Adrenergic nervous activity in patients after surgical correction of tetralogy of fallot

OBJECTIVES The study was done to define the role of the autonomic nervous s ystem in postoperative tetralogy of Fallot. BACKGROUND Subsequent to surgical correction of tetralogy of Fallot, patien ts are at long-term risk of sudden death owing to ventricular electrical in stability. The status of the sympathetic nervous system in these patients, known to play an important role in other patients at risk, remains unknown. METHODS We used I-123 metaiodobenzylguanidine (MIBG) with tomographic imagi ng, combined with assessment of heart rate variability (HRV), to evaluate t he activity of the sympathetic nervous system. We analyzed 22 patients who had undergone total correction of tetralogy of Fallot: 13 with either no or minor ventricular arrhythmias, and 9 with sustained ventricular tachycardi a or ventricular fibrillation. RESULTS Analysis of HRV revealed a reduction in vagal control and sympathet ic dominance in all patients compared with a healthy control group of 20 su bjects. A significant difference was found in the standard deviation of all the adjacent intervals between normal beats (SDNN) in patients with or wit hout severe ventricular arrhythmias. A significant reduction in uptake of I -123 MIBG was demonstrated 30 min after IV injection, and a trend toward re duction after 5 h, associated with reduced washout indices. These data refl ect a decrease in the number of nerve endings in the right and left ventric ular walls, and an inhomogeneous distribution of the adrenergic nervous sys tem. The uptake of MIBG was significantly reduced in the patients at risk o f ventricular tachycardia or fibrillation. CONCLUSIONS Subsequent to surgical correction of tetralogy of Fallot, the p ositive correlation between myocardial uptake of MIBG, SDNN and the QRS dis persion confirmed the usefulness of analysis of the adrenergic nervous syst em to stratify patients at risk of life-threatening arrhythmias. (J Am Coll Cardiol 2001;38:2043-7) (C) 2001 by the American College of Cardiology.