Milrinone's effects on cardiac electrical activity include which of the following?

Milrinone's effects on cardiac electrical activity include which of the following?

• A. Decreased chronotropy and dromotropy
• B. No effect on conduction
• C. Increased chronotropy and dromotropy
• D. Slowed AV conduction

Answer: (C)

Milrinone inhibits PDE-3, which raises cAMP levels inside cardiac cells. That increase enhances both the force of contraction and the activity of pacemaker and conduction tissues. In pacemaker cells, higher cAMP speeds depolarization and raises heart rate (positive chronotropy). In conduction tissue, especially the AV node, higher cAMP speeds conduction (positive dromotropy). So milrinone not only boosts contractility but also speeds heart rate and AV conduction, matching the idea of increased chronotropy and dromotropy. While this drug can predispose to tachyarrhythmias due to increased excitability, the fundamental electrical effect aligns with faster pacemaker activity and faster AV conduction.

Milrinone inhibits PDE-3, which raises cAMP levels inside cardiac cells. That increase enhances both the force of contraction and the activity of pacemaker and conduction tissues. In pacemaker cells, higher cAMP speeds depolarization and raises heart rate (positive chronotropy). In conduction tissue, especially the AV node, higher cAMP speeds conduction (positive dromotropy). So milrinone not only boosts contractility but also speeds heart rate and AV conduction, matching the idea of increased chronotropy and dromotropy. While this drug can predispose to tachyarrhythmias due to increased excitability, the fundamental electrical effect aligns with faster pacemaker activity and faster AV conduction.