Which of the following cardiac lesions is the MOST common valvular involvement in acute rheumatic fever?

Explanation

## Valvular Involvement in Acute Rheumatic Fever **Key Point:** Mitral regurgitation (MR) is the most common valvular lesion in acute rheumatic fever (ARF), occurring in >65% of cases with carditis. ### Frequency of Valve Involvement | Valve | Frequency in ARF | Pattern | |-------|------------------|----------| | Mitral | 65–75% | Regurgitation > Stenosis | | Aortic | 20–30% | Regurgitation > Stenosis | | Tricuspid | 5–10% | Regurgitation (rare) | | Pulmonary | <1% | Very rare | ### Why Mitral Regurgitation Dominates 1. **Acute phase:** Mitral valve leaflets swell and fail to coapt → acute MR 2. **Chronic sequelae:** Repeated inflammation → fibrosis, calcification, and stenosis 3. **Left atrial volume load:** MR is better tolerated initially than stenosis **High-Yield:** In acute carditis, mitral regurgitation is present; in chronic RHD, mitral stenosis develops (the hallmark of chronic rheumatic heart disease). **Clinical Pearl:** The progression from acute MR to chronic mitral stenosis takes years and reflects the natural history of recurrent Group A Streptococcal (GAS) infections and repeated inflammatory insults. ### Aortic Involvement - Aortic regurgitation occurs in ~20–30% of ARF cases - Usually occurs **in combination with mitral disease**, not in isolation - Aortic stenosis is rare in acute ARF (develops only in chronic RHD after decades) **Warning:** Do not confuse acute MR (dominant in ARF) with chronic mitral stenosis (dominant in established RHD). The question asks about acute rheumatic fever, not chronic rheumatic heart disease.