Three-dimensional electroanatomical voltage mapping and histologic evaluation of myocardial substrate in right ventricular outflow tract tachycardia.

OBJECTIVES: We tested whether 3-dimensional electroanatomical voltage mapping (EVM) may help in the differential diagnosis between idiopathic right ventricular outflow tract (RVOT) tachycardia and arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D). BACKGROUND: Right ventricular EVM has been demonstrated to reliably identify low-voltage regions ("electroanatomical scar"), which in patients with ARVC/D correspond to areas of fibrofatty myocardial replacement. METHODS: The study population comprised 27 patients (15 men and 12 women, age 33.9 +/- 8 years) with RVOT tachycardia and no echocardiographic/angiographic evidence of right ventricular (RV) dilation/dysfunction, who underwent EVM and endomyocardial biopsy (EMB) for characterization of ventricular tachycardia (VT) substrate before catheter ablation. RESULTS: Electroanatomical voltage mapping was normal in 20 of 27 patients (74%, group A), with electrogram voltage >1.5 mV throughout the RV. The other 7 patients (26%, group B) showed >/=1 (1.4 +/- 07) RV electroanatomical scar area(s) (bipolar voltage <0.5 mV) that correlated with fibrofatty myocardial replacement at EMB (p < 0.001). Clinical predictors of RV scar were right precordial QRS prolongation (p < 0.001) and VT inducibility (p = 0.001). Catheter ablation successfully eliminated VT in 18 of 20 patients (90%). During a follow-up of 41 +/- 8 months, 3 of 7 patients (43%) from group B received an implantable defibrillator because of life-threatening ventricular arrhythmias, compared with no patients from group A (p = 0.016). CONCLUSIONS: An early/minor form of ARVC/D may mimic idiopathic RVOT tachycardia. Electroanatomical voltage mapping is able to identify RVOT tachycardia due to concealed ARVC/D by detecting RVOT electroanatomical scars that correlate with fibrofatty myocardial replacement at EMB and predispose to sudden arrhythmic death.