What is the main effect of class 3 antiarrhythmics like sotalol and dofetilide?

Class 3 antiarrhythmics, such as sotalol and dofetilide, primarily act by blocking potassium channels. This action is crucial because it prolongs the repolarization phase of the cardiac action potential, leading to an increase in the refractory period of the cardiac tissue. By delaying the repolarization, these medications help restore a normal sinus rhythm in patients with certain types of arrhythmias, particularly atrial fibrillation and atrial flutter.

The effectiveness of these drugs in controlling heart rhythm and preventing reentrant circuit arrhythmias stems from their ability to modify the cardiac action potential duration, ensuring that the heart maintains a more stable electrical environment. This is essential in managing conditions characterized by irregular heartbeats, which can significantly impact overall cardiac function and patient health.