Pathophysiology

Pathophysiology Study Guide

©2018 of 131 3.2 Valvular Function/Dysfunction There are four cardiac valves, in which there are two inflow, or atrioventricular valves, and two outflow, or semilunar valves. The atrioventricular valves are the tricuspid valve, situated on the right side and mitral valve on the left side of the heart. These function by closing during ventricular contraction known as systole so that the blood does not go back to the atrium; they open during diastole so that blood can enter from atria to ventricles. In contrast, the semilunar valves differentiate the ventricles from arterial trunks. At the time of diastole, the left aortic valve closes off the left side of the aorta, while the right pulmonary valve closes off the right ventricle of the heart from the pulmonary artery. When the four valves continue to work properly, the functioning of the heart is normal. In any disorder of cardiac valves, the blood does not flow properly when the orifice is open and may leak during the closed orifice. These abnormalities are known as stenosis and regurgitation respectively. Some of the clinical features of these valvular diseases are discussed below. Mitral Stenosis/Regurgitation Mitral stenosis generally affects women and is caused by rheumatic fever. The scarring starts after the initial attack and can usually be detected within the first 10 years, while major symptoms develop between ten and thirty years. Minor damage happens by way of small lesions developed at the leaflet edges. The normal opening of the valve ranges between 4 to 6 cm 2 at the time of diastole. Stenosis is developed when it reduces to less than 2 cm 2 and causes a murmur as the valve gets turbulent. However, at this level, the circulation is not effected significantly. When the sealing process further reduces the valve size, the pressure in the left atrium rises. When the size is reduced to 1.5cm 2 it causes symptoms like breathlessness during increased activity levels, and this phase is known as mild mitral stenosis. More pronounced symptoms and disability increase during the phase of moderate mitral stenosis, characterized by the size of the orifice of about 1 cm 2 . When the size further reduces between 0.5 and 0.7cm 2 , it is termed as severe mitral stenosis and the patient can suffer from congestive heart failure and severe pulmonary hypertension. Some disabilities caused by mitral stenosis are atrial fibrillation, left atrial thrombi with emboli, respiratory infection, pulmonary hemorrhage, pulmonary edema, and severe pulmonary hypertension. Mitral regurgitation may be developed due to rheumatic fever causing shrinking in the leaflet, a hole in the leaflet due to infective endocarditis, stretching or rupturing of chordae, malfunctioning of ventricular papillary muscle, dilation of left ventricle, and genetic deformation of the valve. The complications associated with mitral regurgitation include atrial fibrillation and sometimes emboli episodes. Treatment includes either repair or replacement of the valve. Aortic Stenosis/Regurgitation When the stenosis of the value occurs due to stiffness of the valve, it is known as valvular aortic stenosis. It generally affects people over the age of 60. In this case, the orifice is significantly reduced, or the valve does not open fully during systole. The mechanism of aortic stenosis includes a rise in adhesion causing fusion of three valve leaflets or stiffening and calcification of leaflets. It may be a genetic disorder where the three leaflets grow together and the central orifice space is limited. Non-genetic aortic stenosis is often the result of rheumatic fever. Further, calcific aortic stenosis is Achieve Page 49