Background: Several studies have demonstrated the importance of mechanoelectrical interaction in patients with surgically corrected tetralogy of Fallot. However, the significance of atrioventricular conduction disturbance, that is PR interval prolongation, on adverse cardiac events in those patients remains to be elucidated.
Methods: We examined electrocardiograms at baseline and their temporal change in a total of 176 patients with repaired tetralogy of Fallot (49% men; median age, 17.4 years). Then, we evaluated their correlation with right ventricular volume and function measured by cardiac magnetic resonance and the significance as a risk factor of adverse cardiac events: lethal ventricular arrhythmias, atrial arrhythmias, heart failure hospitalization, complete atrioventricular block (AVB), and all-cause death.
Results: First-degree AVB was noted in 25 patients (14%). During a median follow-up of 10.0 (5.0-14.2) years, there was a progressive prolongation of PR interval (2.00±3.99 ms/y). Importantly, there were significant correlations between PR interval prolongation and right ventricular enlargement or right ventricular dysfunction. In contrast, in patients who underwent pulmonary valve replacement (n=23), significant shortening of PR interval by pulmonary valve replacement was noted (204±32 versus 176±34 ms; P=0.007). Cox regression analysis showed that first-degree AVB was an independent risk factor for lethal ventricular arrhythmias (hazard ratio, 5.479; 95% CI, 1.181-25.42; P=0.030) and complete AVB (hazard ratio, 27.67; 95% CI, 4.152-184.3; P<0.001) and had a tendency for heart failure hospitalization (hazard ratio, 3.301; 95% CI, 0.864-11.80; P=0.069). In addition, PR interval prolongation >2 ms/y was also a significant risk factor for lethal ventricular arrhythmias, regardless of the presence or absence of first-degree AVB at enrollment (hazard ratio, 24.18; 95% CI, 2.080-281.1; P=0.011).
Conclusions: These results indicate that progressive atrioventricular conduction disturbance is correlated with right ventricular enlargement and could be a useful predictor for increased risk of lethal ventricular arrhythmias in patients with repaired tetralogy of Fallot.
Keywords: Tetralogy of Fallot; atrioventricular block; electrocardiography; heart failure; sudden cardiac death; ventricular tachycardia.