ECG Changes in Tetralogy of Fallot: Association with Right Ventricular Function, Early Age of Repair and Prematurity.

Tetralogy of Fallot (TOF) patients are at risk for long-term adverse events. Electrocardiogram (ECG) abnormalities may reflect ventricular maladaptation and predict complications. We investigated whether ECG changes correlated with cardiac magnetic resonance imaging (CMR) measures of right ventricular (RV) function and their prevalence in less mature myocardium (prematurity or early repair). This retrospective study included 219 TOF patients operated between 2000-01-01 and 2018-12-31. Parameters analyzed included PQ interval, QRS duration, dispersion, fragmentation, QTc, JTc, and right bundle branch block (RBBB) at predefined time points. In patients undergoing pulmonary valve replacement (PVR) with available CMR, measures of RV size and function were compared with ECG variables. Early repair was defined as < 3 months and prematurity < 37 weeks' gestation. Median age at follow-up was 12.3 years (IQR, 8.4;17), and 4.9 months (IQR, 3.4;6.9) at primary repair. PQ interval correlated with RV end-diastolic, stroke and regurgitant volume, whereas RBBB correlated with larger RV. Forty-five patients (21%) underwent early repair (median 2.3 months [IQR 1.3;2.7]) with no significant ECG differences. Forty-one patients (20%) were premature. Premature patients were older at repair versus term (5.8 months [IQR 4.1;7.3] vs. 4.5 months [IQR 3.0;6.3], p = 0.001) but weighed less (5.6 kg [SD 1.2] vs. 6.5 kg [SD 1.7], p = 0.001). PQ interval was shorter in premature patients at multiple time points. Neither prematurity nor early repair were associated with increased reintervention or PVR. These findings support an association between PQ interval and RV volume load. Shorter PQ intervals with prematurity may reflect stiff myocardium, with unknown long-term implications.