Signs of Long QT Syndrome (QT prolongation)

Description

An abnormality in the heart rhythm. The long QT syndrome is sometimes inherited. The following conditions can also cause this disorder: certain medications (eryhtromycin, moxifloxacin, terfenadine), abnormal blood chemistry (low potassium, low calcium, or low magnesium), heart attacks, cocaine abuse, and stroke. The disease produces a lengthening of the interval from the QRS to the T wave on an EKG. This abnormality can lead to lethal heart rhythms such as ventricular tachycardia and Torsades de pointes, and if untreated can result in unexplained fainting (syncope) and death. Once found in a family member, other relatives may need to be tested for the disorder.

Symptoms

Heart racing (palpitations), fainting, breathing problems, sudden death. Exercise may cause the heart racing and symptoms.

Tests

A history and physical exam will be done. The provider will ask about other family members with similar symptoms, death at an early age, or fainting episodes. The diagnosis is made by measuring the QT interval on an EKG. The chemistry of the blood will be measured. Tests to rule out other causes of the abnormal rhythm may be done.

Standard Workup

Chem 12
EKG
Echocardiogram
Troponin
X-Ray

Treatment

Therapy is directed at shortening the QT interval, preventing life threatening heart rhythms, and acutely treating the lethal rhythms. The racing heart rhythms are treated with medications or electrical cardioversion. The QT interval is shortened by correcting the potassium and magnesium levels in the blood, and by avoiding drugs that lengthen the QT interval. A list of drugs that prolong the QT interval can be found at http://www.azcert.org/consumers/med-record.cfm. Preventing the dangerous heart rhythms is done with beta-blocker medications or by inserting an implantable cardioverter-defibrillator (ICD).