Long Qt Syndrome

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Contents 1 More Specific Terms 2 Epidemiology 3 Pathology 4 Genetics 5 Clinical-manifestations 6 Diagnostic-procedures 7 Complications 8 Management 9 More General Terms 10 Additional Terms 11 Internet Database 12 References

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)

Epidemiology

• uncommon
• more common in women than in men

Pathology

• disorder of myocardial repolarization

Genetics

• LTQ1: associated with mutation in KvLQ1 gene
• LTQ2: associated with mutation in HERG gene
• 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

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

• electrophysiological testing
• electrocardiogram: (scoring system for diagnosis)

• parameters

• degree of QT prolongation ( QTc > 530 ms)
• 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

Complications

• increased risk of torsades de pointes
• increased risk of sudden cardiac death

Management

• beta-blockers [2,3]

• non-selective beta-blockers generally recommend

• propranolol
• nadolol

• selective beta-1 antagonists may be equally effective

• atenolol
• metoprolol

• titrate to significantly blunt heart rate response during exercise

• cardioverter-defibrillator implantation
• surgical antiadrenergic therapy

More General Terms

• genetic disease of the heart
• cardiac conduction disorder

Additional Terms

• QT interval
• QT prolongation
• short QT syndrome

Internet Database

OMIM: 152427

References

1. Mayo Internal Medicine Board Review, 1998-99, Prakash UBS (ed) Lippincott-Raven, Philadelphia, 1998, pg 125
2. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
3. 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: [1]
4. Genedis; Note: congenital long QT syndrome website [2]

long QT syndrome