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# Long QT syndrome and torsades de pointes

Long QT means the heart takes too long to recharge after each beat. It can trigger a twisting rhythm called torsades that causes fainting or sudden death.

Updated 2026-11-01

## Structures involved

Tap one to see what it is and open it in 3D.

- [Left ventricle](https://durgical.com/en/anatomy/left-ventricle/)
- [Right ventricle](https://durgical.com/en/anatomy/right-ventricle/)
- [Bundle branches](https://durgical.com/en/anatomy/right-bundle-branch/)
- [Interventricular septum](https://durgical.com/en/anatomy/interventricular-septum/)
- [Sinoatrial (SA) node](https://durgical.com/en/anatomy/sinuatrial-node/)

## Why it happens

- [Mendelian inheritance: autosomal dominant, recessive and X-linked](https://durgical.com/en/general-pathology/mendelian-inheritance-autosomal-dominant-recessive-and-x-linked/)
- [Sudden infant death syndrome: what is known](https://durgical.com/en/general-pathology/sudden-infant-death-syndrome-what-is-known/)
- [The ventricular action potential](https://durgical.com/en/physiology/the-ventricular-action-potential/)
- [Ion channels and gating](https://durgical.com/en/physiology/ion-channels-and-gating/)
- [How arrhythmias arise](https://durgical.com/en/physiology/how-arrhythmias-arise/)
- [The ECG in potassium and calcium disorders](https://durgical.com/en/physiology/the-ecg-in-potassium-and-calcium-disorders/)

## What it is

A disorder of ventricular repolarisation with a prolonged corrected QT interval on the ECG. It may be congenital (ion channel mutations) or acquired (drugs, electrolyte disorders). Its main danger is torsades de pointes, a polymorphic ventricular tachycardia that twists around the baseline and can turn into ventricular fibrillation.

## Who gets it

The congenital form affects about 1 in 2,000 people. The acquired form is far more common in hospitals, where QT-prolonging drugs are often combined with hypokalaemia, hypomagnesaemia or bradycardia, especially in older women. In Colombia, as elsewhere, many common drugs (some antibiotics, antiemetics, antipsychotics and antimalarials) are known causes.

## Causes

- Congenital: mutations in potassium channels (KCNQ1, KCNH2) or sodium channels (SCN5A); Romano-Ward syndrome (autosomal dominant) and Jervell and Lange-Nielsen syndrome (autosomal recessive, with congenital deafness)
- Drugs: class IA and III antiarrhythmics, macrolides and fluoroquinolones, some antipsychotics and antidepressants, methadone, ondansetron, chloroquine and hydroxychloroquine
- Electrolytes: hypokalaemia, hypomagnesaemia, hypocalcaemia
- Bradycardia and high-grade atrioventricular block
- Other: hypothyroidism, hypothermia, starvation (anorexia nervosa), intracranial haemorrhage

## Risk factors

- Female sex
- Combination of two or more QT-prolonging drugs
- Low potassium or magnesium (diuretics, vomiting, diarrhoea)
- Bradycardia, heart failure or structural heart disease
- [Kidney](https://durgical.com/en/anatomy/kidney/) or [liver](https://durgical.com/en/anatomy/liver/) failure that raises drug levels
- Family history of sudden death, unexplained drowning or fainting

## Pathophysiology

Reduced outward potassium current or persistent inward sodium current lengthens the ventricular action potential. Repolarisation becomes uneven across the wall, and early afterdepolarisations can trigger premature beats. A pause followed by a premature beat (short-long-short sequence) typically launches torsades de pointes. Triggers differ by genotype: exercise and swimming (type 1), sudden noise or emotion (type 2), rest or sleep (type 3).

## Classification

- Congenital: LQT1, LQT2, LQT3 (most common types) and rarer forms
- Acquired: drug-induced, electrolyte-related, bradycardia-related
- Rhythm: torsades de pointes (polymorphic ventricular tachycardia with QT prolongation)

## Symptoms and signs

- Sudden fainting, often triggered by exercise, emotion, noise or during sleep
- Palpitations
- Seizure-like episodes (sometimes misdiagnosed as epilepsy)
- Cardiac arrest or sudden death
- Many carriers are asymptomatic

## Red flags

- Syncope with exertion, emotion or a loud noise
- QTc above about 500 ms, or a rise of more than 60 ms after starting a drug
- Runs of polymorphic ventricular tachycardia on the monitor
- Unexplained drowning or sudden death in a young relative

## Diagnosis

**Clinical**
Suspect it in patients with unexplained syncope, seizures or arrest, in those taking QT-prolonging drugs, and in relatives of young people who died suddenly.

**Tests**
12-lead ECG with heart-rate-corrected QT (QTc); values above about 470 ms in men and 480 ms in women are considered prolonged, and above 500 ms carries high risk. Serum potassium, magnesium and calcium; thyroid function; review of all medications. Holter monitoring, exercise testing and genetic testing for congenital forms; screening of first-degree relatives.

**Imaging**
Echocardiography to exclude structural heart disease.

## Differential diagnosis

- Epilepsy
- Vasovagal syncope
- Catecholaminergic polymorphic ventricular tachycardia
- Brugada syndrome
- Polymorphic ventricular tachycardia from ischaemia (normal QT)

## Goal of treatment

Terminate torsades, remove triggers (drugs, electrolyte disorders, bradycardia) and prevent sudden death with long-term therapy in congenital forms.

## Treatment

**Acute**
Torsades de pointes: intravenous magnesium sulfate first line, even when magnesium is normal; immediate defibrillation if pulseless or unstable.

**Acute**
Stop all QT-prolonging drugs and correct potassium and magnesium; increase the heart rate with temporary pacing or isoproterenol when torsades is pause-dependent.

**Medical**
Congenital long QT: non-selective beta-blockers (such as propranolol or nadolol) are first-line long-term therapy, especially for type 1.

**Procedure**
Implantable cardioverter-defibrillator after cardiac arrest or recurrent syncope despite beta-blockers; left cardiac sympathetic denervation in selected cases.

**Lifestyle**
Avoid QT-prolonging drugs (lists are kept up to date), replace electrolytes during vomiting or diarrhoea, and limit genotype-specific triggers such as competitive swimming or sudden alarm sounds.

**Follow-up**
Nursing priorities: measure QTc before and after starting high-risk drugs, keep potassium and magnesium in range, continuous ECG monitoring in high-risk patients and defibrillator readily available.

## Complications

- Torsades de pointes
- Ventricular fibrillation and sudden cardiac death
- Recurrent syncope with injuries
- Inappropriate shocks or device complications

## Prognosis

Untreated symptomatic congenital long QT carries a high risk of sudden death; with beta-blockers, trigger avoidance and a defibrillator when indicated, most patients live normally. Acquired forms usually resolve once the drug is stopped and electrolytes are corrected.

## Prevention

- Check the ECG and electrolytes before and during treatment with QT-prolonging drugs
- Avoid combining QT-prolonging drugs
- Family screening with ECG and genetic testing when a congenital case is found

## Test yourself

Think of the answer, then tap the question to see it.

## What is the first-line drug for torsades de pointes?

Intravenous magnesium sulfate; defibrillate if the patient is pulseless or unstable.

## Which three electrolyte disorders prolong the QT interval?

Hypokalaemia, hypomagnesaemia and hypocalcaemia.

## Which inherited long QT syndrome is associated with congenital deafness?

Jervell and Lange-Nielsen syndrome (autosomal recessive).

## Which drug class is first-line long-term therapy for congenital long QT syndrome?

Beta-blockers, preferably non-selective (propranolol, nadolol).

## Which QTc value marks a high risk of torsades?

A QTc above about 500 ms.

[Add to my cards (5)](https://durgical.app/estudiar/?add=/en/conditions/long-qt-syndrome-and-torsades-de-pointes/)

## Related conditions

- [Cardiac arrest (VF, pulseless VT, asystole, PEA)](https://durgical.com/en/conditions/cardiac-arrest/)
- [Ventricular tachycardia](https://durgical.com/en/conditions/ventricular-tachycardia/)
- [Syncope (vasovagal, orthostatic hypotension, cardiac)](https://durgical.com/en/conditions/syncope/)
- [Hypomagnesaemia](https://durgical.com/en/conditions/hypomagnesaemia/)
- [Anorexia nervosa](https://durgical.com/en/conditions/anorexia-nervosa/)
- [Sudden infant death syndrome (SIDS)](https://durgical.com/en/conditions/sudden-infant-death-syndrome/)
- [Atrioventricular (heart) block](https://durgical.com/en/conditions/atrioventricular-block/)
- [Sinus node dysfunction (sick sinus syndrome) and symptomatic bradycardia](https://durgical.com/en/conditions/sinus-node-dysfunction-and-symptomatic-bradycardia/)
- [Hypertrophic cardiomyopathy](https://durgical.com/en/conditions/hypertrophic-cardiomyopathy/)

Educational information, not medical advice. For any symptom, see a health professional.

Sources: [Long QT Syndrome](https://www.nhlbi.nih.gov/health/long-qt-syndrome) (National Heart, Lung, and Blood Institute (NHLBI), NIH, 2026); [Romano-Ward syndrome](https://medlineplus.gov/genetics/condition/romano-ward-syndrome/) (MedlinePlus Genetics, US National Library of Medicine, 2026).

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/conditions/long-qt-syndrome-and-torsades-de-pointes/