**7. Pathogenesis of development of aortic stenosis**

*Pathogenesis and changes in hemodynamics.* The narrowing of the aortic orifice by more than 50% creates a significant obstruction to the flow of blood from the left ventricle to the systemic circulation. With its narrowing, the minute volume decreases by 75%, although the area of the hole, which is even 10–20% of the norm, is compatible with life [29]. To ensure more or less sufficient systolic ejection in aortic stenosis, a number of compensatory mechanisms are activated. One of them is the lengthening of the systole of the left ventricle and the increase in pressure in the cavity of the left ventricle. As a result, a large pressure gradient

**Figure 11.** *Hemodynamic disturbances in aortic stenosis.*

is created between the aorta and the left ventricle, the latter is sharply hypertrophied without a significant increase in the cavity. The narrowing of the mouth of the aorta, like no other defect, is characterized by severe hypertrophy of the left ventricle. The minute volume remains normal for a long time or slightly decreases, the defect remains compensated. With a pronounced degree of defect or a decrease in the contractility of the left ventricle, the minute volume decreases significantly. In the latter case, the left ventricle dilates, it increases the end-diastolic pressure. This further leads to a rise in pressure in the left atrium, and then retrograde in the pulmonary veins. There is passive (venous) pulmonary hypertension, which does not reach large values and usually does not lead to severe hypertrophy of the right ventricle. Over time, congestion may occur in the systemic circulation. Coronary blood flow in aortic stenosis is reduced, especially during systole, which is explained by the influence of high intraventricular pressure and increased resistance in the thickness of the myocardium to coronary inflow. The main cause of coronary insufficiency is considered to be a disproportion between the increased need for nutrition of a hypertrophied muscle and its relatively low blood supply [30]. Additional factors are slow filling of the aorta, a decrease in systolic and mean pressure in the aorta (especially in the circumference of the valves) (**Figure 11**).
