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Early Afterdepolarizationlike Activity in Patients with Class IA Induced Long QT Syndrome and Torsades de Pointes
Author(s) -
KURITA TAKASHI,
OHE TOHRU,
SHIMIZU WATARU,
SUYAMA KAZUHIRO,
AIHARA NAOHIKO,
TAKAKI HIROSHI,
KAMAKURA SHIRO,
SHIMOMURA KATSURO
Publication year - 1997
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/j.1540-8159.1997.tb03888.x
Subject(s) - torsades de pointes , medicine , qt interval , disopyramide , afterdepolarization , long qt syndrome , cardiology , anesthesia , discontinuation , repolarization , electrophysiology
Early afterdepolarizations (EADs) have been linked to the mechanism of torsades de pointes in long QT syndrome. The purpose of this study was to investigate the role of EADs in Class IA induced torsades de pointes. We studied nine patients with Class IA induced torsades de pointes at the time this arrhythmia was present (acute period, n = 7) and after Class IA therapy was discontinued (chronic period, n = 6). ECCs and monophasic action potentials were recorded in both periods. In the chronic period, electrophysiological studies were performed before and after disopyramide infusion. In the acute period, QT c interval was markedly prolonged (655 ± 32 ms 1/2 ), and EAD‐like activity was recorded in all patients. QT c interval returned to normal (428 ± 45 ms 1/2 ) and EAD‐like activity disappeared after discontinuation of IA drug. Although, in the chronic period, disopyramide infusion prolonged QT c interval from 428 ± 48 ms 1/2 to 479 ± 31 ms 1/2 and induced EAD in three of six patients, the degree was not as marked as observed in the acute period. EADs may play an important role in the genesis of long QT and torsades de pointes. Disopyramide infusion in the chronic period could not reproduce marked repolarization ahnormalities and torsades de pointes.