Long QT Syndrome Medication
- Author: Ali A Sovari, MD, FACP; Chief Editor: Jeffrey N Rottman, MD more...
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.
As previously mentioned, 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. Beta-blockers used in patients with LQTS include the following:
Beta-Adrenergic Blocking Agents
Antiadrenergic therapy effectively protects most patients with long QT syndrome (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. Interruption in beta-blocker therapy may increase the risk of cardiac events.
Propranolol decreases the effect of sympathetic stimulation on the heart. It decreases conduction through the atrioventricular (AV) node and has negative chronotropic and inotropic effects. Consult a 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 an ICD as first-line therapy.
Nadolol is frequently prescribed because of its long-term effect. This agent decreases the effect of sympathetic stimulation on the heart. Nadolol decreases conduction through the AV node and has negative chronotropic and inotropic effects. Consult a 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 an ICD as first-line therapy.
Metoprolol is a selective beta1-adrenergic receptor blocker that decreases the automaticity of contractions. During intravenous (IV) administration, carefully monitor blood pressure, heart rate, and ECG. Consult a cardiologist because dosing varies and is individualized in patients with LQTS. Patients with LQTS who cannot take beta-blockers may require an ICD as first-line therapy.
Atenolol selectively blocks beta1-receptors with little or no effect on beta2 types. Consult a cardiologist because dosing varies and is individualized in patients with LQTS. Patients with LQTS who cannot take beta-blockers may require an ICD as first-line therapy.
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|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)|
|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)|
|JLN1||11p15.5||KVLQT1 or KCNQ1 (homozygotes)||Potassium (IKs)|
|JLN2||21q22.1-22.2||KCNE1 (homozygotes)||Potassium (IKs)|
|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.|
|ECG findings *|
|450-459 in male patient||1|
|Torsade de pointes‡||2|
|Notched T wave in 3 leads||1|
|Low heart rate for age§||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
§Resting heart rate below the second percentile for the age.
¶The same family member cannot be counted in A and B.
#Definite LQTS is defined by an LQTS score of more than 3 (≥4).
|Reference Range, s|
|Children and adolescents (< 15 y)||>0.46||0.44-0.46||< 0.44|