An irregular wide-complex tachycar- dia may be AF with aberrancy, preexcited AF (ie, AF using an accessory pathway for anterograde conduction), atrial flutter, or VT.S6-37 A diagnosis should be established, and consultation with an arrhythmia expert considered.S6-37 6. In 1 study, amiodarone was more effective than lidocaine in terminating incessant VT with improved survival at 24 hours.S6-26 For patients with recurrent, stable VT not in the setting of an AMI, intravenous procainamide has been shown to be superior to lidocaine for terminat- ing the arrhythmia.S6-11 One randomized trial of 62 patients found procainamide superior to amio- darone for termination of stable VT.S6-13 Adverse events, including hypotension were more com- mon with amiodarone, but the difference was not statistically significant. Procainamide and its metabolite n-acetylprocainamide have potassium channel blocking properties that may prolong the QT interval. In patients who already have QT pro- longation, administration of procainamide may further prolong the QT interval and lead to tors- ades de pointes.S6-11,S6-12,S6-26 7. Intravenous lidocaine is an alternative antiar- rhythmic medication of long-standing and widespread familiarity. Compared with no antiarrhythmic medication, lidocaine did not consistently increase a return of spontaneous circulation after defibrillation and was not asso- ciated with improvement in survival to hospital In prospective, blinded, RCTs, lidocaine was less effective than amiodarone in improving hospital admission rates after out-of- hospital cardiac arrest due to shock-refractory VF or polymorphic VT; but there were no differences between the 2 medications in survival to hospital However, in the subset of patients with witnessed SCA due to initial shock- refractory VF or pulseless VT, a subgroup analysis showed that survival to hospital discharge with lidocaine was better than with placebo.S6-5,S6-42 8. 