Causes of sinus tachycardia and inappropriate treatment


Inappropriate sinus tachycardia (IST) is a condition in which a person's heart rate at rest and during exercise is abnormally high for no apparent reason.

IST is defined as a resting heart rate of more than 90 beats per minute on average, which can reach very high levels even with minimal effort. These unnecessarily high heart rates are accompanied by symptoms of rapid heart rate , fatigue, dizziness, or exercise intolerance.

Because the heart rate in the IST is generated by the sinus node (the structure of the heart that controls normal heart rate), the IST is not associated with an abnormal electrical pattern on the ECG.

Although STI can affect anyone, it is more common in young people and affects women more often than men. Most people with TSI are women in their 30s who have experienced symptoms for several years.

IST was only recognized as a syndrome in 1979, and it was not until the late 1980s that it was generally recognized as a true medical education. While IST is now fully recognized as a true disease in all university medical centers, some doctors may not have heard of it or may mistake a fast heart rate for an alarm .

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Some people with IST have no symptoms. For those who do this, the most notable symptoms associated with IST include:

However, IST is often associated with a variety of other symptoms as well, including:

  • Orthostatic hypotension (drop in blood pressure when standing)
  • Blurry vision
  • Dizziness , fainting, or near fainting
  • Perspiration
  • Chest pain
  • Anxiety
  • Headache
Resting To sleep Voltage
Beats per minute 100 or more 80-90 140-150

Palpitations are a noticeable symptom even in the absence of "abnormal" heartbeats. (That is, each heartbeat appears to originate from the sinus node, just like a normal heart rate.) The symptoms that people with IST experience can be disabling and cause anxiety.


The main reason for IST is not yet known. This is likely due to a problem with the way the neuroendocrine system regulates heart rate, a problem within the heart's sinus node itself, or both.

IST can be part of a more general disorder of the autonomic nervous system, a condition called dysautonomia . (The autonomic nervous system controls the "unconscious" functions of the body, such as digestion, breathing, and heart rate.)

A more general dysautonomia would explain why IST symptoms often seem disproportionate to an increased heart rate.

Experts suggest that people with TSI may be hypersensitive to adrenaline; a small amount of adrenaline (as with little effort) causes a marked increase in heart rate.

There is some evidence suggesting structural changes in the sinus node during IST, That is why some specialized cardiologists, electrophysiologists, sometimes treat IST with removal of the sinus node. (more on this below)


Several other specific and treatable medical conditions can be confused with IST, and in a person with abnormal sinus tachycardia, these other causes must be ruled out. These disorders include anemia , fever, infections, hyperthyroidism , pheochromocytoma , diabetes-induced dysautonomia, drug side effects, and substance abuse. These conditions can usually be ruled out with a general medical exam and blood and urine tests.

Additionally, other cardiac arrhythmias , most commonly certain types of supraventricular tachycardia (SVT) , can sometimes be mistaken for IST. It is usually easy for a physician to distinguish SVT from IST by carefully examining the ECG and taking a careful history. This distinction is very important because the treatment of SVT is usually relatively straightforward.

Arrhythmia Discussion Guide

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Treatment for IST can include drug therapy, non-drug therapy, or both. Sometimes refusing treatment is also an option.

Drug therapy

Some STI patients may benefit from drug therapy. However, achieving optimal results often requires trial and error with multiple drugs, alone or in combination.

Research shows that the drug ivabradine can successfully treat some people with STIs. Ivabradine directly affects the "arousal rate" of the sinus node and therefore reduces the heart rate.

Ivabradine is approved in the United States for the treatment of heart failure in some patients, but not STI. However, it has shown moderate benefit in STI patients in trials, and ivabradine is recommended by many experts as a beneficial treatment for this condition. Additionally, several professional organizations now support its use for IST as well.

However, the downside of this drug is that it can be dangerous during pregnancy. Since many people receiving treatment for STIs are women of childbearing age, some researchers have asked for caution and scrutiny before recommending ivabradine.

Beta- blockers are another category of drugs that doctors can prescribe for IST. They block the action of adrenaline in the sinus node, And because people with IST have a greater response to adrenaline, these medications can help reduce the symptoms of IST. However, they are not effective for everyone and can have unpleasant side effects.

Calcium blockers can directly slow down the sinus node, but are only marginally effective in treating IST. Calcium blockers are also associated with side effects like hypotension .

IST is a difficult condition to treat, partly because the causes are not fully understood and partly because even a controlled heart rate does not necessarily improve symptoms.

Because there is some overlap between IST and other dysautonomia syndromes (especially POTS and vasovagal syncope ), medications that are effective in treating these conditions can sometimes be helpful in treating patients with IST. These medications can include:

  • Fludrocortisone is a drug that causes sodium retention. Several dysvegetative syndromes, especially POTS and vasovagal syncope, have been shown to be associated with decreased blood volume. and the sodium-trapping drug can increase blood volume to normal, thereby reducing symptoms.
  • Orvaten (midodrin) is a drug that increases vascular tone and helps prevent a drop in blood pressure.
  • Serotonin reuptake inhibitors are used primarily to treat depression and anxiety, but they have also been shown to be effective in treating some dysautonomia syndromes.

Sometimes the symptoms of IST can be improved with one or more medications.

Effective therapy often requires persistence and trial and error. It requires some patience, understanding and trust between doctor and patient.

Successful treatment of IST (and other dysautonomies) is more likely if the patient and physician share a common treatment goal and can communicate effectively. Sometimes this means that the patient needs to change doctors to find the right patient.

Non-drug therapy

Physical exercises.   When dangerous arrhythmias are ruled out and exercise is safe, a regular exercise program can help to naturally lower your heart rate and improve symptoms over time.

Sinus node ablation: Because the sinus node is sometimes abnormal with IST, some patients may consider ablative therapy (a method in which part of the heart's electrical system is cauterized through a catheter) to alter function or even destroy the sinus node. …

So far, sinus node ablation has had only limited success. Although this procedure can eliminate the IST in almost 80% of people immediately after the procedure, the IST reappears within a few months in the vast majority of these people.

Cognitive Behavioral Therapy (CBT): CBT is an effective form of psychological treatment that can reduce the risk of adverse cardiovascular events in people who experience anxiety as a symptom (or trigger) of their heart disease. CBT will not cure IST and it does not attack it. Rather, treatment aims to correct a person's negative thoughts and help them perceive reality, making anxiety less likely to trigger or aggravate their symptoms.

Pending:   A sensible non-drug approach to treating TSI is to do nothing. Although the natural history of this disorder is not officially documented, it is likely that in most people, IST tends to improve over time. Doing nothing may not work for people with severe symptoms, but many people with mild TSI can tolerate their symptoms if they are confident that they do not have a life-threatening heart disorder and that the problem is likely to improve. in the end by itself.

Get the word of drug information

Once the diagnosis of TSI has been established and it has been determined that simply "waiting" is not an appropriate approach, most experts today recommend starting medication and exercise. If the first few attempts at treatment failed to clear up your symptoms, there are several other medications and combinations you can try. Most specialists currently only recommend ablation therapy in severe cases.

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