Clinical Research
Heart Rhythm Disorder
Three-Dimensional Electroanatomical Voltage Mapping and Histologic Evaluation of Myocardial Substrate in Right Ventricular Outflow Tract Tachycardia

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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.

Abbreviations and Acronyms

ARVC/D
arrhythmogenic right ventricular cardiomyopathy/dysplasia
CMR
cardiac magnetic resonance
EMB
endomyocardial biopsy
EVM
electroanatomical voltage mapping
LV
left ventricle/ventricular
RV
right ventricle/ventricular
RVOT
right ventricular outflow tract
SAECG
signal-averaged electrocardiogram
VT
ventricular tachycardia

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This study was supported by the Ministry of Health, Rome, Italy; the CARIPARO Foundation, Padua, Italy; the Veneto Region, Venice, Italy; and the European Community research contract # QLG1 CT-2000 01091.