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QT Prolongation 





  • Potential for hemodynamic collapse secondary to rapid polymorphic VT & VF

  • Avoid triggers of Torsades de Pointes: sympathetic stimulation, medications, electrolyte disturbances (↓K, ↓Mg, ↓Ca)

  • Congenital long QT: may have pacemaker/AICD, perioperative β-blockade; avoid sympathomimetics





  • Avoid triggers of Torsades:

    • SNS stimulation (pain, nausea, emotional stress, loud noise)

    • Bradycardia, tachycardia, hypertension, hypoxemia, hypercapnia

    • Electrolyte disturbances: ↓K, ↓Mg, ↓Ca

    • QT prolonging medications: antiemetics, antipsychotics, amiodarone, methadone

    • Congenital long QT: avoid beta-agonists, ketamine

  • Continue beta blockade for congenital long QT; ensure optimal AICD function if applicable

  • Preparations for treating Torsades: defibrillator & pads in OR, MgSO4, resuscitation drugs



Various Definitions for Prolonged QTc


  • QTc > 470 ms (males) to > 480 ms (females)  (Anesthesiolgy, 2005)

  • >460 ms (Stoelting Co-existing 6th Ed)

  • >460 regardless of age (Cote 4th Ed) 

  • >470 ms (males) & >480 ms (females) (AHA/ACC Consensus statement 2011)



Treatment of Torsades


  • Defibrillation & CPR as per ACLS

  • Magnesium 2g IV over 2 min (30 mg/kg), q15min x 3; pediatrics 25-50mg/kg bolus

  • Overdrive pacing to 90-110 with transvenous pacemaker

  • Isoproterenol to ↑ HR 90-100

  • ↑ K to 4.5

  • Stop QT prolonging medications: antipsychotics, antiemetics  antibiotics, antifungals, antidysrhythmics, antidepressants, antihistamines, antineoplastics 


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