**Core Concept**
The conduction velocity in the heart varies across different cardiac tissues due to differences in cell structure and ion channel expression. The AV node has the slowest conduction velocity because of its specialized pacemaker-like cells with slow depolarization, which is essential for delaying impulse transmission to allow ventricular filling.

**Why the Correct Answer is Right**
The AV node conducts impulses at a rate of approximately 0.05 m/s, the slowest among all cardiac conduction pathways. This is due to the presence of gap junctions with low conductance and a reliance on slower calcium-dependent depolarization. In contrast, Purkinje fibers, bundle of His, and ventricular myocardial fibers have faster conduction due to abundant gap junctions and rapid depolarization. The AV node’s slow conduction prevents ventricular overfilling and ensures coordinated systolic contraction.

**Why Each Wrong Option is Incorrect**
Option B: Purkinje fibers have the fastest conduction velocity (up to 4 m/s), not slowest.
Option C: Bundle of His conducts at ~1–2 m/s, significantly faster than AV node.
Option D: Ventricular myocardial fibers conduct at ~0.3–1 m/s, still faster than AV node.

**Clinical Pearl / High-Yield Fact**
AV node delay is a key safety mechanism—without it, ventricles would contract too early, leading to inefficient pumping and potential arrhythmias. This is why AV block (especially 2nd or 3rd degree) disrupts cardiac rhythm and can be life-threatening.

✓ Correct Answer: A. AV node