Right Ventricular Outflow Tract Diameter for Event Prediction in Arrhythmogenic Right Ventricular Cardiomyopathy

BACKGROUND: Right ventricular outflow tract (RVOT) dilatation is a phenotypic feature of arrhythmogenic right ventricular cardiomyopathy (ARVC). The echocardiographic RVOT diameter is part of the 2010 Task Force Criteria and is widely measured in clinical practice. Nevertheless, few data exist on its prevalence, diagnostic value, and prognostic significance. OBJECTIVES: This study aimed to explore the association of RVOT diameter with adverse outcomes in ARVC patients without (primary prevention) or with (secondary prevention) previous ventricular arrhythmia (VA), identify the best RVOT diameter for diagnosing ARVC, and understand whether isolated RVOT dilatation occurs in ARVC. METHODS: Patients with definite ARVC and genetic testing results were included in a cross-sectional outcome study. Isolated RVOT dilatation was defined as an enlarged RVOT diameter without concurrent right ventricular (RV) end-diastolic area dilatation. The diagnostic power of RVOT diameter was assessed compared with 100 healthy control subjects. The time to first event after baseline echocardiography was analyzed by Cox regression. RESULTS: The cohort consisted of 370 patients (mean age: 47 years; 56% male; 65% primary prevention; median follow-up: 6.8 years [Q1-Q3: 3.8-10.5 years]; 136 events [100 VA; 35 deaths]). RVOT dilatation occurred in 69% and isolated dilatation in 24% of patients. All RVOT diameters had similar diagnostic power (RVOT3/body surface area, AUC: 0.71 [95% CI: 0.66-0.76]) and a similar association with VA (RVOT3/body surface area, HR: 1.08 [95% CI: 1.04-1.13]; P < 0.001) or death (HR: 1.26 [95% CI: 1.18-1.35]; P < 0.001). Dilated RVOT was associated with a shorter time to VA or death in primary prevention and death in secondary prevention, and its feasibility was higher, its reproducibility was better, and its outcome association was stronger than those of RV free-wall strain. CONCLUSIONS: Isolated RVOT dilatation occurred in >20% of ARVC patients. All RVOT diameters showed good diagnostic power, were strongly associated with time to adverse events, were associated with adverse events in primary and secondary prevention, and exhibited superior feasibility, reproducibility, and outcome association compared with RV free-wall strain.