Long QT syndrome is a heart disorder in which the heart’s electrical system is abnormal. The name comes from the Q-T interval of the electrocardiogram. A tiny electrical current stimulates the heart to contract. As the heart muscle relaxes, its cells recharge (become repolarized). Long QT syndrome affects this phase and can lead to serious heart rhythm disturbances. The syndrome can cause fast, chaotic heartbeats. The syndrome usually affects children and young adults. It usually starts at 8 to 20 years old. It may account for more than 3000 deaths per year in the United States.
The syndrome may be inherited, caused by mutations of genes controlling the heart’s electrical system. When associated with congenital deafness, the syndrome is called Jervell and Lange-Nielsen syndrome. With normal hearing, it’s called Romano-Ward syndrome. An acquired syndrome may be caused by drugs such as quinidine, procainamide, disopyramide, amiodarone, and sotalol. Antidepressants, antipsychotics, certain antihistamines, and use of the antibiotic erythromycin with the antifungal drug ketoconazole, have caused the syndrome.
Symptoms include syncope (fainting), frequent palpitations (rapid heartbeats), and seizures. The syndrome can start without warning symptoms, and sudden death may be the first and last one. Heart rhythm problems may affect blood pressure, which can lead to loss of consciousness and death.
Your health care provider may suspect long QT syndrome from your medical history. The diagnosis is made by measuring the QT interval on an electrocardiogram (ECG).
People may not need therapy if they have no symptoms and no family history of sudden death. However, they should avoid competitive sports, strenuous exercise, and the drugs named previously. People with rhythm disturbances and a family history of sudden death need medications (beta-blockers) and should be evaluated for placement of a permanent pacemaker. Prescribed medicines won’t cure the condition, but they offer some protection against serious abnormal heart rhythms. A beta-blocker may need to be taken indefinitely. People who continue with symptoms, even with medical and pacemaker insertion, should have an implantable defibrillator. This device is put into the body and attached to the heart with wires. It gives the heart an electrical shock to restore the normal rhythm when it starts to have an abnormal rhythm.
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Copyright © 2016 by Saunders, an imprint of Elsevier, Inc.
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