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Long QT Syndrome: Treatment & Medication
Updated: Jun 18, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Treatment
Medical Care
All patients with long QT syndrome (LQTS) should avoid drugs that prolong the QT interval or reduce their serum potassium or magnesium levels. 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 that diminishes the risk of cardiac arrhythmias. They may also reduce the QT interval in some patients.
- Although for years the recommended dosage of beta-blockers was relatively large (eg, propranolol 3 mg/kg/d, or 210 mg/d in a 70-kg individual), recent data suggest that dosages lower than this have a protective effect similar to that of large dosages.
- 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 beta-blockers most frequently used, though atenolol and metoprolol are also prescribed in patients with LQTS. Different beta-blockers demonstrate similar effectiveness in preventing cardiac events in patients with LQTS.
- The implantable cardioverter-defibrillator (ICD) was shown to be highly effective to prevent sudden cardiac death (SCD) in high-risk patients. In a study of 125 patients with LQTS with ICDs, there was 1.3% death in high-risk ICD patients, compared with 16% in non-ICD patients during mean 8-year follow-up (p=0.07).6 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. Use of an ICD may be considered as primary therapy if the patient has a strong family history of SCD. However, since some studies showed that family history of SCD is not an independent risk factor7 , some experts do not recommend ICD therapy based on only a family history of SCD8 . Early ICD therapy should be considered in high-risk patients with Jervell and Lange-Nielsen syndrome, because the efficacy of beta-blockers was found to be more limited in these patients.9
- 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, recent 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.
- Left cervicothoracic stellectomy is another antiadrenergic therapeutic measure used in high-risk patients with 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, and it is more effective in patients with LQT1 than those with other types of LQTS.
- Although this technique decreases the risk of cardiac events, it does not eliminate the risk. Therefore, ICD is superior therapy to cervicothoracic stellectomy.
- 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.
- 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, and 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 the patients. Some experts suggest the use of a beta-blocker combined with mexiletine in patients with LQT3.
- Gene-specific therapy is an area under investigation.
- A summary of guidelines 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 for management of patients with LQTS include:10,11
- 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 is recommended (class IIa) for patients with a normal QTc interval.
- ICD should be implanted for 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; these include LQT2, LQT3, and QTc interval greater than 500 ms.
Consultations
- A cardiologist and a cardiac electrophysiologist are typically consulted when patients with long QT syndrome (LQTS) are evaluated.
- In families of patients with genotypically confirmed LQTS, genetic counseling of patients and family members should be considered.
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. This recommendation is most important for patients with LQT1 or LQT2. See also the Medical Care section.
Medication
No treatment addresses the cause of long QT syndrome (LQTS). Antiadrenergic therapeutic measures (eg, use of beta-blockers, left cervicothoracic stellectomy) and device therapy (eg, use of pacemakers, ICDs) aim to decrease the risk and lethality of cardiac events.
Beta-adrenergic blocking agents
Antiadrenergic therapy effectively protects most patients with LQTS. Beta-blockers, especially propranolol, are the drugs most frequently used in patients with LQTS. Inform patients and their family members that beta-blockers should be continued indefinitely and not stopped. Interruption in beta-blocker therapy may increase the risk of cardiac events.
Propranolol (Inderal)
Decreases effect of sympathetic stimulation on heart. Decreases conduction through atrioventricular (AV) node and has negative chronotropic and inotropic effects. Consult cardiologist because dosing varies and is individualized in patients with LQTS. Patients with asthma should use cardioselective beta-blockers. Patients with LQTS who cannot take beta-blockers may require ICDs as first-line therapy.
Adult
2-3 mg/kg/d PO
Pediatric
Administer as in adults
Coadministration with aluminum salts, barbiturates, nonsteroidal anti-inflammatory drugs (NSAIDs), penicillins, calcium salts, cholestyramine, and rifampin may decrease effects; cimetidine, loop diuretics, and monoamine oxidase inhibitors (MAOIs) may increase toxicity; toxicity of hydralazine, haloperidol, benzodiazepines, and phenothiazines may increase; cardiotoxicity may increase when administered concurrently with calcium channel blockers, quinidine, flecainide, and digoxin (all affect conduction)
Documented hypersensitivity; uncompensated congestive heart failure, bradycardia, cardiogenic shock, AV conduction abnormalities
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Beta-adrenergic blockade may decrease signs of acute hypoglycemia and hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm; withdraw drug slowly and monitor closely; should be taken by pregnant women with LQTS during pregnancy and postpartum period, when risk of cardiac events increases
Nadolol (Corgard)
Frequently prescribed because of long-term effect. Decreases effect of sympathetic stimulation on heart. Decreases conduction through AV node and has negative chronotropic and inotropic effects. Consult cardiologist because dosing varies and is individualized in patients with LQTS. Patients with asthma should use cardioselective beta-blockers. Patients with LQTS who cannot take beta-blockers may require ICDs as first-line therapy.
Adult
20-160 mg/d PO
Pediatric
Administer as in adults
Aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease bioavailability and plasma levels, possibly resulting in decreased pharmacologic effects; toxicity may increase with coadministration of sparfloxacin, phenothiazines, calcium channel blockers, quinidine, flecainide, and oral contraceptives; may increase toxicity of digoxin, flecainide, clonidine, epinephrine, nifedipine, prazosin, verapamil, and lidocaine
Documented hypersensitivity; uncompensated congestive heart failure, bradycardia, asthma, cardiogenic shock, AV conduction abnormalities
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Beta-adrenergic blockade may decrease signs of acute hypoglycemia and hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm; withdraw drug slowly and monitor closely; should be taken by pregnant women with LQTS during pregnancy and postpartum period, when risk of cardiac events increases
Metoprolol (Lopressor)
Selective beta1-adrenergic receptor blocker that decreases automaticity of contractions. During IV administration, carefully monitor BP, heart rate, and ECG. Consult cardiologist because dosing varies and is individualized in patients with LQTS. Patients with LQTS who cannot take beta-blockers may require ICDs as first-line therapy.
Adult
25-200 mg PO bid
Pediatric
Administer as in adults
Aluminum salts, barbiturates, NSAIDs, penicillins, calcium salts, cholestyramine, and rifampin may decrease bioavailability and plasma levels, possibly decreasing pharmacologic effects; toxicity may increase with coadministration of sparfloxacin, phenothiazines, astemizole (recalled from US market), calcium channel blockers, quinidine, flecainide, and contraceptives; may increase toxicity of digoxin, flecainide, clonidine, epinephrine, nifedipine, prazosin, verapamil, and lidocaine
Documented hypersensitivity; uncompensated congestive heart failure, bradycardia, asthma, cardiogenic shock, AV conduction abnormalities
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Beta-adrenergic blockade may reduce signs and symptoms of acute hypoglycemia and may decrease clinical signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm; monitor patient closely and withdraw drug slowly; during IV administration, carefully monitor BP, heart rate, and ECG
Atenolol (Tenormin)
Selectively blocks beta1-receptors with little or no affect on beta2 types. Consult cardiologist because dosing varies and is individualized in patients with LQTS. Patients with LQTS who cannot take beta-blockers may require ICDs as first-line therapy.
Adult
25-200 mg/d PO
Pediatric
Administer as in adults
Coadministration with aluminum salts, barbiturates, calcium salts, cholestyramine, NSAIDs, penicillins, and rifampin may decrease effects; haloperidol, hydralazine, loop diuretics, and MAOIs may increase toxicity
Documented hypersensitivity; congestive heart failure, pulmonary edema, cardiogenic shock, AV conduction abnormalities, heart block (without a pacemaker)
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
Beta-adrenergic blockade may reduce symptoms of acute hypoglycemia and mask signs of hyperthyroidism; abrupt withdrawal may exacerbate symptoms of hyperthyroidism and cause thyroid storm; monitor patients closely and withdraw drug slowly; during IV administration, carefully monitor BP, heart rate, and ECG
More on Long QT Syndrome |
| Overview: Long QT Syndrome |
| Differential Diagnoses & Workup: Long QT Syndrome |
Treatment & Medication: Long QT Syndrome |
| Follow-up: Long QT Syndrome |
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References
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Further Reading
Keywords
long QT syndrome, LQTS, congenital long QT syndrome, Romano-Ward syndrome, Jervell and Lange-Nielsen syndrome, JLN syndrome, ventricular tachyarrhythmias, syncope, cardiac arrest, sudden death, Anderson syndrome, Timothy syndrome
Treatment & Medication: Long QT Syndrome