THE LONG QT SYNDROME-ASSOCIATED WITH INFRA-HISIAN BLOCK

The long QT syndrome (LQTS) is a congenital disease, typically associa ted with life-threatening ventricular arrhythmias torsade de pointes. Cardiac conduction system abnormalities are infrequently observed in L QTS patients. Seventeen-year-old female was admitted to our Department after cardiac resuscitation due to second incident of cardiac arrest within the last year. The base for cardiac arrest was torsade de point es and ventricular fibrillation. The electrocardiogram showed QTc inte rval of 520 msec. Serum calcium, magnesium and potassium were normal. The patient was referred for electrophysiological study. There were no arrhythmias induced. The HV conduction reminded normal until extrasti mulus coupling interval of 480 msec (S1S1=600 msec). At shorter coupli ng intervals the His-Purkinje conduction time increased progressively and was blocked by 420 msec. Recordings of monophasic action potential s from right ventricular midseptal region showed humps corresponding t o early afterdepolarizations. The patient was placed on atenolol and r eferred for ICD implantation.