What is indicated by a PR interval longer than 0.20 seconds?

What is indicated by a PR interval longer than 0.20 seconds?

• A. Normal conduction
• B. A-type heart block
• C. Wolff-Parkinson-White syndrome
• D. Myocardial infarction

Answer: (B)

A PR interval longer than 0.20 seconds indicates a delay in the conduction of electrical impulses from the atria to the ventricles, which is commonly recognized as first-degree atrioventricular (AV) block. In first-degree AV block, the conduction through the AV node is impaired, causing a prolonged PR interval but with every atrial impulse still generating a ventricular response. This condition can be benign and often doesn’t cause symptoms or require treatment. In contrast, normal conduction would present with a PR interval of 0.12 to 0.20 seconds. Conditions like Wolff-Parkinson-White syndrome involve an accessory pathway leading to a premature ventricular contraction, not a prolonged PR interval. Lastly, while myocardial infarction can lead to various conduction abnormalities, a prolonged PR interval specifically points towards the presence of first-degree AV block, rather than being a direct indicator of myocardial infarction itself. Therefore, the correct interpretation of a PR interval longer than 0.20 seconds is indicative of a first-degree heart block.

A PR interval longer than 0.20 seconds indicates a delay in the conduction of electrical impulses from the atria to the ventricles, which is commonly recognized as first-degree atrioventricular (AV) block. In first-degree AV block, the conduction through the AV node is impaired, causing a prolonged PR interval but with every atrial impulse still generating a ventricular response. This condition can be benign and often doesn’t cause symptoms or require treatment.

In contrast, normal conduction would present with a PR interval of 0.12 to 0.20 seconds. Conditions like Wolff-Parkinson-White syndrome involve an accessory pathway leading to a premature ventricular contraction, not a prolonged PR interval. Lastly, while myocardial infarction can lead to various conduction abnormalities, a prolonged PR interval specifically points towards the presence of first-degree AV block, rather than being a direct indicator of myocardial infarction itself. Therefore, the correct interpretation of a PR interval longer than 0.20 seconds is indicative of a first-degree heart block.