What is sinus rhythm?

Generally, sinus rhythm refers to a normal heart rhythm in which the heart's electrical activity originates from the sinoatrial node. A detailed explanation is as follows:

The sinoatrial node is the heart's natural pacemaker, located at the junction of the right atrium and the superior vena cava. Its automatic cells can spontaneously generate regular electrical impulses that travel through the cardiac conduction system to sequentially excite the atria and ventricles, maintaining the heart's normal contraction and relaxation rhythm. The normal frequency of sinus rhythm in adults ranges from 60 to 100 beats per minute. On an electrocardiogram (ECG), it presents as an upright P wave in leads I, II, and aVF, an inverted P wave in lead aVR, a PR interval of 0.12 to 0.20 seconds, and each P wave is followed by a QRS complex. The heart rate of sinus rhythm can be modulated by the autonomic nervous system; for example, heart rate increases during exercise or emotional excitement and decreases during sleep. These physiological fluctuations are considered normal phenomena.

When sinoatrial node function is abnormal or affected by other factors, sinus arrhythmias may occur, including sinus tachycardia, sinus bradycardia, and sinus arrhythmia. Most cases of sinus arrhythmia do not require specific treatment, but clinical symptoms and underlying causes should be evaluated. Conditions such as anemia, hyperthyroidism, and myocarditis may cause abnormal sinus rhythms and require treatment of the underlying disease.

It is recommended to maintain healthy lifestyle habits, balance work and rest, and avoid excessive fatigue to promote overall health.