaluation of RV and left ventricular volumes and function, as well as assessment of myocardial fat and scar. iRVOT patients were similar to controls with respect to RV end-diastolic volumes (81 ± 19 mL/m(2) vs. 79 ± 18 mL/m(2) , P = 0.77) and RV ejection fraction (57 ± 8% vs. 59 ± 7%, P = 0.31). The prevalence of RV chamber dilation, defined using ARVC major task force criteria, was uncommon among iRVOT patients (9%) and controls (7%; P = 1.0). Regional RV wall motion abnormalities were present in 2 iRVOT patients who had concomitant RV dilation or dysfunction. CMR tissue characterization demonstrated absence of both myocardial scar and fat infiltration in all patients and controls. CONCLUSIONS: In patients with the clinical diagnosis of iRVOT tachycardia, CMR reveals RV structure, function, and myocardial tissue characteristics similar to normal controls. These findings suggest that the vast majority of patients with RVOT arrhythmias have a primary electrical disorder that is not a forme-fruste of ARVC.
