QT prolongation: Difference between revisions

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==Background==
==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==
==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
**Drug induced
***Antidyrhythmics
***[[Antiarrhythmics]]
***Phenothiazines
***[[Phenothiazines]]
***[[TCAs]]
***[[TCAs]]
***[[Organophosphates]]
***[[Organophosphates]]
***Antihistamines
***[[Antihistamines]]
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
***Hypokalemia triad
***[[Hypokalemia]] triad
****Long QT, ST depressions, PVCs
****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
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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===
===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]], [https://nizagara-online.net/vardenafil/ Vardenafil]
*Skeletal muscle relaxants
*Skeletal muscle relaxants
**Tizanidine
**[[Tizanidine]]
*Urinary antispasmodics
*Urinary antispasmodics
**Solifenacin
**Solifenacin


==Evaluation==
==Evaluation==
===Workup===
*[[ECG]]
*[[ECG]]
**QTc >440 (male), >460 (female)
*CBC
**>500 = real concern (may result in [[torsades]])
*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


==Management==
==Management==
===Pause Dependent (precipitated by bradycardia)===
===Pause Dependent (precipitated by bradycardia)===
*Unstable/sustained [[torsades]]--> [[defibrilation]] (unsynchronized)
*Unstable/sustained [[torsades]][[defibrilation]] (unsynchronized)
*Stable
*Stable
**Treat underlying prob
**Treat underlying etiology
**Increase HR ([[isoproterenol]] or [[overdrive pacing]])
**Increase HR ([[isoproterenol]] or [[overdrive pacing]])
**[[Magnesium sulfate]] IV
**[[Magnesium sulfate]] IV
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===Adrenergic Dependent (precipited by tachycardia)===
===Adrenergic Dependent (precipited by tachycardia)===
*Unstable/sustained [[torsades]]--> [[defibrilation]] (unsynchronized)
*Unstable/sustained [[torsades]][[defibrilation]] (unsynchronized)
*Stable
*Stable
**Slow HR ([[beta-blockers]])
**Slow HR ([[beta-blockers]])
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==Disposition==
==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]]


==External Links==
==External Links==

Revision as of 23:37, 23 February 2021

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