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Disorders of Cardiac Function

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tissues to produce an autoimmune response through a phenomenon called molecular mimicry 33 (see Chapter 16). Although only a small percentage of persons with untreated GAS pharyngitis develop RF, the incidence of recurrence with a subsequent untreated infection is sub- stantially greater. These observations and more recent studies suggest a genetic predisposition to development of the disease. 6 Clinical Features. Rheumatic fever can manifest as an acute, recurrent, or chronic disorder. The acute stage of rheumatic fever includes a history of an initiating streptococcal infection and subsequent development of discrete inflammatory lesions seen on histopatho- logic exam within the connective tissue elements of the heart, blood vessels, joints, and subcutaneous tis- sues. Within the heart these lesions are called Aschoff bodies. 6 The recurrent phase usually involves extension of the cardiac effects of the disease. The chronic phase is characterized by permanent deformity of the heart valves. Chronic rheumatic heart disease usually does not appear until at least 10 years after the initial attack, sometimes decades later. Most persons with rheumatic fever have a history of sore throat, headache, fever, abdominal pain, nau- sea, vomiting, swollen glands (usually at the angle of the jaw), and other signs and symptoms of streptococcal infection. Other clinical features are related to the acute inflammatory process and the structures involved in the disease process. The course of the disease is character- ized by a constellation of findings that includes cardi- tis, migratory polyarthritis of the large joints, erythema marginatum, subcutaneous nodules, and Sydenham chorea. 6,35 Acute rheumatic carditis , which complicates the acute phase of rheumatic fever, is a pancarditis involv- ing all three layers of the heart. In some cases, the myo- cardium can be so severely affected that the resulting cardiac dilation causes functional mitral insufficiency and even heart failure. Clinical features include pericar- dial friction rubs, arrhythmias, and a new heart mur- mur. Usually, both the pericarditis and myocarditis are self-limited manifestations of the acute stage of the rheu- matic fever. Involvement of the endocardium and val- vular structures produces the permanent and disabling effects of disease. Although any of the four valves can be involved, the mitral and aortic valves are affected most often. During the acute inflammatory stage, the valvular structures become red and swollen, and small vegeta- tive lesions develop on the valve leaflets. These changes gradually proceed to the development of fibrous scar tis- sue, which tends to contract and cause permanent defor- mity of the valve leaflets and shortening of the chordae tendineae. In some cases, the edges or commissures of the valve leaflets fuse together as healing occurs. Polyarthritis is the most common manifestation of rheumatic fever. It may be the only major diagnostic criterion in adolescents and adults. The arthritis most often involves larger joints, particularly the knees and ankles, and is almost always migratory, affecting one joint and then moving to another. Untreated, it lasts

approximately 4 weeks, but it typically responds within 48 hours to salicylates. Polyarthritis usually heals completely. Erythema marginatum lesions are commonly seen on the trunk or inner aspects of the upper arm and thigh, but never on the face. These transitory skin lesions occur early in the course of a rheumatic attack and usu- ally with subcutaneous nodules, which are hard, pain- less, and freely movable masses that usually occur over the extensor muscles of the wrist, elbow, ankle, and knee joints. Chorea (i.e., Sydenham chorea) is the major central nervous system manifestation of rheumatic fever. It is rarely seen after 20 years of age. The onset is typically insidious: the child often is fidgety, cries easily, drops things, and walks clumsily. The choreiform movements are spontaneous, rapid, jerking movements that interfere with voluntary activities. Facial grimaces are common, and speech may be affected. The chorea is self-limited, usually running its course within a matter of weeks or months, but recurrences are not uncommon. Diagnosis. Diagnosis of acute rheumatic fever is made using serologic evidence of GAS infection along with a consideration of the cardinal symptoms and clinical manifestations or Jones criteria, which were developed to assist in standardizing the diagnosis of RF. Serologic tests for streptococcal antibodies (antistreptolysin O and antideoxyribonuclease B) can provide retrospective confirmation of recent streptococcal infection in persons thought to have rheumatic fever. Laboratory markers of acute inflammation include an elevated white blood cell count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). The Jones criteria divide the clinical features of RF into major and minor categories, based on prevalence and specificity. 34,36 The presence of two major signs (i.e., carditis, polyarthritis, chorea, erythema marginatum, and subcutaneous nodules) or one major and two minor signs (i.e., arthralgia, fever, elevated ESR, CRP, or leukocyte count and prolonged PR interval on EKG), accompanied by evidence of a preceding GAS infection (antistreptolysin 0 antibodies, positive throat culture for GAS) indicates a high prob- ability of RF. The use of echocardiography has enhanced the under- standing of both acute and chronic RHD. It is useful in assessing the severity of valvular stenosis and regurgi- tation, chamber size and ventricular function, and the presence and size of pleural effusions. Doppler ultraso- nography may be useful in identifying cardiac lesions in persons who do not show typical signs of cardiac involvement during an attack of RF. 34,36 Treatment and Prevention. It is important that GAS infections be promptly diagnosed and treated to prevent RF. The gold standard for detecting a GAS infection is a throat culture. However, it takes 24 to 48 hours to pro- duce a result, which may delay treatment. Rapid tests for direct detection of GAS antigens are highly specific for GAS infection but are limited in terms of their sensi- tivity (i.e., the person may have a negative test result but