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) work by mitigating the adverse effects of sympathetic stimulation on membrane ion channels, reducing the risk of arrhythmias, particularly in Long QT Types 1 and 2.

About Long QT Syndrome (LQTS)

• Long QT Syndrome (LQTS) is a rare congenital cardiac channelopathy, characterized by a prolonged QT interval on an ECG, increasing the risk of life-threatening arrhythmias.

Torsades de Pointes

Aetiology

• Caused by mutations in genes encoding cardiac potassium, sodium, or calcium ion channels, leading to prolonged QT interval and increased risk for arrhythmias.
• The QT interval reflects ventricular repolarization; when prolonged, it can serve as a substrate for arrhythmias.
• Increased risk of developing polymorphic ventricular tachycardia (Torsades de Pointes) and ventricular fibrillation.

Types

• Romano-Ward Syndrome: Autosomal dominant, associated with QT prolongation and ventricular tachyarrhythmias.
• Jervell and Lange-Nielsen (JLN) Syndrome: Autosomal recessive, associated with congenital deafness, QT prolongation, and ventricular arrhythmias.

Risk Factors

• Increased sympathetic tone can exacerbate symptoms, especially in LQT1 and LQT2.

Clinical Features

• May be asymptomatic or present with syncope, cardiac arrest, or sudden death.
• Symptoms may occur during exertion, rest, or emotional events.
• Family history of sudden cardiac death (SCD) is a key factor.

Diagnostic Criteria (Points-Based)

• QTc > 480 ms: +3 points
• QTc 460-479 ms: +2 points
• QTc 450-459 ms (in males): +1 point
• Torsades de Pointes: +2 points
• T-wave alternans: +1 point
• Notched T wave in 3 leads: +1 point
• Low heart rate for age: +0.5 points
• Syncope with stress: +2 points; without stress: +1 point
• Congenital deafness: +0.5 points
• Family members with confirmed LQTS: +1 point
• Unexplained sudden cardiac death in a family member <30 years old: +0.5 points

Investigations

• ECG: Prolonged QT interval; repeat if inconclusive.
• Blood Tests: FBC, electrolytes (including calcium and magnesium) to rule out other causes of QT prolongation.

Management

• Avoid Drugs That Prolong QT Interval: Also avoid drugs that lower potassium or magnesium. Potassium supplements may be beneficial, especially in LQT2, and can reduce QTc.
• Activity Modifications:
  • Avoid competitive sports, especially in genetically confirmed LQTS cases.
  • Avoid swimming or water sports for LQT1 patients.
  • Minimize exposure to abrupt loud noises (e.g., alarm clocks) in LQT2 patients.
• Beta Blockers: Effective in preventing cardiac events, particularly in LQT1 patients. Common options include propranolol, metoprolol, and atenolol.
• Implantable Cardioverter-Defibrillator (ICD): Highly effective in preventing sudden cardiac death (SCD) in high-risk patients. Used in patients who:
  • Have survived cardiac arrest.
  • Experience syncope despite adequate beta-blocker therapy.
  • Show signs of electrical instability, such as T-wave alternans, or have a very long QTc interval (>550 ms).
• Left Cervicothoracic Sympathectomy (LCSD): An option for high-risk patients who experience recurrent events despite beta-blocker therapy. LCSD has shown effectiveness comparable to ICD with fewer complications.

References

• Management of Patients with Long QT Syndrome. Korean Circ J. 2016 Nov; 46(6): 747-752.