Isometric Relaxation Phase

The isometric relaxation phase is the period from the moment the aortic valves close to the moment the atrioventricular valves open during the cardiac cycle.

At the end of ventricular systole, when the pressure in the aorta exceeds the pressure in the ventricles, the aortic valves close. At this stage, the ventricles relax, but the volume of blood in them does not increase, since the atrioventricular valves are still closed. This period is called the isometric relaxation phase, since the ventricles relax without changing their volume.

As soon as intraventricular pressure drops below the pressure in the atria, the atrioventricular valves open and rapid passive filling of the ventricles begins - the diastolic phase of the cardiac cycle.

Thus, the isometric relaxation phase is a short period of time between systole and diastole of the ventricles, when they relax without filling with blood. This phase prepares the ventricles for efficient filling during diastole.

The isometric relaxation phase is one of the main phases of the cardiac cycle; it lasts 30% of the time of cardiac activity (4 seconds). At the onset of the ventricular contraction phase, the aortic valves are closed and stop pumping blood into the arteries, but the aortic valve begins to close, and the semilunar canal valve and the aortic duct remain open. The heart rests for two seconds, then phasic relaxation of the ventricles occurs. At this time, blood flows freely back to the heart, filling the semilunar canal and the heart and expanding it. This condition is accompanied by physical and mental weakness, overwork, overstrain, exhaustion of the body, both when the heart and other organs and systems are damaged. The presence of symptoms of isometric relaxation most often indicates that a critical phase has arrived when the body’s vital functions begin to be disrupted or