How to manage frequent ventricular tachycardia (VTach) arrest in a patient with myocardial infarction (MI)?

Management of Frequent VTach Arrest in Patients with MI

For patients with frequent ventricular tachycardia arrest in the setting of myocardial infarction, immediate electrical cardioversion followed by intravenous amiodarone is the most effective treatment strategy to reduce mortality. 1

Initial Management Algorithm

1. Immediate Electrical Cardioversion

   • For VF: Unsynchronized shock at 200J, followed by 200-300J, then 360J if needed 1
   • For sustained polymorphic VT with hemodynamic collapse: Unsynchronized shock starting at 200J 1
   • For sustained monomorphic VT with angina, pulmonary edema, or hypotension: Synchronized shock 1

2. Pharmacological Management

   • First-line medication: Amiodarone 150mg IV over 10 minutes, followed by constant infusion of 1.0mg/min for 6 hours, then maintenance infusion of 0.5mg/min 1, 2
   • For drug-refractory polymorphic VT ("electrical storm"): Continue amiodarone and add β-blocker therapy 1

Secondary Pharmacological Options

• Beta-blockers: Particularly valuable for "electrical storm" in the setting of recent MI 1

  • Atenolol: 2.5-5.0mg over 2 minutes to total of 10mg in 10-15 minutes
  • Metoprolol: 2.5-5.0mg every 2-5 minutes to total of 15mg over 10-15 minutes
  • Monitor heart rate, blood pressure, and ECG during administration

• Lidocaine: Alternative if amiodarone is unavailable

  • Bolus: 1.0-1.5mg/kg
  • Supplemental boluses: 0.5-0.75mg/kg every 5-10 minutes (maximum 3mg/kg total loading dose)
  • Maintenance: 2-4mg/min infusion (30-50μg/kg/minute) 1

• Procainamide: Consider if amiodarone and lidocaine are ineffective

  • Loading: 20-30mg/min up to 12-17mg/kg
  • Maintenance: 1-4mg/min infusion 1

Management of Refractory Cases

For drug-refractory polymorphic VT, implement aggressive measures to reduce myocardial ischemia:

1. Optimize anti-ischemic therapy:

   • β-adrenoceptor blockade (if not already administered)
   • Intra-aortic balloon pumping
   • Emergency PTCA/CABG surgery 1

2. Correct contributing factors:

   • Electrolyte abnormalities (particularly potassium and magnesium)
   • Acid-base disturbances
   • Hypoxia 1

Special Considerations

• Dosing adjustments: Reduce amiodarone infusion rates in older patients and those with CHF or hepatic dysfunction 1
• Monitoring: Heart rate, blood pressure, and ECG should be continuously monitored during treatment
• Duration: Antiarrhythmic infusions should typically be discontinued after 6-24 hours with reassessment of arrhythmia management needs 1
• Contraindications to β-blockers: Heart rate <60 bpm, systolic BP <100 mmHg, moderate/severe LV failure, PR interval >0.24 sec, second/third-degree AV block, severe COPD, asthma 1

Important Caveats

• Avoid treating isolated ventricular premature beats, couplets, runs of accelerated idioventricular rhythm, and non-sustained VT 1
• Distinguish true ventricular tachycardia from accelerated idioventricular rhythm (rate <120 bpm), which is usually a harmless consequence of reperfusion 1
• High-dose intravenous amiodarone can cause serious adverse events including hypotension and symptomatic bradycardia, requiring close monitoring 3
• Amiodarone concentrations greater than 3mg/mL in D5W have been associated with high incidence of peripheral vein phlebitis; use concentrations ≤2mg/mL for infusions longer than 1 hour unless using a central venous catheter 2

By following this systematic approach to managing frequent VTach arrest in MI patients, you can effectively stabilize the patient and reduce the risk of mortality while addressing the underlying ischemic process.