Definition
The systole (Greek for contraction), is a part of the heart action. In simple terms, systole is the phase of contraction of the heart, and thus the phase of ejection of blood from the heart through the body and lung circulation. It is replaced by diastole, the relaxation phase of the heart.
This means that during systole the blood is pressed out of the right and left ventricle. The systole thus describes the pumping capacity of the heart and determines the pulse. The duration of the systole remains approximately the same even if the heart rate changes; in an adult person it is about 300 milliseconds long.
Structure of the systole
In systole, a distinction is made between a short mechanical phase of cardiac muscle tension and a longer lasting blood outflow phase. Directly before the tensing phase, the chambers (ventricles) are filled with blood. The sail and pocket valves are firmly closed.
The subsequent contraction of the heart muscle causes the pressure in the two chambers to increase. If the pressure in the chambers exceeds the pressure in the large pulmonary artery and aorta, the outflow phase begins. The pocket valves open and blood flows into the large vessels and from there to the periphery of the pulmonary and body circulation.
At the same time, the two atria fill with blood. To prevent the blood from flowing back from the chambers into the atria during systole, the access is closed by the sail valves. The beginning and end of systole can be detected by various diagnostic means.
Auscultatorily, the outflow phase begins with the 1st heart sound and ends with the 2nd heart sound. In echocardiography, the opening of the aortic valve can be seen at the beginning and the closing of the valve at the end. In the ECG the outflow phase begins with the R-wave and ends with the T-wave. During the entire systole the excitability of the heart muscle is suspended so that no irregularities can occur. This is called the absolute refractory period.
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