Difference between revisions of "QT prolongation"

(Disposition)
(Differential Diagnosis)
 
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==Differential Diagnosis==
 
==Differential Diagnosis==
*Pause Dependent (Aquired)
+
*Pause Dependent (Acquired)
 
**Drug induced
 
**Drug induced
***Antidyrhythmics
+
***[[Antiarrhythmics]]
***Phenothiazines
+
***[[Phenothiazines]]
 
***[[TCAs]]
 
***[[TCAs]]
 
***[[Organophosphates]]
 
***[[Organophosphates]]
***Antihistamines
+
***[[Antihistamines]]
 
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
 
**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
***Hypokalemia triad
+
***[[Hypokalemia]] triad
 
****Long QT, ST depressions, PVCs
 
****Long QT, ST depressions, PVCs
 
**[[Hypothermia]]
 
**[[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
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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===
 
===Drug List===
*Antiarrhythmics
+
*[[Antiarrhythmics]]
 
**[[Amiodarone]], disopyramide, dofetilide, [[flecainide]], ibutilide, mexiletine, [[procainamide]], [[quinidine]], [[sotalol]]
 
**[[Amiodarone]], disopyramide, dofetilide, [[flecainide]], ibutilide, mexiletine, [[procainamide]], [[quinidine]], [[sotalol]]
*Antibiotics
+
*[[Antibiotics]]
**Macrolide
+
**[[Macrolide]]
 
***[[Azithromycin]], [[erythromycin]], [[clarithromycin]]
 
***[[Azithromycin]], [[erythromycin]], [[clarithromycin]]
**Fluoroquinolone
+
**[[Fluoroquinolone]]
 
***[[Ciprofloxacin]], gatifloxacin (most common), [[gemifloxacin]], [[levofloxacin]], [[moxifloxacin]], [[ofloxacin]]
 
***[[Ciprofloxacin]], gatifloxacin (most common), [[gemifloxacin]], [[levofloxacin]], [[moxifloxacin]], [[ofloxacin]]
 
**Other
 
**Other
 
***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]]
 
***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]]
 
*Antidepressants
 
*Antidepressants
**[[Amitriptyline]], citalopram, [[doxepin]], fluoxetine, [[nortriptyline]], paroxetine, sertraline, [[venlafaxine]]
+
**[[Amitriptyline]], citalopram, [[doxepin]], [[fluoxetine]], [[nortriptyline]], paroxetine, sertraline, [[venlafaxine]]
*Antiemetics
+
*[[Antiemetics]]
 
**Dolasetron, [[droperidol]], granisetron, [[ondansetron]]
 
**Dolasetron, [[droperidol]], granisetron, [[ondansetron]]
*Antifungals
+
*[[Antifungals]]
 
**[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]]
 
**[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]]
*Antihypertensives
+
*[[Antihypertensives]]
 
**[[Nicardipine]]
 
**[[Nicardipine]]
 
*Antineoplastics
 
*Antineoplastics
 
**Lapatinib, nilotinib, sunitinib, tamoxifen
 
**Lapatinib, nilotinib, sunitinib, tamoxifen
*Antimalarials
+
*[[Antimalarials]]
 
**[[Chloroquine]], halofantrine
 
**[[Chloroquine]], halofantrine
*Antipsychotics
+
*[[Antipsychotics]]
 
**[[Chlorpromazine]], [[clozapine]], galantamine, [[haloperidol]], [[lithium]], paliperidone, pimozide, [[quetiapine]], [[risperidone]], thioridazine, [[ziprasidone]]
 
**[[Chlorpromazine]], [[clozapine]], galantamine, [[haloperidol]], [[lithium]], paliperidone, pimozide, [[quetiapine]], [[risperidone]], thioridazine, [[ziprasidone]]
*Antivirals
+
*[[Antivirals]]
 
**[[Amantadine]], atazanavir, [[foscarnet]]
 
**[[Amantadine]], atazanavir, [[foscarnet]]
*Diuretics
+
*[[Diuretics]]
 
**Indapamide
 
**Indapamide
 
*Immune suppressants
 
*Immune suppressants
 
**[[Tacrolimus]]
 
**[[Tacrolimus]]
*Opiates
+
*[[Opiates]]
 
**[[Methadone]]
 
**[[Methadone]]
 
*Phosphodiesterase inhibitors
 
*Phosphodiesterase inhibitors
 
**[[Sildenafil]], vardenafil
 
**[[Sildenafil]], vardenafil
 
*Skeletal muscle relaxants
 
*Skeletal muscle relaxants
**Tizanidine
+
**[[Tizanidine]]
 
*Urinary antispasmodics
 
*Urinary antispasmodics
 
**Solifenacin
 
**Solifenacin
  
 
==Evaluation==
 
==Evaluation==
 +
===Workup===
 +
*[[ECG]]
 +
*CBC
 +
*Chem 10
 +
 +
===Diagnosis===
 +
[[File:De-Acquired longQT (CardioNetworks ECGpedia).jpg|thumb|Acquired QT prolongation]]
 
*[[ECG]]
 
*[[ECG]]
 
**On visual inspection, QT takes up more than half the R-R distance
 
**On visual inspection, QT takes up more than half the R-R distance

Latest revision as of 04:30, 25 February 2020

Background

  • Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
    • Males >440-450 ms
    • Females >500 ms
    • Rule of thumb: Normal QT interveal 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

Clinical Features

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

Differential Diagnosis

Drug List

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

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

External Links

References