Which of the following is a type of heart block?

• A. First Degree AV Block
• B. Atrial Fibrillation
• C. Atrial Flutter
• D. Multifocal Atrial Tachycardia

Answer: (A)

Conduction block means the impulse from the atria to the ventricles is slowed or interrupted. First Degree AV Block is the mild form of this, where the AV node conducts every atrial impulse to the ventricles but with a longer delay. On an ECG you’ll see a PR interval longer than 0.20 seconds, with P waves followed by QRS complexes in a 1:1 relationship and a normal QRS width. Because the impulse still gets through to the ventricles, just more slowly, it’s classified as a block, although usually benign.

The other conditions are not blocks. Atrial fibrillation shows chaotic atrial activity with no distinct P waves and an irregularly irregular ventricular response, not a conduction delay. Atrial flutter produces sawtooth atrial patterns often with a rapid atrial rate but still represents atrial rhythm disorder rather than AV conduction block. Multifocal atrial tachycardia involves several atrial foci causing irregular P waves and rate, not a block in the AV pathway.

So the correct option is First Degree AV Block.