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CLINICAL STUDY: PEDIATRIC CARDIOLOGY

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

Luciano Daliento, MD, FESC, FACC^*,*, Antonio Franco Folino, MD, PhD^*, Liana Menti, MD^*, Pierluigi Zanco, MD, Maria Cristina Baratella, MD^* and Sergio Dalla Volta, MD^*

^* Department of Cardiology, University of Padua Medical School, Padua, Italy
Department of Nuclear Medicine, Castelfranco Hospital, Castelfranco Veneto, Italy

Manuscript received March 14, 2001; revised manuscript received August 13, 2001, accepted August 29, 2001.

^* Reprint requests and correspondence: Dr. Luciano Daliento, Department of Cardiology, University of Padua, Via Giustiniani, 2, 35128 Padova, Italy
luciano.daliento{at}unipd.it

OBJECTIVES

The study was done to define the role of the autonomic nervous system in postoperative tetralogy of Fallot.

BACKGROUND

Subsequent to surgical correction of tetralogy of Fallot, patients are at long-term risk of sudden death owing to ventricular electrical instability. 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 ¹²³I metaiodobenzylguanidine (MIBG) with tomographic imaging, combined with assessment of heart rate variability (HRV), to evaluate the 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 tachycardia or ventricular fibrillation.

RESULTS

Analysis of HRV revealed a reduction in vagal control and sympathetic dominance in all patients compared with a healthy control group of 20 subjects. A significant difference was found in the standard deviation of all the adjacent intervals between normal beats (SDNN) in patients with or without severe ventricular arrhythmias. A significant reduction in uptake of ¹²³I MIBG was demonstrated 30 min after IV injection, and a trend toward reduction after 5 h, associated with reduced washout indices. These data reflect a decrease in the number of nerve endings in the right and left ventricular walls, and an inhomogeneous distribution of the adrenergic nervous system. The uptake of MIBG was significantly reduced in the patients at risk of ventricular tachycardia or fibrillation.

CONCLUSIONS

Subsequent to surgical correction of tetralogy of Fallot, the positive correlation between myocardial uptake of MIBG, SDNN and the QRS dispersion confirmed the usefulness of analysis of the adrenergic nervous system to stratify patients at risk of life-threatening arrhythmias.

Abbreviations and Acronyms   ECG = electrocardiogram   FDG = F18-fluorodeoxyglucose   HRV = heart rate variability   MIBG = 123I metaiodobenzylguanidine   NN = normal beats   PET = positron emission tomography   pNN50 = percentage of adjacent (normal beats) intervals differing by more than 50 ms over the entire recording   QP = pulmonary blood flow   QS = systemic blood flow   RMSSD = square root of the mean of the sum of the square differences between adjacent NN intervals   SDNN = standard deviation of all the adjacent intervals between normal beats   SPECT = single-photon emission computed tomography

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