Long QT Syndrome Guidelines

Updated: Nov 30, 2017
  • Author: Ali A Sovari, MD, FACP, FACC; Chief Editor: Mikhael F El-Chami, MD  more...
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Guidelines

Guidelines Summary

Diagnosis

2013 HRS/EHRA/APHRS recommendations

In its 2013 expert consensus statement on inherited primary arrhythmia syndromes, the Heart Rhythm Society/European Heart Rhythm Association/Asia Pacific Heart Rhythm Society (HRS/EHRA/APHRS) recommended a diagnosis of long QT syndrome (LQTS) when any of the following criteria is met [36] :

  • LQTS risk score of at least 3.5 in the absence of a secondary cause for QT prolongation 
  • Presence of confirmed LQTS gene mutation
  • QTc of at least 500 ms in repeated 12-lead electrocardiograms (ECGs) and in the absence of a secondary cause for QT prolongation.

LQTS can also be diagnosed in the presence of a QTc between 480 and 499 ms in repeated 12-lead ECGs in a patient with unexplained syncope in the absence of a secondary cause for QT prolongation and in the absence of a pathogenic mutation.

ESC recommendations

In 2015, the European Society of Cardiology (ESC) released guidelines for the management of ventricular arrhythmias and the prevention of sudden cardiac death (SCD) which included the following modified recommendation for the diagnosis of LQTS [37] :

Class I (Level of evidence: C)

LQTS is diagnosed when any of the following criteria is met:

  • QTc of at least 480 ms in repeated 12-lead ECGs
  • LQTS risk score above 3
  • Presence of a confirmed LQTS gene mutation, irrespective of the QT duration

Class IIa (Level of evidence: C)

LQTS should be considered in patients with an unexplained syncopal episode and a QTc of at least 460 ms in repeated 12-lead ECGs in the absence of secondary causes for QT prolongation

Genetic testing

In 2011, the HRS and EHRA issued a joint expert consensus statement on genetic testing for channelopathies and cardiomyopathies with the following recommendations for LQTS testing [38] :

Comprehensive or LQT1-3 (KCNQ1, KCNH2, and SCN5A)–targeted LQTS genetic testing for:

  • Individuals with a strong clinical index of suspicion for LQTS based on their clinical history, family history, and expressed ECG phenotype (Class I)
  • Asymptomatic individuals with idiopathic QT prolongation on serial 12-lead ECGs defined as QTc longer than 480 ms (prepuberty) or longer than 500 ms (adults) (Class I); may be considered for QTc values above 460 ms (prepuberty) or over 480 ms (adults) (Class IIb)

In addition, mutation-specific genetic testing is recommened for family members following identification of LQTS mutation in an index case. (Class I)

Management and prevention of sudden cardiac death

The following is a summary of recommendations included in the 2015 ESC guidelines for management of of LQTS and preventions of SCD. [37]

Class I (Level of evidence: B)

Lifestyle changes, such as the following:

  • Avoidance of QT-prolonging drugs
  • Correction of electrolyte abnormalities (hypokalemia, hypomagnesemia, hypocalcemia) that may occur during diarrhea, vomiting, or metabolic conditions
  • Avoidance of genotype-specific triggers for arrhythmias (strenuous swimming, especially in LQTS1, and exposure to loud noises in LQTS2 patients)

Beta-blockers for all patients 

Implantable cardioverter-defibrillator (ICD) placement with the use of beta-blockers for patients with a previous cardiac arrest

Class IIa 

Consider beta-blockers for carriers of an LQTS genetic mutation and normal QT interval. (Level of evidence: B)

Consider ICD implantation in addition to beta-blockers in patients with syncope and/or ventricular tachycardia (VT) while receiving an adequate dose of beta-blockers. (Level of evidence: B)

Left cardiac sympathetic denervation should be considered in patients with symptomatic LQTS when (Level of evidence: C):

  • Beta-blockers are ineffective, not tolerated, or contraindicated
  • ICD therapy is contraindicated or refused
  • Patients on beta-blockers with an ICD experience multiple shocks

Class IIb (Level of evidence: C)

Consider sodium channel blockers (mexiletine, flecainide or ranolazine) as add-on therapy to shorten the QT interval in LQTS3 patients with a QTc longer than 500 ms.

Consider an ICD in addition to beta-blocker therapy in asymptomatic carriers of a pathogenic mutation in KCNH2 or SCN5A when the QTc is longer than 500 ms.

Class III (Level of evidence: C)

Invasive electrophysiological study (EPS) with programmed ventricular stimulation (PVS) is not recommended for SCD risk stratification.

The 2015 ESC recommendations summarized above are consistent with the recommendations of the 2006 joint guidelines of the American College of Cardiology, the American Heart Association, and the ESC (ACC/AHA/ESC). [39]  However, the 2013 HRS/EHRA/APHRS recommendations have one significant variance in that beta-blockers are only recommended in patients who are asymptomatic with a QTc of at least 470 ms and/or symptomatic for syncope or documented ventricular tachycardia/ventricular fibrillation (VT/VF). [36]

A scientific statement published in 2015 by the AHA/ACC on athletic competition by persons with known or suspected cardiac channelopathies includes the following recommendations related to LQTS [40] :

  • That a heart rhythm specialist or genetic cardiologist experienced in cardiac channelopathies conduct a thorough evaluation of an athlete in whom such a disorder has been diagnosed or is suspected
  • That asymptomatic athletes who are genotype-positive/phenotype-negative for LQTS, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, early repolarization syndrome, short-QT syndrome, or idiopathic ventricular fibrillation be allowed to take part in all competitive sports if precautionary measures, such as the avoidance of QT-prolonging drugs, are undertaken
  • That an athlete who is symptomatic for LQTS or in whom it can be found electrocardiographically be considered for competitive sports (with the exception of competitive swimming, if the athlete is a previously symptomatic LQT1 host) if precautionary measures have been undertaken, treatment is being administered, and the person has been asymptomatic on therapy for at least 3 months (although treatment involving an ICD is subject to additional recommendations)