## Medical Surgical EKG #7

### Question

A nurse caring for a client on telemetry interprets the electrocardiogram (ECG) as having a bundle branch block based on the following characteristics:

1. A narrow QRS segment
• Rationale:

This answer is not correct because bundle branch blocks present with a wide (not narrow) QRS segment. Bundle branch block occurs when an impulse is blocked as it travels through the bundle branches.

2. A wide QRS segment
• Rationale:

This answer is correct because bundle branch block occurs when an impulse is blocked as it travels through the bundle branches and is reflected on the ECG strip as a widened QRS segment. Electrical impulses travel down the right and left bundle branches at the same speed. A block in one of the branches causes the electrical impulse to travel to the ventricle via an alternate route. The ventricle still contracts; however, it will take longer and the impulse will be slower. One ventricle contracts a fraction of a second slower than the other ventricle. Blocks can be either right or left.

3. An inverted PR interval
• Rationale:

This answer is not correct because bundle branch blocks present with a wide QRS segment, not an inverted PR interval. Bundle branch block occurs when an impulse is blocked as it travels through the bundle branches.

4. A spiked PR interval
• Rationale:

This answer is not correct because bundle branch blocks present with a wide QRS segment, not a spiked PR interval. Bundle branch block occurs when an impulse is blocked as it travels through the bundle branches.

### Overview

Bundle branch block occurs when an impulse is blocked as it travels through the bundle branches. Bundle branch blocks will have a wide QRS segment.

### Learning Outcomes

Bundle branch block occurs when an impulse is blocked as it travels through the bundle branches. Electrical impulses travel down the right and left bundle branches at the same speed. A block in one of the branches causes the electrical impulse to travel to the ventricle via an alternate route. The ventricle still contracts; however, it will take longer and the impulse will be slower. One ventricle contracts a fraction of a second slower than the other ventricle. This is reflected on the ECG strip as a widened QRS segment. Blocks can be either right or left.

### Test Taking Tip

The normal QRS segment should be 0.12-0.20 seconds. Understanding the normal widths of the parts of the ECG will help the student recognize when there is an abnormality which needs to be assessed further.