Stress-induced ventricular arrhythmia after repair of tetralogy of fallot

The combination of ventricular arrhythmias found on routine electrocardiography at rest and elevated right ventricular pressures may be associated with sudden death in patients after repair of tetralogy of Fallot. In this study data were reviewed from 104 patients who underwent treadmill exercise testing with a modified Bruce protocol at a mean age of 13.8 years, an average of 7 years after repair of tetralogy of Fallot. The frequency and form of ventricular arrhythmias as manifested in an electrocardiogram at rest as well as before, during and after treadmill exercise tests were tabulated for each patient. Cardiac catheterizatlon was performed within 1 week of the treadmill test in 82 of the 104 patients and the right ventricular systolic pressure, right ventricular end-diastolic pressure, pulmonary arterial systolic pressure and pulmonary to systemic flow ($\text{Qp}\text{Qs}$) ratio were compared in patients with and without ventricular arrhythmias. In 15 (14 percent) of the 104 patients, ventricular arrhythmia was evident in the electrocardiogram at rest and in 31 (30 percent) it was induced by treadmill exercise; 5 of the 15 with arrhythmia at rest had no arrhythmia during exercise. Compared with the remaining 73 patients, the 31 patients who had ventricular arrhythmias during treadmill testing (1) were older (16.2 versus 12.8 years, p < 0.01, t test) and were tested at a longer interval after repair of tetralogy of Fallot, (2) had greater right ventricular systolic pressure (52.7 versus 41.3 mm Hg, p < 0.005), (3) had greater right ventricular end-diastolic pressure (8.0 versus 6.1 mm Hg, p < 0.001), and (4) had no difference in pulmonary arterial systolic pressure or $\text{Qp}\text{Qs}$ ratio. Uniform premature ventricular complexes were found in 28 patients, multiform premature ventricular complexes in two and ventricular tachycardia in one. Patients whose ventricular arrhythmia appeared with exercise had similar hemodynamic findings to-those whose arrhythmia disappeared with exercise. Two patients, each with elevated right ventricular systolic pressure and multiform premature ventricular complexes, had cardiac arrest at home.It is concluded that (1) treadmill exercise testing is a sensitive method for detecting ventricular arrhythmia in patients after repair of tetralogy of Fallot; (2) ventricular arrhythmia during treadmill exercise is related to abnormal hemodynamic status; (3) multiform premature ventricular complexes, couplets or ventricular tachycardia with exercise testing are highly associated with abnormal hemodynamic status and sudden death; (4) suppression of ventricular arrhythmia with exercise is neither the characteristic nor necessarily the benign response in these patients; and (5) ventricular arrhythmia may be a late developing phenomenon and may increase with longer postoperative intervals. Patients after repair of tetralogy of Fallot should be treated for ventricular arrhythmia detected in the electrocardiogram at rest or during treadmill exercise testing.