Which statement about dromotropic effects is true?

Which statement about dromotropic effects is true?

• A. Both have positive dromotropic effects
• B. Sodium blockers negative; Calcium blockers negative
• C. Both have neutral dromotropic effects
• D. Both have negative dromotropic effects

Answer: (D)

Dromotropic effects describe how fast electrical impulses travel through the heart, especially across the AV node. A negative dromotropic effect means slower conduction, which shows up as a longer PR interval on ECG and can reduce AV nodal conduction. Calcium channel blockers are classic negative dromotropic agents because they block L-type calcium channels in nodal tissue, slowing the upstroke of action potential there and delaying AV nodal conduction. Sodium channel blockers slow conduction in the fast-conducting atrial and ventricular myocardium by inhibiting fast Na+ channels. While the AV node relies more on calcium channels, slowing conduction in the surrounding fast pathways can contribute to overall slower conduction in the heart, and they can extend conduction times in areas that influence AV nodal conduction. So, both classes can produce negative dromotropic effects, making that statement true.

Dromotropic effects describe how fast electrical impulses travel through the heart, especially across the AV node. A negative dromotropic effect means slower conduction, which shows up as a longer PR interval on ECG and can reduce AV nodal conduction.

Calcium channel blockers are classic negative dromotropic agents because they block L-type calcium channels in nodal tissue, slowing the upstroke of action potential there and delaying AV nodal conduction.

Sodium channel blockers slow conduction in the fast-conducting atrial and ventricular myocardium by inhibiting fast Na+ channels. While the AV node relies more on calcium channels, slowing conduction in the surrounding fast pathways can contribute to overall slower conduction in the heart, and they can extend conduction times in areas that influence AV nodal conduction.

So, both classes can produce negative dromotropic effects, making that statement true.