QT prolongation: Difference between revisions
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== | ==Background== | ||
[[File:SinusRhythmLabels.svg|thumb]] | |||
[[File:Grid.png|thumb]] | |||
*Prolonged ventricular repolarization → increased risk of ventricular arrhythmias | |||
**Males >440-450 ms | |||
**Females >500 ms | |||
**Rule of thumb: Normal QT interval 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 | |||
===List of Drugs Causing QT Prolongation=== | |||
*[[Antiarrhythmics]] | |||
**[[Amiodarone]], disopyramide, dofetilide, [[flecainide]], ibutilide, mexiletine, [[procainamide]], [[quinidine]], [[sotalol]] | |||
*[[Antibiotics]] | |||
**[[Macrolide]] | |||
***[[Azithromycin]], [[erythromycin]], [[clarithromycin]] | |||
**[[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]] | |||
**[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]] | |||
*[[Antihypertensives]] | |||
**[[Nicardipine]] | |||
*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 | |||
**[[Tacrolimus]] | |||
*[[Opiates]] | |||
**[[Methadone]] | |||
*Phosphodiesterase inhibitors | |||
**[[Sildenafil]], [https://nizagara-online.net/vardenafil/ Vardenafil] | |||
*Skeletal muscle relaxants | |||
**[[Tizanidine]] | |||
*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== | |||
{{Syncope causes}} | |||
* | ==Evaluation== | ||
===Workup=== | |||
*[[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 | |||
== | ===Determining Cause=== | ||
*Pause Dependent (Acquired) | |||
**Drug induced (see drug list above) | |||
***[[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) | |||
==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]]<ref>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</ref> | |||
===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== | |||
*[[ECG (Main)]] | |||
*[[Torsades de Pointes]] | |||
*[[Hypomagnesemia]] | |||
*[[Hypermagnesemia]] | |||
==External Links== | |||
*[https://www.youtube.com/watch?v=T-wqZfRmKQ4 Amal Mattu's Case of the Week (5/20/2012)] | |||
*[http://youtu.be/jrp_XT07fd4 Amal Mattu's Case of the Week (10/13/2014)] | |||
==References== | |||
<references/> | |||
[[Category:Cardiology]] | |||
[[Category:Toxicology]] | |||
[[Category: |
Latest revision as of 12:40, 14 May 2022
Background
- Prolonged ventricular repolarization → increased risk of ventricular arrhythmias
- Males >440-450 ms
- Females >500 ms
- Rule of thumb: Normal QT interval 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
List of Drugs Causing QT Prolongation
- 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
Syncope Causes
- Cardiovascular-mediated syncope
- Dysrhythmias:
- Cardiovascular disease
- Neurally mediated syncope
- Vasovagal:
- Fear, pain, emotion, valsalva, breath-holding spell
- Situational (associated with):
- Vasovagal:
- Orthostatic hypotension-mediated syncope:
- Volume depletion:
- Autonomic Dysreflexia
- Autonomic failure due to meds
- Other serious causes
- Stroke
- SAH
- TIA
- Vertebrobasilar Insufficiency
- Subclavian steal
- Heat syncope
- Hypoglycemia
- Hyperventilation
- Asphyxiation
- Seizure
- Narcolepsy
- Psychogenic (anxiety, conversion disorder, somatic symptom disorder)
- Toxic (drugs, carbon monoxide, etc.)
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
Determining Cause
- Pause Dependent (Acquired)
- Drug induced (see drug list above)
- 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
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