A 28-year-old woman with a history of acute pharyngitis 3 weeks ago now presents with joint pain, fever, and a new cardiac murmur. Which is the most common cardiac manifestation of acute rheumatic fever caused by Streptococcus pyogenes?

Explanation

## Cardiac Manifestations of Acute Rheumatic Fever **Key Point:** Acute rheumatic fever (ARF) is a post-streptococcal sequela that occurs 2–3 weeks after S. pyogenes pharyngitis. The **acute phase** and **chronic sequelae** produce different cardiac lesions. ### Acute Phase vs. Chronic Sequelae | Phase | Valve Involved | Lesion | Mechanism | | --- | --- | --- | --- | | **Acute (during ARF)** | Mitral > Aortic > Tricuspid | **Acute mitral regurgitation** | Inflammation → valve leaflet edema, papillary muscle dysfunction | | **Chronic (years later)** | Mitral | **Mitral stenosis** | Fibrosis, calcification, commissural fusion | ### Why Acute Mitral Regurgitation is Most Common in Acute Phase 1. **Inflammation of valve apparatus**: Acute carditis causes edema and inflammation of mitral leaflets and chordae tendinae. 2. **Papillary muscle dysfunction**: Acute inflammation impairs papillary muscle contraction, preventing proper valve closure. 3. **Leaflet incompetence**: The valve leaflets fail to coapt during systole, allowing blood to regurgitate into the left atrium. 4. **Reversibility**: Acute mitral regurgitation may improve with anti-inflammatory therapy (salicylates, corticosteroids) as inflammation resolves. **High-Yield:** The **acute** murmur is a **pansystolic (holosystolic) murmur** at the apex (Carey Coombs murmur or acute MR). This is different from the **diastolic murmur of mitral stenosis**, which develops years later due to chronic fibrosis. **Mnemonic:** **ARF Valve Sequence** = **A**cute **M**itral **R**egurgitation → **C**hronic **M**itral **S**tenosis (AMR → CMS) ### Why Other Valves Are Less Common - **Aortic regurgitation**: Can occur acutely but is less common than mitral involvement (mitral valve is affected in ~75% of ARF cases). - **Tricuspid stenosis**: Rare in acute ARF; tricuspid involvement is uncommon (~10% of cases). - **Mitral stenosis**: This is a **chronic** lesion that develops over years due to fibrosis and calcification, not during the acute phase. **Clinical Pearl:** A patient with a new **pansystolic murmur** 2–3 weeks after pharyngitis has **acute mitral regurgitation**. A patient with a **diastolic rumble** and a history of ARF years ago has **chronic mitral stenosis**. ### Jones Criteria Context Carditis (major criterion) includes: - Acute carditis: pericarditis, myocarditis, or endocarditis (acute valve dysfunction) - Chronic carditis: permanent valve damage (stenosis, regurgitation) The question specifically asks about the **most common manifestation**, which in the acute phase is acute mitral regurgitation. [cite:Harrison 21e Ch 297; Robbins 10e Ch 8]