Sinus Tachycardia Resulting in Phase 4 Atrioventricular Block.

Paroxysmal phase 4 block is a type of atrioventricular block that occurs in patients with a diseased His-Purkinje system. It is usually triggered by a premature ventricular contraction or premature atrial contraction or slowing of a sinus rhythm. We report a case of phase 4 atrioventricular block triggered by a sinus tachycardia that slows down and discuss the management plan and the mechanism causing the block.