What is the clinical significance of annulus reversus in echocardiography (echo) and how is it managed?

Annulus Reversus in Echocardiography: Clinical Significance and Management

Annulus reversus is a key diagnostic finding in constrictive pericarditis, characterized by higher medial (septal) e' velocity compared to lateral e' velocity on tissue Doppler imaging, which helps differentiate constrictive pericarditis from restrictive cardiomyopathy and requires pericardiectomy for definitive treatment in symptomatic cases. 1, 2

Definition and Mechanism

• Annulus reversus refers to the reversal of the normal pattern of mitral annular tissue Doppler velocities, where the medial (septal) e' velocity exceeds the lateral e' velocity (medial e':lateral e' ratio >1), contrary to the normal pattern where lateral e' is typically higher than medial e' 1, 2
• This phenomenon is primarily observed in constrictive pericarditis and serves as a distinguishing echocardiographic feature from restrictive cardiomyopathy, where the normal relationship (lateral e' > medial e') is preserved 1, 3
• The physiological basis involves the tethering effect of the adherent pericardium on the lateral LV wall, which limits lateral annular motion more than medial annular motion in constrictive pericarditis 2

Clinical Significance

Diagnostic Value

• Annulus reversus is a critical diagnostic marker that helps differentiate constrictive pericarditis from restrictive cardiomyopathy, which can otherwise present with similar clinical and hemodynamic features 1, 3
• In constrictive pericarditis, the medial e':lateral e' ratio is typically >1 (annulus reversus), while in restrictive cardiomyopathy, the ratio is <1 (normal pattern with reduced velocities) 2, 3
• This finding is part of a constellation of echocardiographic features in constrictive pericarditis, including respiratory variation in mitral and tricuspid inflow velocities, septal bounce, and preserved or enhanced early diastolic mitral annular velocities 3

Prognostic Implications

• The presence of annulus reversus correlates with the severity of constrictive physiology and helps predict the potential benefit from pericardiectomy 3
• Following successful pericardiectomy in clinical responders, there is typically a 50% reduction in the incidence of annulus reversus, indicating resolution of constrictive physiology 3
• Persistent annulus reversus after pericardiectomy may suggest incomplete pericardial removal or irreversible myocardial involvement 3

Relationship with E/e' Ratio

• In constrictive pericarditis, despite elevated left ventricular filling pressures, the E/e' ratio often remains paradoxically normal or low (typically <15), a phenomenon termed "annulus paradoxus" 4
• This represents an inverse relationship between E/e' and pulmonary capillary wedge pressure (PCWP) in constrictive pericarditis, contrary to the direct relationship observed in myocardial diseases 4
• After successful pericardiectomy, the E/e' ratio typically increases from abnormally low values to more normal values (from approximately 4.2 to 6.9) 3

Management Implications

• Identification of annulus reversus should prompt further evaluation for constrictive pericarditis, including assessment of other echocardiographic parameters, CT or MRI imaging, and potentially cardiac catheterization 2, 3
• In symptomatic patients with constrictive pericarditis confirmed by the presence of annulus reversus and other supporting findings, pericardiectomy is the definitive treatment 3
• Following pericardiectomy, echocardiographic follow-up should include assessment of the mitral annular velocity pattern to evaluate for resolution of annulus reversus 3
• In clinical responders to pericardiectomy, multiple echocardiographic parameters improve, including reduction in vena caval congestion, left atrial size, septal bounce, respiratory variation in mitral and tricuspid E velocities, and normalization of the medial e':lateral e' ratio 3

Technical Considerations in Echocardiographic Assessment

• Tissue Doppler imaging should be performed with proper alignment of the ultrasound beam with the mitral annulus motion to accurately measure e' velocities 1
• Multiple cardiac cycles should be analyzed and averaged to account for respiratory variation 3
• Three-dimensional echocardiography may provide additional insights into mitral annular configuration and dynamics, particularly in complex cases 5
• When evaluating for constrictive pericarditis, it's essential to assess multiple parameters rather than relying solely on annulus reversus, as recommended by the American Society of Echocardiography guidelines 1

Common Pitfalls and Caveats

• Annulus reversus should not be confused with mitral annular calcification, which appears as dense echoes in the region of the mitral annulus on M-mode echocardiography 6
• The presence of regional wall motion abnormalities, particularly affecting the lateral wall, may confound the interpretation of mitral annular velocities 1
• In patients with significant arrhythmias, the assessment of annulus reversus may be challenging and require averaging of multiple cardiac cycles 3
• Annulus reversus may persist in some patients after pericardiectomy despite clinical improvement, highlighting the importance of correlating echocardiographic findings with clinical status 3