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The most common sign of long QT syndrome is fainting, due to chaotic beating of the heart. This may occur during exercise (such as playing basketball) or hearing a loud sound. However, not all people with long QT syndrome have any symptoms. Some of them may never develop symptoms throughout their lives. To diagnose long QT syndrome, it is often necessary to perform ECG while you exercise (such as walking on a treadmill) because the QT interval is not always prolonged. In case you cannot exercise to a sufficient degree, the doctor may use certain medications, such as epinephrine (adrenaline), to stimulate your heart. During exercise, epinephrine is produced to make the heart beat faster. Therefore, stimulation by epinephrine mimics exercise. Diagnosis of the disease may also include genetic screening since gene mutations are involved in most cases of long QT syndrome (more info). Long QT syndrome is mainly caused by gene mutations. Nine genes have been found to be associated with the disease. Most of these genes encode ion channels (more info). Many drugs can also prolong the QT interval, including Erythromycin (antibiotic), Terfenadine (antihistamine) and Ketoconazole (antifungal). These drugs may block ion channels, thereby altering membrane potentials. Medications Beta blockers are the first choice in treating long QT syndrome. They can slow the heart rate and reduce the risk of stress-induced arrhythmias. Potassium supplementation may be helpful for certain types of long QT syndrome since it may shorten the QT interval. Medical devices If medications failed or a person has suffered cardiac arrest, doctors may recommend artificial pacemaker or implantable cardioverter-defibrillator (ICD). These devices are implanted under the skin in the chest. They can monitor the rate and rhythm of the heart and try to correct heart rhythm when arrhythmia occurs.
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