SUDDEN CARDIAC DEATH AND POLYMORPHOUS VENTRICULAR-TACHYCARDIA IN PATIENTS WITH NORMAL QT INTERVALS AND NORMAL SYSTOLIC CARDIAC-FUNCTION

This study delineates the clinical spectrum of 15 patients with polymo rphic ventricular tachycardia and normal QT intervals in the absence o f apparent structural heart disease, adverse drug effects, or electrol yte disturbances. Patients presented with either palpitations in (n = 2), presyncope (n = 5), syncope (n = 4), no symptoms (n = 1), or abort ed sudden death (n = 3). Mean age was 41 years (range 20 to 64), and m ean follow-up 38 months (range 4 to 109). Left ventricular function wa s normal as determined by either echocardiogram (n = 9) or left ventri culography (n = 9). Episodes of polymorphic ventricular tachycardia (V T) were analyzed in terms of the preceding interval, and the relation of the initiating coupling interval to the QT interval (coupling inter val/QT interval = polymorphic VT index). The mean QT for the group as a whole was 0.41 +/- 0.02 second. Patients could be separated into 3 d istinct groups. Four patients had polymorphic VT reproducibly induced by exercise and initiated by late-coupled beats (mean polymorphic VT i ndex 1.27 +/- 0.21). Isoproterenol induced polymorphic VT in 3 of 4 pa tients, and all 4 responded to chronic beta blockade. Two patients had polymorphic VT during episodes of coronary artery spasm, and both res ponded to calcium channel blockade. Polymorphic VT unrelated to exerti on or coronary vasospasm occurred in 9 patients. Tachycardia onset was initiated by closely coupled beats (mean polymorphic VT index 0.95 +/ - 0.16), and was preceded by a pause in 4 patients, and no pause in 5 patients. Sudden death occurred in 5 of 9 patients with the shortest p olymorphic VT indexes. Drug therapy and chronic pacing were not reliab le in preventing episodes of sudden death. Invasive electrophysiologic studies, including the use of monophasic action potential recordings, were not useful in the evaluation or management of these patients. Ap propriate therapy for patients presenting with either exercise- or cor onary vasospasm-induced polymorphic VT is usually associated with a go od prognosis. Conversely, patients with spontaneous episodes of short- coupled polymorphic VI have a high incidence of sudden death, and shou ld be considered for automatic implantable cardioverter defibrillator insertion.