Difference between revisions of "QT prolongation"

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==Background==
 
==Background==
*Prolonged ventricular repolarisation --> increased risk of ventricular arrythmias
+
*Prolonged ventricular repolarisation increased risk of ventricular arrythmias
 
*QT interval is from the beginning of the Q wave to the end of the T wave; it is rate dependent and should become proportionately small with increasing rate rate
 
*QT interval is from the beginning of the Q wave to the end of the T wave; it is rate dependent and should become proportionately small with increasing rate rate
 
*An abnormal QT is >440-450 ms (males) and >460-470 ms (females); >500 may result in [[torsades]]
 
*An abnormal QT is >440-450 ms (males) and >460-470 ms (females); >500 may result in [[torsades]]
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==Management==
 
==Management==
 
===Pause Dependent (precipitated by bradycardia)===
 
===Pause Dependent (precipitated by bradycardia)===
*Unstable/sustained [[torsades]]--> [[defibrilation]] (unsynchronized)
+
*Unstable/sustained [[torsades]][[defibrilation]] (unsynchronized)
 
*Stable
 
*Stable
 
**Treat underlying prob
 
**Treat underlying prob
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===Adrenergic Dependent (precipited by tachycardia)===
 
===Adrenergic Dependent (precipited by tachycardia)===
*Unstable/sustained [[torsades]]--> [[defibrilation]] (unsynchronized)
+
*Unstable/sustained [[torsades]][[defibrilation]] (unsynchronized)
 
*Stable
 
*Stable
 
**Slow HR ([[beta-blockers]])
 
**Slow HR ([[beta-blockers]])

Revision as of 17:36, 8 February 2017

Background

  • Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
  • QT interval is from the beginning of the Q wave to the end of the T wave; it is rate dependent and should become proportionately small with increasing rate rate
  • An abnormal QT is >440-450 ms (males) and >460-470 ms (females); >500 may result in torsades

Clinical Features

  • Most are asymptomatic
  • History may or may not include
    • Syncope, cardiac arrest, family history of long QT or sudden death
    • Medication history should always be obtained especially so to avoid interactions and further QT prolongation.

Differential Diagnosis

Drug List

  • 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, vardenafil
  • Skeletal muscle relaxants
    • Tizanidine
  • Urinary antispasmodics
    • Solifenacin

Evaluation

  • ECG
    • quick/imprecise measure: QT takes up more than half the R-R distance
    • Measure QT interval in lead II or V5-6
    • QTc = QT /√R-R
    • Long QT: QTc >440 (male), >460 (female)
    • >500 = real concern (may result in torsades)

Management

Pause Dependent (precipitated by bradycardia)

Adrenergic Dependent (precipited by tachycardia)

Disposition

  • Highly consider admission, especially for QT >500

See Also

External Links

References