---
title: Inappropriate sinus tachycardia
description: What inappropriate sinus tachycardia is, how it differs from an ordinary rise in heart rate, postural orthostatic tachycardia syndrome and episodes of supraventricular tachycardia, how it is recognised and treated, and when urgent help is needed.
type: disease
preset: sinus-tachycardia
aliases:
  - IST
  - inappropriate sinus tachycardia syndrome
  - syndrome of inappropriate sinus tachycardia
sources:
  - tier: guideline
    org: minzdrav-rf
    title: Наджелудочковые тахикардии
    year: 2025
    doi: 10.15829/1560-4071-2025-6448
    url: https://cr.minzdrav.gov.ru/view-cr/619_3
  - tier: guideline
    org: esc
    title: 2019 Рекомендации ESC по лечению пациентов с наджелудочковыми тахикардиями
    year: 2020
    doi: 10.15829/1560-4071-2020-3864
    url: https://doi.org/10.15829/1560-4071-2020-3864
  - tier: reference
    org: msd-manuals
    title: Syndrome of Inappropriate Sinus Tachycardia
    year: 2024
    url: https://www.msdmanuals.com/professional/cardiovascular-disorders/specific-cardiac-arrhythmias/syndrome-of-inappropriate-sinus-tachycardia
  - tier: reference
    org: statpearls
    title: Sinus Tachycardia
    year: 2023
    url: https://www.ncbi.nlm.nih.gov/books/NBK553128/
  - tier: review
    title: '2015 Heart Rhythm Society Expert Consensus Statement on the Diagnosis and Treatment of Postural Tachycardia Syndrome, Inappropriate Sinus Tachycardia, and Vasovagal Syncope'
    year: 2015
    doi: 10.1016/j.hrthm.2015.03.029
    url: https://doi.org/10.1016/j.hrthm.2015.03.029
sources_checked: 2026-10-14
review: null
---

Sinus tachycardia is a sinus rhythm faster than 100 beats per minute: as usual, the sinus node sets the rhythm, only faster.<Cite n={[1, 2]} /> Most often it is a normal response to physical exertion or emotion, not a disease; it can also be the body's way of adapting to another illness.<Cite n={1} /> In inappropriate sinus tachycardia (IST) the heart rate is above 100 beats per minute at rest or with minimal exertion, and this cannot be explained by exertion, emotion, illness or medicines.<Cite n={[1, 2]} /> Only a doctor can make this diagnosis after an assessment: first they rule out other causes of a fast heart rate.<Cite n={[1, 3]} /> In Russian-language guidelines IST is also called non-physiological or "unjustified" sinus tachycardia.<Cite n={[1, 2]} /> The outlook in IST is favourable.<Cite n={[1, 2]} /> But the symptoms often noticeably reduce quality of life.<Cite n={5} />

<Diagram name="inappropriate-sinus-tachycardia">
  <p slot="normal">
    At rest the heart rate is calm, and with exertion or emotion it rises. This is physiological sinus tachycardia, a normal response of the body, not a disease.<Cite n={1} /> The heart rate rises and falls gradually, without sudden attacks.<Cite n={1} /> The curves in the diagram are schematic, not real measurements.
  </p>
  <p slot="disease">
    In IST the heart rate is already raised at rest and rises excessively with light exertion.<Cite n={[1, 2]} /> It still rises and falls gradually, and the rhythm is set by the <Structure id="sa-node">sinus node</Structure>, as it normally is: the P waves on the ECG look the same as in ordinary sinus rhythm.<Cite n={1} />
  </p>
</Diagram>

## Why it happens

<Patient>

Ordinary (physiological) sinus tachycardia happens with exertion, emotional stress, pain and pregnancy. Illnesses cause it too: anxiety and panic attacks, anaemia, fever, dehydration, infections, an overactive thyroid, low blood sugar, and also dangerous conditions such as pulmonary embolism, heart attack, shock and heart failure. Some medicines, stopping beta-blockers, recreational drugs, caffeine and alcohol also speed up the heart.<Cite n={[1, 2]} /> This kind of tachycardia is treated by finding and removing its cause.<Cite n={[1, 2]} />

Why IST happens is not fully known; there are probably several causes.<Cite n={[1, 2, 3]} /> The sinus node itself may be overactive, or its control by the autonomic nervous system may be disturbed, with stronger sympathetic and weaker parasympathetic influence.<Cite n={1} />

IST is rare and is more common in young women, but not only in them.<Cite n={[1, 2, 3]} /> Ordinary sinus tachycardia, by contrast, happens to almost everyone.<Cite n={1} /> IST usually lasts a long time.<Cite n={[1, 2]} />

</Patient>

<Student>

In the Russian Ministry of Health classification, the sinus tachycardias (physiological, non-physiological and sinus nodal re-entry) belong to the supraventricular tachycardias.<Cite n={1} /> The ESC lists possible mechanisms of IST: dysautonomia, neurohormonal dysregulation and intrinsic sinus node hyperactivity.<Cite n={2} /> MSD adds decreased vagal sensitivity and augmented beta-adrenergic sensitivity.<Cite n={3} /> A familial form of IST with a gain-of-function mutation in HCN4 channels has been described, and IgG antibodies to beta-adrenergic receptors are found in patients with IST.<Cite n={[1, 2]} />

In one study of a middle-aged population, 1.2% of those examined, with and without symptoms, met the criteria for IST (resting heart rate above 100 bpm and mean heart rate above 90 bpm on 24-hour Holter monitoring); these are data cited by the 2015 HRS consensus statement.<Cite n={5} />

</Student>

## Symptoms

<Patient>

The picture varies widely: from tachycardia without symptoms, found by chance at an examination, to symptoms that leave a person unable to work.<Cite n={1} /> The most common complaint is a feeling of a racing heart (palpitations). There may be chest pain, difficulty breathing, dizziness and feeling close to fainting.<Cite n={1} /> Breathlessness, poor exercise tolerance, weakness, tiredness, poor tolerance of being upright and anxiety are also described.<Cite n={[2, 3]} />

The outlook is favourable.<Cite n={[1, 2]} /> No deaths from IST are known.<Cite n={5} /> Weakening of the heart muscle because of a constantly fast rhythm (tachycardia-induced cardiomyopathy) is very rare in IST.<Cite n={[1, 5]} /> Whether and how quickly people improve over time is unknown.<Cite n={5} />

</Patient>

<Student>

The sources differ on the risk of tachycardia-induced cardiomyopathy: the ESC states that even long-standing persistent IST does not lead to it, the Russian Ministry of Health guideline that the arrhythmia is rarely or very rarely associated with it, and HRS that IST is rarely associated with it.<Cite n={[1, 2, 5]} /> Little is known about long-term outcomes.<Cite n={[1, 5]} />

</Student>

## How it is diagnosed

<Patient>

IST is a diagnosis of exclusion: the doctor makes it only after ruling out other causes of a fast heart rate, such as heart conditions, infections, anaemia, an overactive thyroid, anxiety, pain, medicines and stimulants.<Cite n={[1, 3]} /> A fast heart rate at rest can be the first sign of a serious illness, so the cause is looked for first.<Cite n={4} />

Besides an [ECG](../../diagnostic/ecg/), [Holter monitoring](../../diagnostic/holter-monitoring/) is usually done: it shows the average heart rate over 24 hours, how it changes with different activities and whether it matches the symptoms. An exercise test shows how the heart rate responds to light exertion, and [echocardiography](../../diagnostic/echocardiography/) helps rule out heart disease. Blood tests are also needed, including blood sugar and thyroid hormones.<Cite n={[1, 3]} /> Routine tests help detect the tachycardia but by themselves rarely give the answer, which is why ruling out other causes matters so much.<Cite n={1} /> An electrophysiological study inside the heart is usually not needed.<Cite n={[1, 2]} />

Similar symptoms occur in [postural orthostatic tachycardia syndrome (POTS)](../postural-orthostatic-tachycardia-syndrome/). In POTS the heart rate rises mainly on standing up, and blood pressure does not fall; in IST the heart rate rises with both physical and emotional stress.<Cite n={[1, 5]} /> Sinus nodal re-entrant tachycardia also has to be told apart: it comes in attacks, with a sudden sharp rise in heart rate, whereas in IST the heart rate rises gradually.<Cite n={[1, 2]} /> Attacks of fast heart rhythm are covered in the article on [supraventricular tachycardia](../supraventricular-tachycardia/).

</Patient>

<Student>

Below are measures that a doctor assesses; they are not a rule for checking yourself with a heart rate monitor or a watch. HRS defines IST as a sinus heart rate >100 bpm at rest (with a mean 24-hour heart rate >90 bpm not due to primary causes) associated with distressing symptoms of palpitations.<Cite n={5} /> According to the ESC, 24-hour ECG monitoring may show a mean heart rate above 90 bpm over 24 hours and above 100 bpm during waking hours; an exercise test may show an excessive rise in heart rate and blood pressure in response to minimal exertion.<Cite n={2} /> The Russian Ministry of Health guideline gives an example: submaximal heart rate is reached as early as the first, minimal stage of an exercise test.<Cite n={1} />

In physiological, non-physiological and sinus nodal re-entrant tachycardia, the 12-lead ECG shows the usual P-wave morphology: positive in I, II and aVF, biphasic or negative in V1.<Cite n={[1, 2]} /> The ESC differential diagnosis: POTS, sinus nodal re-entrant tachycardia, and focal atrial tachycardia from the upper crista terminalis or the right upper pulmonary vein.<Cite n={2} /> An electrophysiological study is done only when sinus nodal re-entrant tachycardia needs to be excluded.<Cite n={2} />

</Student>

## How it is treated

<Patient>

First the doctor looks for reversible causes of the fast heart rate and, where possible, treats them.<Cite n={[1, 2, 5]} /> The outlook in IST is favourable, so treatment is needed only to ease symptoms, and sometimes not at all.<Cite n={2} />

Before medicines, lifestyle changes are tried: more physical activity and avoiding substances that stimulate the heart, such as caffeine.<Cite n={[2, 3]} /> MSD also mentions yoga, meditation and breathing exercises.<Cite n={3} />

If symptoms persist, the doctor may prescribe medicines: a drug that selectively slows the sinus node, on its own or together with a beta-blocker, or a beta-blocker.<Cite n={[1, 2]} /> The doctor decides whether treatment is needed and, if so, which. Treating IST is often difficult: medicines do not help everyone, beta-blockers can have side effects such as constant tiredness, and symptoms can continue even when the heart rate has slowed.<Cite n={[2, 3, 5]} /> HRS experts stress that people with IST need close attention and clear explanations, which can improve the results of treatment.<Cite n={5} />

Catheter ablation (a procedure on the sinus node) is not considered a routine treatment for IST.<Cite n={[2, 5]} />

</Patient>

<Student>

ESC: identification and treatment of reversible causes (I, C); in symptomatic patients, a selective sinus node If-current blocker alone or combined with a beta-blocker should be considered (IIa, B), or a beta-blocker (IIa, C).<Cite n={2} /> The Russian Ministry of Health guideline gives the same recommendations with the same ESC classes.<Cite n={1} /> It notes, however, that evidence on the efficacy and safety of the If-current blocker in IST is still insufficient, and that it is not used in pregnancy or breastfeeding.<Cite n={[1, 2]} /> According to the ESC, combining the If-current blocker with a beta-blocker is more effective in IST than either drug alone.<Cite n={2} /> The choice of drug and dose is the doctor's decision.

HRS is more cautious about beta-blockers in IST than the ESC and the Russian Ministry of Health guideline. HRS also notes that there are no long-term, prospective, placebo-controlled trials of any treatment for IST that have shown a substantial improvement in outcomes.<Cite n={5} /> HRS does not recommend sinus node modification, surgical ablation or sympathetic denervation as part of routine care (III): primary success rates are reasonably good, but symptoms often recur and the complication rates are significant, including the need for permanent pacing, transient or permanent phrenic nerve paralysis and transient superior vena cava syndrome.<Cite n={5} /> The ESC also considers that ablation should not be a routine treatment for IST.<Cite n={2} /> By contrast, in sinus nodal re-entrant tachycardia catheter ablation is recommended for symptomatic patients when medicines have not worked (IIa, C).<Cite n={[1, 2]} />

</Student>

## When to call an ambulance

The outlook in IST itself is favourable.<Cite n={[1, 2]} /> But a fast heart rate at rest can be the first sign of a serious illness, and the causes of ordinary sinus tachycardia include emergencies such as pulmonary embolism, heart attack and shock.<Cite n={[2, 4]} /> Their warning signs are described in the articles on [heart attack](../myocardial-infarction/) and [pulmonary embolism](../pulmonary-embolism/).

**Call your local emergency number (112 in the EU, 911 in the US and Canada, 999 in the UK)** if a racing heart comes with fainting or feeling close to fainting: sudden darkening of vision, weakness, dizziness or a cold sweat.<Cite n={1} />

**See a doctor** if your resting heart rate has become fast for no clear reason: it is important for the doctor to find the cause.<Cite n={4} />

<Quiz />