Reiffel Alyssa J, Reiffel James A
The Division of Cardiology, Department of Medicine,Columbia University Medical Center,New York, New York.
J Atr Fibrillation. 2009 Feb 1;1(5):113. doi: 10.4022/jafib.113. eCollection 2009 Feb-Mar.
Ectopic beats are frequently associated with morphologic repolarization alterations of ensuing sinus beats. Less is known about repolarization duration alterations of post-ectopic sinus beats. In one patient who developed long QT and torsades de pointes upon exposure to a class III antiarrhythmic drug, and was later genotyped as being a carrier for long QT syndrome (LQTS) type 1, review of a pre-drug Holter monitor study revealed marked QT prolongation of post-ectopic sinus beats. In wondering whether this might be a common clue to "concealed" unexpressed LQTS, we realized that we must first characterize the range of post-ectopic QT prolongation present in normals. Prolongation beyond the upper limit of this range might then raise suspicion of possible LQTS and alter the antiarrhythmic drug selection process for the suppression of atrial fibrillation or other arrhythmias. Accordingly, we assessed the presence/degree of repolarization prolongation following premature ectopic impulses in 166 subjects with normal conduction intervals and normal repolarization on their resting 12-lead ECG, 75 of whom had no known associated cardiovascular disorder of any kind. That is, in our subjects, the maximal prolongation of the QT interval of the sinus beat following isolated ventricular and atrial premature complexes was characterized. QT prolongation is common in post ectopic sinus beats. However, in our subjects the uncorrected QT interval of post-ectopic sinus beats never exceeded 480 ms in duration [which was much shorter than that seen (510-590 ms) in our gene carrier].
The QT interval in normal subjects may prolong following premature complexes but not to a value in excess of 480 ms.
异位搏动常与随后窦性搏动的形态学复极改变相关。关于异位后窦性搏动的复极持续时间改变，人们了解较少。在一名患者中，其在使用Ⅲ类抗心律失常药物后出现长QT间期和尖端扭转型室速，后来基因分型显示为长QT综合征（LQTS）1型携带者，回顾用药前的动态心电图监测研究发现异位后窦性搏动有明显的QT间期延长。在思考这是否可能是“隐匿性”未表达的LQTS的常见线索时，我们意识到必须首先确定正常人心电图中异位后QT间期延长的范围。超过该范围上限的延长可能会引发对可能的LQTS的怀疑，并改变用于抑制房颤或其他心律失常的抗心律失常药物选择过程。因此，我们评估了166名静息12导联心电图传导间期正常且复极正常的受试者在过早异位冲动后复极延长的存在情况/程度，其中75人无任何已知的相关心血管疾病。也就是说，在我们的受试者中，对孤立室性和房性早搏后窦性搏动的QT间期最大延长情况进行了特征描述。QT间期延长在异位后窦性搏动中很常见。然而，在我们的受试者中，异位后窦性搏动未经校正的QT间期持续时间从未超过480毫秒[这比我们的基因携带者中观察到的（510 - 590毫秒）要短得多]。
正常受试者在早搏后QT间期可能延长，但不会超过480毫秒。
