QT prolongation: Difference between revisions

Latest revision as of 12:40, 14 May 2022

Background

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, 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

Syncope Causes

Cardiovascular-mediated syncope
- Dysrhythmias:
  - WPW (pre-excitation)
  - Long QT Syndrome/QT prolongation
  - Brugada Syndrome
  - Catecholaminergic polymorphic ventricular tachycardia
  - 2nd/3rd AV Block
  - Afib/aflutter
  - Vtach/torsades
  - Sick sinus syndrome
  - Arrhythmogenic right ventricular dysplasia
  - Short QT syndrome
- Cardiovascular disease
  - Valvular Disease (AS, MS, tricuspid stenosis)
  - Aortic Dissection
  - Myocardial Infarction
  - CHF
  - Hypertrophic Cardiomyopathy
  - PE
  - Pericardial Tamponade
  - Myxoma
  - Pulmonary Hypertension
  - Pacemaker malfunction
Neurally mediated syncope
- Vasovagal:
  - Fear, pain, emotion, valsalva, breath-holding spell
- Situational (associated with):
  - Coughing, micturition, defecation, vomiting, swallowing, postexercise
  - Carotid sinus stimulation
Orthostatic hypotension-mediated syncope:
- Volume depletion:
- Autonomic Dysreflexia
- Autonomic failure due to meds
Other serious causes
- Stroke
- SAH
- TIA
- Vertebrobasilar Insufficiency
- Subclavian steal
- Heat syncope
- Hypoglycemia
- Hyperventilation
- Asphyxiation
- Seizure
- Narcolepsy
- Psychogenic (anxiety, conversion disorder, somatic symptom disorder)
- Toxic (drugs, carbon monoxide, etc.)

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

Pause Dependent (Acquired)
- Drug induced (see drug list above)
- Electrolyte Abnormalities (hypoKalemia, hypoMag, hypoCa)
  - Hypokalemia triad
    - Long QT, ST depressions, PVCs
- Hypothermia
- Diet related (starvation, low protein)
- Severe Bradycardia/AV Block
- Hypothyroid
- Contrast injection
- CVA (intraparenchymal)
- Elevated intracranial pressure and Intracranial hemorrhage
- MI
Adrenergic Dependent
- Congenital
  - Jarvel/Lange-Nielsen
    - (+deafness; AR)
  - Romano-Ward syndrome
    - (normal hearing; AD)
  - Sporadic
  - Mitral valve prolapse
- Acquired
  - CVA (subarachnoid)
  - Autonomic surgery (catechol excess: neck dissection, carotid endarterectomy, truncal vagotomy)

Management

Pause Dependent (precipitated by bradycardia)

Unstable/sustained torsades→ defibrilation (unsynchronized)
Stable
- Treat underlying etiology
- Increase HR >80 (isoproterenol or overdrive pacing)
- Magnesium sulfate IV
- Consider lidocaine, transvenous pacing^[1]

Adrenergic Dependent (precipited by tachycardia)

Unstable/sustained torsades→ defibrilation (unsynchronized)
Stable
- Slow HR (beta-blockers)
- 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

External Links

References

↑ 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

Authors:

[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

[1]

@@ Line 1: / Line 1: @@
-==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
-==DDX==
+===List of Drugs Causing QT Prolongation===
-#Pause Dependent (Aquired)
+*[[Antiarrhythmics]]
-##Drug induced
+**[[Amiodarone]], disopyramide, dofetilide, [[flecainide]], ibutilide, mexiletine, [[procainamide]], [[quinidine]], [[sotalol]]
-###Antidyrhythmics
+*[[Antibiotics]]
-###Phenothiazines
+**[[Macrolide]]
-###[[TCAs]]
+***[[Azithromycin]], [[erythromycin]], [[clarithromycin]]
-###[[Organophosphates]]
+**[[Fluoroquinolone]]
-###Antihistamines
+***[[Ciprofloxacin]], gatifloxacin (most common), [[gemifloxacin]], [[levofloxacin]], [[moxifloxacin]], [[ofloxacin]]
-##[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
+**Other
-##Diet related (starvation, low protein)
+***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]]
-##[[Severe Bradycardia]]/AV Block
+*Antidepressants
-##[[Hypothyroid]]
+**[[Amitriptyline]], citalopram, [[doxepin]], [[fluoxetine]], [[nortriptyline]], paroxetine, sertraline, [[venlafaxine]]
-##Contrast injection
+*[[Antiemetics]]
-##[[CVA]] (intraparenchymal)
+**Dolasetron, [[droperidol]], granisetron, [[ondansetron]]
-##[[MI]]
+*[[Antifungals]]
-#Adrenergic Dependent
+**[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]]
-##Congenital
+*[[Antihypertensives]]
-###Jarvel/Lange-Nielsen
+**[[Nicardipine]]
-####(+deafness; AR)
+*Antineoplastics
-###Romano-Ward synd
+**Lapatinib, nilotinib, sunitinib, tamoxifen
-####(nl hearing; AD)
+*[[Antimalarials]]
-###Sporatic
+**[[Chloroquine]], halofantrine
-###Mitral valve prolapse
+*[[Antipsychotics]]
-##Acquired
+**[[Chlorpromazine]], [[clozapine]], galantamine, [[haloperidol]], [[lithium]], paliperidone, pimozide, [[quetiapine]], [[risperidone]], thioridazine, [[ziprasidone]]
-###[[CVA]] (subarachnoid)
+*[[Antivirals]]
-###Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
+**[[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
-==Treatment==
+==Clinical Features==
-#Pause Dependent (precipitated by bradycard)
+*Most are asymptomatic
-##Unstable/sustained torsades--> unsynch countershock
+*History may include:
-##Stable
+**[[Syncope]]
-###Treat underlying prob
+**[[Cardiac arrest]]
-###Increase HR (isoproterenol or overdrive pacing
+**Family history of long QT or sudden death
-###Magnesium sulfate IV
+*Medication history may include QT prolonging medications
-###Consider amiodarone
-#Adrenergic Dependent (precipited by tachycardia)
-##Unstable/sustained torsades--> unsynch countershock
-##Stable
-###slow HR (B-blockers)
-###May consider magnesium
-==Drug List==
+==Differential Diagnosis==
-#Antiarrhythmics
+{{Syncope causes}}
-##Amiodarone, disopyramide, dofetilide, flecainide, ibutilide, mexiletine, procainamide, quinidine, sotalol
-#Antibiotics
+==Evaluation==
-##Macrolide
+===Workup===
-###Azithromycin, erythromycin, clarithromycin
+*[[ECG]]
-##Fluoroquinolone
+*CBC
-###Ciprofloxacin, gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, ofloxacin
+*Chem 10
-##Other
-###Pentamidine, telithromycin, trimethoprim-sulfamethoxazole
+===Diagnosis===
-#Antidepressants
+[[File:De-Acquired longQT (CardioNetworks ECGpedia).jpg|thumb|Acquired QT prolongation]]
-##Amitriptyline, citalopram, doxepin, fluoxetine, nortriptyline, paroxetine, sertraline, venlafaxine
+*[[ECG]]
-#Antiemetics
+**On visual inspection, QT takes up more than half the R-R distance
-##Dolasetron, droperidol, granisetron, ondansetron
+**Measure QT interval in lead II or V5-6
-#Antifungals
+**QTc = QT /√R-R
-##Fluconazole, itraconazole, ketoconazole, voriconazole
-#Antihypertensives
+===Determining Cause===
-##Nicardipine
+*Pause Dependent (Acquired)
-#Antineoplastics
+**Drug induced (see drug list above)
-##Lapatinib, nilotinib, sunitinib, tamoxifen
+***[[Antiarrhythmics]]
-#Antimalarials
+***[[Phenothiazines]]
-##Chloroquine, halofantrine
+***[[TCAs]]
-#Antipsychotics
+***[[Organophosphates]]
-##Chlorpromazine, clozapine, galantamine, haloperidol, lithium, paliperidone, pimozide, quetiapine, risperidone, thioridazine, ziprasidone
+***[[Antihistamines]]
-#Antivirals
+**[[Electrolyte Abnormalities]] ([[hypoKalemia]], [[hypoMag]], [[hypoCa]])
-##Amantadine, atazanavir, foscarnet
+***[[Hypokalemia]] triad
-#Diuretics
+****Long QT, ST depressions, PVCs
-##Indapamide
+**[[Hypothermia]]
-#Immune suppressants
+**Diet related (starvation, low protein)
-##Tacrolimus
+**[[Severe Bradycardia]]/[[AV Block]]
-#Opiates
+**[[Hypothyroid]]
-##Methadone
+**Contrast injection
-#Phosphodiesterase inhibitors
+**[[CVA]] (intraparenchymal)
-##Sildenafil, vardenafil
+**[[Elevated intracranial pressure]] and [[Intracranial hemorrhage]]
-#Skeletal muscle relaxants
+**[[MI]]
-##Tizanidine
+*Adrenergic Dependent
-#Urinary antispasmodics
+**Congenital
-##Solifenacin
+***Jarvel/Lange-Nielsen
+****(+deafness; AR)
+***Romano-Ward syndrome
+****(normal hearing; AD)
+***Sporadic
+***[[Mitral valve prolapse]]
+**Acquired
+***[[CVA]] (subarachnoid)
+***Autonomic surgery (catechol excess: neck dissection, carotid endarterectomy, truncal vagotomy)
+==Management==
+===Pause Dependent (precipitated by bradycardia)===
+*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
+*Stable
+**Treat underlying etiology
+**Increase HR >80 ([[isoproterenol]] or [[overdrive pacing]])
+**[[Magnesium sulfate]] IV
+**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)===
+*Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
+*Stable
+**Slow HR ([[beta-blockers]])
+**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==
 *[[ECG (Main)]]
 *[[Torsades de Pointes]]
+*[[Hypomagnesemia]]
+*[[Hypermagnesemia]]
+==External Links==
+*[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)]
-==Source ==
+==References==
-*Rosen
+<references/>
-*Tintinalli
-[[Category:Cards]]
+[[Category:Cardiology]]
-[[Category:Tox]]
+[[Category:Toxicology]]