QT离散度增加预示心肌梗死后程序刺激诱发室性心动过速

Increased QTc Dispersion is a New Marker for Predicting Post Myocardial Infarction Ventricular Tachycardia

QT离散度(QTd或QTcd-心率校正QT离散度)反映了心室电活动的非同步性。多数情况下QT离散度增加与心律失常危险性增加有关。本文旨在研究心肌梗死后心室程序电刺激(PES)结果与QT离散度之间的关系。36例陈旧心肌梗死怀疑有室性心动过速(室速)的患者纳入了本研究。其中25例诱发出室速,11例无室速。室速患者的QTcd大于无室速的患者(P<0.01)。前者ECG12导联中最大的QTC(QTc-max)也大于后者是(P<0.01)。18例胺碘酮治疗的患者中诱发室速的比不能诱发的QTc大(P<0.05)。假如以QTcd≥50ms作为PES诱发室速的预测值,其敏感性和特异性分别为72％和73％。假如以QTc-max≥460ms作为PES诱发室速的预测值,其敏感性和特异性分别为60％和73％。总之,QTcd增加和QTc-max延长与PES诱发室速关系密切,这一关系不因使用胺碘酮治疗而改变。

QT dispersion is the difference between the longest QT (QT-max) and the shortest QT (QT-min) in a 12 lead ECG. In many situations increased QT dispersion is an arrhythmia risk. The present study was to determine the relation between QT dispersion and the results of programmed electrical stimulation (PES) in patients of old Q wave myocardial infarction (MI) and to investigate the value of QT dispersion in class Ⅲ drug therapy. Thirty--six patients with previous Q wave MI were sludied. Sustained monomorphic ventricular tachycardia (SMVT) was induced in 25 patients, no ventricular tachyarrhythmias (no-VT) were induced in the remaining 11. Eighteen of 36 patients were on class Ⅲ therapy. SMVT was induced in 11 but not in the remaining 7. QT was measured by a digitizer and corrected for heart rate (QTc). Heart rate corrected QT (QTc) dispersion was greater in patients with SMVT than in patients with no-VT (59ms vs 40ms; P<0.01), so too was QTc-max (472ms vs. 444ms; P= 0.04). If a QTc dispersion value of 50ms were used as cut-off for the prediction of the SMVT initiation the sensitivity and specificity were 72% and 73% respectively. A Cut-off QTc-max value of 460ms had a sensitivity of 60% and specificity of 73%. Furthermore, SMVT patients on class Ⅲ therapy had a significantly greater QTc dispersion than those on the same therapy with no-VT (69ms vs 44ms; P=0.047). In conclusion, both an increased QTc dispersion and QTc prolongation correlated with the induction of SMVT by PES in patients with old Q wave infarction. Smaller QTc dispersion correlated with an antiarrhythmic effect of class Ⅲ therapy assessed by PES. The study validates the application of QTc dispersion as a noninvasive technique for detecting patients at high arriythmia risk with old MI and for assessing antiarrhythmic drug effects.