Most patients are asymptomatic, and the valvular abnormality is discovered incidentally. In a minority of cases, patients complain of palpitations, dyspnea, or atypical chest pain. Auscultation discloses a midsystolic click, caused by abrupt tension on the redundant valve leaflets and chordae tendineae as the valve attempts to close; there is sometimes an associated regurgitant murmur. Although in most instances the natural history and clinical course are benign, approximately 3% of patients develop complications such as hemodynamically significant mitral regurgitation and CHF, particularly if the chordae or valve leaflets rupture. Patients with primary myxomatous degeneration also are at increased risk for the development of infective endocarditis (see later), as well as SCD due to ventricular arrhythmias. Stroke or other systemic infarctions may rarely occur from embolism of thrombi formed in the left atrium.
Rheumatic fever is an acute, immunologically mediated, multisystem inflammatory disease that occurs after group A β-hemolytic streptococcal infections (usually pharyngitis, but also occasionally infections at other sites, such as skin). Rheumatic heart disease is the cardiac manifestation of rheumatic fever. It is associated with inflammation of all parts of the heart, but valvular inflammation and scarring produce the most important clinical features.
The valvular disease principally takes the form of deforming fibrotic mitral stenosis; indeed rheumatic heart disease is essentially the only cause of acquired mitral stenosis. The incidence of rheumatic fever (and thus rheumatic heart disease) has declined remarkably in many parts of the Western world over the past several decades due to a combination of improved socioeconomic conditions, rapid diagnosis and treatment of streptococcal pharyngitis, and a fortuitous (and unexplained) decline in the virulence of many strains of group A streptococci. Nevertheless, in developing countries and economically depressed urban areas in the United States, rheumatic fever and rheumatic heart disease remain important public health problems.
Acute rheumatic fever is a hypersensitivity reaction classically attributed to antibodies directed against group A streptococcal molecules that cross-react with host myocardial antigens (see also Chapter 5). In particular, antibodies against M proteins of certain streptococcal strains bind to proteins in the myocardium and cardiac valves and cause injury through the activation of complement and Fc receptor–bearing cells (including macrophages). CD4+ T cells that recognize streptococcal peptides can cross-react with host antigens and elicit cytokine-mediated inflammatory responses. The characteristic 2-to 3-week delay in symptom onset after infection is explained by the time needed to generate an immune response; streptococci are completely absent from the lesions. Since only a small minority of infected patients develop rheumatic fever (estimated at 3%), genetic susceptibility to the development of the cross-reactive immune responses is likely in those affected. The deforming fibrotic lesions are the predictable consequence of healing and scarring associated with the resolution of the acute inflammation.
MORPHOLOGYAcute rheumatic fever ischaracterizedbydiscreteinflammatoryfociwithinavarietyoftissues.Themyocardialinflammatorylesions—calledAschoff bodies—arepathognomonicforrheumaticfever(