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== | ||
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***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 | ||
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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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==Evaluation== | ==Evaluation== | ||
===Workup=== | |||
*[[ECG]] | *[[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 | |||
==Management== | ==Management== | ||
===Pause Dependent (precipitated by bradycardia)=== | ===Pause Dependent (precipitated by bradycardia)=== | ||
*Unstable/sustained [[torsades]] | *Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized) | ||
*Stable | *Stable | ||
**Treat underlying | **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]] | *Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized) | ||
*Stable | *Stable | ||
**Slow HR ([[ | **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== |
Revision as of 13:06, 30 March 2019
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:
- Syncope
- Cardiac arrest
- Family history of long QT or sudden death
- Medication history may include QT prolonging medications
Differential Diagnosis
- Pause Dependent (Aquired)
- Drug induced
- Antidyrhythmics
- Phenothiazines
- TCAs
- Organophosphates
- Antihistamines
- 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
- Drug induced
- Adrenergic Dependent
- Congenital
- Jarvel/Lange-Nielsen
- (+deafness; AR)
- Romano-Ward synd
- (nl hearing; AD)
- Sporatic
- Mitral valve prolapse
- Jarvel/Lange-Nielsen
- Acquired
- CVA (subarachnoid)
- Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
- Congenital
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
- Sildenafil, vardenafil
- Skeletal muscle relaxants
- Tizanidine
- Urinary antispasmodics
- Solifenacin
Evaluation
Workup
- ECG
- CBC
- Chem 10
Diagnosis
- 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 (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
- 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