Long QT Syndrome

What Is Long QT Syndrome?

Long QT syndrome (LQTS) is a disease that affects the heart’s bottom chambers (ventricles), causing dangerously rapid and irregular heartbeats. LQTS affects the electrical signals that pass through the heart to cause the heartbeat. The irregular heartbeats of LQTS can be life-threatening. The condition occurs when the heart takes longer than normal to recharge after each beat during an electrocardiogram (ECG).

Long QT Syndrome Symptoms

Fainting is the most common symptom of long QT syndrome. An LQTS-induced fainting spell can happen with little to no warning. Just before a fainting incident, some people with LQTS can experience symptoms, including:

• Blurred vision.
• Lightheadedness.
• Weakness.
• Heart palpitations (sensation of fluttering in chest).

Long QT syndrome also causes seizures in some people. Some people don’t experience any symptoms and the condition is discovered during an ECG or another test.

What Causes Long QT Syndrome?

LQTS is categorized as congenital or acquired. In congenital LQTS, an abnormal gene is inherited that causes the heartbeat’s recovery phase to slow down, which can lead to a life-threatening arrhythmia.

Acquired LQTS is caused by some medication, condition or event. Medications that can cause acquired long QT syndrome include certain drugs in the following categories:

• Diuretics
• Antibiotics
• Antiarrhythmics
• Antidepressants
• Serotonin receptor inhibitors or antagonists
• Histamine receptor antagonists

Other causes of acquired long QT syndrome include:

• Anorexia nervosa
• Some bradyarrhythmias (abnormally slow resting heartrates)
• Low levels of calcium, magnesium or potassium
• Injury to the nervous system
• Exposure to toxins

How Is Long QT Syndrome Diagnosed?

Testing is done to check the health of the heart and confirm suspected LQTS. The most common test used to diagnose LQTS is an ECG, which records the heart’s electrical activity on a graph. An ECG can detect fast, slow or otherwise abnormal heart rhythms.

If LQTS symptoms don't occur frequently, they may not be detected on a standard ECG. In that case, your healthcare professional may ask you to wear a heart monitor at home. At-home heart monitoring options include:

• Patch recorder: A patch is attached to the chest to capture two weeks of continuous monitoring of the heart’s electric activity.
• Event recorder: Typically worn for about 30 days, this device records heart activity only at certain times for a few minutes at a time. You push a button when you feel symptoms. In addition, some event recorders automatically record when they detect an irregular heartbeat.

Other tests your healthcare provider my order to confirm an LQTS diagnosis include:

• Exercise stress test: In this test, you walk on a treadmill or pedal on a stationary bike while your heart is monitored. The test shows how the heart reacts to exercise. Sometimes an echocardiogram is performed as part of the test.
• Genetic testing: A genetic test can confirm gene changes associated with congenital LQTS. Check with your insurance provider to see if it is covered.

If you have LQTS syndrome, your healthcare provider may suggest that your family members get genetic testing to check for the disorder. Genetic testing for LQTS can't find all inherited cases of the disease. Families should speak to a genetic counselor before and after testing.

How Is Long QT Syndrome Treated?

LQTS treatment options include medications, implanted devices and surgeries that help manage symptoms and prevent sudden death.

Medication

Most people who have LQTS will be prescribed a beta blocker such as nadolol, even if they don’t have symptoms. Other medications may be prescribed to improve the QT interval or electrolyte levels.

Devices

For some people, a device may be needed to manage LQTS, such as:

• Implantable cardioverter defibrillator (ICD): An ICD is a surgically implanted cardiac device that corrects life-threatening arrhythmias by delivering electrical shocks to restore a regular heart rhythm. LQTS patients with a history of cardiac arrest or symptoms may receive an ICD.
• Pacemaker: Implanted under the skin near the collarbone through a minor surgery, a pacemaker releases electrical impulses to stimulate the heart to maintain a regular heartbeat.

Surgery

Some people with LQTS may require left cardiac sympathetic denervation (LCSD). In this minimally invasive procedure, the nerves that cause the dangerous heart rhythm are surgically disconnected or removed.