Difference between revisions of "QT prolongation"

(Created page with "==Diagnosis== QTc >440 (male) & >460 (female) >500 = real concern *May result in torsades! ==DDX== I. Pause Dependent (Aquired) A. Drug induced* i. ant...")
 
(Pause Dependent (precipitated by bradycardia))
 
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==Diagnosis==
+
==Background==
 +
*Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
 +
**Males >440-450 ms
 +
**Females >500 ms
 +
**Rule of thumb: Normal QT interveal is less than half of preceding RR interval
 +
*QT interval is from the beginning of the Q wave to the end of the T wave
 +
**Rate dependent and should become proportionately shorter with increasing heart rate
  
 +
==Clinical Features==
 +
*Most are asymptomatic
 +
*History may include:
 +
**[[Syncope]]
 +
**[[Cardiac arrest]]
 +
**Family history of long QT or sudden death
 +
*Medication history may include QT prolonging medications
  
QTc >440 (male) & >460 (female)
+
==Differential Diagnosis==
 +
*Pause Dependent (Acquired)
 +
**Drug induced
 +
***[[Antiarrhythmics]]
 +
***[[Phenothiazines]]
 +
***[[TCAs]]
 +
***[[Organophosphates]]
 +
***[[Antihistamines]]
 +
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
 +
***[[Hypokalemia]] triad
 +
****Long QT, ST depressions, PVCs
 +
**[[Hypothermia]]
 +
**Diet related (starvation, low protein)
 +
**[[Severe Bradycardia]]/[[AV Block]]
 +
**[[Hypothyroid]]
 +
**Contrast injection
 +
**[[CVA]] (intraparenchymal)
 +
**[[Elevated intracranial pressure]] and [[Intracranial hemorrhage]]
 +
**[[MI]]
 +
*Adrenergic Dependent
 +
**Congenital
 +
***Jarvel/Lange-Nielsen
 +
****(+deafness; AR)
 +
***Romano-Ward syndrome
 +
****(normal hearing; AD)
 +
***Sporadic
 +
***[[Mitral valve prolapse]]
 +
**Acquired
 +
***[[CVA]] (subarachnoid)
 +
***Autonomic surgery (catechol excess: neck dissection, carotid endarterectomy, truncal vagotomy)
  
>500 = real concern
+
===Drug List===
 +
*[[Antiarrhythmics]]
 +
**[[Amiodarone]], disopyramide, dofetilide, [[flecainide]], ibutilide, mexiletine, [[procainamide]], [[quinidine]], [[sotalol]]
 +
*[[Antibiotics]]
 +
**[[Macrolide]]
 +
***[[Azithromycin]], [[erythromycin]], [[clarithromycin]]
 +
**[[Fluoroquinolone]]
 +
***[[Ciprofloxacin]], gatifloxacin (most common), [[gemifloxacin]], [[levofloxacin]], [[moxifloxacin]], [[ofloxacin]]
 +
**Other
 +
***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]]
 +
*Antidepressants
 +
**[[Amitriptyline]], citalopram, [[doxepin]], [[fluoxetine]], [[nortriptyline]], paroxetine, sertraline, [[venlafaxine]]
 +
*[[Antiemetics]]
 +
**Dolasetron, [[droperidol]], granisetron, [[ondansetron]]
 +
*[[Antifungals]]
 +
**[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]]
 +
*[[Antihypertensives]]
 +
**[[Nicardipine]]
 +
*Antineoplastics
 +
**Lapatinib, nilotinib, sunitinib, tamoxifen
 +
*[[Antimalarials]]
 +
**[[Chloroquine]], halofantrine
 +
*[[Antipsychotics]]
 +
**[[Chlorpromazine]], [[clozapine]], galantamine, [[haloperidol]], [[lithium]], paliperidone, pimozide, [[quetiapine]], [[risperidone]], thioridazine, [[ziprasidone]]
 +
*[[Antivirals]]
 +
**[[Amantadine]], atazanavir, [[foscarnet]]
 +
*[[Diuretics]]
 +
**Indapamide
 +
*Immune suppressants
 +
**[[Tacrolimus]]
 +
*[[Opiates]]
 +
**[[Methadone]]
 +
*Phosphodiesterase inhibitors
 +
**[[Sildenafil]], [https://nizagara-online.net/vardenafil/ Vardenafil]
 +
*Skeletal muscle relaxants
 +
**[[Tizanidine]]
 +
*Urinary antispasmodics
 +
**Solifenacin
  
*May result in torsades!
+
==Evaluation==
 +
===Workup===
 +
*[[ECG]]
 +
*CBC
 +
*Chem 10
  
+
===Diagnosis===
 +
[[File:De-Acquired longQT (CardioNetworks ECGpedia).jpg|thumb|Acquired QT prolongation]]
 +
*[[ECG]]
 +
**On visual inspection, QT takes up more than half the R-R distance
 +
**Measure QT interval in lead II or V5-6
 +
**QTc = QT /√R-R
  
==DDX==
+
==Management==
 +
===Pause Dependent (precipitated by bradycardia)===
 +
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
 +
*Stable
 +
**Treat underlying etiology
 +
**Increase HR >80 ([[isoproterenol]] or [[overdrive pacing]])
 +
**[[Magnesium sulfate]] IV
 +
**Consider [[lidocaine]], [[transvenous pacing]]<ref>Simon HL, Behr ER. Pharmacological treatment of acquired QT prolongation and torsades de pointes. Br J Clin Pharmacol. 2016 Mar; 81(3): 420–427. doi: 10.1111/bcp.12726</ref>
  
 +
===Adrenergic Dependent (precipited by tachycardia)===
 +
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
 +
*Stable
 +
**Slow HR ([[beta-blockers]])
 +
**May consider [[magnesium sulfate]]
  
I. Pause Dependent (Aquired)
+
==Disposition==
 +
*Consider admission, especially for QT >500 or if symptomatic
 +
*May require consultation for discontinuation of QT prolonging medications
 +
*Avoid prescribing medications that may contribute to prolonged QT
  
    A. Drug induced*
+
==See Also==
 +
*[[ECG (Main)]]
 +
*[[Torsades de Pointes]]
 +
*[[Hypomagnesemia]]
 +
*[[Hypermagnesemia]]
  
          i. antidyrhythmics
+
==External Links==
 +
*[https://www.youtube.com/watch?v=T-wqZfRmKQ4 Amal Mattu's Case of the Week (5/20/2012)]
 +
*[http://youtu.be/jrp_XT07fd4 Amal Mattu's Case of the Week (10/13/2014)]
  
          ii. phenothiazines
+
==References==
 +
<references/>
  
          iii. TCAs
+
[[Category:Cardiology]]
 
+
[[Category:Toxicology]]
          iv. organophosphates
 
 
 
          v. antihistamines
 
 
 
    B. Electrolyte abnl (hypoKalemia, hypoMag, hypoCa)
 
 
 
    C. Diet related (starvation, low protein)
 
 
 
    D. Severe bradycardia/AV block
 
 
 
    E. Hypothyroid
 
 
 
    F. Contrast injection
 
 
 
    G. CVA (intraparenchymal)
 
 
 
    H. MI
 
 
 
II. Adrenergic Dependent
 
 
 
    A. Congenital
 
 
 
          i. Jarvel/Lange-Nielsen
 
 
 
          (+deafness; AR)
 
 
 
          ii. Romano-Ward synd
 
 
 
          (nl hearing; AD)
 
 
 
          iii. Sporatic
 
 
 
          iv. Mitral valve prolapse
 
 
 
    B. Acquired
 
 
 
          i. CVA (subarachnoid)
 
 
 
          ii. Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
 
 
 
 
 
 
==Treatment==
 
 
 
 
 
    I. Pause Dependent (precipitated by bradycard)
 
 
 
          A. Unstable/sustained torsades--> unsynch countershock
 
 
 
          B. Stable
 
 
 
              -treat underlying prob
 
 
 
              -increase HR (isoproterenol or overdrive pacing ~100-120bt/min)
 
 
 
              -magnesium sulfated IV
 
 
 
              -may consider amiodarone
 
 
 
    II. Adrenergic Dependent (precipited by tachycardia)
 
 
 
          A. Unstable/sustained torsades--> unsynch countershock
 
 
 
          B. 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)
 
 
 
 
 
 
 
 
 
[[Category:Cards]]
 

Latest revision as of 22:22, 22 September 2021

Background

  • Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
    • Males >440-450 ms
    • Females >500 ms
    • Rule of thumb: Normal QT interveal is less than half of preceding RR interval
  • QT interval is from the beginning of the Q wave to the end of the T wave
    • Rate dependent and should become proportionately shorter with increasing heart rate

Clinical Features

  • Most are asymptomatic
  • History may include:
  • Medication history may include QT prolonging medications

Differential Diagnosis

Drug List

Evaluation

Workup

  • ECG
  • CBC
  • Chem 10

Diagnosis

Acquired QT prolongation
  • ECG
    • On visual inspection, QT takes up more than half the R-R distance
    • Measure QT interval in lead II or V5-6
    • QTc = QT /√R-R

Management

Pause Dependent (precipitated by bradycardia)

Adrenergic Dependent (precipited by tachycardia)

Disposition

  • Consider admission, especially for QT >500 or if symptomatic
  • May require consultation for discontinuation of QT prolonging medications
  • Avoid prescribing medications that may contribute to prolonged QT

See Also

External Links

References

  1. Simon HL, Behr ER. Pharmacological treatment of acquired QT prolongation and torsades de pointes. Br J Clin Pharmacol. 2016 Mar; 81(3): 420–427. doi: 10.1111/bcp.12726