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Thursday, July 24, 2014
Understanding A Prolonged QT Interval
What is prolonged QT?
This question has been forwarded by Anxiety and Stress Disorders:
'Prolonged QT' means that there is a prolongation, or lengthening of the QT interval on the electrocardiogram. The QT interval on the ECG, is measured from the beginning of the QRS complex to the end of the T wave.
A prolonged QT interval indicates an abnormality in electrical activity that leads to irregularities in heart muscle contraction. One of these irregularities is a specific pattern of very rapid contractions (tachycardia) of the lower chambers of the heart called torsade de pointes, a type of ventricular tachycardia. The rapid contractions, which are not effective in pumping blood to the body, result in a decreased flow of oxygen-rich blood to the brain. This can result in a sudden loss of consciousness (syncope) and death.
Both inherited and acquired forms of LQTS have been identified. Most acquired forms are thought to be due to certain drugs including adrenaline (epinephrine), several antihistamines and antibiotics, specific heart medications, diuretics, and others.
Severe weight loss such as is associated with anorexia nervosa can also disrupt ion balances in the heart and result in prolongation of the QT interval. Three inherited forms of LQTS have been described to date.
Jervell and Lange-Neilsen syndrome, named for the physicians who described the condition in 1957, is associated with congenital deafness and is inherited as an autosomal recessive trait. Romano-Ward syndrome, the most common inherited form of LQTS, was first described in the 1960's. It is inherited in an autosomal dominant pattern and is not associated with other physical impairments such as deafness. In 1995, a third type of LQTS was reported in to occur in association with bilateral syndactyly. Little is known about the inheritance of this form, except that reported cases have been sporadic with no associated family history of LQTS.
For more information please visit the MetroHealth website page on Long QT syndrome.
Karen Kutoloski, DO
Assistant Professor of Medicine
School of Medicine
Case Western Reserve University