Role of Right Ventricular Three-dimensional Electroanatomic Voltage Mapping for Arrhythmic Risk Stratification of Patients with Corrected Tetralogy of Fallot or Other Congenital Heart Disease Involving the Right Ventricular Outflow Tract

Background: The post-surgical history of repaired congenital heart disease (rCHD), in particular tetralogy of Fallot (TOF), is often complicated by sudden death. Electrical myocardial abnormalities could be a substrate for malignant ventricular arrhythmias.

Methods And Results: 146 patients with TOF or other rCHD involving a subpulmonary right ventricle, considered to be at high arrhythmic risk, underwent right ventricular (RV) electroanatomic voltage mapping (EVM). Maps showed endocardial scars (<0.5mV) in all cases, mainly involving the RV outflow tract (n=141, 96.6%). In 28 cases (19.2%), other areas were involved. Total scar extension, expressed as % of total endocardial area, was significantly higher in patients with QRS ≥180ms [4.5% (±2.5) vs 2.8% (±2.4), p=0.014], left and right ventricular systolic dysfunction [4.5% (±3.2) vs 2.8% (±2.3), p=0.016 and 3.5% (±3.0) vs 2.6% (±1.9), p=0.03, respectively], premature ventricular contractions (PVCs) [3.2% (±2.6) vs 2.2% (±1.8), p<0.05], exercise-induced PVCs [3.8% (±2.4) vs 2.6% (±2.2), p=0.01], previous shunt [4.0% (±2.7) vs 2.6% (±2.2), p=0.01] and reintervention [4.2% (±3.2) vs 2.6% (±2.0), p=0.008]. Scar size also showed a positive correlation with duration of post-surgical follow-up (ρ=0.01), age at correction (ρ=0.01) and absolute QRS duration (ρ=0.05).

Conclusions: Patients with rCHD involving the right ventricle show electrical scars with variable distribution, not necessarily matching with sites of surgical lesions. Scar extension correlates with some of the risk factors for life-threatening arrhythmias in CHD, such as prolonged QRS. Thus EVM could be considered an additional tool in the assessment of risk stratification in this particular population.