How does rheumatic fever present on echocardiography (echo)?

Echocardiographic Findings in Rheumatic Fever

Rheumatic fever presents on echocardiography primarily with pathological mitral and/or aortic valve regurgitation, with specific Doppler criteria and morphological changes that distinguish it from physiological regurgitation. 1

Key Doppler Findings in Rheumatic Valvulitis

Echocardiography with Doppler is essential for evaluating patients with suspected rheumatic fever, as it can detect both clinical and subclinical carditis. The 2015 American Heart Association guidelines provide specific criteria for pathological valve regurgitation:

Pathological Mitral Regurgitation (all 4 criteria must be met):

• Visible in at least 2 views
• Jet length ≥2 cm in at least 1 view
• Peak velocity >3 m/s
• Pansystolic jet in at least 1 envelope 1

Pathological Aortic Regurgitation (all 4 criteria must be met):

• Visible in at least 2 views
• Jet length ≥1 cm in at least 1 view
• Peak velocity >3 m/s
• Pan diastolic jet in at least 1 envelope 1

Morphological Findings on Echocardiogram

In addition to Doppler evidence of regurgitation, several structural abnormalities may be observed:

Acute Mitral Valve Changes:

• Annular dilation
• Chordal elongation
• Chordal rupture resulting in flail leaflet with severe mitral regurgitation
• Anterior (or less commonly posterior) leaflet tip prolapse
• Beading/nodularity of leaflet tips 1

Aortic Valve Changes:

• Irregular or focal leaflet thickening
• Coaptation defect
• Restricted leaflet motion
• Leaflet prolapse 1

It's important to note that early in acute rheumatic fever, valve morphology may appear normal while Doppler still shows pathological regurgitation 1. In approximately 25% of patients with rheumatic carditis, focal valvular nodules may be observed on the body and tips of the mitral valve leaflets, which typically disappear during follow-up 2.

Prevalence and Distribution of Valve Involvement

Mitral valve involvement is most common in rheumatic carditis, with mitral regurgitation being the predominant finding (84-94% of cases) 2. Isolated aortic regurgitation is less common (approximately 4.4%), while combined mitral and aortic regurgitation occurs in about 13% of cases 3.

Mechanisms of Valve Regurgitation

The primary mechanisms of mitral regurgitation in rheumatic carditis include:

• Ventricular dilation (54-74% of cases)
• Restriction of leaflet mobility (37% of cases)
• Valve prolapse (9-16% of cases)
• Annular dilation (12-21% of cases) 2

Subclinical Carditis

Subclinical carditis refers to cases where there are no auscultatory findings of valvar dysfunction, but echocardiography/Doppler reveals mitral or aortic valvulitis 1. This is an important concept as it occurs in approximately 43% of patients with acute rheumatic fever who have no audible murmur 3.

Clinical Implications and Recommendations

The American Heart Association makes several recommendations regarding echocardiography in rheumatic fever:

1. Echocardiography with Doppler should be performed in all cases of confirmed and suspected acute rheumatic fever
2. Serial echocardiography/Doppler studies should be considered in any patient with diagnosed or suspected acute rheumatic fever
3. Echocardiography/Doppler should be used to assess for carditis in the absence of auscultatory findings, particularly in moderate to high-risk populations
4. Normal echocardiography/Doppler findings should exclude the diagnosis of carditis in patients with a heart murmur otherwise thought to indicate rheumatic carditis 1

Pitfalls and Caveats

When interpreting echocardiographic findings in suspected rheumatic fever, be aware of these potential pitfalls:

1. Physiological valve regurgitation can be detected by Doppler in normal individuals and must be distinguished from pathological regurgitation 1
2. The degree of valvular regurgitation considered "normal" increases with age 1
3. Loading conditions at the time of echocardiography can affect the assessment of regurgitation 1
4. Other conditions like viral myocarditis, endocarditis, and systemic lupus erythematosus can cause valve regurgitation and must be excluded 1
5. Congestive heart failure in rheumatic carditis is invariably associated with hemodynamically significant valve lesions, not isolated myocarditis 2

By understanding these echocardiographic findings and applying the established criteria, clinicians can more accurately diagnose and monitor rheumatic fever, potentially improving outcomes through early detection and appropriate management.