Preoperative Atrial Electrophysiology in Pediatric Tetralogy of Fallot Compared with Ventricular Septal Defect

BACKGROUND: Atrial arrhythmias are common after tetralogy of Fallot (TOF) repair but rare following ventricular septal defect (VSD) repair. While postoperative factors may contribute, preoperative electrophysiological differences could also underlie this different arrhythmia risk. OBJECTIVE: To compare preoperative atrial electrophysiology between pediatric patients with TOF and VSD. METHODS: Intraoperative epicardial mapping was performed in the atria (right atrium (RA), left atrium (LA), pulmonary vein (PV) and Bachmann's Bundle (BB)) of 26 TOF and 41 VSD children. Potential voltage and morphology, as well as conduction properties were analyzed. RESULTS: Despite a lower prevalence of LA dilatation in TOF patients than VSD patients (29% vs 81%, p = 0.004), TOF exhibited lower potential voltages in the LA and PV (LA: 3.4±1.7mV vs 5.3±2.5mV; PV: 1.8 (1.1, 5.6)mV vs 4.7 (1.4, 8.9) mV, both p<0.01) with more low-voltage areas (LA: 12.9 (0.0, 53.7)% vs 4.4 (0.0, 29.0)%; PV: 23.9 (3.6, 47.0)% vs 7.0 (0.0, 35.9)%, both p<0.01), a higher prevalence of conduction block (LA: 0.6 (0.0, 6.5)% vs 0.0 (0.0, 1.2)%, p<0.001) and potentials containing 2 deflections (short double potentials (LA: 12.1 (0.5, 41.8)% vs 8.8 (1.3, 18.9)%, p=0.032); long double potentials (LA: 0.1 (0.0, 13.8)% vs 0.0 (0.0, 2.2)%, p=0.034)). CONCLUSION: Pediatric TOF patients have particularly at the LA and PV more atrial electrophysiological abnormalities than VSD patients, suggesting that atrial electrophysiological alterations at these sites are more pronounced in TOF patients.