Overview of Tachycardias and Fast Heart Rhythms

Tachycardia is the name used to describe a rapid heart rate. Officially, any heart rate that is faster than 100 beats per minute is deemed to be tachycardia—whether or not the tachycardia is considered to be normal or not.

Tachycardia EKG reading
Artpartner-Images / Getty Images

Sinus Tachycardia

Normally, the heart rhythm is controlled by the sinus node, a tiny structure in the upper-right chamber (atrium) that generates the heart's electrical signal. The more rapidly the sinus node fires off electrical signals, the faster the heart rate. 

Sinus tachycardia is when the sinus node is producing electrical signals more than 100 times per minute.

Sinus tachycardia—unless due to exercise, pain, infection, stimulants, or anxiety/stress—is always a physiologic response to an underlying condition, such as:

  • Pain, infection
  • Thyroid disorder
  • Pulmonary embolism
  • Congestive heart failure

It is rarely deemed idiopathic (that is, of unknown cause).

The Abnormal Tachycardias: Cardiac Arrhythmias

However, there are also several kinds of cardiac arrhythmias (abnormal heart rhythms) that cause tachycardia.

There are two general types of arrhythmias that produce tachycardia: the supraventricular tachycardias, which arise in the atria of the heart, and the ventricular tachycardias, which arise in the ventricles. These two types of tachycardia are quite different both in the types of people they usually affect and in the amount of danger they pose.

Supraventricular Tachycardias

Most types of supraventricular tachycardias (SVT) can occur in young, otherwise healthy people, though all arrhythmias happen more in older people. This is especially true for atrial fibrillation, which is much more common in the elderly.

SVT tends to occur as episodes that begin and end quite suddenly, usually without any warning whatsoever.

SVT causes:

  • Significant palpitations
  • Anxiety
  • Lightheadedness or dizziness
  • Weakness
  • Shortness of breath (sometimes)

People who have SVT usually have no symptoms at all in between episodes. But if episodes occur frequently or last for a long time, SVT can prove quite disruptive to a person’s life.

Despite how badly SVT can make you feel, it almost never poses a significant risk to life.

Types of SVT

There are many different varieties of SVT. The most common of these are:

In addition to these common varieties, there are several kinds of SVT that are much less common. 

SVT can almost always be treated effectively. Often, it can be completely eliminated by a procedure called cardiac ablation. Anyone seeking treatment for SVT should see a cardiac rhythm specialist known as a cardiac electrophysiologist.

Ventricular Tachycardias

The ventricular tachycardias include two general kinds of arrhythmia: ventricular tachycardia itself and ventricular fibrillation (VF).

In most cases, these arrhythmias are seen in older people who have significant underlying cardiac disease, especially coronary artery disease (CAD) and heart failure.

Ventricular fibrillation is the most dangerous of the cardiac arrhythmias. When it occurs, it invariably leads to death within a few minutes unless it is stopped.

In VF, the electrical impulses within the ventricles suddenly become completely chaotic, the heart immediately stops beating, and a cardiac arrest occurs. Unless the victim receives effective cardiopulmonary resuscitation, death ensues within minutes.

Ventricular fibrillation is estimated to cause over 300,000 sudden deaths each year in the U.S. alone. Obviously, the best way to deal with ventricular fibrillation is to prevent it.

Ventricular tachycardia is another potentially dangerous arrhythmia originating in the ventricles. While in some people ventricular tachycardia produces only minimal symptoms, more often it produces:

  • Significant palpitations
  • Severe lightheadedness or loss of consciousness
  • Sudden death

In contrast to ventricular fibrillation, ventricular tachycardia allows the heart to continue pumping to at least some extent in many cases. Sudden death may not be immediate and may not occur at all.

The large majority of people with ventricular tachycardia have this arrhythmia as a result of CAD or heart failure.

However, there are much less common types of ventricular tachycardia that occur in people who are young and otherwise healthy. These types of ventricular tachycardia include:

Because all forms of ventricular tachycardia are potentially lethal, anyone with this arrhythmia—no matter what the cause—needs to be evaluated by a specialist in cardiac arrhythmias.

A Word From Verywell

Tachycardias are rapid heart rhythms. There are many kinds of tachycardia, and they vary from being completely normal and benign to being immediately lethal.

If you have a cardiac arrhythmia that is producing tachycardia, you should have a complete medical evaluation.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Olshansky B, Sullivan R. Inappropriate sinus tachycardia. EP Eurospace. 2019 Feb;21(1):194-207. doi:10.1093/europace/euy128

  2. Khurshid Shaan, Choi Seung Hoan, Weng Lu-Chen, et al. Frequency of cardiac rhythm abnormalities in a half million adults. Circulation: Arrhythmia and Electrophysiology. 2018;11(7):e006273. doi:10.1161/CIRCEP.118.006273

  3. Al-Khatib S, Stevenson W, Ackerman M, et al. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden death. Circulation. 2018 Aug;138(13):e272-e391. doi:10.1161/CIR.0000000000000549

  4. Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Circulation. 2016 Sep;133(14):e506-e574. doi:10.1161/CIR.0000000000000311

  5. Bibas L, Levi M, Essebag V. Diagnosis and management of supraventricular tachycardiasCMAJ. 2016;188(17-18):e466-e473. doi:10.1503/cmaj.160079

  6. American Heart Association. Ventricular fibrillation. www.heart.org.

  7. Al-Khatib S, Stevenson W, Ackerman M, et al. 2017 AHA/ACC/HRS guideline for management of patients with ventricular arrhythmias and the prevention of sudden death. Circulation. 2018 Aug;138(13):e272-e391. doi:10.1161/CIR.0000000000000549

  8. American Heart Association. Tachycardia: fast heart rate. Reviewed September 2016.

  9. Kuck KH, Tilz RR, Deneke T, et al. Impact of substrate modification by catheter ablation on implantable cardioverter-defibrillator interventions in patients with unstable ventricular arrhythmias and coronary artery disease. Circulation. 2017 Mar;10(3):e004422. doi:10.1161/CIRCEP.116.004422

By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.