Difference between revisions of "QT prolongation"

(Differential Diagnosis)
 
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==Diagnosis==
+
==Background==
*QTc >440 (male), >460 (female)
+
*Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
*>500 = real concern (may result in torsades)
+
**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
  
==DDX==
+
==Clinical Features==
#Pause Dependent (Aquired)
+
*Most are asymptomatic
##Drug induced
+
*History may include:
###Antidyrhythmics
+
**[[Syncope]]
###Phenothiazines
+
**[[Cardiac arrest]]
###TCAs
+
**Family history of long QT or sudden death
###Organophosphates
+
*Medication history may include QT prolonging medications
###Antihistamines
 
##Electrolyte abnl (hypoKalemia, hypoMag, hypoCa)
 
##Diet related (starvation, low protein)
 
##Severe bradycardia/AV block
 
##Hypothyroid
 
##Contrast injection
 
##CVA (intraparenchymal)
 
##MI
 
#Adrenergic Dependent
 
##Congenital
 
###Jarvel/Lange-Nielsen
 
####(+deafness; AR)
 
###Romano-Ward synd
 
####(nl hearing; AD)
 
###Sporatic
 
###Mitral valve prolapse
 
##Acquired
 
###CVA (subarachnoid)
 
###Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
 
  
==Treatment==
+
==Differential Diagnosis==
#Pause Dependent (precipitated by bradycard)
+
*Pause Dependent (Acquired)
##Unstable/sustained torsades--> unsynch countershock
+
**Drug induced
##Stable
+
***[[Antiarrhythmics]]
###Treat underlying prob
+
***[[Phenothiazines]]
###Increase HR (isoproterenol or overdrive pacing
+
***[[TCAs]]
###Magnesium sulfate IV
+
***[[Organophosphates]]
###Consider amiodarone
+
***[[Antihistamines]]
#Adrenergic Dependent (precipited by tachycardia)
+
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
##Unstable/sustained torsades--> unsynch countershock
+
***[[Hypokalemia]] triad
##Stable
+
****Long QT, ST depressions, PVCs
###slow HR (B-blockers)
+
**[[Hypothermia]]
###May consider magnesium
+
**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)
  
==Drug List==
+
===Drug List===
#Antiarrhythmics
+
*[[Antiarrhythmics]]
##Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
+
**[[Amiodarone]], disopyramide, dofetilide, [[flecainide]], ibutilide, mexiletine, [[procainamide]], [[quinidine]], [[sotalol]]
#Antibiotics
+
*[[Antibiotics]]
##Macrolide
+
**[[Macrolide]]
###Azithromycin, erythromycin, clarithromycin
+
***[[Azithromycin]], [[erythromycin]], [[clarithromycin]]
##Fluoroquinolone
+
**[[Fluoroquinolone]]
###Ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, ofloxacin
+
***[[Ciprofloxacin]], gatifloxacin (most common), [[gemifloxacin]], [[levofloxacin]], [[moxifloxacin]], [[ofloxacin]]
##Other
+
**Other
###Pentamidine, telithromycin, trimethoprim-sulfamethoxazole
+
***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]]
#Antidepressants
+
*Antidepressants
##Amitriptyline, citalopram, doxepin, fluoxetine, nortriptyline, paroxetine, sertraline, venlafaxine
+
**[[Amitriptyline]], citalopram, [[doxepin]], [[fluoxetine]], [[nortriptyline]], paroxetine, sertraline, [[venlafaxine]]
#Antiemetics
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*[[Antiemetics]]
##Dolasetron, droperidol, granisetron, ondansetron
+
**Dolasetron, [[droperidol]], granisetron, [[ondansetron]]
#Antifungals
+
*[[Antifungals]]
##Fluconazole, itraconazole, ketoconazole, voriconazole
+
**[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]]
#Antihypertensives
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*[[Antihypertensives]]
##Nicardipine
+
**[[Nicardipine]]
#Antineoplastics
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*Antineoplastics
##Lapatinib, nilotinib, sunitinib, tamoxifen
+
**Lapatinib, nilotinib, sunitinib, tamoxifen
#Antimalarials
+
*[[Antimalarials]]
##Chloroquine, halofantrine
+
**[[Chloroquine]], halofantrine
#Antipsychotics
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*[[Antipsychotics]]
##Chlorpromazine, clozapine, galantamine, haloperidol, lithium, paliperidone, pimozide, quetiapine, risperidone, thioridazine, ziprasidone
+
**[[Chlorpromazine]], [[clozapine]], galantamine, [[haloperidol]], [[lithium]], paliperidone, pimozide, [[quetiapine]], [[risperidone]], thioridazine, [[ziprasidone]]
#Antivirals
+
*[[Antivirals]]
##Amantadine, atazanavir, foscarnet
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**[[Amantadine]], atazanavir, [[foscarnet]]
#Diuretics
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*[[Diuretics]]
##Indapamide
+
**Indapamide
#Immune suppressants
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*Immune suppressants
##Tacrolimus
+
**[[Tacrolimus]]
#Opiates
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*[[Opiates]]
##Methadone
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**[[Methadone]]
#Phosphodiesterase inhibitors
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*Phosphodiesterase inhibitors
##Sildenafil, vardenafil
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**[[Sildenafil]], [https://nizagara-online.net/vardenafil/ Vardenafil]
#Skeletal muscle relaxants
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*Skeletal muscle relaxants
##Tizanidine
+
**[[Tizanidine]]
#Urinary antispasmodics
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*Urinary antispasmodics
##Solifenacin
+
**Solifenacin
  
==Source ==
+
==Evaluation==
*Rosen
+
===Workup===
*Tintinalli
+
*[[ECG]]
 +
*CBC
 +
*Chem 10
  
[[Category:Cards]]
+
===Diagnosis===
[[Category:Tox]]
+
[[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
 +
 
 +
==Management==
 +
===Pause Dependent (precipitated by bradycardia)===
 +
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
 +
*Stable
 +
**Treat underlying etiology
 +
**Increase HR ([[isoproterenol]] or [[overdrive pacing]])
 +
**[[Magnesium sulfate]] IV
 +
**Consider [[amiodarone]]
 +
 
 +
===Adrenergic Dependent (precipited by tachycardia)===
 +
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
 +
*Stable
 +
**Slow HR ([[beta-blockers]])
 +
**May consider [[magnesium sulfate]]
 +
 
 +
==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==
 +
*[[ECG (Main)]]
 +
*[[Torsades de Pointes]]
 +
 
 +
==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)]
 +
 
 +
==References==
 +
<references/>
 +
 
 +
[[Category:Cardiology]]
 +
[[Category:Toxicology]]

Latest revision as of 04:30, 25 February 2020

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