Makindo Medical Notes

Related Subjects: |ECG-QT interval |Brugada Syndrome |Long QT syndrome (LQTS) Acquired |Long QT syndrome (LQTS) Congenital |Torsades de Pointes |Ventricular Fibrillation |Ventricular Tachycardia |Resuscitation - Adult Tachycardia Algorithm |Automatic Implantable Cardioverter Defibrillator (AICD)

⚠️ Beta blockers (BBs) reduce sympathetic stimulation of cardiac ion channels and protect against arrhythmias, particularly in LQT1 and LQT2. They are first-line therapy for most congenital LQTS patients.

📌 About Long QT Syndrome (LQTS)

• A congenital cardiac channelopathy causing prolonged QT interval and risk of Torsades de Pointes or sudden cardiac death.
• Prevalence: ~1 in 2000; often under-recognised.

⚡ Torsades de Pointes

🧬 Aetiology

• Mutations in potassium, sodium, or calcium channels → delayed ventricular repolarisation.
• QT interval prolongation = substrate for polymorphic VT (torsades) and VF.

🔑 Types

• Romano-Ward: Autosomal dominant, QT prolongation + arrhythmias.
• Jervell & Lange-Nielsen: Autosomal recessive, associated with congenital deafness + higher arrhythmic risk.

📉 Risk Factors

• Increased sympathetic tone (exercise, stress, sudden loud noises).
• Electrolyte disturbance: ↓K⁺, ↓Mg²⁺, ↓Ca²⁺.
• QT-prolonging drugs (see CredibleMeds list).

🧪 Clinical Features

• Syncope (often during exercise, swimming, or emotional stress).
• Palpitations, cardiac arrest, or sudden unexplained death in family.
• May be asymptomatic and detected on ECG screening.

📊 Diagnostic Criteria (Schwartz Score)

• QTc >480 ms = +3 points
• Torsades de Pointes = +2
• Syncope with stress = +2; without stress = +1
• Congenital deafness = +0.5
• Family history of LQTS or sudden death <30 yrs = +0.5–1
• ≥4 points = high probability of LQTS

🧪 Investigations

• ECG: QTc prolongation; repeat if borderline.
• Bloods: FBC, U&E, Ca²⁺, Mg²⁺ to exclude secondary causes.
• Genetic testing: if clinical suspicion strong.

🩺 Management

• Drug avoidance: Stop QT-prolonging drugs, avoid electrolyte disturbance.
• Beta blockers: (propranolol, nadolol, atenolol) = cornerstone, esp. in LQT1.
• ICD: For survivors of cardiac arrest, recurrent syncope despite BBs, or QTc >550 ms with high-risk features.
• LCSD (Left Cervicothoracic Sympathectomy): Considered if recurrent events despite BB therapy and ICD not suitable.
• Lifestyle advice:
  • LQT1 → avoid swimming/strenuous exertion 🏊‍♂️
  • LQT2 → avoid sudden loud noises / alarms 🔔
  • All → avoid competitive sports unless risk-stratified by specialist

📚 Reference

• Management of Patients with Long QT Syndrome. Korean Circ J. 2016