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©2013 UpToDate ® Print Email ACC/AHA guideline summary: Ventricular tachycardia (VT)/ventricular fibrillation (VF) in acute myocardial infarction (MI) Class I - There is evidence and/or general agreement for the following approaches to VT/VF in patients with acute MI •  VF or pulseless VT should be treated with an unsynchronized electric shock with an initial monophasic shock energy of 200 J*; if unsuccessful, a second shock of 200 to 300 J should be given, and, if necessary, a third shock of 360 J. •  Sustained (>30 seconds or causing hemodynamic collapse) polymorphic VT should be treated with an unsynchronized electric shock using an initial monophasic shock energy of 200 J*; if unsuccessful, a second shock of 200 to 300 J should be given, and, if necessary, a third shock of 360 J. •  Episodes of sustained monomorphic VT associated with angina, pulmonary edema, or hypotension (blood pressure <90 mmHg) should be treated with a synchronized electric shock of 100 J initial monophasic shock energy*. Increasing energies may be used if not initially successful. Brief anesthesia is preferred if hemodynamically tolerable. •  Sustained monomorphic VT not associated with angina, pulmonary edema, or hypotension (blood pressure <90 mmHg) should be treated with one of the following regimens: 1. Amiodarone: 150 mg infused over 10 minutes. If further therapy is necessary, repeat 150 mg infusion every 10 to 15 minutes as needed or a constant infusion of 1.0 mg/min for six hours followed by a maintenance infusion of 0.5 mg/min for 18 hours. The total cumulative dose, including additional doses during cardiac arrest, must not exceed 2.2 g over 24 hours. 2. Synchronized electrical cardioversion starting at 50 J monophasic energy. Brief anesthesia is necessary. Class IIa - The weight of evidence or opinion is in favor of benefit for the following modalities in the treatment of VT/VF in patients with acute MI •  For VF or pulseless VT refractory to electric shock, amiodarone (300 mg or 5 mg/kg bolus) followed by a repeat unsynchronized electric shock. •  Electrolyte and acid-base disturbances should be corrected to prevent recurrent episodes of VT/VF when an initial episode of VT/VF has been treated. The serum potassium should be greater than 4.0 meq/L (4.0 mmol/L) and the serum magnesium should be greater than 2.0 mg/dL (0.8 mmol/L).

•  For VF or pulseless VT refractory to electric shock, amiodarone (300 mg or 5 mg/kg bolus) followed by a repeat unsynchronized electric shock. •  Electrolyte and acid-base disturbances should be corrected to prevent recurrent episodes of VT/VF when an initial episode of VT/VF has been treated. The serum potassium should be greater than 4.0 meq/L (4.0 mmol/L) and the serum magnesium should be greater than 2.0 mg/dL (0.8 mmol/L). •  For refractory polymorphic VT, in addition to potassium and magnesium balance: 1. Aggressive attempts to reduce myocardial ischemia, including therapies such as beta blockers, intra-aortic balloon pump, and emergency percutaneous coronary intervention or bypass surgery. 2. Temporary pacing at a higher rate, if the heart rate is less than 60 beats/min or the corrected QT interval is prolonged. Class IIb - The evidence or opinion is less well established for the following modality in the treatment of VT/VF in patients with acute MI •  Intravenous procainamide for VT or shock-refractory VF. The usual regimen is 20 to 30 mg/min loading infusion, up to 12 to 17 mg/kg, which may be followed by an infusion of 1 to 4 mg/min. The length of time required for administration limits the value of this approach. Class III - There is evidence and/or general agreement that the following modalities are not useful in the treatment of VT/VF in patients with acute MI •  The routine use of prophylactic lidocaine for suppression of isolated ventricular premature beats, couplets, runs of accelerated idioventricular rhythm, or nonsustained VT. •  Prophylactic antiarrhythmic therapy when using fibrinolytic agents. * The initial shock energy required with biphasic defibrillators is approximately one-half that with monophasic defibrillators. Data from from Antman, EM, Anbe, DT, Armstrong, PW, et al. ACC/AHA guidelines for the management of patients with ST-elevation myocardial infarction. Available at: www.acc.org/qualityandscience/clinical/statements.htm (accessed August 24, 2006).