Coronary circulation and its features. For normal heart activity, uninterrupted and rapid adaptation to different conditions supplying it with oxygen and blood. 4-5 of all the blood ejected by the heart flows through the coronary vessels. This amount of blood passes through the vessels of the heart both under conditions of relative rest and under conditions of maximum physical work of 4.5-25 lmin. Coronary circulation has a number of features, which include high adaptability to different levels functional state cardiac muscle, the highest oxygen demand is on average twice the oxygen demand of all other tissues, the presence of a dense capillary network on average 2.5103 2500 capillaries per 1 mm2, in skeletal muscle 0.4103 400. From the initial part of the aorta near the aortic valves two arteries branch off, the right and left coronary arteries, going into the thickness of the myocardium, where they branch, forming a capillary network. There are anastomoses between the arteries of the heart.
There are especially many of them in the area of the interventricular septum.
Anastomoses can additionally develop with increased work performed by the heart for a long time, or with disturbances in the blood supply to the myocardium associated with a narrowing of the lumen of one of the coronary arteries. The arteries of the heart are accompanied by veins, which gather into a large venous trunk, the coronary sinus, which flows into the right atrium.
The heart also has smaller veins that drain directly into the atrium. Blood flow in the coronary arteries depends on a number of physiological factors, cardiac and non-cardiac. Cardinal factors include the level of metabolic processes in the myocardium, the tone of the coronary vessels, the pressure in the aorta, heart rate. The intensity of metabolic processes in the myocardium changes significantly under different conditions of the body.
For example, during physical work, the energy expenditure of the heart increases and the amount of coronary blood flow increases. The tone of the coronary vessels, and, consequently, their lumen, ensures the adaptation of the coronary blood flow to the energy needs of the heart. There is a close dependence of coronary blood circulation on the magnitude blood pressure in the aorta.
The best conditions for coronary circulation are created when the blood pressure in an adult is 14.7-18.7 kPa 110-140 mm Hg. st An increase in heart contractions increases blood flow in the coronary vessels only when simultaneously intense metabolic processes in the myocardium. Thus, with an increase in the level of metabolic processes in the myocardium and oxygen consumption by the heart, coronary blood flow always increases. When metabolic processes in the myocardium occur at a low level, due to reduced work of the heart, then coronary blood circulation is significantly reduced.
Extracardiac factors include mechanisms neurohumoral regulation coronary blood flow. The coronary vessels are innervated by the sympathetic and vagus nerves. When the sympathetic nerves are excited, there is usually an increase in coronary blood flow. The vasoconstrictor effect of the vagus nerves in relation to the coronary vessels is currently not recognized by all scientists.
Humoral factors play an important role in the regulation of coronary blood flow. Adrenaline, norepinephrine, histamine in doses that do not affect the functioning of the heart and blood pressure, contribute to the expansion of the coronary arteries and an increase in coronary blood flow. The posterior pituitary hormone vasopressin increases resistance in the coronary arteries and reduces coronary blood flow. Acetylcholine reduces the lumen of the coronary vessels and, therefore, reduces coronary circulation.
Thus, the coronary system and its cardiac and extracardiac regulatory mechanisms ensure adequate nutrition of the heart, depending on the state of the body.
End of work -
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Coronary circulation
| Coronary circulation | |
Heart, anterior view: the right coronary artery and the anterior descending branch of the left coronary artery are visualized. |
|
 Diaphragmatic surface of the heart. |
|
| Catalogs | |
|---|---|
Coronary circulation- blood circulation through the blood vessels of the myocardium. The vessels that deliver oxygenated (arterial) blood to the myocardium are called coronary arteries. The vessels through which deoxygenated (venous) blood flows from the heart muscle are called coronary veins.
Coronary arteries located on the surface of the heart are called epicardial. These arteries are normally capable of self-regulation, ensuring the maintenance of coronary blood flow at a level corresponding to the needs of the myocardium. These relatively narrow arteries are usually affected by atherosclerosis and are susceptible to stenosis with the development of coronary insufficiency. Coronary arteries located deep in the myocardium are called subendocardial.
Coronary arteries belong to the “final blood flow”, being the only source of blood supply to the myocardium: excess blood flow is extremely insignificant, and therefore stenosis of these vessels can be so critical.
Anatomy of the coronary arteries
There are two main trunks of the coronary blood supply - the right one. RCA) and left (English) LCA) coronary arteries. Both of these arteries arise from primary department(root) of the aorta, directly above the aortic valve. The left coronary artery arises from the left aortic sinus, the right - from the right.
The right coronary artery supplies most of the right ventricle of the heart, part of the cardiac septum, and the posterior wall of the left ventricle of the heart. The remaining parts of the heart are supplied by the left coronary artery.
The left coronary artery is divided into two or three, rarely four arteries, of which the most clinically significant are the anterior descending and circumflex branches. The anterior descending branch is a direct continuation of the left coronary artery and descends to the apex of the heart. The circumflex branch departs from the left coronary artery at its beginning at approximately a right angle, bends around the heart from front to back, sometimes reaching back wall interventricular groove.
Options
In 4% of cases there is a third, posterior coronary artery. In rare cases, there is a single coronary artery circumflexing the aortic root.
Sometimes there is duplication of the coronary arteries (the coronary artery is replaced by two arteries located parallel to each other).
Dominance
Artery giving off the posterior descending artery PDA, posterior interventricular artery), determines the dominance of the blood supply to the myocardium.
- If the posterior descending artery arises from the right coronary artery, the right type of dominance of the myocardial blood supply is indicated.
- If the posterior descending artery arises from the circumflex artery (eng. LCX, branches of the left coronary artery), speaks of the left type of dominance of the blood supply to the myocardium.
- The situation of blood supply to the posterior descending artery by both the right and circumflex coronary arteries is called codominant blood supply to the myocardium.
In approximately 70% of cases, the right type of dominance is observed, 20% - codominance, 10% - left type of dominance.
Dominance reflects the source of blood supply to the artery supplying the atrioventricular node.
Physiology of coronary blood flow
Cardiac blood flow at rest is 0.8 - 0.9 ml/g per minute (4% of total cardiac output). At maximum load, coronary blood flow can increase 4 to 5 times. The speed of coronary blood flow is determined by aortic pressure, heart rate, autonomic innervation and, most importantly, metabolic factors.
Venous drainage
Blood flows from the myocardium predominantly (2/3 of coronary blood) into three veins of the heart: large, middle and small. Merging, they form the coronary sinus, which opens into the right atrium. The rest of the blood flows through the anterior cardiac veins and the Tebasian veins.
Notes
Wikimedia Foundation. 2010.
See what “Coronary circulation” is in other dictionaries:
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Blood supply to the heart muscle; carried out through interconnected arteries and veins that penetrate the entire thickness of the myocardium. The arterial blood supply to the human heart occurs mainly through the right and left coronary... ...
Movement of blood in the circulatory system (See. Circulatory system), ensuring the exchange of substances between all tissues of the body and the external environment and maintaining the constancy of the internal environment Homeostasis. The K. system delivers oxygen to tissues,... ... Great Soviet Encyclopedia
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DIVERTICULUS- (from Latin diverticulum road to the side), medical term to designate blindly ending hollow appendages and sac-like protrusions of tubular and hollow organs (philologically the name appendix would be more correct). Most common... ... Great Medical Encyclopedia
| Coronary circulation | |
|---|---|
| Heart, anterior view: the right coronary artery and the anterior descending branch of the left coronary artery are visualized. |
|
 Diaphragmatic surface of the heart. |
|
| Catalogs | |
Coronary circulation- blood circulation through the blood vessels of the myocardium. The vessels that deliver oxygenated (arterial) blood to the myocardium are called coronary arteries. The vessels through which deoxygenated (venous) blood flows from the heart muscle are called coronary veins.
Coronary arteries located on the surface of the heart are called epicardial. These arteries are normally capable of self-regulation, ensuring the maintenance of coronary blood flow at a level corresponding to the needs of the myocardium. These relatively narrow arteries are usually affected by atherosclerosis and are susceptible to stenosis with the development of coronary insufficiency. Coronary arteries located deep in the myocardium are called subendocardial.
Coronary arteries belong to the “final blood flow”, being the only source of blood supply to the myocardium: excess blood flow is extremely insignificant, and therefore stenosis of these vessels can be so critical.
Anatomy of the coronary arteries[ | ]
There are two main trunks of the coronary blood supply - (English RCA) and (English LCA) coronary arteries. Both of these arteries arise from the initial part (root) of the aorta, directly above the aortic valve. The left coronary artery arises from the left aortic sinus, the right - from the right.
The right coronary artery supplies most of the right ventricle of the heart, part of the cardiac septum, and the posterior wall of the left ventricle of the heart. The remaining parts of the heart are supplied by the left coronary artery.
The left coronary artery is divided into two or three, rarely four arteries, of which the most clinically significant are the anterior descending and circumflex branches. The anterior descending branch is a direct continuation of the left coronary artery and descends to the apex of the heart. The circumflex branch departs from the left coronary artery at its beginning at approximately a right angle, bends around the heart from front to back, sometimes reaching the posterior wall of the interventricular groove.
Options [ | ]
In 4% of cases there is a third, posterior coronary artery. In rare cases, there is a single coronary artery circumflexing the aortic root.
Sometimes there is duplication of the coronary arteries (the coronary artery is replaced by two arteries located parallel to each other).
Dominance [ | ]
The artery giving off the posterior descending artery (English PDA, posterior interventricular artery) determines the dominance of the blood supply to the myocardium.
In approximately 70% of cases, the right type of dominance is observed, 20% - codominance, 10% - left type of dominance.
Dominance reflects the source of blood supply to the feeding artery.
Physiology of coronary blood flow[ | ]
Cardiac blood flow at rest is 0.8 - 0.9 ml/g per minute (4% of total cardiac output). At maximum load, coronary blood flow can increase 4 to 5 times. The speed of coronary blood flow is determined by the pressure in the aorta,
The heart is the central “pumping station” of the blood circulation. Stopping heart activity even for a few tens of seconds can lead to serious consequences. Day and night, week after week, month after month and year after year, the heart continuously pumps blood. With each beat, 50-70 ml of blood (a quarter or a third of a glass) is thrown into the aorta. At 70 beats per minute this will be 4-5 liters (at rest). Get up, walk, climb the stairs - and the figure will double or triple. Start running - and it will increase 4, or even 5 times. On average, the heart pumps up to 10 tons of blood per day, even with a lifestyle not associated with hard work, and in a year - 3650 tons. Over the course of a lifetime, the heart - this little worker, the size of which does not exceed the size of a fist - pumps 300 thousand tons. blood, working continuously, without stopping even for a few seconds. The work that a person’s heart does throughout life is sufficient to lift a loaded railway carriage to the height of Elbrus.
To ensure this gigantic work, the heart needs a continuous flow of energy and plastic materials and oxygen. The energy that the heart muscle (myocardium) develops during the day is approximately 20 thousand kgm. Energy consumption is usually calculated in calories. It is known that 1 kcal is equivalent to 427 kgm. Coefficient useful action cardiac and other muscles is approximately 25%. In order to develop energy equal to 20 thousand kgm, the heart must expend approximately 190 kcal per day.
The source of energy is the process of oxidation of sugar or fats, which requires oxygen. When 1 liter of oxygen is consumed, 5 kcal are released; with an energy consumption of 190 kcal per day, the heart muscle must absorb 38 liters of oxygen. Out of 100 ml of flowing blood, the heart absorbs 12-15 ml of oxygen (other organs absorb 6-8 ml). To deliver the required 38-40 liters of oxygen, about 300 liters of blood must flow through the heart muscle per day.
The heart muscle is supplied with blood through the coronary, or coronary, arteries. Coronary circulation has a number of features that distinguish it from blood circulation in other organs and tissues. It is known that in the arterial system there is pulsating blood pressure: it increases during heart contraction and decreases when it relaxes. Increased pressure in the arteries as the heart contracts increases blood flow through organs and tissues. In the vessels of the heart, the opposite ratio is observed. When the heart muscle contracts, intramuscular pressure increases to 130-150 mm, which significantly exceeds the blood pressure in the capillaries. As a result, the capillaries are compressed. Unlike blood flow in other organs and tissues, increased blood flow through the coronary vessels is observed not during the period of contraction, but during relaxation of the heart.
With a slower heart rate, the duration of periods of relaxation (diastole) of the heart increases, which naturally improves coronary blood flow, facilitating nutrition of the heart muscle. With a rare rhythm, the heart works more economically and productively.
Interruptions in the blood supply to the heart muscle reduce energy production and immediately affect the functioning of the heart. It is this condition that occurs in cases of coronary circulatory disorders that are not accompanied by more serious consequences.
Disturbances in the blood supply to the heart muscle can occur with a sharp increase in the oxygen demand of the heart muscle if the body does not have the ability to adequately increase coronary blood flow due to blockage of a vessel with a blood clot, deterioration of patency, or atherosclerosis. In all these cases, there is a decrease in blood delivery to the heart muscle and a significant weakening of heart function (despite the fact that the heart has some reserve devices for emergency provision of its energy). Such reserves in the heart muscle are the reserves of oxygen bound by the pigment - myoglobin, as well as the ability of the heart muscle to produce energy without consuming oxygen (due to anaerobic glycolysis). However, these reserves are low-power. They can provide energy to the myocardium only for a short time. Therefore, the heart can perform its function only if there is an uninterrupted supply of blood to the heart muscle (the amount of blood supply must correspond to the intensity of work).
In the process of evolution, nature has created a complex, “multi-story” system for regulating coronary blood flow. The vascular muscles of the coronary arteries are innervated by fibers of the sympathetic and parasympathetic nervous system. Sympathetic fibers cause constriction of the coronary vessels, and parasympathetic fibers cause dilation. However, such reactions are observed only in experiments on the vessels of a stopped heart. In those cases when the heart continues to work, irritation of sympathetic and parasympathetic fibers causes other reactions.
Under the influence of impulses coming through the sympathetic nerves, the work of the heart muscle increases sharply, the strength of each contraction increases, and the amount of blood ejected by the heart into the vascular system, and contraction frequency. All this leads to a significant increase in energy consumption of the heart muscle and to the accumulation large quantity some metabolic products, which, as we already know, have a local vasodilator effect. Therefore, in a beating heart, irritation of the sympathetic nervous system leads not to a narrowing, but to an expansion of the coronary vessels. The parasympathetic system causes the opposite shifts.
It has been established that the heart has its own mechanism of nervous regulation - the intracardiac nervous system, which continues to function even after the organ’s connections with the brain and brain are completely turned off. spinal cord. The fibers of the intracardiac nervous system innervate not only the heart muscle, but also the muscles of the coronary vessels. Regulation of coronary circulation can be carried out both by mechanisms operating in the organ itself, and through the complex interaction of nerve signals arising in the heart with impulses coming to the heart from the central nervous system.
Numerous, often overlapping regulatory mechanisms ensure adaptation of the level of coronary blood flow to the energy needs of the heart muscle at rest, during physical activity, emotional and mental stress.
The amount of coronary blood flow increases sharply during intense physical activity, during which increased activity of the heart muscle causes an increase in its need for oxygen. The resulting dilation of the coronary vessels leads to a significant increase in the amount of blood flowing through the myocardium.
A similar effect is also exerted by some adverse effects on the body associated with oxygen starvation or the accumulation of the main “slag” of life - carbon dioxide. Mechanisms of regulation of coronary blood flow healthy body quickly and accurately respond to changes in the oxygen demand of the heart muscle or the conditions of its delivery.
Therefore, systematic physical activity, as well as a number of seemingly unfavorable factors and conditions that contribute to the development of oxygen starvation (staying in the mountains, at high altitudes, breathing gas mixtures with a reduced oxygen content and an increased carbon dioxide content, etc.), in in fact, the mechanisms that ensure enhanced delivery of blood and oxygen to the heart muscle are constantly trained. The reserve capabilities of these mechanisms increase and, consequently, increase the resistance of the heart and body to the effects of adverse factors.
This circumstance is especially important. It is possible to improve the condition and capabilities of any regulatory mechanism only when increased demands are placed on the body. Not rest, but intense activity, systematic training, that is, periodic loads alternating with rest, is the only way to strengthen the mechanisms that regulate blood pressure, heart function and coronary blood flow.
Violation of the activity of the regulatory mechanisms described above can cause disorders of the blood supply to the heart muscle, sometimes leading to the appearance of foci of necrosis in it - myocardial infarction.
The possibility of the occurrence of neurogenic heart lesions in the experiment was proven by the prominent Russian pathologist A. B. Fokht. He discovered that when the vagus nerves are irritated, areas of necrosis of the heart muscle appear. When a drop of turpentine is introduced into the trunk of the vagus or sympathetic nerve innervating the heart, an electrocardiogram is recorded, characteristic of coronary circulatory disorders. Degeneration and death of the myocardium occurred after mechanical damage fibers of the cardiac nerves, as well as in case of chronic irritation or damage to areas of the central nervous system that regulate the function of the heart and blood vessels.
Myocardial damage can be reproduced in animal experiments using electrical stimulation vagus nerve using stimuli weaker than those that would slow the heart rate.
When probing the coronary vessels by introducing a thin and flexible polyethylene catheter into the arterial system (if its tailbone touches the mouth of the coronary artery), a clearly visible x-ray examination spasm of the coronary arteries, as well as electrocardiogram changes typical for coronary circulation disorders. Irritation of certain areas of the brain stem causes an increase in blood pressure and changes in the electrocardiogram, characteristic of coronary blood flow disorders.
Clinical experience also indicates the possibility of acute coronary insufficiency when affecting the central nervous system. For example, lesions at the base of the brain caused by acute disorders cerebral circulation, as well as lesions of the interstitial brain or brain stem, are often accompanied by coronary circulatory disorders.
It has been found that emotional and mental stress is accompanied by an increase in the amount of adrenaline, norepinephrine and related products (catecholamines) in the heart muscle, which leads to a significant increase in the energy of contractions and an increase in the heart’s need for oxygen. But if the heart and its coronary vessels are not sufficiently trained, they cannot provide a sharp increase in blood supply to the myocardium. In this case, phenomena of oxygen starvation of the heart muscle, i.e., coronary insufficiency, may occur. A disproportion appears between the myocardial oxygen needs and its supply to the heart with blood. This leads to so-called “angina pectoris”. Almost healthy person At the time of sudden physical or emotional stress, pain in the sternum may occur. In addition, some researchers admit the possibility of direct neurogenic spasm of the coronary vessels.
G.N. Aronova studied the magnitude of coronary blood circulation in the laboratory using electronic sensors implanted into the dog’s heart. In non-anesthetized animals sudden action irritants causing painful reactions and negative emotions (the appearance of fear), a decrease in the amount of coronary blood flow and signs of coronary insufficiency were often noted.
At the Institute of Experimental Pathology and Therapy, negative emotions were induced in male monkeys. For this purpose, the male was separated from the female with whom he had previously been together for a long time. The female was transplanted into an adjacent cage, where another male was placed. All this caused the animal, which remained alone, to scream, worry, fits of rage, and a desire to break the barrier. However, all attempts to connect with the female were in vain. The animal left alone witnessed the intimacy that arises between ex-girlfriend and a new partner. The electrocardiogram showed signs of acute coronary insufficiency. Attacks of violent rage and sharp emotional reactions alternated with periods deep depression. The state of oxygen starvation of the heart muscle intensified, and in a number of experiments the animals died from acute myocardial infarction. An autopsy confirmed the diagnosis. These cruel experiments are necessary in order to understand the mechanisms of heart attack in humans. Doesn't life sometimes bring us similar surprises? Are some situations that lead a person to a heart attack less ruthless, hopeless, and tragic?
It was also found in experiments that experimental neuroses monkeys, occurring under other circumstances, sometimes cause severe disturbances in coronary circulation. Neuroses were reproduced according to the classical Pavlovian method, similar to that used by M.K. Petrova in the experiments on dogs described above (by overstraining the processes of excitation or inhibition or “confusing” these processes). Such injury to the higher parts of the brain was accompanied by the appearance on the electrocardiogram of changes characteristic of coronary insufficiency and myocardial infarction.
A similar state arose even with changes in the usual daily rhythm of life, for example, with a shift in day and night regimes, when at night the monkeys were exposed to influences characteristic of daytime - feeding, exposure to light stimuli, etc., and during the day they were left in conditions of silence and darkness .
The same effect was caused by a regime in which the day was compressed to 12 hours with a 6-hour alternation of “day” and “night,” as well as a regime in which lighting and other stimuli characteristic of daytime influenced animals continuously day and night for many days. If these types of regimes continuously and randomly replaced each other - so that the animal did not have time to adapt to each of them, then after a few months a breakdown of the highest level occurred. nervous activity, often accompanied by coronary circulatory disorders. In some cases, myocardial infarction was detected.
In animal experiments, it was found that coronary circulatory disorders sometimes appeared with skull injuries and even with the introduction of air into the ventricles of the brain.
It is known that coronary circulation is influenced by signals acting through the higher parts of the brain (cortex cerebral hemispheres) by mechanism conditioned reflexes. Changes in blood flow in the heart muscle usually occur not only immediately at the moment of increased cardiac function with increased load, but also in advance, adapting the heart to the upcoming work. However, conditioned signals can not only increase, but also decrease coronary blood flow, which sometimes leads to acute disturbances of coronary circulation.
For remote control of coronary blood flow, a special device was developed, which was applied to one of the coronary arteries of the heart during preliminary surgery. The device was a loop controlled using nylon threads brought out through chest wall on the surface of the animal's body. A few days after the operation, when the wound had healed and the animal had become practically healthy, it was possible by tightening the loop to cause a sudden cessation of blood flow in one of the coronary arteries, and by loosening the loop to restore coronary blood flow.
This technique was used by a group of employees to study the effects of coronary circulatory disorders on the activity of internal organs and systems. After conducting a series of experiments on the same animal, it was then sufficient only to place the animal in the machine and touch the skin in the place where the loop was usually operated in order to cause changes typical of a disturbance in the coronary circulation.
Thus, the experimental setting in which coronary circulatory disorders were systematically reproduced becomes a conditioned signal, causing disturbances without tightening the loop.
Conditioned reflex disorders of coronary circulation can also occur in humans. Let's give a few examples. Once, during the performance of a symphony, the conductor suddenly felt a sharp attack of pain in the chest and had to leave the stage. Vasodilators eliminated the pain. And he continued to work. Then the conductor had to perform the same piece again. As he approached the musical phrase during which the first attack had previously occurred, he again had sharp pains behind the sternum. The conductor refused to perform this symphony, and the attacks stopped.
In another case, sharp pain in the chest occurred in an employee who was rushing to work. The attack was eliminated with vasodilators. But the next day, when he reached the same intersection, the attack of pain repeated. The man had to change the route he took to work, and the attacks stopped. In both cases, we are apparently talking about patients with hidden manifestations of coronary insufficiency, which were activated by the action of typical conditioned signals through the mechanism of a conditioned reflex.
We describe the results of an 8-month observation of a young patient in whom tense anticipation of an unpleasant procedure (injection, intravenous injection, etc.) caused a rise in blood pressure and changes in the electrocardiogram, characteristic of coronary circulatory disorders. It has been noted that in patients with myocardial infarction, talking about the situation and difficulties that preceded the occurrence of a heart attack can cause chest pain and changes in the electrocardiogram, indicating a violation of coronary circulation.
Changes in the electrocardiogram, characteristic of a state of acute coronary insufficiency, were observed in people under hypnosis, when they were instilled with feelings of fear and anger. In experiments conducted in the laboratory of P. V. Simonov, actors and researchers mentally reproduced unpleasant events. With imaginary fear, they experienced increased heart rate and changes in the electrocardiogram, characteristic of coronary blood flow disorders.
During continuous recording of the electrocardiogram in a working environment among train drivers, it was discovered that unexpected emergency situation causes sharp changes in the electrical activity of the heart, characteristic of oxygen starvation of the heart muscle.
Electrocardiogram changes typical for coronary insufficiency have been described in individuals in a state of fear or anxiety. Emotional stress(waiting for surgery, sport competitions and professional nervous tension) can cause changes in the electrocardiogram, indicating a violation of the coronary circulation.
It is known that acute disorders coronary circulation can develop at night during sleep against the background of mental and physical rest. Some researchers tend to see this as evidence of the coronary constricting effect of the vagus nerve, believing that night is the “kingdom of the vagus” (i.e., a state when the tone of the parasympathetic nervous system predominates). In reality, the situation is much more complicated. It has now been proven that sleep is not only rest, peace, and inhibition. During sleep, periods of rest are accompanied by the emergence of states of peculiar active activity of the brain, temporarily disconnected from the influences of the external environment. These are periods of “paradoxical sleep”, during which there is a kind of repeated reproduction and experience of daytime impressions, necessary for systematizing them and consolidating them in memory. Thus, a paradoxical dream is active process, often occurring with phenomena of shifts in the activity of internal organs, characteristic of strong emotional stress.
It has been suggested that coronary circulatory disorders that sometimes occur during sleep appear not against the background of rest, but during paradoxical sleep and the intense brain activity that occurs during it, during which daytime impressions and emotions are often reproduced and experienced again. This assumption was confirmed in a number of subsequent observations.
All of the above makes it clear that even in practically healthy individuals, overstrain of the nervous system and negative emotions can cause the phenomena of coronary insufficiency, i.e. oxygen starvation heart muscle. This can lead to a number of complications: changes in heart rhythm, interruptions (the appearance of extraordinary contractions), and sometimes fluttering of the heart muscle. Acute oxygen starvation of the heart muscle causes an attack of pain, typical changes in the electrocardiogram and other disorders. If impaired blood circulation is not restored, myocardial infarction may occur.
The reserve capabilities of the coronary circulation are so necessary for the body in emergency situations, sharply decrease with atherosclerosis (which often leads to a direct disruption of the blood supply to the heart muscle and other organs).
If coronary circulation is impaired, many diseases can develop that need to be treated promptly. For example, treatment of VSD must begin after the first signs of appearance and preferably in specialized clinics.
The heart is a muscular organ that, like all others, requires oxygen and nutrients. They reach it with the blood through the vascular network of the coronary or coronary arteries. These vessels received this name due to the peculiarities of their location, reminiscent of diverging different sides rays.
The myocardium (heart muscle) is fed by two coronary arteries: the right and left, each of which has several large and many small branches and supplies blood to the corresponding parts of the heart. Both coronary arteries originate from the aortic bulb, their mouths are located directly behind the cusps of the aortic valve, below the free edges of the semilunar valves, receiving the most blood not in systole, like all the others internal organs, and in diastole, when the heart is as relaxed as possible.
During contraction of the ventricles, the valves of the aortic valve block the inlets of the coronary arteries and almost completely stop the flow of blood through them, and when the ventricles relax, the semilunar valves close with the reverse flow of blood through the aorta, and blood from the aorta does not return to the left ventricle. In this case, the aortic sinuses fill with blood, and the entrance holes of the coronary arteries completely open.
The right coronary artery supplies most the myocardium of the right ventricle, part of the cardiac septum, as well as the posterior wall of the left ventricle. The remaining parts of the heart are supplied with blood by the left coronary artery, which is normally divided into two or three, less often four vessels, of which the largest clinical significance have circumflex and anterior descending branches. The latter is a direct continuation of the left coronary artery and goes to the apex of the heart. The circumflex branch departs from the left coronary artery in the area of its origin almost at a right angle and bends around the heart from front to back, in some cases along the posterior wall reaching the interventricular groove.
The artery from which the posterior descending branch arises determines the dominance of the blood supply to the heart muscle. If this is the right coronary artery, they speak of the right type of dominance of the blood supply (about 70%), if this branch is given by the circumflex artery - about the left (approximately 10%). In about 20% of situations, a variant of the so-called codominant blood supply to the heart muscle is noted, when both the right and circumflex coronary arteries take part in the formation of the posterior descending artery.
Dominance, by the way, reflects the source of blood supply to the artery supplying the atrioventricular (atrioventricular or Aschoff-Tavara) node.
The walls of the coronary arteries consist of three layers: the inner, represented by the endothelium, the middle, consisting of muscle elements, and the outer - adventitia. At rest, the rate of cardiac blood flow ranges from 0.8 to 0.9 ml/g per minute (this is 4% of total cardiac output), and at maximum physical activity increases four to five times. In general, this indicator is determined by heart rate, pressure level in the aorta, autonomic innervation and metabolic factors.
Venous outflow is predominantly (about 2/3) carried out through three veins of the heart: large, medium and small, which, merging with each other, form the coronary sinus that opens into the right atrium. The rest of the blood (1/3) flows through the thebesian and anterior cardiac veins.
