Which of the following mechanisms is applicable to the antiarrhythmic activity of quinidine glu-conate (Quinaglute)?
a. Increases conduction velocity in the Purkinje fibers
b. Increases the rate of rise in phase 0 depolarization
c. Blocks slow calcium channels and increases the reactivation rate
d. Suppresses automaticity and prolongs refractory periods
ANS: D
Class IA drugs, such as quinidine, tend to suppress automaticity by lowering the pacemaker po-tential needed to provoke spontaneous depolarization. Refractory periods are prolonged, and premature electrical stimulation is less likely to occur.
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