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Rheumatic heart disease (RHD) is a chronic cardiac condition caused by rheumatic fever, an autoimmune response to group A β-hemolytic streptococcal (GAS) pharyngitis. It results in progressive valvular damage, most commonly affecting the mitral valve, followed by the aortic valve.
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GAS cross-reactive immune response in the heart: The heart is affected by antibodies (generated by B cells) against the group A carbohydrate binding to the surface of the valve and upregulating vascular cell adhesion molecule 1 (VCAM1) on the surface of the valve endothelium. The upregulation of VCAM1 allows T cells expressing integrin α4β1 (also known as VLA4) to adhere to the endothelium and to extravasate into the valve. The inner valve becomes infiltrated by T cells, primarily CD4+ T cells, and Aschoff bodies or granulomatous lesions form underneath the endocardium. Damage to the endothelium and infiltration of T cells into the valve remodels the valve structure, including the chordae tendineae, with malformation of the valve leading to regurgitation or stenosis of the valve. Breakdown of the valve releases collagen and results in further immune-mediated damage to the valve.
Carapetis, J., Beaton, A., Cunningham, M. et al. Acute rheumatic fever and rheumatic heart disease. Nat Rev Dis Primers 2, 15084 (2016). https://doi.org/10.1038/nrdp.2015.84
Most Commonly Affected Valves
| Valve | Frequency | Lesion |
|---|---|---|
| Mitral | ~100% in RHD | Stenosis ± regurgitation |
| Aortic | 20–30% | Regurgitation ± stenosis |
| Tricuspid | ~10% | Regurgitation |
| Pulmonary | <5% | Rarely involved |