Periods and phases of the cardiac cycle: table. What happens in each phase of the cardiac cycle

Ever since childhood, everyone knows that the movement of blood throughout the body provides the heart. To ensure that the whole process is uninterrupted, the heart cycle is a clear scheme of phases that are interchangeable. Each of them is characterized by its blood pressure level and takes a certain amount of time to perform. The entire cycle in a healthy person takes only 0.8 seconds, while it includes a whole list of different phases. The duration of each of them can be determined by graphical registration of the PCG, ECG and sphygmogram, but what happens in each phase of the cardiac cycle is known only by a specialist. Cardiac cycle phases, table To understand this and an ordinary person, this article is presented.

General relaxation

The consideration of each phase of the cardiac cycle( the table will be presented at the end of the article) is easiest to start with the relaxation time of the main muscle of the body. In general, the heart cycle is a change of contractions and relaxation of the heart.

So, the work of the heart begins with a pause, when the atrioventricular valves are open, and the half-month valves are closed. It is in this condition that the heart is completely filled with blood from the veins, which enters it completely freely. What happens in each phase of the cardiac cycle The fluid pressure in the heart and adjacent veins is at the zero level.

Atrial contraction

After the blood completely fills the heart, an excitation begins in its sinus department, provoking to contract at first auricle. In this phase of the cardiac cycle( the table will make it possible to compare the time allocated for each stage), due to the tension of the muscles, the venous vessels are closed, and the blood that comes from them closes in the heart. Further compression of the liquid leads to an increase in the pressure in the filled cavities to a maximum of 8 mm Hg. Art. This causes the movement of fluid through the holes in the ventricles, where its volume reaches 130-140 ml. After this, the systole is replaced by a relaxation of 0.7 seconds and the next phase begins.

Ventricular systole

The stress of the ventricles takes 0.8 seconds and is divided into several periods. The first is an asynchronous contraction of the myocardium, which takes only 0.05 seconds. It is determined by the alternating contraction of the muscles in the ventricles. First of all, the fibers begin to lie near the conducting structures. Rapid exile Voltage continues until the half-month valves are completely open due to the increasing pressure inside the heart cavities. For this, the phase is completed by increasing the internal fluid pressure more than at the moment determined by the pressure in the aorta and arteries - 70-80 and 10-15 mm Hg. Art.respectively.

Isometric systole

The previous phase of the cardiac cycle( the table accurately describes the time of each process) continues with the simultaneous tension of all the muscles of the ventricles, which is accompanied by the closing of the inlet valves. The duration of the period is 0.3 seconds, and the blood all the time moves into the zone of zero pressure. In order for the closed valves not to turn out after the liquid, the heart structure provides for the presence of special tendons and papillary muscles. As soon as the cavities are filled with blood and the valves close, a tension begins to build up in the muscles, which further opens the half-monthly valves and rapidly expels the blood. Until this happens, specialists fix the first tone of the heart, called still systolic. Fast filling At this time, the pressure inside the heart rises above what is in the arteries, and when the left ventricle takes a rounded shape, its impact on the inner surface of the chest determines the apical impulse. This occurs in a centimeter from the mid-inclusive line in the fifth intercostal space.

Exile Period

When the fluid pressure inside the heart exceeds the pressure in the arteries and aorta, the next cycle begins. It is indicated by the opening of the valves for the discharge of blood from the cavities and lasts 0.25 seconds. The entire phase can be divided into rapid and slow exile, which take approximately the same time periods. First, the fluid under pressure quickly rushes into the vessels, but because of their poor flow capacity, the pressure quickly levels out and the blood begins to move back. To prevent this, the systole of the ventricles constantly increases, raising the pressure inside the cavities of the heart for the final release from the blood. At this stage, about 70 ml of liquid is distilled. Since the pressure in the pulmonary artery is low, the release of blood from the left ventricle begins a little later. When all the fluid leaves the heart cavity, the myocardium relaxes the second tone of the heart - diastolic. At this time, the blood again begins to fill the ventricles, because the pressure in them becomes lower.

Relaxation period

All the time the diastole takes 0.47 seconds, and when the blood begins to move in the opposite direction, then under its own pressure closes the semilunar valves. This period is called proto-diastolic. Slow exile Its time is only 0.04 seconds, and after it immediately comes the next period of the cardiac cycle - isometric diastole. It lasts 2 times longer than the previous period of relaxation and provides a decrease in the pressure of the fluid in the ventricles more than in the atria. Thus, the valves between them open and allow blood to pass from one cavity to another. Mostly it is venous blood entering the heart passively.

Filling

The appearance of a third heart tone marks the onset of filling the ventricles of the heart, which can be divided into slow and rapid. Fast filling is determined by the relaxation of the atria, slow - by contrast, tension. Once the heart cavities are fully filled, the next phase of the cycle begins. Until this happens, and the stress of the myocardium provokes the flow of blood into the heart, a fourth tone appears. With intensive work, the heart muscle performs each cycle more quickly.

The reduced content of

The phase of the cardiac cycle shows the table for healthy people in a quiet state, therefore it is considered to be their reference. Of course, minor deviations are often attributed to individual features or slight excitement before the procedure, so fear of differences in registering heart cycles should only be in case of a significant excess of their rate or, conversely, a decrease. Ventricular systole

So, what happens in each phase of the cardiac cycle has been described in detail above, now it is suggested to look at the general picture in a reduced form:

Period

Phase

Duration in seconds

Right ventricle pressure in mmHg

In the left ventricle in mmHg.

In the atria in mmHg

Atrial contraction

0,1

first zero, at the end 6-8

as

as

Systole period

Asynchronous voltage

0,05

6-8, at the end 9-10

also

6-8 constantly

Isometric voltage

0,03

10, at the end 16

10, at the end 81

6-8, at the end zero

Ejection cycle

Fast

0.12

first 16, then 30

first 81, then 120

0→ -1

Slow

0,13

first 30, then 16

first 120, then 81

zero

Relaxation of ventricles

Protodiastolic period

0,04

16, then 14

81, then 79

0- + 1

Isometric relaxation

0,08

14, then zero

79, at the end zero

≈ + 1

Filling cycle

Fast

0,08

zero

zero

zero

Slow

0.17

zero

zero

zero

reduction periods

When a person probes the heartbeat or listens for heartbeat, only 1 and 2 tones are audible, the rest can be seen only with graphic registration.

Periods of the cardiac cycle can also be divided according to other criteria. So, experts distinguish refractory periods - absolute, effective and relative, vulnerable period and supernormal phase.

Differing periods are characterized by the fact that during the first mentioned the heart muscle is not able to contract independently, regardless of the external stimulus. The next period already allows the start of the work of the heart with a slight electrical impulse. Further, the heart is activated already with a strong stimulus. On the ECG, you can see the last two refractory periods in the form of ventricles marked by an electric systole. Asynchronous reduction

Vulnerable cycle period corresponds to muscle relaxation in the completion of all the phases listed above. In comparison with refractory it is considered short. The latter period is an increased excitability of the heart and is detected only in the presence of cardiac depression.

An experienced cardiogram decipherer always knows to which period a particular wave of heartbeat should be attributed, and it will correctly determine if a person has a disease, or if any deviations from the norm should be considered as insignificant features of the body.

Conclusion

Even after a routine heart examination, do not try to decipher the results yourself. This article is offered only for acquaintance so that patients could understand the peculiarities of the work of their heart and could better understand what exactly is not happening in their body. Only an experienced doctor is able to take into account all the nuances of each case at the same time in order to collect them into a single picture and determine the diagnosis. In addition, not all deviations from the above norm can be considered a disease.

It is also important to know that the exact conclusion of any specialist can not be based only on the results of one study. At any suspicion the doctor should appoint passage of additional inspections.