What characterizes a 1st Degree AV Block?

In a 1st Degree AV Block, the most distinguishing feature is a PR interval that exceeds 0.20 seconds. The PR interval represents the time taken for the electrical impulse to travel from the atria to the ventricles, and in this condition, there is a delay in conduction through the AV node. The characteristic longer PR interval is consistent and does not change in duration throughout the rhythm strip.

A PR interval less than 0.20 seconds would indicate normal conduction and does not align with the definition of a 1st Degree AV Block. Unrelated P waves and QRS complexes would suggest a different type of heart block, such as a complete heart block, where the atrial and ventricular activities become dissociated. Lastly, a variable PR interval would indicate fluctuating conduction times and is characteristic of other arrhythmias, rather than the consistent prolongation seen in 1st Degree AV Block.