QT prolongation
Diagnosis
QTc >440 (male) & >460 (female)
>500 = real concern
^May result in torsades!
DDX
- Pause Dependent (Aquired)
- Drug induced*
- antidyrhythmics
- phenothiazines
- TCAs
- organophosphates
- antihistamines
- Electrolyte abnl (hypoKalemia, hypoMag, hypoCa)
- Diet related (starvation, low protein)
- Severe bradycardia/AV block
- Hypothyroid
- Contrast injection
- CVA (intraparenchymal)
- MI
- Drug induced*
- Adrenergic Dependent
- Congenital
- Jarvel/Lange-Nielsen
- (+deafness; AR)
- Romano-Ward synd
- (nl hearing; AD)
- Sporatic
- Mitral valve prolapse
- Jarvel/Lange-Nielsen
- Acquired
- CVA (subarachnoid)
- Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
- Congenital
Treatment
- Pause Dependent (precipitated by bradycard)
- Unstable/sustained torsades--> unsynch countershock
- Stable
- treat underlying prob
- increase HR (isoproterenol or overdrive pacing ~100-120bt/min)
- magnesium sulfated IV
- may consider amiodarone
- Adrenergic Dependent (precipited by tachycardia)
- Unstable/sustained torsades--> unsynch countershock
- Stable
- slow HR (B-blockers)
- 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)