Torsades de pointes and polymorphic ventricular tachycardia are two terms that are often used interchangeably. However, they are not the same!
Torsades is a type of PVT that is characterized by an undulating appearance of the QRS complexes which give the rhythm the appearance of QRS complexes twisting around a central axis. The defining feature of torsades, however, is the presence of a prolonged QTc on the ECG before or after the run of torsades.
Although either rhythm is usually amenable to cardioversion/defibrillation, post-cardioversion treatment is very different between the two. Torsades should be treated with magnesium, whereas PVT can be treated with lidocaine, amio, or procainamide. Beware that treatment of torsades with any of these sodium channel blockers can actually prolong the QTc further and induce intractable torsades.