Essential or secondary arterial hypertension

Systemic arterial hypertension is a disease characterized by an increase in pressure in the arterial blood vessels.

Physiology of arterial hypertension

This information is used to understand the diagnostic procedures and therapy for the treatment of arterial hypertension.

The pressure is determined by the ratio of two factors:

The arterial pressure values are obtained using the formula: P = F x R

P = pressure

F = River

R = resistance

The flow depends on cardiac output:

• Preload -> this is the venous return flow in the diastolic phase. It depends on several factors, but above all on the volume of blood,
• cardiac activity (pump efficiency);

The resistance R is given by the formula:

η = blood viscosity, L = vessel length, r is the mean vascular radius increased by four, it plays an important role in pathophysiology.

The arterial factors that affect pressure are:

• Circulating blood volume,
• cardiac activity,
• blood viscosity,
• Average arterial radius.

Circulating blood volume

The liquid component is bound to the sodium concentration.

If the amount of sodium increases:

• If more water accumulates in the extracellular space and blood plasma,
• Increases the circulating blood mass and thus also the pressure.

In the case of an increased sodium concentration, the arterioles become more sensitive to vasoconstrictive stimuli.

The regulation and concentration of sodium depends on:

• thirst mechanism -> the stimulation of thirst is influenced by the relative concentration of sodium,
• Secretion of ADH (antidiuretic hormone), which acts through the collection tubules of the kidney and causes water retention.

Cardiovascular system

Vasopressin increases peripheral resistance and this causes an increase in arterial pressure.

The relative variation in blood volume (total volume of blood) can also occur due to:

• Accumulation of the amount of blood in some areas.
• Increased tone of postcapillary venules, which affect the venous return of blood to the heart.

The veins are the main depot of the circulatory system. They contain over 50% of the blood.

If the muscle tone of the veins increases, the blood contained in them is reduced.

The result is a larger diastolic filling of the ventricles.

Cardiac activity

The smooth muscles of the heart are controlled by the autonomic vegetative system via:

• the vagus nerve,
• The sympathetic nervous system (which has an opposite effect).

The activity of the sympathetic nervous system consists in the release of the neuronal substances adrenaline and norepinephrine.

These cause:

1. Vasoconstriction
2. increase in heartbeats,
3. A greater contractile force of the heart.

The result is an increase in cardiac output and thus pressure.

The vagus nerve (parasympathetic system) has an opposite effect because it has a vasodilating effect.

Blood viscosity

Blood viscosity has a less important role in the formula.

The viscosity increases at:

• increase in the concentration of blood cells (for example, in polycythemia or multiple myeloma),
• Increase in plasma proteins.

Radius of the artery

This is the most important factor (it is increased to the fourth power). Anything that affects the diameter of small arteries has a dramatic effect on pressure.

There are three basic factors that affect the average radius of the arteries:

1. neurovegetative influences,
2. Angiotensin II,
3. Locally acting substances.

Neurovegetative influence

In the peripheral area, substances that have a vasoconstrictive effect and cause an increase in pressure are:

1. endothelial,
2. thromboxanes.

Substances that reduce this effect are:

1. Nitric oxide
2. Prostaglandins.

Classification of arterial hypertension

Arterial hypertension can be divided into:

1. Essential or primary, if there is no definite cause, but many risk factors are present. This type affects 95% of people who suffer from hypertension.
2. Secondary, if it is caused by an organ disease, for example of the kidneys, adrenal glands or the heart. It affects only 5% of people with hypertension.
3. Malignant hypertension is not caused by cancer, but exists when blood pressure is very high and causes organ damage. For example, swelling called papilledema can be provoked in the eye. In addition, it can lead to insufficiency of the kidney and heart.

Cardiovascular risk factors

• age (male > 55 years, female > 65 years);
• Smoke;
• Alcohol;
• Lack of physical exercise,
• Stress
• Dyslipidemia;
  • total cholesterol > 250 mg/dl or
  • LDL > 155 mg/dl or
  • HDL < 40 in men, < 48 in women
• Family history of early cardiovascular disease
  • 55 years with the man,
  • 65 years with the woman,
• Abdominal obesity (abdominal circumference > 102 cm in men and > 88 cm in women).

Causes of arterial hypertension

Endocrine hypertension

Thyroid problems

High blood pressure can be caused by hyperthyroidism (excess of thyroid hormones) and hypothyroidism (lack of thyroid hormones).

Hyperparathyroidism

The parathyroid glands regulate calcium and phosphorus levels in the body. When the production of parathyroid hormone is excessive, the amount of calcium in the blood also increases. The result is an increase in blood pressure.

Primary hyperaldosteronism

It is characterized by increased aldosterone production.

It is a benign adenoma of the adrenal cortex, consisting of:

1. cells of the zona glomerulosa (producer of aldosterone),
2. In 20-25% bilateral nodular hyperplasia of cortical cells (they are somewhat more difficult to detect),
3. In some cases, real tumor masses stand out.

The aldosterone leads to sodium absorption and potassium excretion, therefore it causes:

• An increase in extracellular fluid,
• A larger volume.

It also increases the sensitivity of smooth muscle cells in the artery walls to vasoconstriction stimuli of the sympathetic system.

Secondary hyperaldosteronism

The reduction in blood flow to the kidneys is perceived by the renin-angiotensin-aldosterone system and causes an increase in the level of aldosterone in the blood. This situation can be observed in:

• Renal artery stenosis
• Extracellular edema (fluid accumulation)
• The reduction in plasma sodium caused by diuretics leads to a decrease in plasma volume. The consequence is the activation of the mechanism of renal regulation.

Pheochromocytoma

It is a tumor that can be located:

• In 90% of cases in the adrenal medulla,
• In 10% of cases, in the amount of:
  • paraganglia (accumulation of neuroendocrine cells),
  • Heart
  • Bladder
  • Prostate
  • Ovaries (paraganglioma).

The chromaffin cells secrete adrenaline and norepinephrine, which lead to an increase in arterial blood pressure.

The doctor suspects pheochromocytoma in a young person who has intermittent hypertensive crises, therefore it is paroxysmal hypertension.

Pathophysiology

Increased intra-abdominal pressure stimulates the release of catecholamines.

This is done at:

1. forward bending of the upper body,
2. Sneeze
3. Strong laughter,
4. Abundant meal,
5. pressing during bowel movements and urination;
6. Deep palpation of the abdomen.

Symptoms

The possible symptoms are:

• Hypertension
• Headache
• Sweats
• Tachycardia
• Anxiety
• chest and abdominal pain,
• nausea and vomiting,
• Shortness of breath.

Cushing’s syndrome

It is characterized by excessive production of cortisol, which has a similar function to aldosterone.

Adrenogenital syndrome

It includes a group of congenital diseases, which is characterized by changes in the metabolism of sex hormones and occur in the adrenal cortex:

• androgens (zona reticularis);
• cortisol (zona fasciculata);
• Aldosterone (zona glomerulosa).

Adrenogenital syndrome is a condition that may be caused by the absence of any of the 5 enzymes involved in the synthesis of cortisol.

In this case, the hypothalamus and pituitary gland have decreased cortisol levels (negative feedback).

In this situation, they stimulate the production of CRH (corticotropin-releasing hormone) and ACTH (adrenocorticotropic hormone).

The result is:

• Overstimulation of the adrenal cortex.
• Increased production of substances that act like aldosterone and cause hypertension.

Acromegaly

This condition is characterized by increased production of somatotropic hormone (STH), which is generally caused by pituitary adenoma.

Patients have growth of the bones of the skull and hands.

In adulthood, the changes in body structures also affect soft tissues.

Hypertension, which is present in 20-50% of patients affected by acromegaly, causes:

1. An increase in plasma volume,
2. Increased sensitivity of vessels to angiotensin II.

Renal hypertension

Nephrovascular hypertension

The most common form of secondary hypertension is nephrovascular hypertension.

Renal artery stenosis leads to a decrease in blood circulation pressure in the kidney.

The result is the activation of the renin-angiotensin-aldosterone mechanism, which causes:

• An increase in plasma volume,
• Sodium retention.

Causes:

• In 90% of cases, atherosclerotic plaque formation in the elderly, often in both kidneys;
• In 10% there is a thickening of the arterial wall in the distal area (last part), which is then referred to as fibromuscular dysplasia.

Hypertensive nephropathy

All nephropathies can lead to hypertension:

1. Glomerulonephritis
2. Pyelonephritis
3. Diabetic nephropathy,
4. Analgesic nephropathy (renin-releasing tumors).

The development of hypertension can be the result of:

1. malfunction of afferent arterioles in the region of the juxtaglomerular apparatus;
2. The kidney is unable to produce substances such as prostaglandins and bradykinin, which lower blood pressure, or it produces too many substances with an effect that increases blood pressure;
3. Impairment of sodium excretion.

Other causes of hypertension

1. neurogenic hypertension: brain diseases such as trauma or neoplasms that cause an increase in intracranial pressure;
2. Polycythemia: causes an increase in viscosity, which can lead to hypertension;
3. Preeclampsia: Problem that may occur after the twentieth week of pregnancy. It is accompanied by various ailments of organs and systems, including the kidney. Occurs as proteinuria and edema, with seizures (in case of eclampsia), disseminated intravascular coagulation (DIC), etc.
4. Sleep apnea. Breathing is often interrupted during sleep, resulting in reduced oxygen uptake into the body.
5. Aortic coarctation: a stenosis below the aortic arch, downstream from the arteries that carry blood to the brain and arms. During physical examination, the doctor notices a missing or severely weakened pulse in the groin;
6. Side effect of drugs or other substances:
   • carbenoxolone,
   • Cortisone
   • Nasal spray
   • monoamine oxidase inhibitors (I-MAO),
   • contraceptives containing estrogens,
   • Discontinuation of blood pressure medication too quickly,

Signs and symptoms of arterial hypertension

Most people with high blood pressure have no signs or symptoms of it, even when high levels are reached.

According to a study by Di Tullio et all – (Istituto di Richerche Farmacologiche Mario Negri, Università di Milano, Italy), the following symptoms appear to be due to high blood pressure or hypertension therapy:

• Severe headache in the back of the head, they can be pulsating. Often they are more intense in the morning and when they wake up.
• Shortness
• Pulsating noises or tinnitus (humming) in the ears
• Vertigo
• Nosebleeds (rare)
• Fatigue

Complications and consequences of arterial hypertension

Complications may include:

1. Vascular
2. In the area of the organs concerned.

The most serious problems occur in the area of the cardiovascular system:

• Arteriosclerosis – in the large and medium arteries, especially in the coronary arteries. Their course becomes convoluted and the blood flow becomes turbulent. The consequences are damage to the endothelium, a dissection of the aorta, rupture of plaques or thrombus formation.
• Arteriolosclerosis (in the arterioles), with microbleeding, inflammation and fibrinoid necrosis (degeneration with accumulation of fibrinogen and other plasma proteins) in the affected organs.

The increase in blood pressure values leads to organic changes:

1. A difficult work of the left ventricle of the heart. The result is ventricular hypertrophy, dilation and decompensation. In addition, the heart works harder and consumes more O₂. Since coronary blood flow is reduced in atherosclerosis, ischemic heart disease occurs (risk of myocardial infarction).
2. In the area of the brain develop: thrombosis (due to atherosclerosis), bleeding (caused by the rupture of microaneurysms), these changes can lead to coma. Unfortunately, on CT you do not see such lesions, because they are very small and associated with changes in microcirculation.
3. The kidney is less supplied with blood due to arteriosclerosis and arteriolosclerosis. This can lead to irreversible damage to the kidney up to renal insufficiency. The increase in pressure in the capillaries of the renal globules leads to a change in blood flow in the renal corpuscles.
4. The eye is one of the most commonly affected organs. Over time, high blood pressure can cause damage to the blood vessels of the retina. In the microcirculation of the eye:
   • If the arteries narrow,
   • If arterio-venous crossovers form (the vein has a meandering course and runs perpendicular to the artery),
   • One can observe occlusions and infarctions, “cotton-wools” and “flame-like” inflammation are formed,
   • The most advanced is the papilla edema of the optic nerve with a risk of thrombosis. At this stage, hypertensive retinopathy can lead to visual impairment and also blindness.
5. Malignant (accelerated) hypertension means that diastolic blood pressure is very high, higher than 120-130 mmHg. Direct damage to the vascular endothelium is observed. The result is the release of endothelin-1, which causes vasoconstriction. In addition, renin production is not inhibited (as should be done with the increase in arterial pressure), but increases.

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