Diferencia entre revisiones de «QT prolongation»
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==Diagnosis==
==Background==
*QTc >440 (male), >460 (female)
[[File:SinusRhythmLabels.svg|thumb]]
*>500 = real concern (may result in torsades)
[[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==
==Differential Diagnosis==
*Pause Dependent (Aquired)
{{Syncope causes}}
**Drug induced
 
***Antidyrhythmics
==Evaluation==
***Phenothiazines
===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]]
***[[TCAs]]
***[[Organophosphates]]
***[[Organophosphates]]
***Antihistamines
***[[Antihistamines]]
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
***[[Hypokalemia]] triad
****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
**[[CVA]] (intraparenchymal)
**[[CVA]] (intraparenchymal)
**[[Elevated intracranial pressure]] and [[Intracranial hemorrhage]]
**[[MI]]
**[[MI]]
*Adrenergic Dependent
*Adrenergic Dependent
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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===
==Management==
*Antiarrhythmics
===Pause Dependent (precipitated by bradycardia)===
**Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
*Antibiotics
**Macrolide
***Azithromycin, erythromycin, clarithromycin
**Fluoroquinolone
***Ciprofloxacin, gatifloxacin, 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, vardenafil
*Skeletal muscle relaxants
**Tizanidine
*Urinary antispasmodics
**Solifenacin
 
==Treatment==
===Pause Dependent (precipitated by bradycard)===
*Unstable/sustained [[torsades]]--> [[defibrilation]] (unsynchronized)
*Stable
*Stable
**Treat underlying prob
**Treat underlying etiology
**Increase HR ([[isoproterenol]] or [[overdrive pacing]])
**Increase HR >80 ([[isoproterenol]] or [[overdrive pacing]])
**[[Magnesium sulfate]] IV
**[[Magnesium sulfate]] IV
**Consider [[amiodarone]]
**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)===
===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==
*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==
*[[ECG (Main)]]
*[[ECG (Main)]]
*[[Torsades de Pointes]]
*[[Torsades de Pointes]]
*[[Hypomagnesemia]]
*[[Hypermagnesemia]]


==Source ==
== Calculators ==
*Rosen
{{QTc_Calculator}}
*Tintinalli


==External Links==
==External Links==
[http://youtu.be/jrp_XT07fd4 Amal Mattu's Case of the Week (10/13/2014)]
*[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)]


[[Category:Cards]]
==References==
[[Category:Tox]]
<references/>
[[Category:Cardiology]]
[[Category:Toxicology]]

Revisión actual - 15:07 21 mar 2026

Background

SinusRhythmLabels.svg
Grid.png
  • 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

Clinical Features

  • Most are asymptomatic
  • History may include:
  • Medication history may include QT prolonging medications

Differential Diagnosis

Syncope Causes

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

Determining Cause

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

Calculators

Corrected QT Interval (QTc)

Corrected QT Interval (QTc)
Parameter Value
QT Interval (ms)
Heart Rate (bpm)
RR Interval (ms) — auto-calculated from HR ms
Results
QTc (Bazett's) — QT / √(RR in sec) ms
QTc (Fridericia) — QT / ∛(RR in sec) ms
Interpretation (Bazett's QTc)
<440 ms Normal QTc for males.
<460 ms Normal QTc for females.
440–500 ms Borderline/Prolonged — Monitor closely. Review medications for QT-prolonging drugs.
>500 ms Significantly prolonged — High risk for Torsades de Pointes. Discontinue offending agents. Check Mg²⁺/K⁺/Ca²⁺.
References
  • Bazett HC. An analysis of the time-relations of electrocardiograms. Heart. 1920;7:353-370.
  • Fridericia LS. Duration of systole in electrocardiogram. Acta Med Scand. 1920;53:469-486.
  • Viskin S. Long QT syndromes and torsade de pointes. Lancet. 1999;354:1625-1633. PMID 10560690.

External Links

References

  1. ↑ 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
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