Tachycardia is a fast heart rate. The heart normally beats between 60 and 100 times each minute. When the heart rate exceeds 100 beats per minute, tachycardia is said to exist.

What is the significance of tachycardia?

Tachycardia does not have to signal something bad. As a matter of fact, it is a normal physiologic response to a variety of conditions. The heart pumps oxygen and nutrient-rich blood throughout the body. Sometimes, the body needs more of these nutrients than at other times. For instance, if you run up a few flights of stairs your heart rate may speed up significantly to allow the delivery of an increased amount of nutrients to vital tissues. The body simply requires more oxygen to meet its needs when you exercise. Though, if you are a well-conditioned athlete, such as a regular runner, your heart rate will not speed up as much in response to an exercise challenge.

Sometimes, however, the tachycardia is due to a more significant physiologic stress. For instance, if you have a high fever or severe anemia your heart rate will likely speed up. Likewise, if you are dehydrated from sitting in the hot sun all day and not replenishing fluids adequately or you simply have a bad case of diarrhea, your heart rate is likely to speed up as well. Doing so is the normal physiologic response to the stress of these conditions. By speeding up its rate, the heart is able to pump more blood throughout the body. When these conditions cease to exist, the tachycardia goes away.

At other times a rapid heart rate is frankly pathologic, such as in certain primary heart conditions. Atrial fibrillation is a very common heart condition in which the heart rate may climb to be very fast. This is the results of the atria, the upper chambers of the heart, quivering, so to speak and not pumping effectively. The atria are actually beating at a much faster rate than the overall heart rate. Fortunately, typically, some of the impulses are blocked. Otherwise, the heart rate may get so high it could be immediately life-threatening.

Another serious form of tachycardia is ventricular tachycardia, in which the ventricles, which are the major chambers of the heart, beat very fast. While this may be due to something easily fixed, such as a low blood potassium or magnesium level, it can also be due to severe underlying heart disease. If ventricular tachycardia is prolonged or becomes unstable, cardiac arrest can occur.

Fortunately, most cases of tachycardia are benign. Even anxiety can make your heart race, so consider your heart rate in context. If you just worked out on the treadmill for 45 minutes and your heart rate is fast but you feel fine, you likely are fine. However, if you are sitting reading a boring novel and your heart rate is very high and you feel dizzy, short of breath, have chest discomfort, or experience other untoward symptoms, seek medical attention immediately. It is always better to be safe than sorry.