long QT syndrome
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Etiology
- some are inherited
- most are acquired
- risk factors
- hypokalemia, hypomagnesemia
- structural heart disease
- medications
- risk factors
Epidemiology
- uncommon
- more common in women than in men
Pathology
- disorder of myocardial repolarization
Genetics
- LTQ1: associated with mutation in KvLQ1 gene
- pathogenic variant of the C-terminus[5]
- LTQ2: associated with mutation in HERG gene[5]
- LTQ3: associated with mutation in SCN5A gene
- LTQ4: associated with mutation in ANK2 gene
- LTQ5: associated with mutation in KCNE1 gene
- LTQ6: associated with mutation in KCNE2 gene
- LTQ7: associated with mutation in KCNJ2 gene
- aLQTS: (acquired) defects in ALG10B may reduce susceptibility
* referral for electrophysiological testing takes preference to genotyping[2]
Clinical manifestations
- occurrence of symptoms in otherwise young healthy patients
- syncope - often follows stressful situation
- seizures
- sudden death
- congenital deafness
- family members with long QT syndrome or history of sudden death at a young age
Diagnostic procedures
- electrocardiogram: (scoring system for diagnosis)
- parameters
- degree of QT prolongation (QTc > 530 msec)*
- torsades de pointes
- T-wave alternans
- notched T-waves in 3 leads
- low heart rate relative to age
- possible scores: 0-9
- < 2 low probability
- 2-3 intermediate probability
- > 3 high probability
- parameters
- electrophysiological testing (referral)[2]
* QTc > 460 msec, > 500 msec[2]
Complications
- increased risk of torsades de pointes*
- increased risk of sudden cardiac death*
* risk increased with physical or emotional stress
Management
- beta-blockers[2][3][6]
- symptomatic without history of syncope
- non-selective beta-blockers generally recommended
- selective beta-1 antagonists may be equally effective
- titrate to significantly blunt heart rate response during exercise
- amiodarone is contraindicated as it may further increase the QTc interval
- cardioverter-defibrillator implantation
- survivors of cardiac arrest
- recurrent syncope while taking beta-blocker
- QTc interval > 500 msec
- surgical antiadrenergic therapy
- exercise restriction[2]
More general terms
More specific terms
- long QT syndrome type 1 (LQT1, Romano-Ward syndrome)
- long QT syndrome type 2
- long QT syndrome type 3
- long QT syndrome type 4 (sick sinus syndrome with bradycardia)
- long QT syndrome type 5
- long QT syndrome type 6
- long QT syndrome type 7 (Andersen syndrome, Andersen cardiodysrhythmic periodic paralysis, LQT7)
- long QT syndrome type 9
- long QT syndrome type 10
- long QT syndrome type 11 (LQT11)
- long QT syndrome type 14 (LQT14)
- long QT syndrome type 14 (LQT15)
Additional terms
References
- ↑ Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 125
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17, 18, 19. American College of Physicians, Philadelphia 1998, 2012, 2015, 2018, 2023.
- ↑ 3.0 3.1 Hobbs JB et al, Risk of aborted cardiac arrest or sudden cardiac death during adolescence in the long-QT syndrome. JAMA 2006, 296:1249 PMID: https://www.ncbi.nlm.nih.gov/pubmed/16968849
- ↑ Goldenberg I, Moss AJ. Long QT syndrome. J Am Coll Cardiol. 2008 Jun 17;51(24):2291-300. PMID: https://www.ncbi.nlm.nih.gov/pubmed/18549912
- ↑ 5.0 5.1 5.2 Shimizu W, Makimoto H, Yamagata K et al Association of Genetic and Clinical Aspects of Congenital Long QT Syndrome With Life-Threatening Arrhythmias in Japanese Patients. JAMA Cardiol. Published online February 13, 2019 PMID: https://www.ncbi.nlm.nih.gov/pubmed/30758498 https://jamanetwork.com/journals/jamacardiology/fullarticle/2724694
Zareba W Sex and Genotype in Long QT Syndrome Risk Stratification. JAMA Cardiol. Published online February 13, 2019 PMID: https://www.ncbi.nlm.nih.gov/pubmed/30758500 https://jamanetwork.com/journals/jamacardiology/fullarticle/2724693 - ↑ 6.0 6.1 European Society of Cardiology Ventricular Arrhythmia Clinical Practice Guidelines (ESC, 2022) Medscape. Sept 30, 2022 https://reference.medscape.com/viewarticle/981520
Zeppenfeld K, Tfelt-Hansen J, de Riva M et al 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death. European Heart Journal, Volume 43, Issue 40, 21 October 2022, Pages 3997-4126 PMID: https://www.ncbi.nlm.nih.gov/pubmed/36017572 https://academic.oup.com/eurheartj/article/43/40/3997/6675633 - ↑ Roden DM Clinical practice. Long-QT syndrome. N Engl J Med 2008;358:169-76. PMID: https://www.ncbi.nlm.nih.gov/pubmed/18184962 https://www.nejm.org/doi/pdf/10.1056/NEJMcp0706513
- ↑ Genedis; Note: congenital long QT syndrome website http://www.tau.ac.il/lifesci/bioinfo/genedis/heart/long_qt.html