What disorders can cardioversion be used to treat?

Several. Cardioversion can convert most ventricular arrhythmias (i.e. Originating from bottom part of the heart) to normal rhythm, and several supraventricular (i.e. From top part of the heart). Atrial fibrillation is the most commonly cardioverted rhythm, with very high success rates. Other supraventricular rhythms (e.g. Psvt, atrial tachycardia, avnrt) can also be treated, though not as reliably.
Cardio version. We use it to treat rapid abnormal rhythms, especially those causing instability.