## ECG Question #12

### Question

The nurse is caring for a client on the telemetry unit and upon reviewing the electrocardiogram, determines that the PR interval is less than .20 second, QRS measures .08 second and is regular, and the rate is 74 beats per minute. These findings are interpreted as:

1. First degree heart block
• Rationale:
2. Atrial fibrillation
• Rationale:
3. Second degree heart block
• Rationale:
4. Normal sinus rhythm
• Rationale:

### Explanation

Normal sinus rhythm consists of heart rate between 60 and 100 beats per minute with regular rhythm. Normal sinus rhythm on the ECG is represented by PR interval measures 0.12 – 0.20 second, and the QRS complex measures 0.04 – 0.10 second. In first degree heart block the ventricular rate depends upon the underlying rhythm and the PR interval is greater than 0.20 seconds. In atrial fibrillation, the atrial rate is 300 to 600 bpm with the ventricular rate between 120 to 200 bpm. In second degree heart block the ventricular and atrial rate depends upon the underlying rhythm and the PR interval becomes longer with each succeeding complex.