Sodium channel blockers have which dromotropic effect?

Sodium channel blockers have which dromotropic effect?

• A. Positive
• B. Negative
• C. Neutral
• D. None

Answer: (B)

Dromotropy is about how quickly the electrical impulse conducts through the heart, especially the AV node. Sodium channel blockers dampen the fast sodium current that drives the rapid upstroke of the action potential in atrial, ventricular, and Purkinje fibers. By reducing the slope of phase 0, they slow the spread of impulses through these tissues. Slower conduction equals a negative dromotropic effect. While AV nodal conduction is mainly calcium-dependent, the overall effect of blocking sodium channels is to reduce conduction velocity in the fast pathways, reinforcing a negative dromotropic impact.

Dromotropy is about how quickly the electrical impulse conducts through the heart, especially the AV node. Sodium channel blockers dampen the fast sodium current that drives the rapid upstroke of the action potential in atrial, ventricular, and Purkinje fibers. By reducing the slope of phase 0, they slow the spread of impulses through these tissues. Slower conduction equals a negative dromotropic effect. While AV nodal conduction is mainly calcium-dependent, the overall effect of blocking sodium channels is to reduce conduction velocity in the fast pathways, reinforcing a negative dromotropic impact.