Hypertension

Hypertension is the clinical diagnosis when the average of at least two blood pressure values are unambiguously over 140/90 mmHg, and blood pressure measurements take place at rest, with at least 1 week between two measurements, at least 3 times, and after at least 10 minutes in rest.

Based on values expressed in mmHgs, more exact classification is also possible; the subgroups are the following:

• 1) optimal (systolic: <120; diastolic: <80),

• 2) normal (systolic: <130; diastolic: <85),

• 3) high-normal (systolic: 130-139; diastolic: 85-89),

• 4) mild hypertension (systolic: 140-159; diastolic: 90-99),

• 5) moderate hypetension (systolic: 160-179; diastolic: 100-109),

• 6) severe hypertension (systolic: ≥180; diastolic: ≥110)

The rule while assigning the individual cases is that when systolic and diastolic values belong to different groups the worse has to be taken into account. The background of clinically measured pressure values is the hemodynamic law that if the cross-section of a vessel reduces by the half, then vascular resistance against blood flow increases sixteen-fold. The so-called peripheral vascular resistance is formed by small arteries and arterioles, the so-called resistance vessels. The task of resistance vessels is to convert pulsating aortic type blood flow with great pressure fluctuation in a way that although the pressure of blood flow reaching the tissues becomes significantly lower compared to the aortic pressure, but it is still has constant pressure and continuous flow.

So, peripheral vascular resistance is mainly determined by the resistance vessels’ luminal diameter, and the lesser is determined by the resultant of vasoconstrictive and vasodilative factors affecting resistance vessels. Vasoconstrictors include angiotensin II, catecholamines, thromboxan, leukotrienes and endothelin. Vasodilators include prostaglandines, kinins and nitrogen monoxide.