Have you ever wondered how fast can the human heart beat? If you have, and you have not figured it out yet, then you may be in for a surprise (which itself could increase your heart beat).
Firstly, let’s look at what is normal.
The normal human heart beats at a rate of 60 – 80 beats per minute. It is not exactly 72 beats per minute like you might have read elsewhere.
In the medical world, a normal heart rate lies between 60 to 100 beats per minute. A slow heart rate (called bradycardia) is a rate below 60 beats per minute. A high heart rate (called tachycardia) is a rate above a 100 beats a minute.
When you look at the heart rate, it is not just the rate at which it beats that is important, but also the rhythm with which it beats.
In other words, the time interval between each beat must be the same. For example, if your heart beats at 60 beats a minute, the time interval between each beat will be exactly one second.
How does the human heart rate compare to other living organisms?
As you can see, we are a little bit on the slower side compared to other animals.
Slow Heart Beats
A slow heart beat is a rate below 60 beats per minute.
There may be a number of reasons why your heart beat might be slow. A slightly slow heart beat can be normal for some, especially for those who exercise regularly.
So if you are someone who walks for an hour a day or runs long distances, then don’t be surprised if your heart rate is between 40 to 60 beats a minute when you are resting.This can be normal for you.
If you are on certain medications such as beta blockers, your heart rate will reduce. The whole purpose of giving this medicine is the keep the heart beat slow, so that the heart muscle is nice and relaxed. A slow heart rate from beta blockers improves the efficiency of the heart.
In some cases, a slow heart beat may not be normal. This is sometimes due to a condition called heart block. This condition may require a pacemaker as treatment.
Slow heart beats can also be seen in certain medical conditions such as hypothyroidism (under-active thyroid gland) or altered levels of salts in the blood. Treating the cause usually restores normal rate and rhythm.
Fast Heart Beats
It is normal for your heart to beat fast when you are excited, when exercising or when you are scared. This is due to the release of a compound called adrenaline.
When exercising, your heart rate can go up to 200 beats a minute. This is seen if your exercise routine is very aggressive, such as sprinting.
In most exercise routines, it is recommended that you do not exceed 80% of your target heart rate. Your target heart rate is defined generally as 220 – age in years.
So if your heart rate is high due to any of the above reasons, then naturally you would expect it to come down once you have stopped exercising and relaxed a little.
However, there are certain conditions where the heart can beat very fast and quite erratically. But before I go into that, let me just briefly tell you about the structure of the heart.
The heart is broadly divided into a top and bottom chamber, and a left and right side. The image below will make it easier for you to understand.
The top chambers are called the atria and the bottom chambers the ventricles. The electrical generator in the heart is located at the top right hand corner of the right atrium. Once electricity is generated, it is transmitted through a series of cables to the bottom chambers.
So, as one would expect, the top chamber will contract first, followed by the bottom chamber.
Structure of the human heart. The top chambers are atria, and the bottom chambers are ventricles.
The electrical signals generated will decide what the heart rate is. For example, if 75 electrical impulses are generated a minute, the normal heart will beat at 75 beats a minute.
Now, if the heart rate increases due to some clinical reason, it is probably because there is a problem with the generator itself or the cables in between.
In one condition called ‘supraventricular tachycardia‘, a part of the electricity that is conducted through the cables returns back to the generator via an extra cable. This forms a type of a loop.
By returning like this, the heart rate effectively doubles. In other words, the heart can beat at around 150 beats a minute.
In another condition called ‘atrial flutter’, the atrium beats at 300 beats a minute, while the ventricle beats at 150 beats a minute. Every second beat from the top is transmitted to the bottom chamber.
In atrial fibrillation, the atrium beat irregularly at a rate well above 300. Have you noticed how your body shivers when you are feeling cold? Just imagine a part of your heart ‘shivering’ in the same manner.
It is not just the bottom chamber that contracts fast. Sometimes, the bottom chamber i.e ventricle can beat extremely fast and erratically as well.
There are 2 worrying conditions where the ventricle beats very fast – ventricular tachycardia and ventricular fibrillation.
In ventricular tachycardia, the ventricle beats at a rate of 100 beats a minute or more. While this may not sound as much, the ventricle itself becomes less efficient.
This means that at 100 beats a minute, the heart is not able to pump blood properly.
In ventricular fibrillation (VF), the ventricle contracts extremely fast, possibly at a rate of 300 to 400 beats a minute. Unfortunately, this is not compatible with life. Patients with VF collapse and suffer a cardiac arrest, and the only way to get them out of it is to shock them with a defibrillator.
Most patients with a heart attack who do not go to hospital die at home due to VF. Those who are in hospital can receive timely treatment which is life-saving.
Our heart is a wonderful and powerful vital organ. It can beat at extremely high rates trying to keep the person alive. But sometimes, it just cannot cope.