QT prolongation: Difference between revisions

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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)
*QT interval is from the beginning of the Q wave to the end of the T wave; it is rate dependent and should become proportionately small with increasing rate rate
*An abnormal QT is >440-450 ms (males) and >460-470 ms (females); >500 may result in [[torsades]]
*A useful rule of thumb is that a normal QT is less than half the preceding RR interval
 
==Clinical Features==
*Most are asymptomatic
*History may or may not include
**[[Syncope]], [[cardiac arrest]], family history of long QT or sudden death
**Medication history should always be obtained especially so to avoid interactions and further QT prolongation.


==Differential Diagnosis==
==Differential Diagnosis==
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***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
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**Contrast injection
**Contrast injection
**[[CVA]] (intraparenchymal)
**[[CVA]] (intraparenchymal)
**[[Elevated intracranial pressure]] and [[Intracranial hemorrhage]]
**[[MI]]
**[[MI]]
*Adrenergic Dependent
*Adrenergic Dependent
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===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
*Antiemetics
**Dolasetron, droperidol, granisetron, ondansetron
**Dolasetron, [[droperidol]], granisetron, [[ondansetron]]
*Antifungals
*Antifungals
**Fluconazole, itraconazole, ketoconazole, voriconazole
**[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]]
*Antihypertensives
*Antihypertensives
**Nicardipine
**[[Nicardipine]]
*Antineoplastics
*Antineoplastics
**Lapatinib, nilotinib, sunitinib, tamoxifen
**Lapatinib, nilotinib, sunitinib, tamoxifen
*Antimalarials
*Antimalarials
**Chloroquine, halofantrine
**[[Chloroquine]], halofantrine
*Antipsychotics
*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
**[[Amantadine]], atazanavir, [[foscarnet]]
*Diuretics
*Diuretics
**Indapamide
**Indapamide
*Immune suppressants
*Immune suppressants
**Tacrolimus
**[[Tacrolimus]]
*Opiates
*Opiates
**Methadone
**[[Methadone]]
*Phosphodiesterase inhibitors
*Phosphodiesterase inhibitors
**Sildenafil, vardenafil
**[[Sildenafil]], vardenafil
*Skeletal muscle relaxants
*Skeletal muscle relaxants
**Tizanidine
**Tizanidine
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**Solifenacin
**Solifenacin


==Treatment==
==Evaluation==
*Pause Dependent (precipitated by bradycard)
*[[ECG]]
**Unstable/sustained torsades--> unsynch countershock
**quick/imprecise measure: QT takes up more than half the R-R distance
**Stable
**Measure QT interval in lead II or V5-6
***Treat underlying prob
**QTc = QT /√R-R
***Increase HR (isoproterenol or overdrive pacing
**Long QT: QTc >440 (male), >460 (female)
***Magnesium sulfate IV
**>500 = real concern (may result in [[torsades]])
***Consider amiodarone
 
*Adrenergic Dependent (precipited by tachycardia)
==Management==
**Unstable/sustained torsades--> unsynch countershock
===Pause Dependent (precipitated by bradycardia)===
**Stable
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
***Slow HR (B-blockers)
*Stable
***May consider magnesium
**Treat underlying prob
**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==
*Highly consider admission, especially for QT >500


==See Also==
==See Also==
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*[[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]]

Revision as of 18:40, 1 May 2018

Background

  • Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
  • QT interval is from the beginning of the Q wave to the end of the T wave; it is rate dependent and should become proportionately small with increasing rate rate
  • An abnormal QT is >440-450 ms (males) and >460-470 ms (females); >500 may result in torsades
  • A useful rule of thumb is that a normal QT is less than half the preceding RR interval

Clinical Features

  • Most are asymptomatic
  • History may or may not include
    • Syncope, cardiac arrest, family history of long QT or sudden death
    • Medication history should always be obtained especially so to avoid interactions and further QT prolongation.

Differential Diagnosis

Drug List

Evaluation

  • ECG
    • quick/imprecise measure: QT takes up more than half the R-R distance
    • Measure QT interval in lead II or V5-6
    • QTc = QT /√R-R
    • Long QT: QTc >440 (male), >460 (female)
    • >500 = real concern (may result in torsades)

Management

Pause Dependent (precipitated by bradycardia)

Adrenergic Dependent (precipited by tachycardia)

Disposition

  • Highly consider admission, especially for QT >500

See Also

External Links

References

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