Malignant familial long QT syndrome.

We report a family with congenital long QT syndrome, an inherited disorder of myocardial repolarization in which affected individuals have prolongation of corrected QT interval on the electrocardiogram and a tendency to develop ventricular arrhythmia, leading to syncope, convulsion or sudden death. Our family is characterized by several affected members (11/16), early onset of symptoms, malignant course prior to diagnosis and good response to beta-blocker therapy. The genetic basis of long QT syndrome has been traced to defective proteins encoding cardiac ion channels. Diagnosis is based on an unexplained prolongation of QT interval >0.45 second in the presence of suggestive symptoms or evidence, or both of a familial pattern. Beta-adrenergic blocker therapy gives symptomatic relief in 80%-85% of patients. Precipitating factors like vigorous exercise especially swimming and exposure to significant emotional or auditory stimuli should be avoided. Occasional patients require in addition, a demand cardiac pacemaker, left cardiac sympathectomy or an implantable cardioverter-defibrillator, or both. Regular follow up is mandatory even after subsidence of symptoms.