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During systole, the blood is pumped into the body circulation (red) and the pulmonary circulation (blue).
Schematic representation of an EKG with labels

The systole ( [old] Greek συστολή - [the] contraction or [the] shortening ) is part of the cardiac cycle . To put it simply, it is the tension phase and therefore the blood outflow phase of the heart, in contrast to diastole , the relaxation phase and thus blood inflow phase. During systole, the blood is pressed out of the right and left heart chambers ( ventricles ). The systole describes the pumping capacity of the heart. It determines the pulse and the pulse amplitude .

The duration of the systole remains fairly constant even when the heart rate changes , whereas the duration of the diastole varies considerably. The systole is about 300 milliseconds long in the adult human .

The ventricular systole is divided into a short mechanical myocardial tension phase and a longer blood outflow phase . Immediately before the tension phase, the chambers are filled with blood, and the leaflet and pocket valves are closed. The heart muscle contracts , which increases the pressure. In the outflow phase, the pressure in the chambers exceeds the pressure in the pulmonary trunk (pulmonary artery) and aorta , the pocket valves open, and blood flows into the large vessels.

The mechanical outflow phase begins

  • in the phonocardiogram or auscultation with the 1st heart sound
  • in echocardiography with the opening of the aortic valve
  • in the EKG with the R wave

The mechanical outflow phase ends

  • in the phonocardiogram or auscultation with the 2nd heart sound
  • in echocardiography with the closure of the aortic valve
  • in the ECG with the T wave

Before the systole, the ventricles are stretched and filled with blood, the atria are contracted. During systole, the two chambers contract simultaneously. The blood is thus pumped into the pulmonary artery and the aorta, from where it flows to the periphery of the body and lungs . At the same time, the atria expand and fill with blood. Thus does not flow into the atria during systole the blood from the chambers into which access is with the sails flap valve-like closed. After the systole, the muscle relaxes (diastole). The blood collected in the atria flows through the opening leaflet valves into the heart chambers. The pocket flaps are now closed so that the blood, which has been pumped through the systole into the aorta and pulmonary artery, cannot flow back into the chambers.

The excitability of the heart muscle is removed during systole (absolute refractory).

Note: The atrial systole falls into the late diastole of the ventricle.

Clinical pictures

Individual evidence

  1. ^ Duden: Systole , accessed on April 5, 2015.