Name a drug class known to prolong QT and increase torsades risk.

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QT prolongation stems from delayed ventricular repolarization. When repolarization is extended, the risk of early afterdepolarizations rises, which can trigger torsades de pointes, a dangerous polymorphic ventricular tachycardia. The drug class most classically linked to prolonging the QT and increasing torsades risk is the ones that block potassium channels during repolarization, prolonging the action potential duration. In practice, this is the class of antiarrhythmics known as class III. They slow repolarization by blocking potassium currents, which lengthens the QT interval and raises torsades risk, especially with other risk factors or electrolyte disturbances. It’s worth noting that amiodarone, a member of this class, also prolongs QT but tends to have a lower torsades risk because of its multiple ion-channel effects; other class III drugs (like dofetilide or sotalol) can carry a higher torsades risk. In contrast, beta-blockers (class II) and calcium channel blockers (class IV) do not primarily prolong QT in a way that raises torsades risk.