Tieleman R G, Crijns H J, Wiesfeld A C, Posma J, Hamer H P, Lie K I
Department of Cardiology, University Hospital, Groningen, The Netherlands.
Br Heart J. 1995 Jan;73(1):37-40. doi: 10.1136/hrt.73.1.37.
The mechanism responsible for the reported high incidence of ventricular arrhythmias in mitral valve prolapse is not clear. Electrocardiographic studies show an increased occurrence of repolarisation abnormalities on the 12 lead surface electrocardiogram, indicating regional differences in ventricular recovery. The purpose of this study was to investigate whether dispersion of refractoriness was an arrhythmogenic mechanism.
QT dispersion was measured in 32 patients with echocardiographically documented mitral valve prolapse and ventricular arrhythmias on 24 hour Holter recordings. QT dispersion was defined as the difference between the maximum and minimum average QT interval in any of the 12 leads of the surface electrocardiogram. QT dispersion corrected for heart rate was calculated by Bazett's formula. The results were compared with the data from 32 matched controls without a history of cardiac disease. Patients taking drugs that influence the QT interval and patients with a QRS duration > 120 ms were excluded.
QT dispersion was greater in patients with mitral valve prolapse than in matched controls (60 (20) v 39 (11 ms) respectively, P < or = 0.001) as was corrected QT (64 (20 ms) v 43 (12 ms) respectively, P < or = 0.001). There was no significant difference in minimum or maximum QT intervals between the two groups.
QT dispersion on the 12 lead surface electrocardiogram was greater in patients with mitral valve prolapse with ventricular arrhythmias than in normal controls, but the maximum QT interval was not increased. The results accord with the hypothesis that regional shortening and lengthening of repolarisation times in patients with mitral valve prolapse may account for the increased dispersion of refractoriness.
二尖瓣脱垂患者室性心律失常发生率较高，其机制尚不清楚。心电图研究显示，12导联体表心电图复极异常的发生率增加，提示心室复极存在区域差异。本研究旨在探讨不应期离散是否为心律失常的发生机制。
对32例经超声心动图证实有二尖瓣脱垂且24小时动态心电图记录有心室心律失常的患者测量QT离散度。QT离散度定义为体表心电图12导联中任一导联最大平均QT间期与最小平均QT间期之差。采用Bazett公式计算心率校正的QT离散度。将结果与32例无心脏病史的匹配对照组数据进行比较。排除服用影响QT间期药物的患者及QRS时限>120ms的患者。
二尖瓣脱垂患者的QT离散度大于匹配对照组（分别为60（20）ms和39（11）ms，P≤0.001），校正QT离散度也是如此（分别为64（20）ms和43（12）ms，P≤0.001）。两组间最小或最大QT间期无显著差异。
有室性心律失常的二尖瓣脱垂患者12导联体表心电图的QT离散度大于正常对照组，但最大QT间期未增加。结果符合如下假设：二尖瓣脱垂患者复极时间的区域性缩短和延长可能导致不应期离散增加。
