Blood pressure: pathogenesis and etiology

Blood pressure is a very significant diagnostic indicator of the state of the cardiovascular system. Some patients neglect this indicator in vain, because adequate blood supply to all organs and systems depends on it. Any deviation of the level of blood pressure from the norm determines changes in the body. Hypotension is dangerous by weakening the blood supply to the brain, kidneys and heart muscle, which together leads to collapse. A sharp jump in pressure upwards poses an even greater threat, since the integrity of the vessels is at risk, and the heart may not withstand the load.

Mechanisms of BP regulation

An important diagnostic indicator in the form of blood pressure regulates many systems in the human body. Such a well-coordinated mechanism includes several components that will not allow blood pressure to change dramatically and form a threat to life.

In the regulation of blood pressure, the most important thing is the correspondence of the volume of blood ejected by the heart to the caliber of the vessels where it enters. The study of hemodynamic issues made it possible to establish a formula for calculating blood pressure. So, this indicator is equal to the product of the minute volume of blood and the total peripheral resistance. These two multipliers are mediated by several factors.

The volume of blood ejected by the heart per minute is determined by:

• the power of a symbolic blow,
• heart rate,
• the total volume of blood in the body with an emphasis on extracellular fluid.

The resistance that the blood receives at the exit from the heart is formed due to a certain lumen of the vessels where the biological fluid is ejected, as well as the viscosity and stiffness of the same vessels. Each of these indicators, with its change, is reflected in the level of blood pressure

In fact, the regulation of blood pressure is a much more complex mechanism, about which many volumes have been written. For some systematization, the key points of regulation are divided into components for pressure stimulation and their inhibitory antagonists. They also highlight central and local management mechanisms, as well as feedback to improve the system.

A direct increase in blood pressure can be caused by direct influence through the sympathetic nervous system, which affects directly the heart. Local vasoconstriction is carried out through the release of biologically active substances such as catecholamines and prostaglandins.

React to low pressure and special reflex zones:

• carotid sinus,
• aortic.

They recognize low blood specific gravity and excite the parasympathetic nervous system, as well as release intravascular active substances: bradykinin and endothelial vasodilator.

A detailed study of all mechanisms of blood pressure regulation over many decades has made it possible to formulate an accurate concept of the etiopathogenesis of arterial hypertension. The schematic representation of this concept is led by etiological reasons.

The leading roles in the formation of the disease and its acquisition of a chronic course are played by:

1. burdened heredity,
2. malnutrition with excess salt,
3. lack of regular sports and any other physical activity.

Often arterial hypertension occurs in combination with atherosclerosis, so it is worth considering its etiology for hypertension.

Many works are devoted to the neurogenic theory of hypertension. Even Soviet scientists pointed to psycho-emotional stresses as stabilizers of arterial hypertension. Further studies have identified them not as the most important causes, but only as serious provocative mechanisms.

Arterial hypertension has several classifications according to various parameters. Pathogenetically, the following forms of the disease are distinguished:

• The hyperdrenergic type of hypertension is characterized by an increase in pressure without sudden jumps, but for a long time. The heart ejects blood with great intensity, but vascular resistance increases slightly. The clinical picture, which is based on such a pathogenesis, is expressed by a rapid heartbeat, a feeling of pulsation of the brain vessels, facial flushing, sweating, anxiety for no apparent reason.
• Hyperhydration or sodium-dependent form of hypertension in etiology has a large volume of fluid intake. It attracts water and table salt, which contains positively charged sodium, which increases the volume of fluid outside the cells. Such edema has pronounced swelling on the eyelids, the face looks puffy, the fingers go numb, there may be paresthesias. Diuretics have a pronounced therapeutic effect, bringing the specific mass of blood to the norm.
• The pathogenesis of calcium-dependent hypertension is associated with the direct content of calcium inside the cells. Approximately a fifth of patients suffer from this form of pathology, and an increased concentration of calcium is observed in their urine. Parathormone is involved in calcium metabolism, which is elevated in plasma in this pathology. The intracellular pool of the trace element is normalized when taking calcium channel blockers. The disease can be detected quite simply, since any instant salt with calcium immediately removes high blood pressure.

• Another pathogenetic form of hypertension is angiotensin-dependent. Frequent spasms of the arteries in such cases determine the increase in the diastolic index. Hypertension is characterized by a pronounced malignant course with damage to the fundus, frequent complications in the form of heart attacks or strokes.

The variety of pathogenetic forms of the disease is applicable only to primary hypertension.

Essential form of the disease

In the generally accepted world classification, arterial hypertension is divided into essential or primary and symptomatic.

In the genesis of the disease, the following key points are distinguished:

• Numerous epidemiological studies have revealed a direct relationship between essential hypertension and salt intake. This product contains the most important trace elements of a positive charge, namely potassium and sodium. They take part in the regulation of water metabolism. Sodium in the vascular bed attracts water to itself, thereby increasing the specific gravity of the blood, while potassium has the opposite properties. Naturally, when eating salty foods, blood pressure does not rise instantly; this takes more than one month or even a year. Statistics reflect the fact that African residents, whose daily salt intake is 2 times less than that of Europeans, do not suffer from arterial hypertension and do not acquire it with age. But the Japanese daily salt intake is higher than even the European one, and hypertension is 2 times more common there.

If there is a diet to adjust and limit the amount of salt, then blood pressure can change and become stable. It all depends on the individual susceptibility of the patient to the amount of salt in food.

• Hereditary predisposition largely determines the incidence of essential hypertension. Statistical data reflect the onset of the disease in persons of mature age spontaneously, however, in the anamnesis of patients, close relatives had hypertensive pathology. Hypertension can also be passed down through generations, although the exact mechanisms by which high blood pressure genes are mediated have not been established. Some studies reflect that patients predisposed to hypertension have fewer nephrons in the kidneys, and sodium reabsorption is also more intense, which increases the specific mass of the blood.

• Special attention deserves the theory of the scientist Folkov, which has become widespread and correctly explains many points of pressure regulation. The scientist determined that the essential form of hypertension is associated with excessive activation of the sympathetic-adrenal organization. This effect is realized by an increase in the volume of blood passing through the heart per minute, as well as in the formation of additional resistance from the vascular bed. The sympathetic-adrenal system is not always in an excited state: two etiological reasons lead to this - constant stressful situations, as well as a genetically determined dysfunction of the higher nerves involved in the regulation of pressure. This system acquires excessive activity with age, when some endocrine glands undergo involution, and the adrenal glands acquire guiding influence.
• The pressure is also regulated by a complex renin-angiotensin-aldosterone system, a point on the zones and biological substances are produced in the kidneys and in the vessels themselves. Thus, renin is elevated in a large number of patients who are diagnosed with arterial hypertension for the first time. Hyperrenin pathology proceeds quite malignantly and torments its patients. The therapeutic effect of angiotensin-converting enzyme inhibitors confirms the direct involvement of the reninren-aldosterone system in the regulation of blood pressure. However, in the elderly, plasma renin is reduced, the cause of which has not been established.

• Obesity and arterial hypertension also act as two interrelated pathologies. Each acquired kilogram of fat mass is reflected in an increase of several units of the symbolic indicator of pressure. World statistics show that more than half of patients with coronary insufficiency are overweight in combination with hypertension. It is obesity and an unbalanced diet, together with bad habits and physical inactivity, that become predictors of high blood pressure. Despite the promotion of a healthy lifestyle, overweight is increasingly observed among the population. For example, in the United States, one in three people is obese or close to it. Naturally, this problem is personal for each patient, but medical care should not leave it unattended. In addition, type 2 diabetes mellitus often joins the duet of arterial hypertension and obesity. The latter reduces all types of cellular metabolism, which contributes to an even greater increase in body weight and the accumulation of adipose tissue.

Other theories of pathogenesis

Many theories of the pathogenesis of arterial hypertension often mislead patients and potential patients. But it is possible to understand them if in each theory we single out the main mechanism on which all regulatory forces rely. Many theories are complicated only at first glance, since each author has his own clinical experience and research base.

You should not strictly adhere to one of the theories, since the individuality of each person is also reflected in the pathogenesis of arterial hypertension.

• The theoretical views of the Soviet scientists Lang and Myasnikov are reflected in the conceptual forms of the initiation of hypertension by reducing the inhibitory effect on the cerebral cortex. The absence of pressor influence on some subcortical centers is accompanied by their overexcitation. Clinically, this is reflected by vasoconstriction, and, therefore, an increase in pressure. The vascular bed of the kidneys also falls under the influence, and these organs are actively involved in the regulation of blood pressure. Scientists have identified the cause of the inhibitory effect on the cortex in its constant stimulation as a result of stressful situations. Prolonged nerve impulses kill the tone of the subcortical centers, which makes it impossible for them to perform their functions. The pathological state of the nervous system was put forward by many authors as the main factor in the occurrence of arterial hypertension, but it was Lang who found a scientific and practical explanation for this. The scientist Myasnikov supplemented this theory and pointed out the connection between nervous regulation and humoral factors.
• Fundamentally different views are presented in the theory of the scientist Gauthoni. The initiation of hypertension is directly related to a decrease in the excretory function of the kidneys, namely the excretion of sodium and water. Pressure even in a normal person during the day due to many factors. But if the volumetric mechanism of pressure regulation is weakened in the kidneys, then water is retained in the body. She stays directly in the bloodstream, creating a state of hypervolemia. The volume of blood has a high specific gravity, which means that it creates excessive pressure on the vascular bed. Pressor hormones in such cases cannot act and lower blood pressure, since it is necessary to remove the water component that creates pressure. Hypertension in such cases is persistent, so the use of diuretics should be systemic. Excess salt in the daily diet is the main etiology of a dangerous disease with high blood pressure, according to an eminent scientist.

• Postnov and Orlov proposed a hereditary weakness of cellular pumps for the initiation mechanism of hypertension and proved that such a theory exists. First of all, this concerns the smooth muscle cells of the vascular wall, where calcium and sodium pumps do not function quite correctly. Positively charged calcium is removed from the cells through the endoplasmic reticulum, and if the pump is not working, it accumulates inside the cells, preventing sodium from penetrating into the intercellular space. The high content of such positively charged ions inside the cells of smooth muscle tissue causes vasospasm and their sensitivity to pressor factors of pressure regulation. This theory has opened a new era in the study of the mechanisms of hypertension. From that moment, genetic studies began to be carried out to establish DNA regions that cause membrane weakness in hypertension. The etiology and pathogenesis of the disease have become more detailed and relevant to reality.

Currently, physicians and scientists adhere to the synthesized theory. It is a complex of the above-described opinions of world scientists and does not exclude any named item. Naturally, stress and psycho-emotional overload, as well as developing obesity and physical inactivity, can contribute to the implementation of a hereditarily mediated weakness of the membranes of smooth muscle cells.

Pathogenetic complications of hypertension

The multifactorial pathogenesis of the disease mediates many complications of hypertension. They are mainly observed from the side of the heart, but hypertension and kidneys are affected, especially if they have concomitant retinopathy.

Among the complications are:

1. With acquired increased pressure of a systemic nature, the heart muscle is at risk in the first place. She receives the main blow, so that hypertrophy of both ventricles occurs. The lack of treatment causes the growing weakness of this chamber, the expanded cavity is not able to perform its function in its former volume. There is heart failure or angina on the background of coronary heart disease. An enlarged myocardium requires more oxygen, and against the background of increased pressure this is impossible to do, so the heart begins to inevitably suffer. Left ventricular hypertrophy is detected even during a general examination of the patient, when an increased push in the chest is detected in the systole phase. Auscultatory heart murmurs can be heard due to blood regurgitation, as well as additional tones. It is necessary to prevent the complications of hypertension in the form of cardiac pathology due to the fact that any form of heart failure can suddenly lead to a heart attack or cerebral hemorrhage.
2. Increased pressure is reflected in the smallest afferent and efferent arterioles of the renal glomeruli. They show sclerotic changes, so that the excretory function of the kidneys is reduced. A large amount of protein is excreted in the urine, as well as red blood cells. One tenth of chronic hypertensive patients die due to kidney failure.
3. The nervous system also takes a hit due to increased pressure. The pathogenesis of the disease neurologically upsets the functionality of the retina and central nerves. It is the smallest vessels of the visual bottom that reflect how far hypertension has gone in its development. The optic nerve reacts to hypertension by the appearance of hemorrhage in it, swelling, accumulation of exudate. The vision of patients falls, patients hardly distinguish the details of objects and practically do not see at dusk. The progression of the disease leads to blindness. Symptoms of a neurogenic disorder are manifested in the form of headaches with predominant localization in the occipital region that occur in the morning or after lunchtime. Pain may be replaced by dizziness, vibrating tinnitus, fainting. The etiology of some forms of encephalopathy lies in arterial hypertension. Increased pressure in such cases is difficult to correct, the consciousness of patients is clouded, the pressure inside the skull increases and the full clinical picture of retinopathy unfolds. Pathological conditions are observed in the complex, focal symptoms occur extremely rarely. Neurological disorders of any one function are associated with local cerebral hemorrhage or infarction.
4. The etiology and pathogenesis of high blood pressure determine two mechanisms of ischemic brain damage. In combination with hypertension, atherosclerosis is usually present, which gives thrombus formation. In another case, hypertension determines the formation of the smallest aneurysms, the rupture of which gives rise to hemorrhage.

Hypertensive conditions are extremely common throughout the world. Approximately one third of the world's inhabitants suffer from high blood pressure in adulthood, and by the age of 60, the disease affects every second. Knowledge of the pathogenesis of the disease will make it possible to resist this scourge of modern medicine. Not only doctors should be educated in this problem, competent patients will be a real gift for the treating specialist. Each person can independently listen to himself and suspect some symptoms that are subject to further diagnosis.