The physiological significance of atrial delay is such that the contraction of the atria and ventricles do not occur simultaneously, but sequentially, so that the ventricles can ensure the pumping of nutrient-rich arterial blood and the atria recycle the old blood with metabolic waste products. There are four cavities inside the heart: the left atrium, the right atrium, the left ventricle, and the right ventricle, which are not connected to each other between atria and ventricles, and are blocked by valves between atria and ventricles, with the atria connected to veins and the ventricles connected to arteries, which can ensure a one-way flow of blood. When the electrical signal from the sinus node causes the atria to contract and a slight delay in the atrioventricular node area then causes the ventricles to contract, the atrial and ventricular contractions do not occur simultaneously, but are sequentially ordered in order to complete the pumping function. If they contract at the same time, fresh and old blood will be mixed together and the human body will have to develop panic, shortness of breath, dizziness, and the human body will be depressed without effective nutritional supplementation and other symptoms.