Broad complex tachycardia

ECG shows rate of >100bpm and QRS complexes >120ms (>3 small squares).

Differential diagnosis : Ventricular tachycardia (VT) including torsade de pointes, SVT with aberrant conduction, e.g. AF or atrial flutter, with bundle branch block. Pre-excited tachycardias, e.g. AF, atrial flutter, or AV re-entry tachycardia, with underlying WPW.

If in doubt, treat as VT

Management

• If Pulse not palpable, treat as arrest
• Oxygen: if SaO2<90%
• IV access
• ECG
  • Connect to a cardiac monitor
  • Have a defibrillator ready
• CXR
• Check for Adverse signs
  • Shock (e.g. BP <90mmHg, pulse >100)
  • Chest pain/ischemia on ECG
  • Heart failure
  • Syncope
• If at least one of Adverse signs exists (or hemodynamically unstable)
• Sedation
• Up to 3 synchronized DC shocks (120–150J for the first, then 150–360J subsequently*)
• Check and correct
  • K+ : up to 60mmol KCl at 30mmol/h (via central line)
  • Mg2+ : 4mL 50% magnesium sulfate over 30min (via central line)
  • Ca2+
• Amiodarone 300mg IV over more than 20min (via central line)
  • Peripherally only in emergency
  • Consider repeat shock
  • Then 900mg/24h IVI (via central line)
  • For refractory cases consider procainamide or sotalol.
• If No Adverse signs (hemodynamically stable)
• Correct electrolyte problems esp. low K+, Mg2+, Ca2+ (as above)
• If regular rhythm VT or uncertain rhythm give amiodarone (as above) (avoid if long QT)
• If known history of SVT and BBB treat as for narrow complex tachycardia with e.g. adenosine
• If irregular rhythm Seek expert help
  • Diagnosis is usually one of
    • AF with bundle branch block
    • Pre-excited AF: consider amiodarone
    • Polymorphic VT, e.g. torsade de pointes; give Mg2+ 2g IVI
• If no success or becomes unstable
• Sedation
• Synchronized DC shock
• After correction of VT
  • Establish the cause
  • Maintenance anti-arrhythmic therapy.
  • If VT occurs after MI, give IV amiodarone infusion for 12–24h;
  • If 24h after MI, also start oral anti-arrhythmic: sotalol (if good LV function) or amiodarone (if poor LV function).
  • Prevention of recurrent VT: surgical isolation of the arrhythmogenic area or an implantable cardioverter defibrillator (ICD).

Special Conditions

• Ventricular fibrillation: Use non-synchronized DC shock (there is no R wave to trigger defibrillation)
• SVT with aberrant conduction: Manage as SVT with e.g. adenosine
• Ventricular extrasystoles (ectopics): Patients with frequent ectopics post-MI have a worse prognosis, but there is no evidence that anti-dysrhythmic drugs improve outcome, indeed they may increase mortality.
• Torsade de pointes:
  • If congenital: treated by high doses of Beta-blockers.
  • If acquired: long-QT syndromes:
  • Stop all predisposing drugs
  • Correct hypokalemia
  • Magnesium sulfate (2g IV over 10min).
  • Alternatives include: overdrive pacing (pace at a faster rate, then slow reduce) or isoprenaline IVI to increase heart rate.