Changes during exercise of ECG intervals related to increased risk for ventricular arrhythmia in repaired tetralogy of Fallot and their relationship to right ventricular size and function
Purpose: Our study aimed to assess pro-arrhythmogenic electrocardiographic changes during maximal physical exercise in patients operated for Tetralogy of Fallot (TOF). Methods: TOF patients prospectively underwent: 1) bicycle ergometry, 2) cardiac MRI, and 3) 24-hour Holter. ECG data was analyzed at rest, at 60% of peak exercise and at peak exercise. R-R duration, QRS-, QT- and JT-duration and dispersions were assessed. Changes of ECG parameters during exercise were calculated and correlated to RV volume, RVEF, RV wall-mass, PR-percentage and VO2max. Exercise ECG data from healthy controls were used as reference. Results: Thirty-one patients (mean age at repair (SD) 0.8 (0.5) years, age at study 16 (5) years) and 25 controls (age 12 (2) years) were included. With exercise mean QTc and JTc dispersions increased in patients (p < 0.001), but not in controls. At peak exercise JTc dispersion was larger in patients (p < 0.01). QTc did not change with exercise in patients (p = 0.14) and decreased in controls (p < 0.05). At all levels of exercise mean QTc, QRS and QRS dispersion were larger in patients (all p < 0.001). Significant associations were found for; 1) a larger increase of JTc dispersion with a higher PR-percentage, a larger RV volume, a larger RV wall-mass, 2) a larger QTc increase with a larger RV volume and worse RVEF. Conclusion: During physical exercise inhomogeneity of repolarisation, known to predispose for re-entry ventricular arrhythmia, increases in repaired TOF. Larger inhomogeneity is found with more severe PR.