---
title: Short QT syndrome
description: What short QT syndrome is, why this rare inherited ion channel disease is dangerous because of arrhythmias, how it is detected, which treatment approaches clinical guidelines describe and when urgent help is needed.
type: disease
preset: short-qt-syndrome
aliases:
  - SQTS
  - short QT interval syndrome
  - short QT interval
  - shortened QT interval
sources:
  - tier: guideline
    org: minzdrav-rf
    title: Желудочковые нарушения ритма сердца. Внезапная сердечная смерть
    year: 2025
    doi: 10.15829/1560-4071-2025-6670
    url: https://cr.minzdrav.gov.ru/view-cr/569_2
  - tier: guideline
    org: esc
    title: 2022 ESC Guidelines for the management of patients with ventricular arrhythmias and the prevention of sudden cardiac death
    year: 2022
    doi: 10.1093/eurheartj/ehac262
    url: https://doi.org/10.1093/eurheartj/ehac262
  - tier: reference
    org: msd-manuals
    title: Short QT Interval Syndromes
    year: 2026
    url: https://www.msdmanuals.com/professional/cardiovascular-disorders/arrhythmogenic-cardiac-disorders/short-qt-interval-syndromes
  - tier: guideline
    org: nice
    title: Transient loss of consciousness ('blackouts') in over 16s (CG109)
    year: 2023
    url: https://www.nice.org.uk/guidance/cg109
  - tier: reference
    org: msd-manuals
    title: Overview of Channelopathies
    year: 2026
    url: https://www.msdmanuals.com/professional/cardiovascular-disorders/arrhythmogenic-cardiac-disorders/overview-of-channelopathies
  - tier: reference
    org: msd-manuals
    title: Cardiopulmonary Resuscitation (CPR) in Adults
    year: 2026
    url: https://www.msdmanuals.com/professional/critical-care-medicine/cardiac-arrest-and-cardiopulmonary-resuscitation-cpr/cardiopulmonary-resuscitation-cpr-in-adults
sources_checked: 2026-10-14
review: null
---

Short QT syndrome (SQTS) is a rare inherited channelopathy: the QT interval on the [ECG](../../diagnostic/ecg/) is shortened, and the risk of life-threatening arrhythmias is raised.<Cite n={1} /> The ion channel changes in it are the opposite of those in [long QT syndrome](../long-qt-syndrome/).<Cite n={3} /> Together with long QT syndrome, [Brugada syndrome](../brugada-syndrome/) and [catecholaminergic polymorphic ventricular tachycardia](../catecholaminergic-polymorphic-ventricular-tachycardia/), SQTS is one of the channelopathies: diseases in which arrhythmias arise without obvious structural heart disease.<Cite n={[1, 5]} /> Its main danger is polymorphic [ventricular tachycardia](../ventricular-tachycardia/) and [ventricular fibrillation](../ventricular-fibrillation/), which often cause sudden death.<Cite n={3} />

<Diagram name="short-qt-syndrome">
  <p slot="normal">
    The QT interval on the ECG is the time from the start of the QRS complex to the end of the T
    wave; it reflects the electrical systole of the ventricles.<Cite n={1} /> Its length depends on
    heart rate, so doctors use the QTc, the interval corrected for heart rate.<Cite n={1} />
  </p>
  <p slot="disease">
    In SQTS the electrical activation of the ventricular cells is shorter than usual, so the QT
    interval on the ECG is shortened.<Cite n={[1, 3]} /> The diagram is simplified: the T wave is
    simply moved closer to the QRS, and the dashed line shows where it ends normally; the diagram
    does not show the shape of the waves in this syndrome. The shorter the QT, the more likely
    ventricular arrhythmias are.<Cite n={3} />
  </p>
</Diagram>

## Why it happens

<Patient>

The cause is changes (mutations) in genes for the ion channels of heart cells.<Cite n={[1, 3]} /> For example, potassium channels that end the cell's activation work harder than usual, or sodium or calcium channels work more weakly than usual.<Cite n={3} /> As a result, the cells of the atria and ventricles recover faster after each activation, which sets the stage for dangerous arrhythmias in which the electrical activation travels in a circle.<Cite n={1} />

Most often the syndrome is inherited in an autosomal dominant way, meaning that one parent can pass it on to a child; the disease shows itself more often in men.<Cite n={3} /> Very rarely a short QT is acquired.<Cite n={3} /> The syndrome is very rare, but it probably often goes unrecognised.<Cite n={[1, 3]} />

</Patient>

<Student>

Shortening of the action potential and effective refractory period of atrial and ventricular cardiomyocytes sets the stage for life-threatening re-entrant arrhythmias.<Cite n={1} /> According to MSD, the action potential shortens most in the ventricular epicardium; the resulting transmural dispersion of repolarisation may lead to polymorphic VT or VF.<Cite n={3} /> The mechanisms are gain of function of repolarising potassium channels, or loss of function of depolarising sodium or calcium channels or of the Cl⁻/HCO₃⁻ exchanger.<Cite n={3} />

Mutations are found most often in the potassium channel genes KCNH2 (IKr), KCNQ1 (IKs) and KCNJ2 (IK1) and in the anion exchanger gene SLC4A3 (AE3); in its section on SQTS the Russian Ministry of Health guideline also names the calcium channel genes CACNA1C and CACNB2b.<Cite n={[1, 3]} /> Together, documented channelopathies account for up to 40% of sudden cardiac deaths in non-athletes aged 35 or younger without structural heart or coronary artery disease; this is the share of the whole group, not of SQTS alone.<Cite n={5} />

</Student>

## Symptoms

<Patient>

As long as there is no arrhythmia, the person feels nothing.<Cite n={3} /> If [atrial fibrillation](../atrial-fibrillation/) or a ventricular arrhythmia starts, there may be palpitations, feeling faint, fainting or cardiac arrest.<Cite n={3} /> The syndrome is life-threatening at any age, including in babies in the first months of life.<Cite n={1} />

</Patient>

<Student>

According to MSD, 40% of people with symptoms of SQTS have had a cardiac arrest by the age of 40.<Cite n={3} />

</Student>

## How it is diagnosed

<Patient>

A doctor will think of SQTS if a person without heart disease has had an unexplained cardiac arrest or fainting, or relatives have had this, and also if a short QT is found by chance on an ECG done for another reason.<Cite n={3} />

The main test is an ordinary 12-lead ECG.<Cite n={[1, 3]} /> The diagnosis is not made on one number: along with the length of the QTc, the doctor considers past fainting and cardiac arrests, family history and genetic test results.<Cite n={3} /> QTc thresholds for the diagnosis differ between guidelines.<Cite n={[1, 2, 3]} /> If the QT is short but there are no other signs, the person may simply be monitored.<Cite n={3} /> Further tests may include longer heart rhythm recording, such as [Holter monitoring](../../diagnostic/holter-monitoring/), and tests that show the structure of the heart, such as [echocardiography](../../diagnostic/echocardiography/).<Cite n={3} />

Genetic testing is recommended once the diagnosis is made, but it finds a mutation in only a minority of patients, so a negative result does not rule out the syndrome.<Cite n={[1, 2, 3]} /> First-degree relatives are asked about symptoms and have an ECG; if a mutation has been found in the patient, they are offered a genetic test even if they have no complaints and their ECG is normal.<Cite n={[1, 3]} /> If a relative died suddenly and the post-mortem found no clear cause, close relatives are advised to see a cardiologist.<Cite n={[1, 2]} />

</Patient>

<Student>

ESC 2022: it is recommended that SQTS is diagnosed with a QTc ≤ 360 ms and at least one of a pathogenic mutation, a family history of SQTS, or survival from a VT/VF episode without heart disease (I C).<Cite n={2} /> SQTS should be considered with a QTc ≤ 320 ms (IIa C); with a QTc of 320–360 ms, it should be considered after arrhythmic syncope (IIa C) and may be considered if a relative died suddenly before the age of 40 (IIb C).<Cite n={2} />

The Russian Ministry of Health guideline makes the diagnosis in adults using the Gollob score (Appendix G2): points are given for the QTc (< 370 ms: 1 point, < 350 ms: 2, < 330 ms: 3) and also for other ECG features, arrhythmias and fainting, family history and genotype; with 4 points or more the probability of SQTS is high.<Cite n={1} /> In children and adolescents under 20, the refined criteria are a QTc < 316 ms, a corrected J–Tpeak < 181 ms and early ventricular repolarisation.<Cite n={1} /> NICE, when an ECG is read manually after a transient loss of consciousness in people over 16, counts a corrected QT of less than 350 ms as short; this is a threshold for the first assessment of a blackout, not for the diagnosis.<Cite n={4} />

Genetic testing is indicated in everyone diagnosed with SQTS (ESC, I C), but it finds a mutation in only 20% of patients according to the Russian guideline and in 20–30% according to MSD.<Cite n={[1, 2, 3]} /> An implantable loop recorder should be considered in young patients (IIa C).<Cite n={2} /> Programmed electrical stimulation is not recommended for SCD risk stratification in SQTS (ESC III C; Russian guideline: in adults).<Cite n={[1, 2]} />

</Student>

## How it is treated

<Patient>

The main way to prevent sudden death is an implantable cardioverter-defibrillator (ICD); it is recommended for people who have survived a cardiac arrest or who have had sustained ventricular tachycardia recorded.<Cite n={[1, 2, 3]} /> How an ICD works is explained in the article on [ventricular fibrillation](../ventricular-fibrillation/). After a faint that was probably caused by an arrhythmia, an ICD is also discussed.<Cite n={[2, 3]} /> In other cases the decision is made individually, taking into account family history and the length of the QTc: there are no general rules yet.<Cite n={1} />

If an ICD is needed but cannot be used or the person declines it, and also for a person without symptoms whose family has had sudden deaths, the doctor may consider an antiarrhythmic medicine.<Cite n={[1, 2]} /> The guidelines differ on which one.<Cite n={[1, 2]} /> The ESC advises that athletes with heart diseases that carry a risk of sudden death are managed according to separate guidelines on sports eligibility.<Cite n={2} /> The doctor decides on the approach together with the patient.

</Patient>

<Student>

An ICD is recommended in SQTS for survivors of cardiac arrest and/or patients with documented spontaneous sustained VT (ESC I C; Russian guideline: I C on the ESC scale).<Cite n={[1, 2]} /> An ICD should be considered after arrhythmic syncope (ESC IIa C).<Cite n={2} />

An antiarrhythmic drug may be considered when an ICD is indicated but contraindicated or refused, and in patients without symptoms with a family history of SCD (IIb C); the ESC and MSD name one drug for this, and the Russian guideline names a different one, and only for patients over 18.<Cite n={[1, 2, 3]} />

</Student>

## When to call an ambulance

**Someone suddenly collapses, does not respond and is not breathing or is only gasping**: this may be cardiac arrest.<Cite n={6} />

- Shout for help and call your local emergency number at once (112 in the EU, 911 in the US and Canada, 999 in the UK); if someone else is there, let them make the call and, if possible, fetch a defibrillator.<Cite n={6} />
- Start CPR without delay, as the ESC and the MSD Manual advise.<Cite n={[2, 6]} /> How to do chest compressions and use an automated external defibrillator is explained in the article on [ventricular fibrillation](../ventricular-fibrillation/).

If a person has lost consciousness, even briefly, call an ambulance too.<Cite n={1} /> Fainting during physical exertion is especially worrying: NICE treats it as a reason for urgent cardiovascular assessment.<Cite n={4} />

The Russian Ministry of Health guideline advises calling an ambulance if an episode of arrhythmia comes with dizziness, weakness, feeling faint, loss of consciousness or a racing heartbeat, and also for any episode of feeling faint or losing consciousness.<Cite n={1} /> An ambulance is also called when an implanted cardioverter-defibrillator has gone off.<Cite n={1} />

Even if the person has come round, NICE (for people over 16) treats the following as red flags after a blackout: an ECG abnormality, including a short QT interval, a blackout during exertion, and a family history of sudden cardiac death in people younger than 40 or an inherited heart condition: such a person is referred urgently for cardiovascular assessment, and a specialist reviews the referral within 24 hours.<Cite n={4} />

<Quiz />