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A PR interval greater than 0.20 seconds indicates which condition?

  1. Second degree heart block

  2. First degree heart block

  3. Atrial fibrillation

  4. Normal sinus rhythm

The correct answer is: First degree heart block

A PR interval greater than 0.20 seconds is characteristic of first-degree heart block. In this condition, the electrical signals from the atria to the ventricles are delayed, resulting in a longer PR interval. This delay reflects an abnormal conduction through the atrioventricular (AV) node, but the overall rhythm remains regular, and all atrial impulses are eventually conducted to the ventricles. In contrast, second-degree heart block can present with a variety of PR intervals, including some that are normal or some that progressively lengthen until a QRS complex is dropped. Atrial fibrillation is characterized by an irregularly irregular rhythm and does not have a defined PR interval, and normal sinus rhythm is defined by a PR interval that falls between 0.12 and 0.20 seconds, thus not exceeding 0.20 seconds.