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 ~100-120bt/min)
      3. magnesium sulfated IV
      4. may 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

amiodarone

aresenic trioxide

bepridil

beta agonists

chloroquine

cisapride

clarithromycin

disopyramide

dofetilde

dolasetron

droperidol

erythromycin

flecainide

fluoxetine

foscarnet

fosphenytoin

gatifloxacin

haloperidol

ibutilide

indapamide

isradipine

levofloxacin

levomethadyl

mefloquine

moexipril

moxifloxacin

naratriptan

nicardipine

octreaotide

pentamidine

phenothiazines

pimozide

procainamide

quetiapine

quinidine

quinine

reisperidone

sertraline

sotalol

sparfloxacin

sumatriptan

tamoxifen

tizanidine

TCAs

venlafazine

ziprasidone

thioridazine>ziprasidone>risperidone>haloperidol

Source

2/14/06 DONALDSON (adapted from Rosen, Pharmacopia, qtdugs.org)