A racing heart isn’t always irregular, and an irregular heartbeat can sometimes be racing.

It’s important to know what the exact meaning is of these two terms, as they are often indiscriminately interchanged by writers – including those for medical sites.

When you see the words “irregular heartbeat,” what comes to mind?

It makes sense if you think of a beat that’s flip-flopping or skipping, or a beat with extras here and there, or some other erratic pattern.

When you see “racing heart,” it makes sense to think of a faster-than-normal rate of beating. Instead of:

th-thump……th-thump……th-thump……, it goes:

th-thump..th-thump..th-thump.

You wouldn’t think “racing” means:

th-thump….thumpety-thump.…thumpety….th-thump.

“To understand this concept best, one must think of the heart as having speed and rhythm,” says Yaser Elnahar, MD, a cardiologist with Hunterdon Cardiovascular Associates in NJ.

“A ‘racing heart’ (speed) is a normal physiologic response to activity [or anxiety],” continues Dr. Elnahar.

“When we exercise, the heart rate increases as a way to increase the amount of blood pumped.”

Run up several flights of stairs and you’ll get a racing heart rate.

“However, some people get ‘racing heart’ while they are at rest, and that is not normal. This can be seen in several arrhythmias such as atrial fibrillation.”

There are many different kinds of arrhythmias. Some types amount to nothing more than annoyances, while others require medication, ablation (eradication of cardiac tissue that causes incorrect electrical signals) and, in the most severe cases, an implantable cardiodefibrillator.

“An irregular heartbeat (rhythm) can be racing or at normal rates,” says Dr. Elnahar.

An example of an irregular heartbeat that’s simultaneously racing or sped up is what happens when you’re faced with sudden severe anxiety.

The heart rate speeds up (flight or fight response), yet at the same time, you may feel some so-called flip-flopping or what seems like a missing or extra beat.

These are likely premature ventricular contractions caused by anxiety, occurring with a rapid pulse.

Once the anxiety passes, the pulse returns to normal, and the sensation of erratic episodes of beating disappears.

“We are frequently concerned about atrial fibrillation/flutter because that can be irregular and rapid, and is a common cause of stroke.”

Dr. Elnahar has publications in the Journal of Atrial Fibrillation, the Journal of Clinical Medicine and Research, Reports in Medical Imaging, and more.