What is Inappropriate Sinus Tachycardia?

An abnormal heart rhythm is called an arrhythmia. A fast heart rate – a resting heart rate greater than 100 beats per minute in adults – is called tachycardia. Inappropriate sinus tachycardia (IST) is a condition where the heart beats very rapidly for no known reason.

People with IST commonly have a resting heart rate greater than 100 beats per minute, or their average heart rate is greater than 90 beats per minute at rest. (Note that infants and children normally have a faster heart rate than adults.) Other people with IST may experience a normal heart rate when resting, but find it shoots up very quickly during light physical activity.

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What happens to a heart with IST?

The heart’s electrical signal typically starts in the sinoatrial (SA) node, which is found in the heart’s upper chambers, or atria. The SA node receives signals from nerves which cause the heart to beat more rapidly or slowly, depending on the body’s needs. This electrical signal travels throughout the heart to the lower chambers, or ventricles, and creates the heartbeat.

Several situations normally cause the heart to beat faster, such as an elevated body temperature (fever), moderate or intense exercise, anxiety, or increased stress. But in people with IST, the heart beats faster for unknown reasons. The heart rate may increase on its own without any stimulation, or the heart rate rises because of a trigger. When the heart beats too rapidly due to IST, it may not be able to fill properly between beats. Slightly less blood may then circulate out to the body which can lead to dizziness, shortness of breath, and/or other abnormal symptoms.

Symptoms of IST

Some people with IST have symptoms and others do not. Symptoms may include:

  • Uncomfortable sensation of a rapid heartbeat (palpitations)
  • Shortness of breath
  • Dizziness
  • Fainting
  • Chest pain
  • Anxiety
  • Headaches
  • Decreased ability to exercise

Kristiana’s story

Since the age of 14, North Carolina resident Kristiana Rigney’s health journey has been grueling: three hip surgeries, with the most recent procedure three years ago. During post-surgical rehab, she recognized a pattern of feeling out of breath, and was unable to walk on the treadmill or progress in therapy. After “normal” at-home activities left the 20-year-old feeling fatigued, she was referred to a cardiologist and saw six subspecialty physicians in three states—North Carolina, Minnesota and Tennessee—hoping to find a resolution that would improve her quality of life. Her mother, Jennifer, canvassed medical journals and found HCA Midwest Health physician Dr. DJ Lakkireddy.

Learn more about Kristiana’s journey

What are causes of inappropriate sinus tachycardia?

There are many potential triggers for IST. IST is sometimes triggered from abnormal nerve signals that increase the heart rate. Other times, doctors find that nerves which lower the heart’s rate are not performing as they should. IST sometimes begins after an individual has an infection from a virus. Additional potential triggers include:

  • Caffeine
  • Alcohol
  • Nicotine
  • Illegal drugs such as cocaine
  • Overactive thyroid (hyperthyroidism)
  • Fever
  • Anxiety
  • Anemia
  • Very low blood pressure
  • Heart attack
  • Heart failure
  • Lung disease
  • Pain

People who experience tachycardia from any or many of these triggers can be considered to potentially have IST. Yet some people found to have IST experience a higher heart rate even when none of these triggers are present.

Diagnosing inappropriate sinus tachycardia

IST has sometimes been diagnosed as an anxiety disorder when it is actually a medical or electrophysiological disorder. An electrophysiologist with Kansas City Heart Rhythm Institute will review your health history and perform a physical exam to detect when and what may be causing the rapid heartbeat.

You may be asked to undergo some tests to help determine a diagnosis and a course of treatment. These tests may include:

  • Chest X-ray to view the heart and lungs
  • Echocardiogram to check the size, structure, and function of the heart
  • Electrocardiogram to analyze the heart’s electrical rhythm and the type of tachycardia
  • Continuous monitoring of the heart rhythm for a short period of time via a small, wearable device called a Holter monitor
  • Implantable loop recorder implanted just beneath the chest skin to monitor heart rhythm for an extended period of time
  • Blood tests to look for other causes of the tachycardia

Living with inappropriate sinus tachycardia

Our heart arrhythmia specialists offers surgical and non-surgical treatments for patients to help manage IST, including:

  • Eliminating potential triggers or stimulants in your diet such as caffeine, nicotine, and alcohol
  • Taking medication to slow the heart rate such as ivabradine, beta-blockers, or calcium channel blockers
  • Exercising to improve heart health
  • Catheter ablation: During this procedure, a small catheter is threaded through an artery to the heart to emit energy that will destroy a tiny amount of tissue that is triggering the tachycardia
  • Sinus node sparing hybrid ablation procedure: HCA Midwest Health electrophysiologists and cardiac surgeons not only perform this advanced, highly-effective and cutting-edge surgery—they are also lead physicians of clinical studies in this revolutionary approach to arrhythmia treatment. A cardiac surgeon—in collaboration with an electrophysiologist—performs this advanced, minimally invasive sinus node sparing ablation to treat and cure inappropriate sinus tachycardia. The procedure can last two to three hours and patients usually go home in a day or two. Benefits include:
    • Significantly improves heart rate
    • Higher success rates than previous radiofrequency sinus node ablation
    • Minimal risk of complications
    • Lower risk of damaging the sinus node
    • Very rare need for a pacemaker
    • Reduces the need for additional surgeries

Your surgery will take place at Centerpoint Medical Center, Overland Park Regional Medical Center or Research Medical Center. Here is a list of items for you and your caregiver to review:

Centerpoint Medical Center:

Overland Park Regional Medical Center:

Research Medical Center:

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Leading the charge for new treatments

Our physicians are international leaders in pioneering new research that helps doctors all over the world better diagnose and treat inappropriate sinus tachycardia. Below is a sampling of recent research led by our heart arrhythmia experts.