正常成人QT_(max)、QT_(min)在十二导心电图的分布规律及临床意义

Distribution and clinical significance of normal adult's QT_(max) and QT_(min) in 12-lead electrocardiogram

目的 找出正常成人最大QT间期 (QTmax)和最小QT间期 (QTmin)在十二导心电图的分布规律 ,提高QT离散度的敏感性。方法 对 5 82例正常成人进行十二导心电图同步记录检查 ,找出QTmax和QTmin在各导联的数量和在十二导心电图中的分布规律 ,统计各导联缺失和不同导联组合缺失时的QT离散度均值 ,观察其对QTd的影响。结果 5 82例心电图平均QTd 35 3± 9 5ms,各导联QT间期均值avL最小 ,V2 、V3 导联最大。aVL导联中 92 %为QTmin,无一例为QTmax,V2 、V3 两个导联中QTmax占 97% ,QTmin大部分分布在Ⅰ、aVL、V1导联 ,以单一或同时在两个导联中存在为主 ,4 0 %单一存在aVL导联中。QTmax大多分布在V2～ 5的胸导联中 ,同时在三个或三个以上导联中存在为主。缺乏相应导联时对QTd的影响由大到小为 :Ⅰ、aVL、V1→avL、V1→V2 、V3 、V4→Ⅰ、aVL→V2 、V3 →aVL→Ⅰ、V1。Ⅱ、Ⅲ、avF和V4～ 6导联缺失时 ,对QTd的影响不大 (P >0 0 5 )。结论 如果十二导心电图中只有aVL或Ⅰ、aVL导联为QTmax或V2 、V3 导联都为QTmin,即使QTd只有 2 0～ 30ms也可以视为异常。不同导联及其组合的缺失 ,对QTd的影响不同。测量QTd时以不能少于八个或八个以上导联作为条件并不够 ,应加上不要缺乏aVL导联 ,Ⅰ、V1和V2 、V3 导联不能同时?

Objective By studying the distribution of adult's QT max and QT min in ECG 12 lead to increase the sensitivity of QT dispersion. Method 582 normal adults undergone ECG examination were studied respectively. QT max and QT min were calculated in each lead, and the mean of QT dispersion (QTd) was also calculated in the absence of different lead or lead combinations.Results The mean of QTd was 35 3±9 5 ms. The mean of QT interval was minimal in aVL and maximal in V 2 and V 3. 92% of QT intervals were QT min without QT max in aVL, and 97% were QT max in V 2 and V 3. Most QT min distributed in Ⅰ, aVL and V 1, and mainly existed in single or double leads, and 40% of them existed in aVL. Most QT max distributed in V 2 to V 5, existed in at least three leads. When the matched lead was absent, QTd was affected from maximal to minimal: Ⅰ, aVL, V 1→aVL, V 1→V 2,V 3,V 4→Ⅰ, avL→V 2, V 3→aVL→Ⅰ,V 1. When Ⅱ, Ⅲ, aVF and V 4 to V 6 were absent, QTd was not affected ( P >0.05).Conclusion If QT intervals are QT max only in aVL or Ⅰ and aVL, or QT min both in V 2 and V 3, the QTd is considered abnormal even though QTd is 20 to 30 ms. QTd is different in absence of different lead or lead combinations. It is not accurate to calculate QTd only by 8 leads or more, because avL must be included, while Ⅰ or V 1 and V 2 or V 3 never disappear at the same time. QTd is also affected by the blood supply to the heart, because any absent lead caused by determined ECG position will affect the sensitivity of QTd.