Most cardiotoxic local anaesthetic agent

Bupivacaine is more prone to prolong QTc interval and induce ventricular tachycardia or cardiac depression should not bbe used for intravenous regional analgesia (Bier's). Levobupivacaine is equally potent but less cardiotoxic and less prone to cause seizures then bupivacaine. Ref Katziung 12th ed