Fragmented QRS is associated with torsades de pointes in patients with acquired long QT syndrome.
BACKGROUND
Acquired long QT syndrome (LQTS) is a disease due to a secondary repolarization abnormality induced by various predisposing factors. In contrast to congenital LQTS, risk factors that produce acquired LQTS include organic heart diseases that often exhibit depolarization abnormality. Although various repolarization parameters have been evaluated in acquired LQTS, the existence of depolarization abnormality in association with torsades de pointes (TdP) has not been reported.


OBJECTIVE
The purpose of this study was to evaluate both repolarization (QT components) and depolarization parameters (fragmented QRS [fQRS]) in acquired LQTS patients with markedly prolonged QT interval.


METHODS
Seventy patients with acquired severe QT prolongation (QTc ≥ 550 ms) were studied. Thirty-two patients had syncope or TdP (syncope group). Thirty-eight patients did not have any symptoms (asymptomatic group). The existence of fQRS and QT components (QT, QTc, Tpe [interval between peak and end of T wave] intervals, and U-wave voltage) was analyzed.


RESULTS
The syncope group had more frequent fQRS (81%) than did the asymptomatic group (21%, P < .01) and the incidence of fQRS was not different before and after removal of predisposing factors. The incidence of organic heart disease was not different between the two groups. No differences in QTc interval were noted between the syncope and asymptomatic groups, although the syncope group had longer QT and Tpe intervals and higher U wave than the asymptomatic group (P < .01).


CONCLUSIONS
Acquired predisposing factors promoted repolarization abnormality (especially prolongation of QT and Tpe intervals), and the existence of fQRS had an important role in the development of TdP in patients with acquired LQTS.
Haraoka
Kayo
K
Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Morita
Hiroshi
H
Saito
Yukihiro
Y
Toh
Norihisa
N
Miyoshi
Toru
T
Nishii
Nobuhiro
N
Nagase
Satoshi
S
Nakamura
Kazufumi
K
Kohno
Kunihisa
K
Kusano
Kengo F
KF
Kawaguchi
Kenji
K
Ohe
Tohru
T
Ito
Hiroshi
H
D000368:Aged; D000369:Aged, 80 and over; D004562:Electrocardiography; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D016015:Logistic Models; D008133:Long QT Syndrome / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016171:Torsades de Pointes / Q000453:epidemiology / Q000503:physiopathology*