QT prolongation

Diagnosis

• QTc >440 (male), >460 (female)
• >500 = real concern (may result in torsades)

DDX

1. Pause Dependent (Aquired)
   1. Drug induced
      1. Antidyrhythmics
      2. Phenothiazines
      3. TCAs
      4. Organophosphates
      5. Antihistamines
   2. Electrolyte abnl (hypoKalemia, hypoMag, hypoCa)
   3. Diet related (starvation, low protein)
   4. Severe bradycardia/AV block
   5. Hypothyroid
   6. Contrast injection
   7. CVA (intraparenchymal)
   8. MI
2. Adrenergic Dependent
   1. Congenital
      1. Jarvel/Lange-Nielsen
         1. (+deafness; AR)
      2. Romano-Ward synd
         1. (nl hearing; AD)
      3. Sporatic
      4. Mitral valve prolapse
   2. Acquired
      1. CVA (subarachnoid)
      2. Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)

Treatment

1. Pause Dependent (precipitated by bradycard)
   1. Unstable/sustained torsades--> unsynch countershock
   2. Stable
      1. Treat underlying prob
      2. Increase HR (isoproterenol or overdrive pacing
      3. Magnesium sulfate IV
      4. Consider amiodarone
2. Adrenergic Dependent (precipited by tachycardia)
   1. Unstable/sustained torsades--> unsynch countershock
   2. Stable
      1. slow HR (B-blockers)
      2. May consider magnesium

Drug List

1. Antiarrhythmics
   1. Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
2. Antibiotics
   1. Macrolide
      1. Azithromycin, erythromycin, clarithromycin
   2. Fluoroquinolone
      1. Ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, ofloxacin
   3. Other
      1. Pentamidine, telithromycin, trimethoprim-sulfamethoxazole
3. Antidepressants
   1. Amitriptyline, citalopram, doxepin, fluoxetine, nortriptyline, paroxetine, sertraline, venlafaxine
4. Antiemetics
   1. Dolasetron, droperidol, granisetron, ondansetron
5. Antifungals
   1. Fluconazole, itraconazole, ketoconazole, voriconazole
6. Antihypertensives
   1. Nicardipine
7. Antineoplastics
   1. Lapatinib, nilotinib, sunitinib, tamoxifen
8. Antimalarials
   1. Chloroquine, halofantrine
9. Antipsychotics
   1. Chlorpromazine, clozapine, galantamine, haloperidol, lithium, paliperidone, pimozide, quetiapine, risperidone, thioridazine, ziprasidone
10. Antivirals
    1. Amantadine, atazanavir, foscarnet
11. Diuretics
    1. Indapamide
12. Immune suppressants
    1. Tacrolimus
13. Opiates
    1. Methadone
14. Phosphodiesterase inhibitors
    1. Sildenafil, vardenafil
15. Skeletal muscle relaxants
    1. Tizanidine
16. Urinary antispasmodics
    1. Solifenacin

Source

• Rosen
• Tintinalli