Diferencia entre revisiones de «QT prolongation»

Revisión actual - 15:07 21 mar 2026

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

Calculators

Corrected QT Interval (QTc)

Corrected QT Interval (QTc)
Parameter	Value
QT Interval (ms)
Heart Rate (bpm)
RR Interval (ms) — auto-calculated from HR	ms
Results
QTc (Bazett's) — QT / √(RR in sec)	ms
QTc (Fridericia) — QT / ∛(RR in sec)	ms

Interpretation (Bazett's QTc)
<440 ms	Normal QTc for males.
<460 ms	Normal QTc for females.
440–500 ms	Borderline/Prolonged — Monitor closely. Review medications for QT-prolonging drugs.
>500 ms	Significantly prolonged — High risk for Torsades de Pointes. Discontinue offending agents. Check Mg²⁺/K⁺/Ca²⁺.

References
Bazett HC. An analysis of the time-relations of electrocardiograms. Heart. 1920;7:353-370. Fridericia LS. Duration of systole in electrocardiogram. Acta Med Scand. 1920;53:469-486. Viskin S. Long QT syndromes and torsade de pointes. Lancet. 1999;354:1625-1633. PMID 10560690.

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]

@@ Línea 1: / Línea 1: @@
 ==Background==
-*Prolonged ventricular repolarisation → increased risk of ventricular arrythmias
+[[File:SinusRhythmLabels.svg|thumb]]
+[[File:Grid.png|thumb]]
+*Prolonged ventricular repolarization → increased risk of ventricular arrhythmias
 **Males >440-450 ms
 **Females >500 ms
-**Rule of thumb: Normal QT interveal is less than half of preceding RR interval
+**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
-==Clinical Features==
+===List of Drugs Causing QT Prolongation===
-*Most are asymptomatic
+*[[Antiarrhythmics]]
-*History may include:
-**[[Syncope]]
-**[[Cardiac arrest]]
-**Family history of long QT or sudden death
-*Medication history may include QT prolonging medications
-==Differential Diagnosis==
-*Pause Dependent (Aquired)
-**Drug induced
-***Antidyrhythmics
-***Phenothiazines
-***[[TCAs]]
-***[[Organophosphates]]
-***Antihistamines
-**[[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 synd
-****(nl hearing; AD)
-***Sporatic
-***Mitral valve prolapse
-**Acquired
-***[[CVA]] (subarachnoid)
-***Autonomic surg (catechol excess: neck dissection, carotid endarterect, truncal vagotomy)
-===Drug List===
-*Antiarrhythmics
 **[[Amiodarone]], disopyramide, dofetilide, [[flecainide]], ibutilide, mexiletine, [[procainamide]], [[quinidine]], [[sotalol]]
-*Antibiotics
+*[[Antibiotics]]
-**Macrolide
+**[[Macrolide]]
 ***[[Azithromycin]], [[erythromycin]], [[clarithromycin]]
-**Fluoroquinolone
+**[[Fluoroquinolone]]
 ***[[Ciprofloxacin]], gatifloxacin (most common), [[gemifloxacin]], [[levofloxacin]], [[moxifloxacin]], [[ofloxacin]]
 **Other
 ***[[Pentamidine]], telithromycin, [[trimethoprim-sulfamethoxazole]]
 *Antidepressants
-**[[Amitriptyline]], citalopram, [[doxepin]], fluoxetine, [[nortriptyline]], paroxetine, sertraline, [[venlafaxine]]
+**[[Amitriptyline]], citalopram, [[doxepin]], [[fluoxetine]], [[nortriptyline]], paroxetine, sertraline, [[venlafaxine]]
-*Antiemetics
+*[[Antiemetics]]
 **Dolasetron, [[droperidol]], granisetron, [[ondansetron]]
-*Antifungals
+*[[Antifungals]]
 **[[Fluconazole]], [[itraconazole]], [[ketoconazole]], [[voriconazole]]
-*Antihypertensives
+*[[Antihypertensives]]
 **[[Nicardipine]]
 *Antineoplastics
 **Lapatinib, nilotinib, sunitinib, tamoxifen
-*Antimalarials
+*[[Antimalarials]]
 **[[Chloroquine]], halofantrine
-*Antipsychotics
+*[[Antipsychotics]]
 **[[Chlorpromazine]], [[clozapine]], galantamine, [[haloperidol]], [[lithium]], paliperidone, pimozide, [[quetiapine]], [[risperidone]], thioridazine, [[ziprasidone]]
-*Antivirals
+*[[Antivirals]]
 **[[Amantadine]], atazanavir, [[foscarnet]]
-*Diuretics
+*[[Diuretics]]
 **Indapamide
 *Immune suppressants
 **[[Tacrolimus]]
-*Opiates
+*[[Opiates]]
 **[[Methadone]]
 *Phosphodiesterase inhibitors
-**[[Sildenafil]], vardenafil
+**[[Sildenafil]], [https://nizagara-online.net/vardenafil/ Vardenafil]
 *Skeletal muscle relaxants
-**Tizanidine
+**[[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}}
 ==Evaluation==
+===Workup===
+*[[ECG]]
+*CBC
+*Chem 10
+===Diagnosis===
+[[File:De-Acquired longQT (CardioNetworks ECGpedia).jpg|thumb|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)
+***[[Antiarrhythmics]]
+***[[Phenothiazines]]
+***[[TCAs]]
+***[[Organophosphates]]
+***[[Antihistamines]]
+**[[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==
@@ Línea 95: / Línea 107: @@
 *Unstable/sustained [[torsades]]→ [[defibrilation]] (unsynchronized)
 *Stable
-**Treat underlying prob
+**Treat underlying etiology
-**Increase HR ([[isoproterenol]] or [[overdrive pacing]])
+**Increase HR >80 ([[isoproterenol]] or [[overdrive pacing]])
 **[[Magnesium sulfate]] IV
-**Consider [[amiodarone]]
+**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)===
@@ Línea 107: / Línea 119: @@
 ==Disposition==
-*Highly consider admission, especially for QT >500
+*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]]
+== Calculators ==
+{{QTc_Calculator}}
 ==External Links==
@@ Línea 119: / Línea 138: @@
 ==References==
 <references/>
 [[Category:Cardiology]]
 [[Category:Toxicology]]