The heart is one of the most important organs in the human body, and the electrocardiogram, which is often performed during medical examinations, can detect abnormalities in the rhythm and speed of the heartbeat at rest. In addition, there is also an ambulatory ECG test, which uses an ambulatory ECG detector to continuously record the patient’s ECG activity for 24 hours or even longer, and with the help of computer analysis, it can detect arrhythmias and myocardial ischemia that are not easily detected by conventional ECG. When ordinary people see the ECG results, they are really confused! The curves go up and down, so they can’t figure out if they are sick or not, so they have to skip the images and look directly at the text diagnosis below. And most people’s test results say: sinus rhythm. It feels like you don’t know whether you are healthy or sick even after seeing the text, so what is “sinus rhythm” all about? What is sinus rhythm? Is a sinus arrhythmia on an ECG normal or pathological? Sinus rhythm is a normal heart rhythm that is generated by a “generator” that exists in the heart. This generator is located in the upper right atrium and is called the “sinus node”. It emits electrical impulses, which are transmitted to the atria and ventricles in turn through the heart’s special conduction system, causing the atria and ventricles to contract, and then pumping blood throughout the body, which nourishes all cells, tissues and organs of the body and ensures normal physiological functions. Therefore, the sinus node is the supreme “command” of the body’s autonomous rhythm. Sometimes, you may see “sinus arrhythmia” in the ECG results. This means that the origin of the heartbeat is unchanged, but the rhythm is irregular. Sinus arrhythmias can occur in normal people. The autonomic nerves in the body have an effect on the heart’s activity. During the day, the heart is innervated by sympathetic nerves and the heart rate is faster; at night, the heart is innervated by the vagus nerve and the heart rate becomes slower. As you can see, the heart rate is not constant. How many heartbeats per minute is normal? Why can’t the heart beat too fast or too slow? Although the normal standard for heart rate on ECG is 60-100 beats per minute, studies have confirmed: a normal person should keep it at 60-75 beats per minute. However, athletes have a slower heart rate, which is known as the “longevity heart rate”. This is because each beat of the heart can pump blood throughout the body, so if the heart beats once, it is not necessary to beat more frequently and faster to maintain normal blood circulation. The faster the beat, the greater the wear and tear on the heart. In an athlete with a slow heart rate, the energy consumed by the heartbeat and the wear and tear on the heart will be reduced accordingly. In addition, if the sinus node is diseased and the heart is not beating, the heart rate will slow down, and this heart rate cannot be called the “longevity heart rate”! Also, in the elderly, a slow heart rate can lead to a lack of blood supply to the brain. Therefore, a heartbeat that is too fast or too slow is not good for health. Next time you see a medical report that says “sinus rhythm”, don’t worry about it! Remember, sinus rhythm is actually a normal heart rhythm.