II. Risk Factors: Medication-Induced Torsades de Pointes

  1. Female gender
  2. Elderly
  3. Hypokalemia
  4. Hypocalcemia
  5. Severe Hypomagnesemia
  6. Hepatic or renal dysfunction
  7. Bradycardia
  8. Atrial Fibrillation Cardioversion recently
  9. Congestive Heart Failure
  10. Left Ventricular Hypertrophy
  11. Myocardial Infarction
  12. Concurrent Digoxin use
  13. Concurrent Diuretic use
  14. Baseline QT Prolongation or subclinical Long QT
  15. Multiple concurrent agents that prolong QT
  16. Rapid infusion of agents known to cause Prolonged QT

III. Causes: Medications associated with QT Prolongation (and Torsades de Pointes)

  1. General
    1. Higher doses of predisposing drug raise risk
    2. Rapid drug administration raises risk
  2. Overall associated medication classes causing Prolonged QT interval
    1. Amphetamines
    2. Antiarrhythmics
      1. Procainamide
      2. Dofetilide
      3. Sotalol
    3. Anticholinergics
    4. Antihistamines
      1. Hydroxyzine (associated more with QT Prolongation than other Antihistamines)
      2. Diphenhydramine
    5. Anti-emetics
      1. Ondansetron (Zofran)
      2. Dolasetron (Anzemet)
      3. Granisetron
      4. If QTc is already prolonged, Metoclopramide (Reglan), Palonosetron (Aloxi), Prochlorperazine are safe alternatives
      5. 5HT3 agents are unlikely to cause harm (even at highest dose, Ondansetron prolongs QTc only 20 ms)
        1. Freedman (2014) Ann Emerg Med 64(1): 19-25 +PMID:24314899 [PubMed]
        2. Moffett (2016) Acad Emerg Med 23(1): 102-5 +PMID: 26720490 [PubMed]
    6. Decongestants
    7. Diuretics
    8. Antimicrobials
      1. Fluoroquinolones
        1. Class effect (includes Levofloxacin, Moxifloxacin)
        2. Consider lower risk agent: Ciprofloxacin
      2. Macrolides
        1. Includes Clarithromycin, Erythromycin, Azithromycin
        2. Three fold increased risk of Sudden Cardiac Death while on Azithromycin
          1. Ray (2013) N Engl J Med 366(20): 1881-90 [PubMed]
      3. Antifungals
        1. Fluconazole
        2. Ketoconazole
        3. Itraconazole
      4. Other agents
        1. Quinine
        2. Pentamidine
    9. Opioids
      1. Highest risk agents: Methadone, Buprenorphine, Oxycodone
      2. Consider lower risk agents: Morphine
    10. Phenothiazines
    11. Protease Inhibitors
    12. Antipsychotics
      1. Highest risk: Thioridazine, pimozide, Haloperidol, chlorperazine
      2. Some risk: Geodon, Fanapt, Invega, Saphris, Seroquel
      3. Consider lower risk agents: Abilify, Latuda, Zyprexa
    13. Antidepressants
      1. Highest risk
        1. Tricyclic Antidepressants (Amitriptyline, Desipramine)
        2. Trazodone
        3. Citalopram (especially in combination with Cytochrome P450 2C19)
          1. Limit Citalopram to 20-40 mg/day
          2. Limit Escitalopram to 10-20 mg/day
      2. Some risk
        1. Venlafaxine
        2. SSRIs in general (e.g. Fluoxetine)
      3. Consider lower risk agents: Bupropion, Duloxetine, Mirtazapine
    14. Sympathomimetics
    15. Vasodilators

IV. Causes: Medications that more commonly cause Torsades

  1. Bepridil
  2. Disopyramide
  3. Dofetilide
  4. Ibutilide
  5. Procainamide
  6. Quinidine
  7. Sotalol

V. Causes: Medications that less frequently cause Torsades

  1. Amiodarone
  2. Arsenic trioxide
  3. Chlorpromazine
  4. Cisapride
  5. Clarithromycin
  6. Domperidone
  7. Droperidol
  8. Erythromycin
  9. Halofantrine
  10. Haloperidol
  11. Lidoflazine
  12. Mesoridazine
  13. Methadone
  14. Pentamidine
  15. Pimozide
  16. Sparfloxacin
  17. Thioridazine

VI. Labs

  1. Basic metabolic panel
  2. Serum Magnesium

VII. Imaging

  1. Consider Echocardiogram
    1. Excludes structural heart disease

VIII. Management

  1. Stop offending agent
  2. Correct electrolyte abnormalities, considering 5H5T causes (esp. Potassium abnormalities)
  3. Consider Magnesium Sulfate 1-2 grams prophylactically
  4. Indications to consider telemetry admission
    1. QTc Interval >500 ms
    2. QTc interval increased 60 ms over baseline
    3. T-Wave alternans
    4. Atrioventricular Block
    5. QRS Widening
    6. Syncope
  5. Manage Torsades de Pointes
    1. See Torsades de Pointes
    2. Electrical cardioversion (Nonsynchronized)
    3. Magnesium Sulfate 2 grams
      1. May be repeated in 5-15 minutes
      2. May be continued as infusion Magnesium 3 to 20 mg/min IV for Prolonged QTc
    4. Overdrive pacing
      1. Set at rate >100 bpm
    5. Other measures
      1. Isoproterenol has been used historically and is generally not recommended
        1. Dosing was bolus and infusion with titrate to Heart Rate >100 bpm

IX. References

Images: Related links to external sites (from Bing)

Related Studies (from Trip Database) Open in New Window