What Is Inappropriate Sinus Tachycardia?
Sinus tachycardia is when your body sends out electrical signals to make your heart beat faster. Hard exercise, anxiety, certain drugs, or a fever can spark it. When it happens without any clear reason, it’s called inappropriate sinus tachycardia (IST).
Your heart rate might shoot up with just a little movement or stress. It might be high even when you’re doing nothing. IST is most common in women and people assigned female at birth who are in their 30s. Symptoms can last for months or years. You might not notice it at first.
As a general rule, you can be diagnosed with IST if your heart beats more than 100 times a minute when you are at rest or an average of at least 90 times a minute throughout the day.
Inappropriate sinus tachycardia vs. POTS
Another condition that can cause spikes in your heart rate is postural orthostatic tachycardia syndrome (POTS). The biggest difference between POTS and IST is that people with POTS get symptoms only when they stand up, while people with IST can have a racing heart while sitting, lying down, or standing. In both conditions, a fast heart rate can start even if you're not moving much.
Where does sinus tachycardia originate?
The electrical signals that tell your heart to beat faster come from a part of the heart called the sinoatrial (SA) node. This is your heart's natural pacemaker. It gets signals from your autonomic nervous system -- the part of your nervous system that sends out hormones that normally increase or decrease your heart rate depending on your activity, such as exercising or sleeping.
Inappropriate Sinus Tachycardia Symptoms
Some people don’t notice any symptoms. But the main symptom is a faster pulse that comes out of nowhere. In adults, this means it’s over 100 beats per minute. You might notice that you can get your pulse up to 150 with very little effort. Other symptoms include:
- Difficulty exercising
- Trouble catching your breath
- Chest pain
- Dizziness
- Fainting
- Headache
- Anxiousness
IST usually doesn’t lead to serious long-term health issues, but you should still talk to your doctor if you have any of these symptoms. They could be signs of another health problem.
Inappropriate Sinus Tachycardia Causes
Doctors don’t fully understand why IST happens. In some cases, nerves might mistakenly send signals to speed up your heart rate. The nerves that lower your heart rate might not work right, either.
A viral infection can lead to IST in some people. In those cases, symptoms sometimes go away suddenly after a few months or years.
People with inappropriate sinus tachycardia might also get bigger heart rate spikes than most people do when they experience:
Inappropriate sinus tachycardia and COVID-19
Some people with so-called long COVID (who get symptoms weeks, months, or years after a COVID infection) report having heart rate problems, such as IST or POTS. Studies disagree on how common inappropriate sinus tachycardia is among people with long COVID. For example, a study at one hospital found IST in 20% of patients with long COVID, while a much larger study of patients from multiple countries found a rate of just 2%. One reason may be that the studies defined a high heart rate differently.
Inappropriate Sinus Tachycardia Diagnosis
Your doctor will ask you about your health history and symptoms. An obvious sign would be a racing heart. But something else may be causing your fast pulse, such as certain heart and thyroid conditions or mental health issues such as anxiety.
These tests can help your doctor figure out if it’s IST:
- Blood tests to check for other fast heartbeat causes
- An EKG (electrocardiogram) to analyze your heart’s electrical pulses
- A Holter monitor to track heart activity for 24 hours or more
- A chest X-ray for pictures of your heart
- An echocardiogram to check your heart’s size, strength, and ability to pump blood
Inappropriate Sinus Tachycardia Treatment
Your doctor may suggest a “wait-and-see” approach if your symptoms aren’t causing major problems. You might be advised to avoid triggers such as nicotine, alcohol, or caffeine.
Exercise and eating well can help keep your heart strong. They also help with conditions that can make IST worse, such as diabetes, high blood pressure, and being overweight. Getting enough fluid can also help.
Your doctor may prescribe drugs such as ivabradine, beta-blockers, or calcium channel blockers to help.
In some cases, your doctor might recommend mental health help, such as a kind of talk therapy called cognitive behavioral therapy. The therapist might teach you deep breathing exercises and other coping techniques.
If such treatments don't work and you have severe IST symptoms, your doctor might suggest a procedure called catheter ablation. The procedure uses energy to destroy a very small part of the heart causing the fast heartbeats. But it doesn't always work. And it has risks, including a chance of destroying too much heart tissue, making a permanent pacemaker necessary.
Takeaways
If you often have a fast heartbeat — more than 100 beats a minute — even when you aren't exercising, under stress, sick with a fever, or in other situations where a fast pulse is expected, talk to your doctor. Let them know if you also have symptoms such as dizziness, fainting, or trouble breathing. You could have inappropriate sinus tachycardia. It's not usually harmful to your overall health, but your doctor can confirm or rule out the diagnosis and suggest treatments to help you feel better.
Inappropriate Sinus Tachycardia FAQs
Will inappropriate sinus tachycardia go away?
It varies. When the condition starts after an infection, it usually goes away, though it might take months or even years. Some people have symptoms that come and go in response to a trigger, such as caffeine. Eventually, those kinds of symptoms may stop as well. Others have symptoms that go on for a long time and interfere with daily life, making inappropriate sinus tachycardia a chronic condition.
What is the difference between appropriate and inappropriate sinus tachycardia?
Appropriate sinus tachycardia is a fast heartbeat that has an obvious explanation — such as exercise, emotional stress, or a fever. Inappropriate sinus tachycardia happens with no clear reason.
How do you live with inappropriate sinus tachycardia?
If your symptoms are mild, don't happen often, or don't interfere with your daily life, you can go on with your life as usual. You can be reassured that inappropriate sinus tachycardia is unlikely to harm your overall health. If your symptoms are more severe or disabling — because you're fainting or can't exercise, for example — you can work with your doctor to find solutions. If you can identify and stay away from personal triggers such as caffeine, nicotine, or getting dehydrated, that can help, too.
