Management implications for patients with congenital LQTS and positive genetic testing

Population (clinical features)	Interventions
Population (clinical features)	Avoid triggers including medications that prolong the QT interval (www.crediblemeds.org) when possible*	Beta blockade with a nonselective beta blocker (nadolol or propranolol)	Implantable cardioverter/ defibrillator (ICD)	Left cardiac sympathetic denervation (LCSD)
History of sudden cardiac arrest (SCA)	All individuals	All individuals	Usually appropriate. However, if SCA occurred in a patient with LQT1 before the diagnosis was made and there is a strong desire to avoid an ICD, a non-ICD treatment with beta blockade and LCSD is possible.	Can be used to intensify treatment if VF-terminating ICD shocks occur.
History of symptoms (arrhythmogenic syncope and arrhythmogenic syncope followed by seizures)	All individuals	All individuals	Generally indicated for symptomatic LQT2 (for women with QTc >500 ms, men with QTc >500 ms) and symptomatic LQT3 with QTc >550ms.	Can be used if beta blockade is not tolerated or if there is a breakthrough event despite adherence to beta blockade.
Asymptomatic with prolonged QT interval on ECG	All individuals	All individuals	Can be considered for asymptomatic individuals with LQT2 or LQT3 who has a QTc >500 ms.	Can be considered if beta blockade is not tolerated.
Normal ECG (QTc <470 ms) with positive genetic testing for a congenital LQTS-susceptibility variant	All individuals	Individualized decision; often suggested for family members identified by variant-specific cascade testing	Not indicated.	Not indicated.

This table is intended as an information summary for individuals with genetic testing that reveals a pathogenic or likely pathogenic variant (PV or LPV) in a definite/strong evidence congenital LQTS-susceptibility gene and who are diagnosed with congenital LQTS. Some variants in some congenital LQTS genes can also cause other congenital rhythm disorders, and consultation with a cardiac rhythm specialist is advised to ensure the correct diagnosis and appropriate therapy so that necessary interventions are provided and unnecessary interventions are avoided. Refer to UpToDate for additional details.

LQTS: long QT syndrome; ICD: implantable cardioverter/defibrillator; LCSD: left cardiac sympathetic denervation; SCA: sudden cardiac arrest; VF: ventricular fibrillation; ms: milliseconds; ECG: electrocardiogram.

* Besides medications that prolong the QT interval, other triggers for QT prolongation and/or LQTS-triggered cardiac events may include dehydration, hypokalemia, hypomagnesemia, some types of exercise (such as swimming in LQT1), and in some patients, loud noises and psychologic stress. Refer to UpToDate for a complete list.

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Management implications for patients with congenital LQTS and positive genetic testing