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Circulation. 2018;138:e272–e391. DOI: 10.1161/CIR.0000000000000549 September 25, 2018 e299 CLINICAL STATEMENTS AND GUIDELINES

findings,S6-7 and emergency coronary angiography should be considered (rather than later in the hospital stay or not at all) for unstable patients with a suspected cardiac etiology regardless of whether the patient is comatose or awake.S6-9,S6-39 In 1 observational study of patients resuscitated from SCA who did not have ST elevation and had angiography, one third were found to have a culprit lesion and coronary intervention appeared to be associated with a greater likelihood of favorable neurologic outcome.S6-10 5.	 The initial management of any tachycardia should proceed according to published AHA advanced cardiovascular life support guidelines.S6-40 Immediate cardioversion should be performed for hemodynamic instability at presentation or if it develops subsequently. An ECG should be obtained for stable rhythms. Wide-complex tachycardias, defined by a QRS duration ≥0.12 s,S6-37 can be due to VT, SVT with aberrancy, preexcited tachycardia, or a paced rhythm such as pacemaker-mediated tachycardia. An irregular wide-complex tachycardia 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 terminating the arrhythmia.S6-11 One randomized trial of 62 patients found procainamide superior to amiodarone for termination of stable VT.S6-13 Adverse events, including hypotension were more common 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 prolongation, administration of procainamide may further prolong the QT interval and lead to torsades de pointes.S6-11,S6-12,S6-26 7.	 Intravenous lidocaine is an alternative antiarrhythmic 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 associated with improvement in survival to hospital discharge.S6-4,S6-14,S6-41 In prospective, blinded, RCTs, lidocaine was less effective than amiodarone in improving hospital admission rates after out-ofhospital cardiac arrest due to shock-refractory VF or polymorphic VT; but there were no differences between the 2 medications in survival to hospital discharge.S6-4,S6-5 However, in the subset of patients with witnessed SCA due to initial shockrefractory 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.	 In a large meta-analysis of antiarrhythmic medications in the setting of AMI, beta blockers were associated  with a significant reduction in mortality.S6-16 Beta blockers can be effective in suppressing recurrent VF in patients with recent MI, with an associated improvement in survival.S6-17 9.	 In patients with recurrent VT/VF (VT/VF storm) in the setting of a recent MI that is refractory to amiodarone and/or lidocaine and repeated cardioversion, administration of a beta blocker has been shown to improve survival at 1 week. For those who did not survive, mortality was mostly due to recurrent VF. Survival at 1 year was also better in those treated with a beta blocker.S6-17,S6-18 Other measures to reduce sympathetic tone including sedation and general anesthesia are also often used. 10.	 Epinephrine produces beneficial effects in patients during cardiac arrest, primarily because of its alpha-adrenergic (ie, vasoconstrictor) effects.S6-1 These alpha-adrenergic effects can increase coronary and cerebral perfusion pressure during CPR. The value and safety of the beta-adrenergic effects of epinephrine are controversial because they may increase myocardial work and reduce subendocardial perfusion.S6-1 One trial assessed short-term and longer-term outcomes when comparing standard-dose epinephrine to placebo.S6-23 Standard-dose epinephrine was defined as 1 mg given intravenously or intraosseously every 3 to 5 minutes. For both survival to discharge and survival to discharge with good neurologic outcome, there was no benefit with standard-dose epinephrine; however, the study was underpowered for analysis of either of these outcomes. There was, nevertheless, improved survival to hospital admission and improved return of spontaneous circulation with the use of standard-dose epinephrine. A number of trials have compared outcomes of standard-dose epinephrine with those of high-dose epinephrine. These trials did not demonstrate any benefit for high-dose epinephrine over standard-dose epinephrine in relation to survival to discharge with a good neurologic recovery, survival to discharge, or survival to hospital admission.S6-1,S6-19,S6-21,S6-22 11.	 Amiodarone was more effective than lidocaine in terminating incessant VT with improved survival

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