Which statement is true regarding the use of dofetilide and its effect on cardiac action potential?

The statement that dofetilide inhibits the delayed rectifier potassium current is accurate and highlights the primary mechanism of action of this medication. Dofetilide is classified as a class III antiarrhythmic agent, and its primary effect is to block specific potassium channels responsible for the repolarization of cardiac action potentials, specifically the rapid component of the delayed rectifier potassium current (IKr). This inhibition leads to a prolongation of the action potential duration and the refractory period in cardiac tissue, which is crucial for its effectiveness in treating certain types of arrhythmias, such as atrial fibrillation and atrial flutter.

The other options describe mechanisms that do not apply to dofetilide. It does not stimulate sodium influx, as that would involve a different class of antiarrhythmic agents. Dofetilide also does not significantly affect calcium channels, which are more relevant to other antiarrhythmics or inotropic agents. Finally, dofetilide does not cause prolonged phase 0 depolarization; rather, it prolongs the action potential’s duration primarily by prolonging repolarization. Understanding these mechanisms is essential for the application and management of therapies using dofetilide in clinical practice.