Classification and mechanism of Torsade de Pointes initiation in patients with congenital long QT syndrome

Aims To examine the initiating mode of Torsade de Pointes (TdP) in patients congenital tong 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, three consecutive preceding RR intervals defined as C-2, C-1, and C-0, the timing of imitiating premature ventricular contraction (PVC) and the cycle length (CL) of TdP. Three different initiating patterns were observed: (1) a "short-tong-short" (SLS) pattern (23 patients, 72 TdP, 65%) defined as one or more short-long cycles followed by an initiating short-coupled PVC (C-1 > C-2 and C-0), (2) an "increased sinus rate" (ISR) pattern (8 patients, 28 TdP,. 25%) defined as a gradual increase sinus rate with or without T-wave alternans (C-2 greater than or equal to C-1 greater than or equal to C-0), and (3) a "changed depolarization" (CD) pattern (5 patients, 11 TdP, 10%) defined as a sudden tong PVC or fusion beat followed by short-coupled PVC. The C-0 was shorter in ISR SLS and CD (mean C-0: 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 ISR, while it occurred after the T-wave peak in SLS and CD. The CL of TdP was in ISR than in SLS (256 vs. 295 ms, P < 0.05). Conclusions Our data show the existence of three predominant initiating modes TdP in patients with congenital LQTS and suggests a differential mechanism of initiation of TdP for each mode. (C) 2004 The European Society of Cardiology. Published by Elsevier Ltd. All reserved.