THE LONG QT SYNDROME IN CHILDREN - AN INTERNATIONAL STUDY OF 287 PATIENTS

Background. The Pediatric Electrophysiology Society studied children w ith the long QT syndrome (LQTS) to describe the features of LQTS in pa tients less than 21 years old, define potential ''low-risk'' and ''hig h-risk'' subpopulations, and determine optimal treatment. Methods and Results. Patients less than 21 years old were included if either QT(c) was more than 0.44; they had unexplained syncope, seizures, or cardia c arrest preceded by emotion or exercise; or family history of LQTS. W e found 287 patients from 26 centers in seven countries. Mean +/- SD a ge at presentation was 6.8 +/- 5.6; 9% presented with cardiac arrest, 26% with syncope, and 10% with seizures. Of those with symptoms, 67% h ad symptoms related to exercise. Family history was positive for long QT interval in 39% and for sudden death in 31%. Hearing loss was prese nt in 4.5%. A normal QT(c) was present in 6%, and QT(c) of more than 0 .60 was in 13%. Atrioventricular block occurred in 5%, but 13 of 15 pa tients had second-degree atrioventricular block (2:1), and only two of 287 had complete atrioventricular block. Ventricular arrhythmias were found on 16% of initial routine ECGs: 4% uniform premature ventricula r contractions, 5% multiform premature ventricular contractions, 1% mo nomorphic ventricular tachycardia, and 6% torsade de pointes. Overall, treatment was effective for symptoms in 76% and for ventricular arrhy thmias in 60%. There was no difference between propranolol and other b eta-blockers in effective treatment. Left stellectomy was performed in nine patients, and defibrillators were implanted in four, no sudden d eath occurred in these 13 patients. In follow-up (duration, 5.0 +/- 4 years; age, 10.9 +/- 6.3 years), 5% had cardiac arrest, 4% had syncope , and 1% had seizures. The two multivariate predictors of symptoms at follow-up were symptoms at presentation and propranolol failure. Sudde n death occurred in 8%; multivariate predictors of sudden death were l ength of QT(c) at presentation of more than 0.60 and medication noncom pliance. Conclusions. The appearance of 2:1 atrioventricular block, mu ltiform premature ventricular contractions, and torsade de pointes are relatively more common in children with LQTS than other children and should raise the index of suspicion for LQTS. Because 9% of patients p resented with cardiac arrest and no preceding symptoms, perhaps prophy lactic treatment in asymptomatic children is indicated. Asymptomatic p atients with normal QT(c) and positive family history may be a low-ris k group. Patients with QT(c) of more than 0.60 are at particularly hig h risk for sudden death, and if treatment is not effective, considerat ion should be given to cardiac sympathetic denervation, pacemaker impl antation, and perhaps implantation of a defibrillator.