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.

Three-dimensional electroanatomic voltage mapping increases accuracy of diagnosing arrhythmogenic right ventricular cardiomyopathy/dysplasia.

BACKGROUND: Three-dimensional electroanatomic voltage mapping offers the potential to identify low-voltage areas that correspond to regions of right ventricular (RV) myocardial loss and fibrofatty replacement in patients with arrhythmogenic RV cardiomyopathy/dysplasia (ARVC/D). METHODS AND RESULTS: Thirty-one consecutive patients (22 men and 9 women; mean age, 30.8+/-7 years) who fulfilled the criteria of the Task Force of the European Society of Cardiology and International Society and Federation of Cardiology (ESC/ISFC) for ARVC/D diagnosis after noninvasive clinical evaluation underwent further invasive study including RV electroanatomic voltage mapping and endomyocardial biopsy (EMB) to validate the diagnosis. Multiple RV endocardial, bipolar electrograms (175+/-23) were sampled during sinus rhythm. Twenty patients (group A; 65%) had an abnormal RV electroanatomic voltage mapping showing > or =1 area (mean 2.25+/-0.7) with low-voltage values (bipolar electrogram amplitude <0.5 mV), surrounded by a border zone (0.5 to 1.5 mV) that transitioned into normal myocardium (>1.5 mV). Low-voltage electrograms appeared fractionated with significantly prolonged duration and delayed activation. In 11 patients (group B; 35%), electroanatomic voltage mapping was normal, with preserved electrogram voltage (4.4+/-0.7 mV) and duration (37.2+/-0.9 ms) throughout the RV. Low-voltage areas in patients from group A corresponded to echocardiographic/angiographic RV wall motion abnormalities and were significantly associated with myocyte loss and fibrofatty replacement at EMB (P<0.0001) and familial ARVC/D (P<0.0001). Patients from group B had sporadic disease and histopathological evidence of inflammatory cardiomyopathy (P<0.0001). During the time interval from onset of symptoms to the invasive study, 11 patients (55%) with electroanatomic low-voltage regions received an implantable cardioverter/defibrillator because of life-threatening ventricular arrhythmias, whereas all but 1 patient with a normal voltage map remained stable on antiarrhythmic drug therapy (P=0.02). CONCLUSIONS: Three-dimensional electroanatomic voltage mapping enhanced accuracy for diagnosing ARVC/D (1) by demonstrating low-voltage areas that were associated with fibrofatty myocardial replacement and (2) by identifying a subset of patients who fulfilled ESC/ISFC Task Force diagnostic criteria but showed a preserved electrogram voltage, an inflammatory cardiomyopathy mimicking ARVC/D, and a better arrhythmic outcome.