Cardiac cycle phases what is the duration of the table

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Schematic relationship of the phases of the heart cycle,

, FCG, sphygmograms. The ECG teeth, the numbers of the PCG tones and parts of the sphygmogram are indicated: a – anacrot, d – dicrot, k – catacrot. Phase numbers correspond to the table. Saved timeline scale.

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A summary table of periods and phases of the cardiac cycle with approximate pressures in the chambers of the heart and the position of the valves is shown at the bottom of the page.

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Ventricular systole

100px Heart systole - Cardiac cycle phases what is the duration of the table

Ventricular systole is a period of ventricular contraction, which allows blood to be pushed into the arterial bed.

In the contraction of the ventricles, several periods and phases can be distinguished:

  • The period of tension is characterized by the onset of contraction of the muscle mass of the ventricles without changing the volume of blood inside them.
    • Asynchronous contraction is the onset of ventricular myocardial stimulation when only individual fibers are involved. Ventricular pressure changes are enough to close the atrioventricular valves at the end of this phase.
    • Isovolumetric contraction – almost the entire ventricular myocardium is involved, but changes in the volume of blood inside them do not occur, since the outgoing (semilunar – aortic and pulmonary) valves are closed. The term isometric contraction is not entirely accurate, since at this time there is a change in the shape (remodeling) of the ventricles, tension of the chords.
  • The period of exile – characterized by the expulsion of blood from the ventricles.
    • Rapid expulsion – the period from the moment of opening the lunar valves to the achievement of systolic pressure in the ventricular cavity – the maximum amount of blood is ejected during this period.
    • Slow expulsion is a period when pressure in the ventricular cavity begins to decrease, but there is still more diastolic pressure. At this time, blood from the ventricles continues to move under the action of the kinetic energy communicated to it, until the pressure in the cavity of the ventricles and the efferent vessels is equalized.

In a state of calm, the adult heart ventricle ejects 60 ml of blood for each systole (stroke volume). The heart cycle lasts up to 1 s, respectively, the heart makes 60 beats per minute (heart rate, heart rate). It is easy to calculate that even at rest, the heart distills 4 liters of blood per minute (cardiac output, MOS).

Diastole

100px Heart diastole - Cardiac cycle phases what is the duration of the table

Diastole is a period of time during which the heart relaxes to receive blood. In general, it is characterized by a decrease in pressure in the ventricular cavity, the closure of lunar valves and the opening of the atrioventricular valves with the advancement of blood into the ventricles.

  • Ventricular diastole
    • Protodiastole – the period of the onset of myocardial relaxation with a drop in pressure lower than in the efferent vessels, which leads to the closure of semilunar valves.
    • Isovolumetric relaxation – is similar to the phase of the isvolumetric contraction, but exactly the opposite. There is an elongation of muscle fibers, but without changing the volume of the ventricular cavity. The phase ends with the opening of the atrioventricular (mitral and tricuspid) valves.
  • Filling period
    • Fast filling – the ventricles rapidly restore their shape in a relaxed state, which significantly reduces the pressure in their cavity and draws blood from the atria.
    • Slow filling – the ventricles have almost completely restored their shape, the blood already flows due to the pressure gradient in the vena cava, where it is 2-3 mm higher. Art.

Atrial systole

It is the final phase of diastole. At a normal heart rate, the contribution of atrial contractions is small (about 8%), since the blood already fills the ventricles over a relatively long diastole. However, with an increase in the frequency of contractions, the duration of diastole generally decreases and the contribution of atrial systole to the filling of the ventricles becomes very significant.

This period is divided into two phases. Slow corresponds to atrial systole, fast – to diastole. Before a new cardiac cycle begins, the ventricles, as well as the atria, have time to completely fill up with blood. In this regard, when a new volume arrives with systole, the total intraventricular amount will increase only by 20-30%.

A summary table of periods and phases of the cardiac cycle with approximate pressures in the chambers of the heart and the position of the valves is shown at the bottom of the page.

Ventricular systole

im124 Heart systole - Cardiac cycle phases what is the duration of the table

Ventricular systole is a period of ventricular contraction, which allows blood to be pushed into the arterial bed.

In the contraction of the ventricles, several periods and phases can be distinguished:

  • The period of tension is characterized by the onset of contraction of the muscle mass of the ventricles without changing the volume of blood inside them.
    • Asynchronous contraction is the onset of ventricular myocardial stimulation when only individual fibers are involved. Ventricular pressure changes are enough to close the atrioventricular valves at the end of this phase.
    • Isovolumetric contraction – almost the entire ventricular myocardium is involved, but changes in the volume of blood inside them do not occur, since the outgoing (semilunar – aortic and pulmonary) valves are closed. The term isometric contraction is not entirely accurate, since at this time there is a change in the shape (remodeling) of the ventricles, tension of the chords.
  • The period of exile – characterized by the expulsion of blood from the ventricles.
    • Rapid expulsion – the period from the moment of opening the lunar valves to the achievement of systolic pressure in the ventricular cavity – the maximum amount of blood is ejected during this period.
    • Slow expulsion is a period when pressure in the ventricular cavity begins to decrease, but there is still more diastolic pressure. At this time, blood from the ventricles continues to move under the action of the kinetic energy communicated to it, until the pressure in the cavity of the ventricles and the efferent vessels is equalized.
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In a state of calm, the ventricle of the heart of an adult for each systole ejects 50-70 ml of blood (shock, or systolic, volume) [1]. The heart cycle lasts up to 1 s, respectively, the heart makes 60 beats per minute (heart rate, heart rate). It is easy to calculate that even at rest, the heart distills 4 liters of blood per minute (minute volume of blood, IOC).

Diastole

im124 Heart diastole - Cardiac cycle phases what is the duration of the table

Diastole is a period of time during which the heart relaxes to receive blood. In general, it is characterized by a decrease in pressure in the ventricular cavity, the closure of lunar valves and the opening of the atrioventricular valves with the advancement of blood into the ventricles.

  • Ventricular diastole
    • Protodiastole – the period of the onset of myocardial relaxation with a drop in pressure lower than in the efferent vessels, which leads to the closure of semilunar valves.
    • Isovolumetric relaxation – similar to the phase of isovolumetric contraction, but exactly the opposite. There is an elongation of muscle fibers, but without changing the volume of the ventricular cavity. The phase ends with the opening of the atrioventricular (mitral and tricuspid) valves.
  • Filling period
    • Fast filling – the ventricles rapidly restore their shape in a relaxed state, which significantly reduces the pressure in their cavity and draws blood from the atria.
    • Slow filling – the ventricles have almost completely restored their shape, the blood already flows due to the pressure gradient in the vena cava, where it is 2-3 mm higher. Art.

Atrial systole

It is the final phase of diastole. At a normal heart rate, the contribution of atrial contractions is small (about 8%), since the blood already fills the ventricles over a relatively long diastole. However, with an increase in the frequency of contractions, the duration of diastole generally decreases and the contribution of atrial systole to the filling of the ventricles becomes very significant.

External manifestations of cardiac activity

The following groups of manifestations are distinguished:

  • Electrical – ECG, Ventriculocardiography
  • Sound – Auscultation, Phonocardiography
  • Mechanical:
    • Apical impulse – palpation, apexcardiography
    • Pulse wave – palpation, sphygmography, phlebography
    • Dynamic effects – a change in the center of gravity of the chest in the heart cycle – dynamocardiography
    • Ballistic effects – shaking the body at the time of the ejection of blood from the heart – ballistic cardiography
    • Resize, position and shape – ultrasound, x-ray
Heart cycle phases
PeriodPhaset,
1Atrial systole0,1ОЗStart ≈0

Start ≈0

Stress period2Asynchronous reduction0,05O → ZЗ6-8 → 9-106-8 → 9-106 – 8
3Isovolumetric contraction0,03ЗS → O10 → 1610 → 816-8 → 0
Period of exile4Quick exile0,12ЗО16 → 3081 → 1200 → -1
5Slow exile0,13ЗО30 → 16120 → 81≈0
Ventricular diastole6Protodiastole0,04ЗO → Z16 → 1481 → 790- 1
7Isovolumetric relaxation0,08S → OЗ14 → 079 → 0≈ 1
Filling period8Quick fill0,09ОЗ≈0≈0≈0
9Slow filling0,16ОЗ≈0≈0≈0
This table is designed for normal pressure indicators in a large (120/80 mm Hg) and small (30/15 mm Hg) circles of blood circulation, a cycle duration of 0,8 s.

Accepted abbreviations:
t – phase duration, AV valves – position of atrioventricular (atrioventricular: mitral and tricuspid) valves, SL valves – position of semilunar valves (located on the paths of exile: aortic and pulmonary), PPancreas – pressure in the right ventricle, PLV – pressure in the left ventricle, Patria – pressure in the atria (combined due to a slight difference), О – open valve position, З – closed valve position.

Heart contractions

This phase lasts about 0,3 s. All ventricular fibers contract at the same time. The beginning of the process leads to the fact that with the valves still half-closed, the blood flow is sent to the zero pressure zone. So the atria are involved in the heart cycle and its phases. The atrioventricular valves lying in the bloodstream close.

Tendon filaments prevent their inversion in the atrial cavity. Papillary muscles give even greater stability to the valves. As a result, the ventricular cavities are closed for a certain period. And until the pressure in them rises above the indicator necessary to open the half-month valves, a significant reduction in the fibers will not occur. Only internal stress increases. With an isometric contraction, thus, all heart valves are closed.

The frequency of contractions in an adult is in the range of 60-90 beats per minute. The heart rate in children is slightly higher. For example, in infants, the heart beats almost three times more – 120 times per minute, and babies up to 12-13 years old have a heartbeat of 100 beats per minute. Of course, these are approximate indicators, because due to various external factors, the rhythm can have a duration of either longer or shorter.

The main organ is shrouded in nerve fibers that regulate all three phases of the cycle. Strong emotional experiences, physical activity and much more increase the impulses in the muscle that come from the brain. Undoubtedly, physiology plays an important role in the activity of the heart, or rather, its changes. For example, an increase in carbon dioxide in the blood and a decrease in oxygen gives a powerful impetus to the heart and improves its stimulation. In the event that changes in the physiology affected the vessels, then this leads to the opposite effect and the heart rate decreases.

For example, high body temperature speeds up the rhythm, and low – slows down. Hormones, for example, also have a direct effect, as come with blood to the body and increasing the rhythm of contractions.

The heart cycle is one of the most complex processes in the human body, because It involves many factors. Some of them directly influence, others affect indirectly. But the totality of all processes allows the heart to carry out its work.

The structure of the heart cycle is the most important process that supports the life of the body. A complex body with its own generator of electrical impulses, physiology and control of the frequency of contractions – works all my life. Three major factors influence the occurrence of organ diseases and its fatigue – lifestyle, genetic traits and environmental conditions.

The main organ (after the brain) is the main link in the blood circulation, therefore, affects all metabolic processes in the body. The heart in a split second displays any failure or abnormality. Therefore, it is so important for each person to know the basic principles of work (three phases of activity) and physiology. This makes it possible to determine violations in the work of this body.

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Expulsion of blood

This is the next period that goes into the heart cycle. It begins by opening the valves of the pulmonary artery and aorta. Its duration is 0,25 s. This period consists of two phases: slow (about 0,13 s) and fast (about 0,12 s) expulsion of blood. Aortic valves open at a pressure level of 80, and pulmonary – about 15 mm RT. Art.

Through the relatively narrow openings of the arteries, the entire volume of expelled blood can pass immediately. This is approximately 70 ml. In this regard, with a subsequent reduction in the myocardium, a further increase in blood pressure in the ventricles occurs. So, in the left it increases to 120-130, and in the right – 20-25 mm RT. Art. A rapid ejection of part of the blood into the vessel is accompanied by a formed increased gradient between the aorta (lung arteries) and the ventricle.

Due to the low throughput, the vessels begin to overflow. Now pressure begins to rise in them. Between the vessels and ventricles there is a gradual decrease in the gradient. As a result, blood flow slows down. In the pulmonary artery, the pressure is low. In this regard, the expulsion of blood from the left ventricle begins somewhat later than from the right.

Notes

  1. ↑ Physiology. Basics and functional systems./Sudakov K.V .. – Moscow: Medicine, 2000. – P. 327. – 784 p. – ISBN 5-225-04548-0.

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This page was last edited on June 2, 2019 at 09:54.

Diastole

When the vascular pressure rises to the indices of the ventricular cavities, the expulsion of blood stops. From this moment begins diastole – relaxation. This period lasts about 0,47 s. With the termination of ventricular contraction, the period of the end of the expulsion of blood coincides. As a rule, in the ventricles, the end-systolic volume is 60-70 ml.

Completion of exile provokes the closure of half-month valves with the reverse current contained in the blood vessels. This period is called prodiastolic. It lasts about 0,04 s. From this moment the tension subsides and isometric relaxation begins. It lasts 0,08 s. After it, the ventricles straighten under the influence of the blood filling them.

The duration of atrial diastole is about 0,7 s. The filling of the cavities is carried out mainly by venous, passively incoming blood. Nevertheless, it is possible to highlight the “active” element. With the contraction of the ventricles, the plane of the atrioventricular septum displaces toward the apex of the heart.

Table

The above describes in detail how the cardiac cycle proceeds. The table below reflects all the steps briefly.

Tatyana Jakowenko

Editor-in-chief of the Detonic online magazine, cardiologist Yakovenko-Plahotnaya Tatyana. Author of more than 950 scientific articles, including in foreign medical journals. He has been working as a cardiologist in a clinical hospital for over 12 years. He owns modern methods of diagnosis and treatment of cardiovascular diseases and implements them in his professional activities. For example, it uses methods of resuscitation of the heart, decoding of ECG, functional tests, cyclic ergometry and knows echocardiography very well.

For 10 years, she has been an active participant in numerous medical symposia and workshops for doctors - families, therapists and cardiologists. He has many publications on a healthy lifestyle, diagnosis and treatment of heart and vascular diseases.

He regularly monitors new publications of European and American cardiology journals, writes scientific articles, prepares reports at scientific conferences and participates in European cardiology congresses.

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