Etiology and Key Theories of Development
Essential hypertension is a multifactorial pathology. Its onset is driven by a complex combination of genetic predisposition and adverse environmental influences. Modern pathology recognizes three main etiological theories:
- Neurogenic Theory (G.F. Lang, A.L. Myasnikov): A leading role is attributed to chronic psychoemotional strain, frequent stress, conflicts, and sustained attention demands.
- Renal-Body Fluid Theory (A. Guyton): Based on a hereditary defect in the mechanisms controlling blood pressure by the kidneys.
- Membrane Theory (Yu.V. Postnov, S.N. Orlov): Genetically determined impairment of cell membrane ion pumps leads to disturbed intracellular calcium and sodium ion exchange.
The disease exhibits polygenic inheritance and familial clustering. Significant risk factors include dietary factors (excess dietary sodium combined with potassium, calcium, and magnesium deficiencies), constitutional factors (overweight/obesity), and occupational hazards (constant noise, vibration, and the need to suppress negative emotions, particularly common among physicians and educators).
Neurogenic Pathogenesis and Stages of Dysregulation
According to the concepts of P.K. Anokhin, G.F. Lang, and A.L. Myasnikov, prolonged stress acts as the triggering mechanism. It reduces the inhibitory influence of the cerebral cortex on subcortical structures. As a result, a stagnant focus of excitation forms in the hypothalamo-pituitary system. This causes persistent hyperactivation of pressor autonomic centers, disturbances in protein and lipid metabolism, and, consequently, arteriolar spasm.
Blood pressure dysregulation progresses through two key stages:
- Initial Stage (Compensation): The initial rise in blood pressure is detected by baroreceptors in the carotid sinus and aortic arch. They stimulate the vasomotor center in the medulla oblongata, which temporarily returns parameters to normal.
- Progression (Adaptation Failure): With continuous stress, the load on baroreceptors increases until they become exhausted. Central regulation is disrupted, and the sympathoadrenal system (SAS) is actively recruited. An excess of catecholamines is released into the bloodstream, provoking an additional and now sustained rise in blood pressure.
Hemodynamic Mechanisms
The primary hemodynamic cause of essential hypertension is an inadequate increase in total peripheral vascular resistance. Peripheral arteriolar tone increases due to several factors:
- Vascular Wall Edema: Water and sodium retention cause an "imbibition effect," narrowing the vascular lumen and increasing its sensitivity to vasoconstrictors.
- Direct Vasoconstriction: The action of pressor agents such as angiotensin II, cortisol, prostaglandin F2α, and cyclic guanosine monophosphate (cGMP).
- Ionic Factor: Intracellular accumulation of calcium (Ca2+) within arteriolar smooth muscle cells stimulates their contraction.
- Deficiency of Vasodilators: A drop in the synthesis of depressor substances (prostaglandins E, A, D, prostacyclin, and bradykinin).
Renal Factor and the Vicious Circle of Hypervolemia
Spasm of the renal arterioles combined with sympathetic influences activates the juxtaglomerular apparatus. The renin-angiotensin-aldosterone system (RAAS) is triggered, further enhancing vasoconstriction. High RAAS activity leads to vasoconstrictive hypertension, whereas low activity leads to hypervolemic hypertension.
Simultaneously, the renal-body fluid mechanism is engaged. In response to rising pressure, the kidneys decrease sodium excretion. Water and sodium retention occur, expanding plasma volume and extracellular fluid volume (hypervolemia). This leads to increased venous return and cardiac output.
A vicious circle forms: plasma volume expansion stimulates the secretion of atrial natriuretic peptide. Attempting to compensate for hypervolemia, the peptide inhibits Na+/K+-ATPase to enhance renal sodium excretion. However, this mechanism acts systemically: sodium and water are retained within erythrocytes and arteriolar walls. As a result, vascular resistance paradoxically increases, and blood pressure continues to rise.