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Circulatory Function

U N I T 5

have a streptococcal infection). Thus a negative antigen test result should be confirmed with a throat culture when a streptococcal infection is suspected. 36 Treatment of acute RF is designed to control the acute inflammatory response and prevent cardiac complica- tions and recurrence of the disease. During the acute phase, antibiotics, anti-inflammatory drugs, and selec- tive restriction of activities are prescribed. Penicillin, or another antibiotic in penicillin-sensitive patients, is the treatment of choice. 36 Salicylates and corticosteroids can be used to suppress the inflammatory response, but should not be given until the diagnosis of RF is con- firmed. Surgery, including valve repair and replacement, is indicated for chronic rheumatic valve disease and is determined by the severity of the symptoms or cardiac dysfunction. Persons who had RF are at high risk for recurrence after subsequent GAS throat infections. Penicillin is the treatment of choice for secondary prophylaxis, but sul- fadiazine or erythromycin may be used in those who are allergic to penicillin. The duration of prophylaxis depends on whether residual valvular disease is present or absent. It is recommended that persons with persis- tent valvular disease receive low-dose antibiotic prophy- laxis for at least 5 years after the acute episode of RF or until age 21 years if there is no evidence of carditis. 35 Valvular Heart Disease The past several decades have brought remarkable advances in the treatment of valvular heart disease. This is undoubtedly due to improved methods for noninva- sive monitoring of ventricular function, improvement in prosthetic valves, advances in valve reconstruction, and the development of guidelines to improve the timing of surgical interventions. 37 Nevertheless, valvular heart disease continues to produce considerable mortality and morbidity. Hemodynamic Derangements The function of the heart valves is to promote unidi- rectional flow of blood through the chambers of the heart. Dysfunction of the valves can result from a num- ber of disorders including congenital defects, trauma, ischemia, degenerative changes, and inflammation. Although any of the heart valves can become diseased, the most commonly involved are the mitral and aortic valves. Disorders of the pulmonary and tricuspid valves are less common, probably because of the low pressure in the right side of the heart. The heart valves consist of thin leaflets of tough, flex- ible, endothelium-covered fibrous tissue firmly attached at the base to the fibrous valve rings (see Chapter 17). The leaflets of the heart valves may be damaged or inflammed, which can deform their line of closure. Healing of the valve leaflets is associated with increased collagen content and scarring, causing the leaflets to shorten and stiffen. Another problem is that the edges of the healing valve leaflets can fuse together so that the valve does not open or close properly.

Thickened and stenotic valve leaflets

Retracted fibrosed valve leaflets

A

B

FIGURE 19-13. Disease of the aortic valve as viewed from the aorta. (A) Stenosis of the valve opening. (B) An incompetent or regurgitant valve that is unable to close completely.

Two types of mechanical disruption occur with val- vular heart disease: narrowing of the valvular opening, so it does not open properly, and distortion of the valve, so it does not close properly (Fig. 19-13). Stenosis refers to a narrowing of the valve orifice and failure of the valve leaflets to open normally (Fig. 19-14). Significant narrowing of the valve orifice increases the resistance to blood flow through the valve, converting the normally smooth laminar flow to a less efficient turbulent flow. This increases the work and volume of the chamber emptying through the narrowed valve—the left atrium in the case of mitral stenosis and the left ventricle in aor- tic stenosis. An incompetent or regurgitant valve does not close properly, thereby permitting the backward flow of blood to occur when the valve should be closed. When the aortic valve is affected, blood flows back into the left ventricle during diastole. When the mitral valve is affected, blood flows back into the left atrium dur- ing systole. Stenosis and regurgitation can occur in pure forms, or these abnormalities may exist in the same valve. Alterations in hemodynamic function that accom- pany aortic and mitral valve stenosis and regurgitation are illustrated in Figure 19-15.

FIGURE 19-14. Gross pathology of rheumatic heart disease: aortic stenosis. Fused aortic valve leaflets and opened coronary arteries from above. (From the Centers for Disease Control and Prevention Public Health Images Library No. 848. Courtesy of Edwin P. Ewing, Jr.)