What is the intended effect of lidocaine and amiodarone in ventricular tachyarrhythmias?

• A. Shorten ventricular refractory period
• B. Increase AV nodal conduction
• C. Promote atrial automaticity
• D. Suppress ventricular automaticity

Answer: (D)

The goal in using lidocaine and amiodarone for ventricular tachyarrhythmias is to suppress abnormal automaticity in the ventricles, making it harder for ectopic impulses to trigger or sustain the tachyarrhythmia. Lidocaine is a sodium-channel blocker that preferentially acts on depolarized, ischemic ventricular tissue, reducing the slope of phase 0 and dampening ectopic pacemaker activity. Amiodarone has broad effects that prolong repolarization and increase the ventricular refractory period, which raises the threshold for impulse propagation and helps interrupt reentry circuits. By lowering the likelihood of spontaneous ventricular impulses and prolonging the time during which tissue cannot be re-excited, these drugs help stabilize the rhythm. Shortening the refractory period or increasing AV nodal conduction would not prevent VT and could worsen it, and promoting atrial automaticity is not relevant to ventricular tachyarrhythmias.