Which medication is primarily indicated for tachyarrhythmias?

Sotalol is primarily indicated for the treatment of tachyarrhythmias due to its properties as a Class III antiarrhythmic agent. It works by prolonging the repolarization phase of the cardiac action potential, which helps to stabilize the heart rhythm. This mechanism makes Sotalol particularly effective for managing various types of rapid heart rhythms, including atrial fibrillation and ventricular tachycardia.

The other medications listed, while they are beta-blockers and can have some effect on heart rate, do not have the same primary indication for tachyarrhythmias as Sotalol. Pindolol, Atenolol, and Nadolol are primarily used for conditions like hypertension and angina, and while they may help control heart rate, their specific designation for significant cardiac arrhythmias is not as pronounced as with Sotalol.