ECG : Q Wave

The electrocardiogram (ECG) is a crucial tool in assessing the electrical activity of the heart. Among the various components of an ECG, the Q wave holds significant importance. The picture below illustrates a small negative wave immediately preceding the large QRS complex. This negative deflection is known as a Q wave, which represents the initial phase of ventricular depolarization specifically in the interventricular septum.

• Q Wave: Any negative deflection that precedes an R wave on the ECG.
• Size: Typically less than 2 small squares on the ECG grid, indicating a small amount of conduction.

The Q wave forms as the electrical stimulus passes through the bundle of His and begins to depolarize the septum from left to right. This occurs just before the stimulus separates into the left and right bundle branches. The septal depolarization is a brief event and produces a small deflection on the ECG.

In a normal ECG, Q waves can be seen in specific leads and are considered physiological. These leads typically reflect the initial left-to-right depolarization of the interventricular septum.

The leads where normal Q waves are commonly observed include:

1. Leads I and aVL: These leads look at the heart from the...