Long QT Syndrome

Overview

Healthcare providers can diagnose long QT syndrome during a routine electrocardiogram (EKG). To make a diagnosis, they measure the QT interval on the EKG. If your QT interval is longer than 450 milliseconds, you may have long QT syndrome.

Your doctor will ask you if you have a:

Family history of long QT syndrome.
Family history of unexplained fainting, seizures or cardiac arrest.
History of fainting, seizures or cardiac arrest, especially with exercise.

What tests will be done to diagnose long QT syndrome?

In addition to an electrocardiogram (EKG), testing may include:

Blood tests.
Genetic testing.
Exercise stress test.
Ambulatory monitor.

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Symptoms

When to see a doctor

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Complications

Blood clots are a dangerous complication of atrial fibrillation (AFib). Blood clots can lead to stroke.

The risk of stroke from AFib increases as you grow older. Other health conditions also may increase the risk of a stroke due to AFib. These conditions include:

High blood pressure.
Diabetes.
Heart failure.
Some types of heart valve disease.

Blood thinners are commonly prescribed to prevent blood clots and strokes in people with atrial fibrillation.

Prevention

Healthy lifestyle choices can reduce the risk of heart disease and may prevent atrial fibrillation (AFib). Here are some basic heart-healthy tips:

Control high blood pressure, high cholesterol and diabetes.
Don't smoke or use tobacco.
Eat a diet that's low in salt and saturated fat.
Exercise at least 30 minutes a day on most days of the week unless your health care team says not to.
Get good sleep. Adults should aim for 7 to 9 hours daily.
Maintain a healthy weight.
Reduce and manage stress.

By Mayo Clinic Staff

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Diagnosis & treatment

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