Differential diagnosis between idiopathic right ventricular outflow tract tachycardia and arrhythmogenic right ventricular cardiomyopathy/dysplasia by 3-D electroanatomic voltage mapping of the right ventricle

Abstract

Differential diagnosis between idiopathic right ventricular outflow tract (RVOT) tachycardia and minor and/or early form of arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is challenging. We assessed whether 3-D electroanatomic mapping, because its ability to detect low-voltage areas that correspond to regions of RV fibrofatty replacement, can differentiate between the two conditions. The study population comprised 24 consecutive patients (13 males and 11 females, mean age 34±11 years) with recurrent ventricular tachycardia (VT) originating from the RVOT, and without echocardiographic evidence of RV dilatation/dysfunction. 3-D geometry of the RV depicting the peak-to-peak amplitude of the bipolar electrograms recorded at multiple endocardial sites was constructed in real-time. Activation mapping showed that all VTs arose from the RVOT: anteroseptally in 11, anterolaterally in 9, posterolaterally in 3, and close to the His bundle in one. Voltage mapping was normal in 17 of 24 patients (70%, Group A), with electrogram voltage > 1.5 mV throughout the RV. The other 7 patients (30%, Group B), had abnormal voltage mapping showing 2±1.4 areas with bipolar electrogram amplitude <0.5 mV (scar). Two patients from Group B had abnormalities limited to the RVOT, whereas in the other 5 the disease also involved the anterior (4 patients), the inferobasal (3 patients), and the apical (2 patients) regions. Independent predictors of electroanatomic scars were right precordial QRS prolongation (p<0.001) and inducibility at programmed ventricular stimulation (p <0.01). Catheter ablation successfully eliminated VT in 13 of 15 patients. During a follow-up of 26±9 months, 3 out of 7 patients (57%) from Group B received an ICD after having experienced syncope or cardiac arrest, whereas all patients from Group A had an uneventful outcome (p=0.02). Electroanatomic RV scars were detected in nearly 30% of patients with RVOT tachycardia, suggesting an underlying early/minor form of ARVC/D at risk of lifethreatening arrhythmic events.