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
 +
 
 +
==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)
+
*Pause Dependent (Acquired)
##Drug induced
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**Drug induced
###Antidyrhythmics
+
***[[Antiarrhythmics]]
###Phenothiazines
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***[[Phenothiazines]]
###[[TCAs]]
+
***[[TCAs]]
###[[Organophosphates]]
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***[[Organophosphates]]
###Antihistamines
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***[[Antihistamines]]
##[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
+
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
##Diet related (starvation, low protein)
+
***[[Hypokalemia]] triad
##[[Severe Bradycardia]]/AV Block
+
****Long QT, ST depressions, PVCs
##[[Hypothyroid]]
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**[[Hypothermia]]
##Contrast injection
+
**Diet related (starvation, low protein)
##[[CVA]] (intraparenchymal)
+
**[[Severe Bradycardia]]/[[AV Block]]
##[[MI]]
+
**[[Hypothyroid]]
#Adrenergic Dependent
+
**Contrast injection
##Congenital
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**[[CVA]] (intraparenchymal)
###Jarvel/Lange-Nielsen
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**[[Elevated intracranial pressure]] and [[Intracranial hemorrhage]]
####(+deafness; AR)
+
**[[MI]]
###Romano-Ward synd
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*Adrenergic Dependent
####(nl hearing; AD)
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**Congenital
###Sporatic
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***Jarvel/Lange-Nielsen
###Mitral valve prolapse
+
****(+deafness; AR)
##Acquired
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***Romano-Ward syndrome
###[[CVA]] (subarachnoid)
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****(normal hearing; AD)
###Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
+
***Sporadic
 +
***[[Mitral valve prolapse]]
 +
**Acquired
 +
***[[CVA]] (subarachnoid)
 +
***Autonomic surgery (catechol excess: neck dissection, carotid endarterectomy, truncal vagotomy)
 +
 
 +
===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]], vardenafil
 +
*Skeletal muscle relaxants
 +
**[[Tizanidine]]
 +
*Urinary antispasmodics
 +
**Solifenacin
 +
 
 +
==Evaluation==
 +
===Workup===
 +
*[[ECG]]
 +
*CBC
 +
*Chem 10
  
==Treatment==
+
===Diagnosis===
#Pause Dependent (precipitated by bradycard)
+
[[File:De-Acquired longQT (CardioNetworks ECGpedia).jpg|thumb|Acquired QT prolongation]]
##Unstable/sustained torsades--> unsynch countershock
+
*[[ECG]]
##Stable
+
**On visual inspection, QT takes up more than half the R-R distance
###Treat underlying prob
+
**Measure QT interval in lead II or V5-6
###Increase HR (isoproterenol or overdrive pacing
+
**QTc = QT /√R-R
###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==
+
==Management==
#Antiarrhythmics
+
===Pause Dependent (precipitated by bradycardia)===
##Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
+
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
#Antibiotics
+
*Stable
##Macrolide
+
**Treat underlying etiology
###Azithromycin, erythromycin, clarithromycin
+
**Increase HR ([[isoproterenol]] or [[overdrive pacing]])
##Fluoroquinolone
+
**[[Magnesium sulfate]] IV
###Ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, ofloxacin
+
**Consider [[amiodarone]]
##Other
+
 
###Pentamidine, telithromycin, trimethoprim-sulfamethoxazole
+
===Adrenergic Dependent (precipited by tachycardia)===
#Antidepressants
+
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
##Amitriptyline, citalopram, doxepin, fluoxetine, nortriptyline, paroxetine, sertraline, venlafaxine
+
*Stable
#Antiemetics
+
**Slow HR ([[beta-blockers]])
##Dolasetron, droperidol, granisetron, ondansetron
+
**May consider [[magnesium sulfate]]
#Antifungals
+
 
##Fluconazole, itraconazole, ketoconazole, voriconazole
+
==Disposition==
#Antihypertensives
+
*Consider admission, especially for QT >500 or if symptomatic
##Nicardipine
+
*May require consultation for discontinuation of QT prolonging medications
#Antineoplastics
+
*Avoid prescribing medications that may contribute to prolonged QT
##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==
Line 87: Line 122:
 
*[[Torsades de Pointes]]
 
*[[Torsades de Pointes]]
  
==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 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