Electrocardiographic differentiation of idiopathic right ventricular outflow tract ectopy from early arrhythmogenic right ventricular cardiomyopathy

The differentiation between idiopathic right ventricular outflow tract (RVOT) arrhythmias and early arrhythmogenic right ventricular cardiomyopathy (ARVC) can be challenging. We aimed to assess whether QRS morphological features and coupling interval of ventricular ectopic beats (VEBs) can improve differentiation between the two conditions. Twenty desmosomal-gene mutation carriers (13 females, mean age 43 years) with no or mild ARVC phenotypic expression and 33 age- and sex-matched subjects with idiopathic RVOT arrhythmias were studied. All patients exhibited isolated monomorphic VEBs with left bundle branch block/inferior axis morphology. The predictive value of ectopic QRS morphology and coupling interval was evaluated. Five ectopic QRS features were significantly more common in desmosomal-gene mutation carriers than in idiopathic RVOT-ventricular arrhythmia patients: maximal QRS duration > 160 ms (60 vs. 27%, P = 0.02), intrinsicoid deflection time > 80 ms (65 vs. 24%, P = 0.01), initial QRS slurring (40 vs. 12%, P = 0.04), QS pattern in lead V1 (90 vs. 36%, P < 0.001), and QRS axis > 90A degrees in limb leads (60 vs. 24%, P = 0.01). In the multivariate analysis, intrinsicoid deflection time > 80 ms [odds ratio (OR) = 9.9], QS pattern in lead V1 (OR = 28), and QRS axis > 90A degrees (OR = 5.7) remained independent predictors of early ARVC. The coupling interval did not differ between the two groups. In patients with RVOT VEBs and no major electrocardiographic or echocardiographic abnormalities, the ectopic QRS morphology aids in the differential diagnosis between idiopathic RVOT arrhythmias and early ARVC.