First-Degree AV Block — ECG Academy Lesson

Learn to identify first-degree AV block by its prolonged PR interval, understand why it is a delay rather than a true block, and recognize the causes and clinical significance.

Learning Objectives

• Define first-degree AV block as a conduction delay with a PR interval greater than 0.20 seconds
• Explain why first-degree AV block is not actually a "block" — every impulse conducts
• Measure the PR interval accurately and identify when it exceeds 0.20 seconds (5 small boxes)
• List common causes including medications, ischemia, and increased vagal tone
• Describe the monitor tech response to first-degree AV block and criteria for monitoring progression