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===
*[[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
 
===Determining Cause===
*Pause Dependent (Acquired)
**Drug induced (see drug list above)
***[[Antiarrhythmics]]
***[[Phenothiazines]]
***[[TCAs]]
***[[TCAs]]
***[[Organophosphates]]
***[[Organophosphates]]
***Antihistamines
***[[Antihistamines]]
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
***[[Hypokalemia]] triad
****Long QT, ST depressions, PVCs
**[[Hypothermia]]
**Diet related (starvation, low protein)
**Diet related (starvation, low protein)
**[[Severe Bradycardia]]/AV Block
**[[Severe Bradycardia]]/[[AV Block]]
**[[Hypothyroid]]
**[[Hypothyroid]]
**Contrast injection
**Contrast injection
**[[CVA]] (intraparenchymal)
**[[CVA]] (intraparenchymal)
**[[Elevated intracranial pressure]] and [[Intracranial hemorrhage]]
**[[MI]]
**[[MI]]
*Adrenergic Dependent
*Adrenergic Dependent
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***Jarvel/Lange-Nielsen
***Jarvel/Lange-Nielsen
****(+deafness; AR)
****(+deafness; AR)
***Romano-Ward synd
***Romano-Ward syndrome
****(nl hearing; AD)
****(normal hearing; AD)
***Sporatic
***Sporadic
***Mitral valve prolapse
***[[Mitral valve prolapse]]
**Acquired
**Acquired
***[[CVA]] (subarachnoid)
***[[CVA]] (subarachnoid)
***Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
***Autonomic surgery (catechol excess: neck dissection, carotid endarterectomy, truncal vagotomy)


===Drug List===
==Management==
*Antiarrhythmics
===Pause Dependent (precipitated by bradycardia)===
**Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
*Unstable/sustained [[torsades]][[defibrilation]] (unsynchronized)
*Antibiotics
**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
 
==Treatment==
===Pause Dependent (precipitated by bradycard)===
*Unstable/sustained [[torsades]]--> [[defibrilation]] (unsynchronized)
*Stable
*Stable
**Treat underlying prob
**Treat underlying etiology
**Increase HR ([[isoproterenol]] or [[overdrive pacing]])
**Increase HR >80 ([[isoproterenol]] or [[overdrive pacing]])
**[[Magnesium sulfate]] IV
**[[Magnesium sulfate]] IV
**Consider [[amiodarone]]
**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)===
===Adrenergic Dependent (precipited by tachycardia)===
*Unstable/sustained [[torsades]]--> [[defibrilation]] (unsynchronized)
*Unstable/sustained [[torsades]][[defibrilation]] (unsynchronized)
*Stable
*Stable
**Slow HR ([[B-blockers[[)
**Slow HR ([[beta-blockers]])
**May consider [[magnesium sulfate]]
**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==
==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