Which condition is characterized by a PR interval greater than 0.20 but consistent?

The condition characterized by a PR interval greater than 0.20 seconds, but remains consistent, is 1st degree AV block. In this condition, the electrical signals from the atria to the ventricles are delayed, resulting in a prolonged PR interval that consistently exceeds 0.20 seconds on the ECG tracing.

This is different from other types of conduction blocks. For instance, in 2nd degree block type 1, also known as Mobitz type 1 or Wenckebach, the PR interval progressively lengthens until a QRS complex is dropped, making it inconsistent. In 3rd degree AV block, there is a complete dissociation between atrial and ventricular activity, resulting in irregular pacing rhythms and variable PR intervals. Atrial fibrillation does not feature a distinct PR interval at all, as it presents with an irregularly irregular rhythm and absence of consistent atrial contractions.

Thus, recognizing the consistent nature of the prolonged PR interval is key to identifying 1st degree AV block accurately.