13th March 2024

Management

All patients should be advised on avoiding medications that may prolong the QT interval, such as tricyclic antidepressants. Patients should replace electrolytes if experiencing vomiting or diarrhoea, as hypokalaemia and hypomagnesemia can increase the risk of a prolonged QT interval. Patients should also avoid competitive sports.

Regardless of whether patients are symptomatic or not, a beta blocker, usually propranolol or nadolol, should be started to prevent ventricular tachyarrhythmias. 

In addition, those with congenital LQTS who have not had a cardiac event but are at high risk (QTc >500ms in those with LQT1 or 2, or men with LQT3 with a QTc >550 ms) or in any patient with congenital LQTS who has experienced a previous cardiac event, should be considered for the following treatments:

1st line treatments in conjunction with beta-blockers:

• Implantable cardioverter-defibrillator (ICD) if they have had a previous cardiac event, recurrent syncope on beta blockers or Jervell and Lange-Nielsen syndrome
• Mexiletine can be considered in individuals with LQT3

2nd line treatment in conjunction with beta-blockers:

• Left cervicothoracic sympathectomy (resection of lower half of left stellate ganglion as well as other thoracic ganglia to partially denervate the heart) can be considered in those unable to tolerate beta blockers; those receiving multiple ICD shocks, recurrent syncope despite beta blockers or Jervell and Lange-Nielsen syndrome.

3rd line treatment in conjunction with beta-blockers:

• Permanent pacemaker can be considered alongside beta blockers if a patient has ongoing symptoms despite cervicothoracic sympathectomy.

Patients should have minimum annual ECG monitoring as well as an ECG check after starting or dose adjustment of beta blockers. Exercise testing or Holter monitoring can be used to assess adequate beta-blockade after starting beta blockers.