What is Long QT Syndrome (LQTS)?

Long QT Syndrome is a heart conduction disorder. LQTS gets its name from a characteristic appearance on an electrocardiogram (ECG) where the time interval between the Q-wave and T-wave is longer than usual (see diagram). LQTS is usually an inherited or genetic condition that is passed down through families in an autosomal dominant way–this means that a parent who carries the gene for LQTS has a 50% chance of passing it onto each of his or her children. SInce many people with LQTS do not have any symptoms, a patient may not realize they are a carrier until someone else in their family experiences symptoms.

Effects and Symptoms

Syncope or fainting is the most common symptom of LQTS. Other symptoms can be palpitations, seizures or even sudden death. Patients with LQTS may experience symptoms when the body is producing high levels of adrenaline, such as during exercise or during times of stress. Symptoms can also be triggered by a sudden surprise or a loud noise, or even occur during rest or sleep. Most people who experience symptoms of LQTS have their first episode by the age of 40.

Diagnosis

Many people with LQTS become aware of their condition only from the results of an ECG performed for an unrelated reason, because they have a family history of LQTS or because of genetic test results.

Testing for LQTS includes an ECG and exercise stress test. Both can be normal. These tests allow your cardiologist to observe the electrical behavior of a heart at different heart rates. An alternative to treadmill stress testing for someone who cannot exercise is catecholamine provocation testing, in which adrenaline is administered through an intravenous (IV) line while the heart rhythm is monitored. A diagnosis of LQTS is made when the characteristic QT prolongation is observed. 

Genetic testing is done in those with clinical LQTS and for first degree relatives of those who have positive genetic testing. There are many genes associated with LQTS and hundreds of mutations have been identified within these genes. A gene mutation can be identified in most people with a clinical diagnosis of LQTS.

Management and Treatment

There is no cure for LQTS, but there are effective treatments. All patients who have symptoms should receive treatment. In most cases, physicians recommend that all children and young adults with LQTS–even those without symptoms–should be treated. Symptoms may occur at any time, with sudden death sometimes being the first symptom.

Those with LQTS are advised to avoid triggers and medications that cause prolonged QT intervals. A list of drugs to be avoided can be found at this website: www.crediblemeds.org

The usual treatment involves taking a medication called a beta-blocker every day. Beta blockers prevent the response of the heart to adrenaline, reducing the likelihood of arrhythmia or abnormal heart rhythm. Repeated treadmill stress tests may help to determine the correct dose. Beta blockers are usually very successful at controlling arrhythmias if they are taken regularly. Regular follow up with your cardiologists is needed to monitor whether the arrhythmia is well controlled. Growing children need their medication dose adjusted regularly.

If symptoms continue despite appropriate doses of medication, there are other treatments. Left cardiac sympathetic denervation (LCSD) is a surgery in which the nerves that are responsible for adrenaline delivery to the heart are removed. An ICD or implantable cardioverter defibrillator, a device that can abort an abnormal rhythm when it happens, is rarely needed.

http://www.crediblemeds.org