Paeds · cardiology
Long-QT syndrome and channelopathies
Also known as LQTS · Long QT syndrome · Congenital long QT syndrome · Catecholaminergic polymorphic ventricular tachycardia · CPVT · Brugada syndrome · Inherited arrhythmia syndromes
Fellowship guide to long-QT syndrome and the inherited channelopathies in children: what a prolonged QTc means, the three cardinal genotypes (LQT1, LQT2, LQT3) and their trigger-specific biology, the Schwartz diagnostic score, the syncope-or-seizure child who needs a 12-lead ECG, beta-blocker-first management, left cardiac sympathetic denervation and ICD thresholds, and the related entities CPVT, Brugada syndrome and short-QT syndrome, with the AHA/HRS, ESC and CSANZ guideline positions.
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Target exams
Red flags
- A child with syncope during exercise, swimming, emotional stress, or on waking from sleep needs a 12-lead ECG before being labelled vasovagal or epileptic — channelopathy is the missed diagnosis that kills
- A QTc above 500 milliseconds confers high risk of arrhythmic events regardless of symptoms — do not delay beta-blocker initiation and specialist referral
- Catecholaminergic polymorphic ventricular tachycardia (CPVT) has a normal resting ECG and a structurally normal heart — bidirectional or polymorphic VT during exercise testing betrays it; an untriggered exercise ECG in an at-risk child is a missed CPVT
- Beta-blockers are effective in LQT1 and LQT2 but markedly less so in LQT3 — genotype guides intensity of therapy and the ICD threshold
- A child who has a breakthrough arrhythmic event on maximally tolerated beta-blockers needs escalation to left cardiac sympathetic denervation or an implantable cardioverter defibrillator — do not simply increase the dose
Life stages
Care settings
Clinical exam formats
Board mappings
- Cardiology
- Inherited arrhythmia syndromes
- Long-QT syndrome
- Paediatric Cardiology — inherited channelopathies
- General Paediatrics learning goal — recognise syncope due to arrhythmia
- Genotype-specific management and lifelong surveillance
- Clinical Applications
- Long Cases
- Short Cases
- Communication scenarios
- Cardiology: recognises and manages inherited arrhythmia syndromes
- Syncope: distinguishing arrhythmic from vasovagal
- Lifelong follow-up and genetic counselling
- Foundation of Practice (FOP)
- Applied Knowledge in Practice (AKP)
- Clinical
- History
- Communication
- Cardiovascular examination and ECG interpretation
- General Pediatrics Content Outline — Domain 9: Cardiology
- Subspecialty: Pediatric Cardiology — inherited arrhythmias
- Sudden cardiac death risk stratification
- Patient Care 1: History and Physical Examination
- Patient Care 4: Clinical Reasoning
- Medical Knowledge 1: Clinical Knowledge of inherited arrhythmia syndromes
- Systems-Based Practice 1: multidisciplinary cardiac genetic care
- Medical Expert
- Collaborator
- Pediatrics: Core EPA — recognise and stabilise inherited arrhythmia
Overview & Definition
Picture the eight-year-old girl brought to the emergency department after collapsing during a school swimming carnival — she was pulled from the pool unconscious, briefly stiffened, and recovered fully within minutes. Her mother, who has fainted "all her life," wonders whether this was a fit. The triage label says "vasovagal or seizure — query epilepsy." That child carries the whole story of long-QT syndrome: an arrhythmic collapse triggered by exertion, mislabelled as a seizure or a faint, in a family with a heritable tendency to sudden death. One twelve-lead ECG, read for the QT interval, would have changed everything. [1] [2]
Long-QT syndrome is the commonest inherited cardiac arrhythmia syndrome, with a prevalence of about one in two thousand individuals. It is defined by prolongation of the corrected QT interval on the surface electrocardiogram, reflecting delayed repolarisation of the ventricular myocardium. The delayed repolarisation creates a vulnerable window in which early afterdepolarisations can arise, triggering the characteristic polymorphic ventricular tachycardia known as torsades de pointes, which may terminate spontaneously as a faint or progress to ventricular fibrillation and sudden cardiac death. [2] [10]
The clinical importance of LQTS rests on three facts. It is treatable: beta-blockers reduce events by roughly two-thirds and more aggressive therapy is available for the high-risk subset. It is under-diagnosed: syncope during exertion or emotion is routinely mislabelled as vasovagal or epileptic, and the first presentation in a family is sometimes the proband's sudden death. And it is heritable in an autosomal dominant pattern, so a diagnosis in one person carries implications for first-degree relatives who may be asymptomatic but at risk. [1] [6]
References15ShowHide
- [1]Schwartz PJ, Moss AJ, Vincent GM, Crampton RS Diagnostic criteria for the long QT syndrome. An update. Circulation, 1993.PMID 8339437
- [2]Abrams DJ, Macrae CA Long QT syndrome. Circulation, 2014.PMID 24709866
- [3]Napolitano C, Priori SG, Schwartz PJ, et al. Genetic testing in the long QT syndrome: development and validation of an efficient approach to genotyping in clinical practice. JAMA, 2005.PMID 16414944
- [4]Priori SG, Wilde AA, Horie M, Cho Y, Behr ER, et al. HRS/EHRA/APHRS expert consensus statement on the diagnosis and management of patients with inherited primary arrhythmia syndromes. Heart Rhythm, 2013.PMID 24011539
- [5]Moss AJ, Zareba W, Hall WJ, Schwartz PJ, Crampton RS, et al. Effectiveness and limitations of beta-blocker therapy in congenital long-QT syndrome. Circulation, 2000.PMID 10673253
- [6]Bagnall RD, Weintraub RG, Ingles J, Duflou J, Yeates L, et al. A prospective study of sudden cardiac death among children and young adults. N Engl J Med, 2016.PMID 27332903
- [7]Vyas H, Ackerman MJ Epinephrine QT stress testing in congenital long QT syndrome. Circulation, 2006.PMID 16962127
- [8]Schwartz PJ, Priori SG, Cerrone M, Spazzolini C, Odero A, et al. Left cardiac sympathetic denervation in the management of high-risk patients affected by the long-QT syndrome. Circulation, 2004.PMID 15051644
- [9]Priori SG, Blomström-Lundqvist C, Mazzanti A, Blom N, Borggrefe M, et al. 2015 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. Europace, 2015.PMID 26318695
- [10]Goldenberg I, Moss AJ Long QT syndrome. J Am Coll Cardiol, 2008.PMID 18549912
- [11]Crotti L, Johnson CN, Graf E, et al. Calmodulin mutations associated with recurrent cardiac arrest in infants. Circulation, 2013.PMID 23388215
- [12]Cerrone M, Priori SG A clinical approach to inherited arrhythmias. Circ Cardiovasc Genet, 2012.PMID 23074337
- [13]Bhuiyan ZA, van den Berg MP, van Tintelen JP, et al. Expanding spectrum of human RYR2-related disease: new electrocardiographic, structural, and genetic features. Circulation, 2007.PMID 17875969
- [14]Kawada S, Morita H, Antzelevitch C, et al. Shanghai Score System for Diagnosis of Brugada Syndrome: validation of the score system and system reclassification of patients. JACC Clin Electrophysiol, 2018.PMID 29929664
- [15]Providência R, Karim N, Srinivasan N, et al. Impact of QTc formulae in the prevalence of short corrected QT interval and impact on probability of diagnosis of short QT syndrome. Heart, 2018.PMID 28954836