As a cardiac electrophysiist, I specialize in the study of the electrical activity of the heart. During the QRS complex on an electrocardiogram (ECG), a series of crucial events occur within the heart's conduction system.

Firstly, the QRS complex represents the ventricular depolarization. This is the process by which the electrical impulses generated by the sinoatrial (SA) node, which is the heart's natural pacemaker, spread through the ventricles, causing them to contract. The contraction of the ventricles is what pumps blood out to the body.

The QRS complex is divided into three phases:
1. The Q wave is usually the first downward deflection and represents the initial depolarization of the septum.
2. The R wave is the subsequent upward deflection and signifies the spread of depolarization to the rest of the ventricles.
3. The S wave is the final downward deflection and indicates the completion of ventricular depolarization.

During this time, the ventricular muscle fibers are rapidly becoming excited, and this electrical activity is what we see on the ECG as the QRS complex. It's important to note that the QRS complex is typically less than 0.12 seconds in duration in a normal ECG.

Here's the translation in Chinese:

作为心脏电生理学专家，我专门研究心脏的电活动。在心电图（ECG）上的QRS波群期间，心脏的传导系统中发生了一系列关键事件。

首先，QRS波群代表心室去极化。这是由窦房结（SA结）产生的电脉冲传播到心室，导致心室收缩的过程。心室的收缩是将血液泵送到全身的动力。

QRS波群分为三个阶段：

1. Q波通常是第一个向下的偏转，代表隔膜的初始去极化。

2. R波是随后向上的偏转，意味着去极化向心室其余部分的传播。

3. S波是最后的向下偏转，表明心室去极化的完成。

在这段时间里，心室肌纤维正在迅速变得兴奋，这种电活动就是我们在心电图上看到的QRS波群。值得注意的是，正常的心电图中QRS波群的持续时间通常少于0.12秒。

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The first wave is the P wave, which represents the depolarization of the atria. This happens right before the atria contract and push blood into the ventricles. The next wave is called the QRS wave. This wave is much larger than the P wave, and it represents the depolarization of the ventricles.read more >>