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Fast and slow torsade de pointes--electrocardiographic characteristics
Piotr Kukla1, Teresa Słowiak-Lewińska, Kazimierz Szczuka
1Department of Internal Medicine, Klimontowicz Hospital, Gorlice, Poland.
Background:
Clinical value of electrocardiographic features of torsade de pointes (TdP) has not yet been well established.
Aim:
To compare the mode of onset and ECG characteristics of slow (s-TdP) and fast (f-TdP) episodes of TdP.
Methods:
54 episodes of TdP recorded in 6 patients (5 females, one male, mean age 64.4 years) with acquired long QT syndrome were analysed. Baseline rate of TdP (V-V), ventricular rate variability (VRV), coupling interval (CI) at the onset of TdP, prematurity index (PI) and the first cycle length (FCL) were compared between 31 s-TdP (<200 beats/min) and 23 f-TdP (> or =220) episodes of TdP.
Results:
Episodes of f-TdP were preceded by a significantly faster basal rhythm than s-TdP (R-R interval: 922 ms vs 1062 ms, p=0.03). QT interval was almost identical in both groups (517 ms vs 515 ms, NS, respectively). No significant differences were noted in the CI of the initiating beat (488 ms vs 472 ms, NS) nor in the PI (0.53 vs 0.47, NS). TdP was most frequently spontaneously terminated by a gradual slowing of the tachycardia rate; 58% of s-TdP and 39% of f-TdP episodes stopped in this way. An acceleration of ventricular rate before termination of TdP was noted in 32% of s-TdP and in 26% of f-TdP episodes. Episodes of f-TdP were longer than s-TdP episodes (mean of 19.7 vs 6.7 ventricular complexes per one episode, p=0.0003). There were significant differences in the VRV parameter (p=0.0005) and FCL (p=0.004) between both types of TdP. Faster TdP were characterised by lower ventricular rate variability (VRV - 19.5 msec) than s-TdP (VRV - 39.4 msec). Of 54 episodes of TdP, 9 (16.6%) degenerated into VF and required DC shock. Of 31 s-TdP episodes, one (3.2%) degenerated into VF compared with 8 (34.7%) episodes of f-TdP (p<0.04).
Conclusions:
Episodes of fast TdP were characterised by a longer duration, shorter first cycle of the arrhythmia and lower ventricular rate variability than episodes of slow TdP. Fast episodes of TdP were preceded by faster baseline rhythm before TdP. Faster TdP more frequently degenerated into VF than slower episodes.