Long qt Syndrome - Long qt Syndrome Information
Congenital long QT syndrome is an uncommon disease that is characterized by recurrent syncope, a long QT interval (usually 0.5–0.7 second), documented ventricular arrhythmias, and sudden death. It may occur in the presence (Jervell syndrome, Lange-Nielsen syndrome) or absence (Romano-Ward syndrome) of congenital deafness. Inheritance may be autosomal recessive or autosomal dominant (Romano-Ward). Specific genetic mutations affecting membrane potassium and sodium channels have been identified and help delineate the mechanisms of susceptibility to arrhythmia.
Blockers are the most effective therapy for congenital long QT syndrome and are often used in conjunction with permanent pacemakers, since low heart rates predispose to ventricular arrhythmias. ICDs are effective in patients who continue to have life-threatening ventricular arrhythmias while taking -blockers. Refractory acute arrhythmic episodes may be treated by local anesthetic block of the left stellate ganglion, and recurrent episodes can be treated by resection of this ganglion as well as of the first three to five thoracic ganglia.
Acquired long QT interval secondary to use of antiarrhythmic agents or antidepressant drugs, electrolyte abnormalities, myocardial ischemia, or significant bradycardia may result in ventricular tachycardia (particularly torsade de pointes, ie, twisting about the baseline into varying QRS morphology). Notably, many drugs that are in some settings effective for the treatment of ventricular arrhythmias prolong the QT interval. Prudence dictates that drug therapy that prolongs the QT interval beyond 500 ms be discontinued.
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