QT prolongation

Revision as of 05:55, 24 November 2016 by Teledoc4u (talk | contribs) (Clinical Features)

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 in males should be more than 450 ms and for females is 470 ms.

Clinical Features

  • Most QT prolongations are asymptomatic.
  • Hisotry may or may not include

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

See Also

External Links

References