On an ECG atrial flutter is characterized by absence of normal P wave.

在ECG上，心房扑动的特征是没有正常的P波。

Presence of a normal P wave therefore indicates sinus rhythm.

因此，正常P波的出现表明窦性心律。

You will remember from section I that normal T waves tend to be slightly asymmetrical in shape and less than 50% of the height of the proceeding all waves.

从第一部分，我们知道，正常T波往往在形状上稍微不对称，高度小于所有波的50%。

Next, the ectopic beat could happen during the PR segment, and because the ectopic depolarization happens relatively slowly, oftentimes, it will combine with the normal depolarization wave coming down the ventricular conduction system, resulting in a ventricular fusion beat.

其次，异位心搏可能发生在PR间期，因为异位去极化相对缓慢，它常会和在心室传导系统中下行的正常除极波融合，导致室性融合心搏。