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Long QT Syndrome

Your heartbeat is a complex bodily function — many systems must work in unison. Disruptions in the electrical activity of your heart can lead to problems. Long QT syndrome (LQTS) is one of them.

LQTS is a rare heart disorder. Its name stems from a reading on the electrocardiogram (ECG) machine, which doctors use to evaluate your heartbeat. The ECG machine records and measures each of your heartbeats as five “waves.” Each wave has a different letter designation: P, Q, R, S, and T. The relationship between the Q and T waves is important and is known as the QT interval. When the interval lasts longer than it normally should, it disrupts the timing of your heartbeat and can cause dangerous arrhythmias, or irregular heart rates. This is known as long QT syndrome.

Illustration of a cross section of the heart and electrical pathways. Inset box shows normal heart rhythm


LQTS can come out of nowhere. Often, the first symptom occurs when you lose consciousness from the dangerous arrhythmia that LQTS causes. You can then suffer from cardiac arrest, or die, if you do not get immediate treatment. Sometimes, strenuous exercise, stress, shock, or fright can trigger LQTS.

Who’s at risk?

Often, LQTS seems to be genetic — passed down through families. If one of your family members is diagnosed with LQTS, experts recommend that you and your other family members — parents, siblings, children — get tested as well. In rare instances, medications can cause acquired LQTS. More than 50 drugs list LQTS as a risk. Ask your doctor for a full explanation of the risks of all medications you're taking.


An electrocardiogram is the primary way to detect LQTS. If your health care provider detects that the interval between the Q and T waves of your heartbeat is longer than it should be, you might have LQTS. Exercise can trigger LQTS, and your doctor may require you to take a treadmill test. Genetic blood tests may identify the abnormal gene that can sometimes cause LQTS.


Beta-blockers may help manage LQTS and prevent its dangerous complications. These medications help prevent a sudden heart attack. In addition, your doctor may recommend that he or she implant an electrical device, such as an implantable cardioverter defibrillator or a pacemaker, in your chest. These devices detect and correct your irregular heartbeat when it happens.


The most serious risk associated with LQTS is the chance of sudden death from cardiac arrest. This may happen to about half of all people with inherited, untreated LQTS, within the span of about a decade.


Close medical follow-up is important for successful LQTS management. Medications, implanted medical devices (such as pacemakers), and lifestyle changes each can play a role in decreasing your risk for a cardiac event. Lifestyle changes can minimize your chances of dying of LQTS. Avoid strenuous exercise and activities, high-stress situations, startling noises, and other shocking situations that could trigger LQTS. A diet that contains added potassium may also help prevent the complications of LQTS. However, consult your health care provider before using any kind of potassium supplement or making any dietary changes. Always wear an emergency medical alert bracelet or necklace.

When to call the doctor

The primary symptom of LQTS is fainting. If this happens, seek emergency medical help immediately.

Long QT Syndrome - WellSpan Health

Author: Myers, Wyatt
Online Medical Reviewer: Bass III, Pat F., MD, MPH
Online Medical Reviewer: Fraser, Marianne, MSN, RN
Last Review Date: 2013-01-02T00:00:00
Published Date: 2014-12-04T00:00:00
Last Review Date: 2013-01-11T00:00:00
© 2015 WellSpan Health. All Rights Reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.

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