Takahashi N, Ito M, Inoue T, Koumatsu K, Takeshita Y, Tsumabuki S, Tamura M, Inoue K, Maeda T, Saikawa T
Department of Laboratory Medicine, Oita Medical University.
J Cardiol. 1993;23(1):99-106.
We examined the clinical characteristics and electrocardiographic findings of 7 patients having the acquired long QT syndrome who developed torsades de pointes while receiving no antiarrhythmic drugs. A total of 43 episodes of torsades de pointes were documented among these patients. Underlying heart diseases were present in 6 patients and hypopotassemia (< or = 3.3 mEq/l) in 4. Four had bradycardia (< or = 52 beats/min) immediately before the development of torsades de pointes. The QTc intervals measured immediately before the episodes of torsades de pointes were significantly longer than those 6-24 hours before the episodes (0.69 +/- 0.10 vs 0.56 +/- 0.10 sec, p < 0.05), while heart rates did not differ significantly between these 2 periods (54 +/- 12 vs 58 +/- 15 beats/min). The ventricular rate of torsades de pointes was 192 +/- 24 beats/min. A "long-short initiating cycle" was noted in all 43 episodes, and the initiating premature ventricular beat (PVB) showed the "R on T(U)" phenomenon in 42 of the episodes. A notched T-U complex due to a prominent slow wave (U wave) at the end of the T wave was noted in 5 patients immediately before the episodes of torsades de pointes. Prolongation of the preceding RR interval was directly related to the increase of the U wave amplitude, which caused an increased likelihood of the occurrence of PVBs near the peak of the U wave. Torsades de pointes developed from the largest U wave. Direct current cardioversion was transiently effective for treating torsades de pointes, and intravenous lidocaine, atropine and verapamil were effective in some cases.(ABSTRACT TRUNCATED AT 250 WORDS)
我们研究了7例获得性长QT综合征患者的临床特征和心电图表现，这些患者在未使用抗心律失常药物的情况下发生了尖端扭转型室速。这些患者共记录到43次尖端扭转型室速发作。6例患者存在基础心脏病，4例有低钾血症（≤3.3 mEq/L）。4例在尖端扭转型室速发作前即刻出现心动过缓（≤52次/分钟）。尖端扭转型室速发作前即刻测量的QTc间期显著长于发作前6 - 24小时（0.69±0.10秒对0.56±0.10秒，p<0.05），而这两个时期的心率无显著差异（54±12次/分钟对58±15次/分钟）。尖端扭转型室速的心室率为192±24次/分钟。所有43次发作均出现“长短启动周期”，42次发作中起始室性早搏（PVB）表现为“R on T（U）”现象。5例患者在尖端扭转型室速发作前即刻可见T波末端因明显的慢波（U波）导致的切迹T - U复合波。前一个RR间期的延长与U波振幅的增加直接相关，这导致在U波峰值附近发生室性早搏的可能性增加。尖端扭转型室速由最大的U波引发。直流电复律对治疗尖端扭转型室速有短暂疗效，静脉注射利多卡因、阿托品和维拉帕米在某些情况下有效。（摘要截短于250字）
