Difference between revisions of "QT prolongation"

(Text replacement - "==Diagnosis==" to "==Evaluation==")
(Differential Diagnosis)
 
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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]], 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 ([[B-blockers]])
+
**Slow HR ([[beta-blockers]])
 
**May consider [[magnesium sulfate]]
 
**May consider [[magnesium sulfate]]
  
 
==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==

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