CHAPTER 35 Valvular Heart Disease
2 Describe common findings of the history and physical examination in patients with valvular heart disease
3 Which tests are useful in the evaluation of valvular heart disease?
Echocardiography is recommended for:
7 How does a normal pressure-volume loop appear?
The AB segment is ventricular filling, BC is isovolumic contraction, CD is ejection, and DA is isovolumic relaxation. D point represents the aortic valve closing, A the mitral valve (MV) opening, B the MV closing, and C the aortic valve opening. Stroke volume through the aortic valve is the distance between C and D points. End-systolic volume can be measured at the D point, and end-diastolic volume can be measured at the B point. The end-systolic pressure–volume relationship slope is a measure of contractility. A horizontal-clockwise shift of the slope represents a decrease in contractility (Figure 35-1).
9 How can be the severity of aortic stenosis characterized by echocardiography?
AS severity is graded on the basis of a variety of hemodynamic and natural history data using definitions of valve area, mean pressure gradient, and aortic jet velocity (Table 35-1).
Mild | Severe | |
---|---|---|
Aortic valve area (cm2) | >1.5 | <1 |
Mean aortic valve pressure gradient (mm Hg) | <25 | >40 |
Aortic jet velocity (m/s) | <3 | >4 |
11 How are the compensatory changes in the left ventricle represented by a pressure-volume loop?
Because of the AS, the left ventricle is working with higher intraventricular pressures to generate a normal stroke volume. The higher systolic wall tension initiates myocardial thickening and LV hypertrophy (LVH). The hypertrophied left ventricle has increased contractility to accomplish the pressure work (Figure 35-2). LVH decreases the wall tension during systole, improving the relationship of systolic work to oxygen demand. As the AS increases, LV systolic pressure increases to the level at which LVH cannot normalize the wall tension. At this point the heart starts dilating, resulting in systolic dysfunction and decreasing CO.