Right ventricular outflow tract diameter in diagnosis of arrhythmogenic right ventricular cardiomyopathy

Abstract

Background/Introduction: Enlargement of the right ventricular outflow tract (RVOT) is a key phenotypic feature of arrhythmogenic right ventricular cardiomyopathy (ARVC). Echocardiography can be used to assess the RVOT and its diameter. Purpose(s): This study aimed at investigating a) whether ARVC can cause isolated RVOT dilatation in general or in certain genotypes, b) which RVOT diameter shows the best discriminatory power for ARVC diagnosis and c) how the right ventricular end-diastolic diameter (RVEDD) compares to the RVOT diameters. Method(s): This study included patients with genetic testing and fulfilling the revised 2010 Task Force Criteria for definite ARVC. Participants were recruited from three prospective ARVC registries. Healthy asymptomatic subjects served as controls. Four echocardiographic RVOT diameters (Figure 1), RVEDD, and right ventricular end diastolic area (RVEDA) were measured and indexed to body surface area (BSA). Isolated RVOT dilatation was defined as RVOT diameter above the upper reference limit (2 standard deviation method derived from control) without concurrent RVEDA enlargement. Receiver operating characteristic curves were used to compare the discriminatory power of each diameter. Result(s): A total of 370 ARVC patients and 100 healthy subjects were enrolled. All RVOT diameters were larger in ARVC patients compared to control (mean (SD) RVOT2/BSA: 19.6 (4.0) mm/m2; control: 16.5 (2.4) mm/m2). A dilated RVOT occurred in 189 (51%) and an isolated dilatation in 66 (18%) of patients. The prevalence of isolated dilatation within a specific genotype were as follows: 13% 95% CI: 9% to 20%] in PKP2, 23% 14% to 35%] in DSP, 12% 4% to 30%] in DSG2, 26% 13% to 45%] in others, and 20% 14% to 28%] in gene-elusive patients. All RVOT diameters showed similar discriminatory power to differentiate ARVC patients from healthy subjects (RVOT2/BSA area under the curve (AUC) 0.75 95% CI: 0.7-0.8]) and were comparable to RVEDD/BSA (AUC 0.70 0.65-0.75]) (Figure 2). Conclusion(s): An isolated RVOT dilatation is observed in almost 20% of patients regardless of the genotype. All RVOT diameters showed similar discriminatory power and were at least as useful as RVEDD.