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Long QT Syndrome Treatment & Management

  • Author: Ali A Sovari, MD, FACP; Chief Editor: Jeffrey N Rottman, MD  more...
 
Updated: Dec 31, 2015
 

Approach Considerations

All patients with long QT syndrome (LQTS) should avoid drugs that prolong the QT interval or that reduce their serum potassium or magnesium level. Potassium and magnesium deficiency should be corrected.

Although treating asymptomatic patients is somewhat controversial, a safe approach is to treat all patients with congenital LQTS because sudden cardiac death can be the first manifestation of LQTS.

Beta-blockers are drugs of choice for patients with LQTS. The protective effect of beta-blockers is related to their adrenergic blockade, which diminishes the risk of cardiac arrhythmias. They may also reduce the QT interval in some patients.

Consultations

A cardiologist and a cardiac electrophysiologist are typically consulted when patients with LQTS are evaluated.

In families of patients with genotypically confirmed LQTS, genetic counseling of patients and family members should be considered.

Inpatient care

Patients with LQTS are frequently hospitalized in a monitored unit after they have a cardiac event (eg, syncope, cardiac arrest) to enable immediate rescue if cardiac arrhythmias recur.

Follow-up

Asymptomatic individuals with LQTS usually do not require hospitalization. However, carefully evaluate them and provide follow-up care in an ambulatory setting. A cardiologist or a cardiac electrophysiologist should examine patients with LQTS on a regular basis.

Guidelines

The following is a summary of guidelines for the management of patients with LQTS, as suggested by the American College of Cardiology, the American Heart Association, and the European Society of Cardiology, in collaboration with the European Heart Rhythm Association and the Heart Rhythm Society[11, 12] :

  • No participation in competitive sports for patients with the diagnosis established by means of genetic testing only
  • Beta-blockers should be given to patients who have QTc-interval prolongation (>460 ms in women and >440 ms in men) and are recommended (class IIa) for patients with a normal QTc interval
  • An implantable cardioverter-defibrillator (ICD) should be used in survivors of cardiac arrest and is recommended (class IIa) for patients with syncope while receiving beta-blockers; ICD therapy can be considered (class IIb) for primary prevention in patients with characteristics that suggest high risk (including LQT2, LQT3, and QTc interval >500 ms)
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Beta-Blockers

Beta-blockers are effective in preventing cardiac events in approximately 70% of patients, whereas cardiac events continue to occur despite beta-blocker therapy in the remaining 30%.

Propranolol and nadolol are the most frequently used beta-blockers, though atenolol and metoprolol are also prescribed in patients with long QT syndrome (LQTS). Different beta-blockers demonstrate similar effectiveness in preventing cardiac events in patients with LQTS.

Response to beta-blocker therapy may vary depending on the triggering event. A study by Goldenberg et al found that in patients with LQT1, beta-blocker therapy is effective when exercise triggers the event but is ineffective if the event happens during sleep or arousal.[13]

Although for years the recommended dosage of beta-blockers was relatively large (eg, propranolol 3 mg/kg/day, or 210 mg/day in a 70-kg individual), data now suggest that lower dosages have a protective effect similar to that of large ones.

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Pacemakers and ICDs

The ICD has been shown to be highly effective in preventing sudden cardiac death in high-risk patients. In a study of 125 patients with long QT syndrome (LQTS) who received an ICD, there was a 1.3% death rate in high-risk ICD patients, compared with 16% in non-ICD patients, during a mean 8-year follow-up.[14] High-risk patients are defined as those with aborted cardiac arrest or recurrent cardiac events (eg, syncope or torsade de pointes) despite conventional therapy (ie, beta-blocker alone) and those with very prolonged QT interval (>500 ms).

An alternative is beta blockade in combination with a pacemaker and/or stellectomy in some patients.

The use of an ICD may be considered as primary therapy if the patient has a strong family history of sudden cardiac death. However, since some studies showed that a family history of sudden cardiac death is not an independent risk factor,[15] some experts do not recommend ICD therapy based only on a family history of sudden cardiac death.[16]

Early ICD therapy should be considered in high-risk patients with JLN syndrome, because the efficacy of beta-blockers has been found to be more limited in these patients.[17]

The usefulness of implanted cardiac pacemakers is based on the premise that pacing eliminates arrhythmogenic bradycardia, decreases heart-rate irregularities (eliminating short-long-short sequences), and decreases repolarization heterogeneity, diminishing the risk of torsade de pointes ventricular tachycardia. Pacemakers are particularly helpful in patients with documented pause-bradycardia–induced torsade de pointes and in patients with LQT3.

However, data indicate that cardiac events continue to occur in high-risk patients with cardiac pacing. Because newer models of ICDs include a cardiac pacing function, cardiac pacing (without defibrillators) is unlikely to be used in patients with LQTS. Pacing alone may be used in low-risk patients with LQT3.

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Stellectomy

Left cervicothoracic stellectomy is another antiadrenergic therapeutic measure used in high-risk patients with long QT syndrome (LQTS), especially in those with recurrent cardiac events despite beta-blocker therapy.

Stellectomy decreases the risk of cardiac events in high-risk patients with LQTS, although it is more effective in patients with LQT1 than in those with other types of LQTS.

Although this technique decreases the risk of cardiac events, it does not eliminate the risk. Therefore, the use of an ICD is superior to cervicothoracic stellectomy. However, cervicothoracic stellectomy may be indicated in some high-risk patients and in patients who have several ICD discharges while being treated with beta blockade and an ICD.

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Considerations in Physical Activity

Physical activity, swimming, and stress-related emotions frequently trigger cardiac events in patients with long QT syndrome (LQTS). Therefore, discourage patients from participating in competitive sports.

The triggering effect of exercise and tachycardia, and therefore the protective effect of beta-blockers, varies depending on the type of LQTS.

Exercise and tachycardia trigger LQT1 events. Therefore, patients with LQT1 should avoid strenuous exercise; beta-blockers are expected to provide excellent help by preventing cardiac events. Syncope and sudden cardiac death during swimming or diving are strongly related to LQT1. Therefore, patients with LQT1 should avoid swimming with no supervision. LQT2 is also exercise induced but to a lesser degree than LQT1.

Tachycardia and exercise do not trigger LQT3; events typically happen during sleep. Because tachycardia is not a trigger, the role of beta-blockers in preventing the cardiac events of LQT3 is debated. Mexiletine, a sodium channel blocker, may improve protection in this subgroup of patients. Some experts suggest the use of a beta-blocker combined with mexiletine in patients with LQT3.

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Gene Therapy

Gene-specific therapy is an area under investigation in the treatment of long QT syndrome (LQTS). For example, since LQT3 is associated with gain-of-function mutations in sodium channels, antiarrhythmic agents with sodium channel blocking properties have been suggested as gene-specific therapy for patients with LQTS3. Nevertheless, this area is complex and requires further investigations and studies.

For instance, Ruan and colleagues found that mexiletine, a sodium channel blocker, can facilitate F1473 mutant protein trafficking, resulting in a net effect of further increase in sodium current and worsening of QT prolongation in a subset of patients with LQTS3 who have this specific mutation.[18]

Trigger-specific risk stratification and therapy have been suggested by some studies. For example, Kim and colleagues showed that certain types of mutations in LQT2 are associated with certain triggering events (exercise triggers vs arousal triggers vs nonarousal/nonexercise triggers) and that patients with exercise-related triggering events respond to the treatment with beta-blockers.[19]

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Drugs To Be Avoided in LQTS

Anesthetics or asthma medication

Epinephrine (adrenaline) for local anesthesia or as an asthma medication should be avoided in patients with long QT syndrome (LQTS).

Antihistamines

Antihistamines to be avoided include the following:

  • Terfenadine (Seldane [recalled from US market]) - For allergies
  • Astemizole (Hismanal [recalled from US market]) - For allergies
  • Diphenhydramine (Benadryl) - For allergies

Antibiotics

Antibiotics to be avoided include the following:

  • Erythromycin (E-Mycin, EES, EryPed, PCE) - For lung, ear, and throat infections
  • Trimethoprim and sulfamethoxazole (Bactrim, Septra) - For urinary, ear, and lung infections
  • Pentamidine (Pentam, intravenous) - For lung infections

Heart medications

Heart medications to avoid in patients with LQTS include the following:

  • Quinidine (Quinidine, Quinidex, Duraquin, Quinaglute) - For heart rhythm abnormalities
  • Procainamide (Pronestyl) - For heart rhythm abnormalities
  • Disopyramide (Norpace) - For heart rhythm abnormalities
  • Sotalol (Betapace) - For heart rhythm abnormalities
  • Probucol (Lorelco) - For high triglycerides, cholesterol
  • Bepridil (Vascor) - For chest pain (angina)
  • Dofetilide (Tikosyn) - For atrial fibrillation
  • Ibutilide (Corvert) - For atrial fibrillation

Gastrointestinal medications

Cisapride (Propulsid), for esophageal reflux and acid indigestion, should be avoided.

Antifungal drugs

Antifungal agents to be avoided include the following:

  • Ketoconazole (Nizoral) - For fungal infections
  • Fluconazole (Diflucan) - For fungal infections
  • Itraconazole (Sporanox) - For fungal infections

Psychotropic drugs

The following psychotropic drugs should be avoided in patients with LQTS:

  • Tricyclic antidepressants (Elavil, Norpramin, Vivactil) - For depression
  • Phenothiazine derivatives (Compazine, Stelazine, Thorazine, Mellaril, Trilafon) - For mental disorders
  • Butyrophenones (Haloperidol) - For mental disorders
  • Benzisoxazole (Risperdal) - For mental disorders
  • Diphenylbutylpiperidine (Orap) - For mental disorders

Medications for potassium loss

Potassium-loss medications to be avoided include the following:

  • Indapamide (Lozol) - For water loss, edema
  • Other diuretics
  • Medications - For vomiting and diarrhea
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Contributor Information and Disclosures
Author

Ali A Sovari, MD, FACP Fellow in Clinical Cardiac Electrophysiology, Cedars Sinai Medical Center/Heart Institute

Ali A Sovari, MD, FACP is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Physician Scientists Association, American Physiological Society, Biophysical Society, Heart Rhythm Society, Society for Cardiovascular Magnetic Resonance

Disclosure: Nothing to disclose.

Coauthor(s)

Abraham G Kocheril, MD, FACC, FACP, FHRS Professor of Medicine, University of Illinois College of Medicine

Abraham G Kocheril, MD, FACC, FACP, FHRS is a member of the following medical societies: American College of Cardiology, Central Society for Clinical and Translational Research, Heart Failure Society of America, Cardiac Electrophysiology Society, American College of Physicians, American Heart Association, American Medical Association, Illinois State Medical Society

Disclosure: Nothing to disclose.

Ramin Assadi, MD Assistant Professor of Medicine, Division of Interventional Cardiology, Loma Linda University Medical Center

Ramin Assadi, MD is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Medical Association, Society for Cardiovascular Angiography and Interventions

Disclosure: Nothing to disclose.

Arnold S Baas, MD, FACC, FACP Associate Professor of Medicine, Division of Cardiology, University of California, Los Angeles, David Geffen School of Medicine; Attending Physician, Ronald Reagan UCLA Medical Center

Arnold S Baas, MD, FACC, FACP is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Federation for Medical Research, American Society of Echocardiography

Disclosure: Nothing to disclose.

Chief Editor

Jeffrey N Rottman, MD Professor of Medicine, Department of Medicine, Division of Cardiovascular Medicine, University of Maryland School of Medicine; Cardiologist/Electrophysiologist, University of Maryland Medical System and VA Maryland Health Care System

Jeffrey N Rottman, MD is a member of the following medical societies: American Heart Association, Heart Rhythm Society

Disclosure: Nothing to disclose.

Acknowledgements

Brian Olshansky, MD Professor of Medicine, Department of Internal Medicine, University of Iowa College of Medicine

Brian Olshansky, MD is a member of the following medical societies: American Autonomic Society, American College of Cardiology, American College of Chest Physicians, American College of Physicians, American College of Sports Medicine, American Federation for Clinical Research, American Heart Association, Cardiac Electrophysiology Society, Heart Rhythm Society, and New York Academy of Sciences

Disclosure: Guidant/Boston Scientific Honoraria Speaking and teaching; Medtronic Honoraria Speaking and teaching; Guidant/Boston Scientific Consulting fee Consulting; Novartis Honoraria Speaking and teaching; Novartis Consulting fee Consulting

Justin D Pearlman, MD, ME, PhD, FACC, MA Chief, Division of Cardiology, Director of Cardiology Consultative Service, Director of Cardiology Clinic Service, Director of Cardiology Non-Invasive Laboratory, Director of Cardiology Quality Program KMC, Dartmouth-Hitchcock Medical Center, Dartmouth Medical School

Justin D Pearlman, MD, ME, PhD, FACC, MA is a member of the following medical societies: American College of Cardiology, American College of Physicians, American Federation for Medical Research, International Society for Magnetic Resonance in Medicine, and Radiological Society of North America

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

References
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Marked prolongation of QT interval in a 15-year-old male adolescent with long QT syndrome (LQTS) (R-R = 1.00 s, QT interval = 0.56 s, QT interval corrected for heart rate [QTc] = 0.56 s). Abnormal morphology of repolarization can be observed in almost every lead (ie, peaked T waves, bowing ST segment). Bradycardia is a common feature in patients with LQTS.
Genetically confirmed long QT syndrome (LQTS) with borderline values of QT corrected for heart rate (QTc) duration (R-R = 0.68 s, QT interval = 0.36 s, QT interval corrected for heart rate [QTc] = 0.44 s) in a 12-year-old girl. Note the abnormal morphology of the T wave (notches) in leads V2-V4.
ECG of a 13-year-old female who had a syncopal event while running to a school bus. She awoke after a few seconds, and her subsequent clinical course was uneventful.
Table 1. Genetic Background of Inherited Forms of LQTS (Romano-Ward syndrome: LQT1-6, Anderson syndrome: LQT7, Timothy syndrome: LQT8, and Jervell and Lang-Nielsen syndrome: JLN1-2)
Type of LQTS Chromosomal Locus Mutated Gene Ion Current Affected
LQT1 11p15.5 KVLQT1 or KCNQ1 (heterozygotes) Potassium (IKs)
LQT2 7q35-36 HERG, KCNH2 Potassium (IKr)
LQT3 3p21-24 SCN5A Sodium (INa)
LQT4 4q25-27 ANK2, ANKB Sodium, potassium and calcium
LQT5 21q22.1-22.2 KCNE1 (heterozygotes) Potassium (IKs)
LQT6 21q22.1-22.2 MiRP1, KNCE2 Potassium (IKr)
LQT7 (Anderson syndrome) 17q23.1-q24.2 KCNJ2 Potassium (IK1)
LQT8 (Timothy syndrome) 12q13.3 CACNA1C Calcium (ICa-Lalpha)
LQT9 3p25.3 CAV3 Sodium (INa)
LQT10 11q23.3 SCN4B Sodium (INa)
LQT11 7q21-q22 AKAP9 Potassium (IKs)
LQT12   SNTAI Sodium (INa)
JLN1 11p15.5 KVLQT1 or KCNQ1 (homozygotes) Potassium (IKs)
JLN2 21q22.1-22.2 KCNE1 (homozygotes) Potassium (IKs)
Table.
Findings on physical examination usually do not indicate a diagnosis of long QT syndrome (LQTS), though some patients may present with excessive bradycardia for their age, and some patients may have hearing loss (congenital deafness), indicating the possibility of JLN syndrome. Skeletal abnormalities, such as short stature and scoliosis are seen in LQT7 (Andersen syndrome), and congenital heart diseases, cognitive and behavioral problems, musculoskeletal diseases, and immune dysfunction may be seen in those with LQT8 (Timothy syndrome). Also perform the physical examination to exclude other potential reasons for arrhythmic and syncopal events in otherwise healthy people (eg, heart murmurs caused by hypertrophic cardiomyopathy, valvular defects).    
     
Hinterseer et al found that increased short-term variability of QT interval, ie, STV(QT), in symptomatic patients with congenital long-QT syndrome (LQTS) could be a useful noninvasive additive marker for diagnostic screening to bridge the gap while waiting for results of genetic testing. This study is the first in humans to observe this association.[9]    
Table 2. Diagnostic Criteria for LQTS
Criterion Points
ECG findings *
QTc, ms† >480 3
460-469 2
450-459 in male patient 1
Torsade de pointes‡ 2
T-wave alternans 1
Notched T wave in 3 leads 1
Low heart rate for age§ 0.5
Clinical history
Syncope║ With stress 2
Without stress 1
Congenital deafness 0.5
Family history  
A. Family members with definite LQTS# 1
B. Unexplained sudden cardiac death < 30y in an immediate family member 0.5
*In the absence of medications or disorders known to affect these electrocardiographic features.



†QTc calculated by Bazett's formula



‡Mutually exclusive



§Resting heart rate below the second percentile for the age.



||Mutually exclusive



¶The same family member cannot be counted in A and B.



#Definite LQTS is defined by an LQTS score of more than 3 (≥4).



Table 3. Definition of QTc Based on Age- and Sex-Specific Criteria
Group Prolonged



QTc, s



Borderline



QTc, s



Reference Range, s
Children and adolescents (< 15 y) >0.46 0.44-0.46 < 0.44
Men >0.45 0.43-0.45 < 0.43
Women >0.46 0.45-0.46 < 0.45
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