Systole in clinical parlance refers to the tightening and subsequent contraction phase of the two ventricles of the heart. During the contraction phase, the two leaflet valves through which blood flowed from the two atria into the ventricles are closed, and the two leaflet valves in the left and right ventricles open. Blood is pumped almost simultaneously from the left ventricle into the large systemic circulation and from the right ventricle into the pulmonary circulation.
What is systole?
Systole, in clinical parlance, refers to the tightening and subsequent contracting phases of the two chambers of the heart. Systole is part of the heart rhythm, which can be divided into the two main phases of systole (heartbeat phase) and diastole (relaxation phase). Strictly speaking, it is systole and diastole of the two chambers (ventricles) of the heart, because during the systole of the chambers, the two atria go through their diastolic phase and vice versa. Systole of the ventricles begins with the tense phase, during which all four heart valves are closed. As pressure builds, the two pocket valves, the aortic valve of the left ventricle and the pulmonic valve of the right ventricle, open. The contracting ventricular muscles now force blood into the aorta, the major artery of the body, and into the pulmonary artery (arteria pulmonalis). The duration of systole remains relatively constant, even with varying physical exertion, and is about 300 to 400 milliseconds in adult humans. However, the time of diastole can vary considerably depending on the oxygen demand of the body, resulting in a high degree of heart rate variability. In a healthy, normally athletic individual, the pulse rate can therefore vary from about 60 heartbeats per minute (resting pulse) to 160 to 200 (maximum rate), with the maximum rate decreasing as a function of age.
Function and task
The heart maintains blood circulation with its beating rhythm. The systoles of the right and left ventricles occur simultaneously and are electrically controlled by sinus and AV nodes as well as by the His bundle and Purkinje fibers. Systole thus corresponds to the working cycle of the heart. As soon as the pressure built up in the ventricles during systole exceeds the residual diastolic pressure in the aorta and pulmonary artery, the two leaflet valves, the aortic valve and the pulmonary valve, open. When diastole sets in, the blood pressure in the chambers drops due to the relaxing heart muscles, and there is a risk of backflow of blood. To prevent this, the two leaflet valves close again. They open and close passively, which means that, unlike the two leaflet valves, they do not have their own muscularly supported, active closing or opening mechanism. The blood that is pumped from the left ventricle into the aorta is oxygen-rich because it has previously undergone, at the walls of the alveoli, an exchange of gases between carbon dioxide and oxygen. After it passes through the body tissues via the aorta with all its branches and ramifications down to the level of the arterioles and capillaries, the reverse metabolic process takes place. Carbon dioxide is absorbed by the blood in the capillaries and oxygen diffuses through the capillary walls into the surrounding tissue. The body can only benefit optimally from the important process of systole if all other components also function accordingly. Above all, the electrical control of the heartbeat is of particular importance. In addition, the functionality of the four heart valves must also be ensured so that the heart can build up the necessary pressure. Optimal elasticity of the arteries must also be ensured, since they influence arterial blood pressure via the elasticity of their walls. The proper functioning of the heart rhythm and its functionality can be determined to a certain extent by listening to the specific heart sounds using a stethoscope and with the help of an electrocardiogram (ECG).
Diseases and ailments
The effectiveness of systole depends primarily on the functionality of the heart valves and arteries. In turn, the functioning of systole itself depends on the proper supply of oxygen and nutrients to the heart muscles and on electrical impulses.Pathological disturbances in the supply of the heart muscle as well as cardiac arrhythmias due to faulty initiation or faulty transmission of electrical impulses, lead to the most frequently diagnosed cardiac problems. A frequent clinical picture results from sclerotically altered coronary vessels. Typical symptoms of the disease include chest pain or pressure that may radiate to the lower jaw, shoulders or arms. The symptoms can be signs of an impending heart attack (myocardial infarction), which is triggered by the occlusion of a coronary artery. Even more common are cardiac arrhythmias caused by faulty generation of the electric shock impulse or faulty conduction of the initiated impulse. The most common cardiac arrhythmia is atrial fibrillation, which is usually not immediately life-threatening but often results in reduced performance. Atrial fibrillation is usually accompanied by arrhythmias or tachycardia (palpitations). Chronic atrial fibrillation increases the risk of secondary damage, such as myocardial enlargement and stroke, because clots can form in the atrium due to the disordered blood flow. These can be washed out and cause vascular occlusion in the brain. Most commonly, atrial fibrillation is associated with a loss of sinus rhythm, which is initiated by the sinus node in the left atrium and transmitted to the heart muscle via the AV node, His bundle, and Purkinje fibers. Less common, but also far more dangerous, is so-called ventricular fibrillation, in which disordered excitations can occur within the ventricles at a rate of up to 800 beats per minute. Because the chambers can no longer fill and empty due to the high frequency of beats, the condition is immediately life-threatening.
