QT prolongation: Difference between revisions

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==Diagnosis==
==Background==
*QTc >440 (male), >460 (female)
[[File:SinusRhythmLabels.svg|thumb]]
*>500 = real concern (may result in torsades)
[[File:Grid.png|thumb]]
*Prolonged ventricular repolarization → increased risk of ventricular arrhythmias
**Males >440-450 ms
**Females >500 ms
**Rule of thumb: Normal QT interval 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
 
===List of Drugs Causing QT Prolongation===
*[[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
 
==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


==Differential Diagnosis==
==Differential Diagnosis==
#Pause Dependent (Aquired)
{{Syncope causes}}
##Drug induced
 
###Antidyrhythmics
==Evaluation==
###Phenothiazines
===Workup===
###[[TCAs]]
*[[ECG]]
###[[Organophosphates]]
*CBC
###Antihistamines
*Chem 10
##[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
 
##Diet related (starvation, low protein)
===Diagnosis===
##[[Severe Bradycardia]]/AV Block
[[File:De-Acquired longQT (CardioNetworks ECGpedia).jpg|thumb|Acquired QT prolongation]]
##[[Hypothyroid]]
*[[ECG]]
##Contrast injection
**On visual inspection, QT takes up more than half the R-R distance
##[[CVA]] (intraparenchymal)
**Measure QT interval in lead II or V5-6
##[[MI]]
**QTc = QT /√R-R
#Adrenergic Dependent
 
##Congenital
===Determining Cause===
###Jarvel/Lange-Nielsen
*Pause Dependent (Acquired)
####(+deafness; AR)
**Drug induced (see drug list above)
###Romano-Ward synd
***[[Antiarrhythmics]]
####(nl hearing; AD)
***[[Phenothiazines]]
###Sporatic
***[[TCAs]]
###Mitral valve prolapse
***[[Organophosphates]]
##Acquired
***[[Antihistamines]]
###[[CVA]] (subarachnoid)
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
###Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
***[[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)
 
==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>


==Treatment==
===Adrenergic Dependent (precipited by tachycardia)===
#Pause Dependent (precipitated by bradycard)
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
##Unstable/sustained torsades--> unsynch countershock
*Stable
##Stable
**Slow HR ([[beta-blockers]])
###Treat underlying prob
**May consider [[magnesium sulfate]]
###Increase HR (isoproterenol or overdrive pacing
###Magnesium sulfate IV
###Consider amiodarone
#Adrenergic Dependent (precipited by tachycardia)
##Unstable/sustained torsades--> unsynch countershock
##Stable
###Slow HR (B-blockers)
###May consider magnesium


==Drug List==
==Disposition==
#Antiarrhythmics
*Consider admission, especially for QT >500 or if symptomatic
##Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
*May require consultation for discontinuation of QT prolonging medications
#Antibiotics
*Avoid prescribing medications that may contribute to prolonged QT
##Macrolide
###Azithromycin, erythromycin, clarithromycin
##Fluoroquinolone
###Ciprofloxacin, gatifloxacin, 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, vardenafil
#Skeletal muscle relaxants
##Tizanidine
#Urinary antispasmodics
##Solifenacin


==See Also==
==See Also==
*[[ECG (Main)]]
*[[ECG (Main)]]
*[[Torsades de Pointes]]
*[[Torsades de Pointes]]
*[[Hypomagnesemia]]
*[[Hypermagnesemia]]


==Source ==
==External Links==
*Rosen
*[https://www.youtube.com/watch?v=T-wqZfRmKQ4 Amal Mattu's Case of the Week (5/20/2012)]
*Tintinalli
*[http://youtu.be/jrp_XT07fd4 Amal Mattu's Case of the Week (10/13/2014)]


==External Links==
==References==
[http://youtu.be/jrp_XT07fd4 Amal Mattu's Case of the Week (10/13/2014)]
<references/>


[[Category:Cards]]
[[Category:Cardiology]]
[[Category:Tox]]
[[Category:Toxicology]]

Latest revision as of 12:40, 14 May 2022

Background

SinusRhythmLabels.svg
Grid.png
  • Prolonged ventricular repolarization → increased risk of ventricular arrhythmias
    • Males >440-450 ms
    • Females >500 ms
    • Rule of thumb: Normal QT interval 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

List of Drugs Causing QT Prolongation

Clinical Features

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

Differential Diagnosis

Syncope Causes

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

Determining Cause

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
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