What results from atrial tissue becoming irritable?

The correct answer is based on the understanding that when atrial tissue becomes irritable, it can lead to the early firing of impulses from the atria, which constitutes Premature Atrial Complexes (PACs). PACs occur when ectopic foci in the atria generate impulses before the next expected sinus impulse. This early depolarization results in an irregular heart rhythm characterized by an altered P wave on the ECG, which may be hidden within the preceding T wave or appear as a distinct P wave that is different from the sinus P waves.

The condition arises from factors such as increased caffeine intake, alcohol consumption, stress, or certain medications, all of which can cause the atrial tissue to become more excitable. This irritability leads to the premature contractions observed in PACs.

Understanding PACs is essential because they can be benign in some patients but might also represent a precursor to more serious arrhythmias if the underlying irritability is not addressed.