Copyright © 2004 by the European Society of Cardiology.
Clinical research
Classification and mechanism of Torsade de Pointes initiation in patients with congenital long QT syndrome
Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, 5-7-1 Fujishiro-dai, Suita 565-8565, Japan
Received March 30, 2004; revised August 3, 2004; accepted August 26, 2004 * Corresponding author. Tel.: 81 6 6833 5012; fax: 81 6 6872 7486 (E-mail: wshimizu{at}hsp.ncvc.go.jp).
AIMS: To examine the initiating mode of Torsade de Pointes (TdP) in patients with congenital long QT syndrome (LQTS).
METHODS AND RESULTS: We evaluated 111 episodes of TdP recorded on the electrocardiograms of 24 patients with congenital LQTS, and clarified the initiating mode, the three consecutive preceding RR intervals defined as C2, C1, and C0, the timing of initiating premature ventricular contraction (PVC) and the cycle length (CL) of TdP. Three different initiating patterns were observed: (1) a "short-long-short" sequence (SLS) pattern (23 patients, 72 TdP, 65%) defined as one or more short–long cardiac cycles followed by an initiating short-coupled PVC (C1>C2 and C0), (2) an "increased sinus rate" (ISR) pattern (8 patients, 28 TdP, 25%) defined as a gradual increase in sinus rate with or without T-wave alternans (C2
C1C0), and (3) a "changed depolarization" (CD) pattern (5 patients, 11 TdP, 10%) defined as a sudden long-coupled PVC or fusion beat followed by short-coupled PVC. The C0 was shorter in ISR than SLS and CD (mean C0: 488 vs. 587 and 603 ms, respectively; P<0.05). Therefore, the initiating PVC appeared near the T-wave peak of the last beat before onset in ISR, while it occurred after the T-wave peak in SLS and CD. The CL of TdP was shorter in ISR than in SLS (256 vs. 295 ms, P<0.05).
CONCLUSIONS: Our data show the existence of three predominant initiating modes of TdP in patients with congenital LQTS and suggests a differential mechanism of initiation of TdP for each mode.
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