Dromotropic agents primarily affect conduction speed in which cardiac structure?

Dromotropic agents primarily affect conduction speed in which cardiac structure?

• A. AV node
• B. SA node
• C. Bundle of His
• D. Purkinje fibers

Answer: (A)

Dromotropic effects refer to changes in how quickly electrical impulses travel through the heart. The AV node is the gatekeeper between the atria and ventricles, providing the deliberate delay that allows ventricles to fill properly. Because this AV nodal delay is what determines how fast the ventricles are paced after atrial activity, drugs that alter conduction speed mostly act at the AV node. Negative dromotropes slow AV nodal conduction, lengthening the PR interval, while positive dromotropes speed it up. The SA node governs heart rate (chronotropy), and the Bundle of His with Purkinje fibers conduct rapidly to the ventricles, so they’re less the primary target for dromotropic modulation. Thus, the AV node is the structure where conduction speed is primarily affected.

Dromotropic effects refer to changes in how quickly electrical impulses travel through the heart. The AV node is the gatekeeper between the atria and ventricles, providing the deliberate delay that allows ventricles to fill properly. Because this AV nodal delay is what determines how fast the ventricles are paced after atrial activity, drugs that alter conduction speed mostly act at the AV node. Negative dromotropes slow AV nodal conduction, lengthening the PR interval, while positive dromotropes speed it up. The SA node governs heart rate (chronotropy), and the Bundle of His with Purkinje fibers conduct rapidly to the ventricles, so they’re less the primary target for dromotropic modulation. Thus, the AV node is the structure where conduction speed is primarily affected.