Difference between revisions of "QT prolongation"

(Clinical Features)
Line 1: Line 1:
 
==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 in males should be more than 450 ms and for females is 470 ms.
+
*An abnormal QT is >440-450 ms (males) and >460-470 ms (females); >500 may result in [[torsades]]
  
 
==Clinical Features==
 
==Clinical Features==
*Most QT prolongations are asymptomatic.
+
*Most are asymptomatic  
 
*History may or may not include
 
*History may or may not include
 
**[[Syncope]], [[cardiac arrest]], family history of long QT or sudden death
 
**[[Syncope]], [[cardiac arrest]], family history of long QT or sudden death
Line 103: Line 103:
  
 
==Disposition==
 
==Disposition==
 +
*Highly consider admission, especially for QT >500
  
 
==See Also==
 
==See Also==

Revision as of 13:38, 4 December 2016

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