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The congenital long QT syndromes in childhood
R G Weintraub1, R M Gow, J L Wilkinson
1Department of Cardiology, Royal Children's Hospital, Melbourne, Victoria, Australia.
Insights
Congenital long QT syndrome in children is serious, with a 4.5% annual mortality rate. Early diagnosis and monitoring with Holter and exercise tests are crucial for managing this condition.
Area of Science:
- Pediatric Cardiology
- Clinical Electrophysiology
- Genetic Cardiovascular Diseases
Background:
- Congenital long QT syndrome (LQTS) is a rare genetic disorder affecting cardiac repolarization.
- It predisposes individuals to life-threatening ventricular arrhythmias and sudden cardiac death.
- Early identification and management are critical in pediatric populations.
Purpose of the Study:
- To evaluate the clinical characteristics, mortality, and diagnostic utility of Holter monitoring and exercise testing in children with congenital LQTS.
- To assess the effectiveness of conventional therapy in this pediatric cohort.
Main Methods:
- Retrospective analysis of 23 pediatric patients diagnosed with congenital LQTS.
- Review of clinical history, symptoms, family history, and treatment responses.
- Analysis of treadmill exercise tests and ambulatory Holter electrocardiographic monitoring data.
Main Results:
- A significant proportion (61%) had a family history of LQTS.
- Syncope was the most common initial symptom (69%).
- The overall mortality rate was 4.5% per year, with younger patients and those unresponsive to beta-blockers experiencing higher mortality.
- Exercise testing revealed significant QTc interval prolongation during recovery.
- Holter monitoring identified characteristic T-wave changes, including T-wave alternations in non-survivors.
Conclusions:
- Congenital LQTS carries a substantial mortality risk in childhood, even with standard treatment.
- Ambulatory Holter monitoring and treadmill exercise testing are valuable tools for diagnosis and treatment monitoring in pediatric LQTS.
- Younger age at diagnosis is a risk factor for poor outcomes.
Abstract:
Twenty-three children and young persons with a congenital long QT syndrome were identified; the median age at the time of referral was 10 years (range 4 days to 19 years) and 14 patients (61%) had a family history of the syndrome. Among the 19 patients with symptoms, the initial symptom was syncope in 13 (69%), aborted sudden death in 5 (26%) and near drowning in 1 (5%). There were three deaths during a combined follow-up period of 67 patient-years (average annual mortality rate 4.5%). Patients who did not respond to therapy with a beta-adrenergic blocker and those who died were significantly younger than the remaining patients at the time of diagnosis (p less than or equal to 0.05 for both). Analysis of 44 treadmill exercise tests performed by 16 patients revealed significant prolongation of the median corrected QT (QTc) interval in response to exercise, with maximal prolongation present after 2 min of recovery (median QTc interval 0.52 s versus a baseline value of 0.47 s, p less than 0.001). Characteristic changes in T wave configuration were noted in 8 of 15 patients on at least one occasion during ambulatory Holter electrocardiographic monitoring, including T wave alternation in two patients, both of whom died shortly afterward. It is suggested that the congenital long QT syndrome is associated with a significant mortality rate in childhood despite the use of conventional therapy in symptomatic patients. Ambulatory Holter monitoring and treadmill exercise testing may be helpful, both in confirming the diagnosis of a long QT syndrome and in monitoring the adequacy of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)