QT prolongation: Difference between revisions
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**Rate dependent and should become proportionately shorter with increasing heart rate | **Rate dependent and should become proportionately shorter with increasing heart rate | ||
===Drug List=== | ===Drug List=== | ||
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*Urinary antispasmodics | *Urinary antispasmodics | ||
**Solifenacin | **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== | |||
*Pause Dependent (Acquired) | |||
**Drug induced | |||
***[[Antiarrhythmics]] | |||
***[[Phenothiazines]] | |||
***[[TCAs]] | |||
***[[Organophosphates]] | |||
***[[Antihistamines]] | |||
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]]) | |||
***[[Hypokalemia]] triad | |||
****Long QT, ST depressions, PVCs | |||
**[[Hypothermia]] | |||
**Diet related (starvation, low protein) | |||
**[[Severe Bradycardia]]/[[AV Block]] | |||
**[[Hypothyroid]] | |||
**Contrast injection | |||
**[[CVA]] (intraparenchymal) | |||
**[[Elevated intracranial pressure]] and [[Intracranial hemorrhage]] | |||
**[[MI]] | |||
*Adrenergic Dependent | |||
**Congenital | |||
***Jarvel/Lange-Nielsen | |||
****(+deafness; AR) | |||
***Romano-Ward syndrome | |||
****(normal hearing; AD) | |||
***Sporadic | |||
***[[Mitral valve prolapse]] | |||
**Acquired | |||
***[[CVA]] (subarachnoid) | |||
***Autonomic surgery (catechol excess: neck dissection, carotid endarterectomy, truncal vagotomy) | |||
==Evaluation== | ==Evaluation== | ||
Revision as of 12:33, 14 May 2022
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
Drug List
- Antiarrhythmics
- Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
- Antibiotics
- Macrolide
- 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
- Antihypertensives
- 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
- Opiates
- Phosphodiesterase inhibitors
- Skeletal muscle relaxants
- 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
- Pause Dependent (Acquired)
- Drug induced
- Electrolyte Abnormalities (hypoKalemia, hypoMag, hypoCa)
- Hypokalemia triad
- Long QT, ST depressions, PVCs
- Hypokalemia triad
- Hypothermia
- Diet related (starvation, low protein)
- Severe Bradycardia/AV Block
- Hypothyroid
- Contrast injection
- CVA (intraparenchymal)
- Elevated intracranial pressure and Intracranial hemorrhage
- MI
- Adrenergic Dependent
- Congenital
- Jarvel/Lange-Nielsen
- (+deafness; AR)
- Romano-Ward syndrome
- (normal hearing; AD)
- Sporadic
- Mitral valve prolapse
- Jarvel/Lange-Nielsen
- Acquired
- CVA (subarachnoid)
- Autonomic surgery (catechol excess: neck dissection, carotid endarterectomy, truncal vagotomy)
- Congenital
Evaluation
Workup
- ECG
- CBC
- Chem 10
Diagnosis
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- 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)
- Unstable/sustained torsades→ defibrilation (unsynchronized)
- Stable
- Treat underlying etiology
- Increase HR >80 (isoproterenol or overdrive pacing)
- Magnesium sulfate IV
- Consider lidocaine, transvenous pacing[1]
Adrenergic Dependent (precipited by tachycardia)
- Unstable/sustained torsades→ defibrilation (unsynchronized)
- Stable
- Slow HR (beta-blockers)
- 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
External Links
References
- ↑ 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