Primary and Secondary Forms
Based on etiology (origin), hypertension is divided into two major groups:
- Primary (essential, idiopathic) — no clear identifiable cause for the elevated blood pressure is found.
- Secondary (symptomatic) — a specific underlying pathology leading to elevated blood pressure is identified (e.g., kidney disease or an endocrine disorder).
Determinants of Blood Pressure
Blood pressure levels depend on a combination of three key factors:
- Tone of smooth muscle cells in the vascular wall (importantly, in certain forms of pathology, tone may not be elevated and can even be reduced).
- Cardiac output (minute volume of blood).
- Circulating blood volume (CBV).
Depending on the cardiac output, three hemodynamic variants are distinguished:
- Hyperkinetic: cardiac output is increased, while total peripheral vascular resistance (TPVR) is normal or decreased.
- Hypokinetic: cardiac output is decreased, but TPVR is significantly increased.
- Eukinetic: cardiac output is normal, TPVR is increased.
A mixed (systolic-diastolic) variant also occurs.
Classification by Initiating Pathogenetic Link
Depending on the initial mechanism, there are five main groups of arterial hypertension:
- Neurogenic (accounting for about 50% of cases). Divided into centrogenic and reflexogenic forms. Often resulting from organic brain damage (trauma, encephalitis, tumors, ischemia), leading to activation of the sympathetic nervous system and hormone release.
- Endocrine. Associated with adrenal pathology (pheochromocytoma, hyperaldosteronism), thyroid disorders (hyper- and hypothyroidism), or pituitary pathology (Cushing's disease).
- Hypoxic (metabolic). Develops due to oxygen deprivation in organs, most commonly in the brain and kidneys. Includes ischemic (e.g., renovascular hypertension), venous-congestive, and hypoxic forms.
- Hemic. Caused by alterations in the blood properties themselves—increased blood volume or viscosity (e.g., in polycythemia or hyperproteinemia).
- Mixed. Simultaneous or sequential engagement of multiple mechanisms (e.g., during allergic reactions).
Grades of Blood Pressure Elevation
To assess the severity of the condition, a classification based on blood pressure levels is used (values in mmHg):
| Category | Systolic BP | Diastolic BP |
|---|---|---|
| Optimal | < 120 | < 80 |
| Normal | < 130 | < 85 |
| High normal | 130–139 | 85–89 |
| Grade I (mild) | 140–159 | 90–99 |
| Grade II (moderate) | 160–179 | 100–109 |
| Grade III (severe) | > 180 | > 110 |
| Isolated systolic | > 140 | < 90 |
Risk factors contributing to the development of the pathology include a positive family history, renal and vascular pathologies (including aortic coarctation and Takayasu arteritis), endocrine disorders, metabolic syndrome, and psychophysiological traits (frequent stress, choleric personality type).