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The long QT syndrome in children. An international study of 287 patients
1Duke University Medical Center, NC 27710.
Insights
This study identifies key features of congenital long QT syndrome (LQTS) in children, highlighting risk factors for sudden death and effective treatments. Early identification and management are crucial for improving outcomes in pediatric LQTS patients.
Area of Science:
- Pediatric Cardiology
- Clinical Electrophysiology
- Genetics
Background:
- Long QT syndrome (LQTS) is a critical condition affecting children, necessitating a detailed understanding of its presentation and risk stratification.
- The Pediatric Electrophysiology Society initiated a study to characterize LQTS in patients under 21 years old.
Purpose of the Study:
- To describe the clinical features of LQTS in pediatric patients.
- To define distinct low-risk and high-risk subpopulations within this age group.
- To determine optimal therapeutic strategies for managing LQTS in children.
Main Methods:
- A multicenter study involving 287 pediatric patients (<21 years) diagnosed with LQTS.
- Inclusion criteria included QTc > 0.44, unexplained syncope/seizures/cardiac arrest, or family history of LQTS.
- Data collected included presenting symptoms, ECG findings (QTc, arrhythmias), family history, and treatment outcomes.
Main Results:
- Presenting symptoms varied, with 9% experiencing cardiac arrest, 26% syncope, and 10% seizures, often exercise-related.
- Significant findings included QTc > 0.60 in 13% and various ventricular arrhythmias in 16% of patients.
- Treatment was effective for symptoms in 76% and arrhythmias in 60%; propranolol showed no difference from other beta-blockers.
Conclusions:
- Specific ECG findings like 2:1 atrioventricular block and torsade de pointes are more common in pediatric LQTS, increasing suspicion.
- Prophylactic treatment may be indicated for asymptomatic children, especially those with a positive family history.
- Patients with QTc > 0.60 face high sudden death risk, warranting consideration of advanced therapies like cardiac sympathetic denervation or defibrillator implantation.
Background:
The Pediatric Electrophysiology Society studied children with the long QT syndrome (LQTS) to describe the features of LQTS in patients less than 21 years old, define potential "low-risk" and "high-risk" subpopulations, and determine optimal treatment.
Methods And Results:
Patients less than 21 years old were included if either QTc was more than 0.44; they had unexplained syncope, seizures, or cardiac arrest preceded by emotion or exercise; or family history of LQTS. We found 287 patients from 26 centers in seven countries. Mean +/- SD age at presentation was 6.8 +/- 5.6; 9% presented with cardiac arrest, 26% with syncope, and 10% with seizures. Of those with symptoms, 67% had symptoms related to exercise. Family history was positive for long QT interval in 39% and for sudden death in 31%. Hearing loss was present in 4.5%. A normal QTc was present in 6%, and QTc of more than 0.60 was in 13%. Atrioventricular block occurred in 5%, but 13 of 15 patients 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 ventricular contractions, 5% multiform premature ventricular contractions, 1% monomorphic ventricular tachycardia, and 6% torsade de pointes. Overall, treatment was effective for symptoms in 76% and for ventricular arrhythmias in 60%. There was no difference between propranolol and other beta-blockers in effective treatment. Left stellectomy was performed in nine patients, and defibrillators were implanted in four; no sudden death 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. Sudden death occurred in 8%; multivariate predictors of sudden death were length of QTc at presentation of more than 0.60 and medication noncompliance.
Conclusions:
The appearance of 2:1 atrioventricular block, multiform 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 presented with cardiac arrest and no preceding symptoms, perhaps prophylactic treatment in asymptomatic children is indicated. Asymptomatic patients with normal QTc and positive family history may be a low-risk group. Patients with QTc of more than 0.60 are at particularly high risk for sudden death, and if treatment is not effective, consideration should be given to cardiac sympathetic denervation, pacemaker implantation, and perhaps implantation of a defibrillator.