The heart is like a water pump constantly supplies oxygen and nutrients to all other organs in our body. In a long-term observation, people have realized that human life is based on a working heart. Therefore, we use heartbeat as a criterion to judge life or death.

Here comes the question, what kind of heartbeat is normal, and what is abnormal?

The heart is a muscular organ composed of four chambers - two upper chambers (atria) and two lower chambers (ventricles). The normal heartbeat is regulated by the sinoatrial node located in the right atrium. Then, how does it work? We all know if you accidentally get your hands stimulated by current or static electricity, your hand will contract instantly. This is how the electric current works on muscles. The middle school biology lesson tells us that current stimulation can cause muscle contraction. Those specialized cells located at the sinoatrial node generate electrical impulses to cause a rhythmical contraction of the cardiac muscles, which is known as heartbeat. This current is so weak that it cannot be felt. Since the normal heartbeat is regulated by the sinoatrial node, normal sinus rhythm is defined as the rhythm of a healthy heart.

In adults, normal sinus rhythm usually accompanies a heart rate of 60 to 100 beats per minute, which varies from person to person. Moreover, everyone's heart rate is not constant throughout the day. A normal adult's heart rate can slow down to 37-40 beats per minute during sleep, while it can speed up to 120-130 beats per minute during the day. The heart rate depends on numerous factors. People who exercise regularly tend to have a slower heart rate. On the contrary, those who lack exercise, have irregular lives and insomnia tend to have a faster heart rate. Movements like taking deep breath, lying down will slow down your heart rate, while nervousness, drinking tea or coffee, exercising will make your heartbeat faster. Due to the complexity of the human body, the same person may respond differently to the same stimulus at different times. When you are in good condition, you will feel no discomfort in your heartbeat. However, when you are not well-rested or tired, the same action may cause a feeling of palpitation. A heart rate of more than 100 beats per minute is called sinus tachycardia. Normal people have sinus tachycardia at certain times of the day. If the heart rate does not exceed 100 beats per minute throughout the day, it may be abnormal. A heart rate below 60 beats per minute is called sinus bradycardia, which is common during sleep. If an adult's slowest heart rate drops less than 50 beats per minute during sleep, it may also be abnormal. If your heart rate is consistently higher than 100 beats per minute or lower than 60 beats per minute, don't panic and make an appointment with your doctor .

Heart arrhythmias occur when the electrical impulses that coordinate your heartbeats don't work properly, suggesting that the heart has lesions that discharge abnormally. Doctors must capture an electrocardiogram when an arrhythmia occurs to determine where the arrhythmia originated. According to the location of the origin, arrhythmia can be divided into atrial arrhythmia, atrioventricular junctional arrhythmia and ventricular arrhythmia. Generally speaking, the risk and severity of atrial arrhythmia and atrioventricular junctional arrhythmia are relatively lower, ventricular arrhythmia is relatively serious. Problems in this area will be introduced in the article "What Is Tachycardia".