QT prolongation: Difference between revisions
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==Differential Diagnosis== | ==Differential Diagnosis== | ||
*Pause Dependent ( | *Pause Dependent (Acquired) | ||
**Drug induced | **Drug induced | ||
*** | ***[[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]] | **[[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 | ***Romano-Ward syndrome | ||
****( | ****(normal hearing; AD) | ||
*** | ***Sporadic | ||
***Mitral valve prolapse | ***[[Mitral valve prolapse]] | ||
**Acquired | **Acquired | ||
***[[CVA]] (subarachnoid) | ***[[CVA]] (subarachnoid) | ||
***Autonomic | ***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]] | ||
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**Other | **Other | ||
***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]] | ***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]] | ||
* | *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]] | ||
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**[[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 |
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:
- 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
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
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