What is the role of echocardiography (echo) in assessing constrictive pericarditis?

Echocardiographic Assessment of Constrictive Pericarditis

Echocardiography is essential in diagnosing constrictive pericarditis, with specific findings that can differentiate it from restrictive cardiomyopathy with high sensitivity and specificity. 1

Key Echocardiographic Features

Anatomical Findings

• Pericardial thickening (>3mm), though echocardiography has limited accuracy in measuring this compared to CT/MRI 1
• Inferior vena caval enlargement that doesn't collapse with inspiration
• Mild atrial enlargement with normal-sized left ventricle
• Normal or preserved ventricular systolic function

Hemodynamic Findings (Most Diagnostic)

1. Respiration-related ventricular septal shift (highest sensitivity)

   • Septal "wobble" or bounce during respiration
   • Severity can be graded based on septal motion patterns 2:
     • Mild: Single wobble during normal respiration
     • Moderate: "Double wobble" (septum bows into LV in early diastole, relaxes, then deviates again after atrial contraction)
     • Severe: Pan-diastolic septal motion into LV cavity

2. Doppler findings (pathognomonic when combined)

   • Exaggerated respiratory variation (>25%) in mitral inflow E velocity 1
   • Preserved or increased medial mitral annular e' velocity (≥9 cm/s) - highly specific 3, 4
   • Medial e'/lateral e' ratio ≥0.91 (annulus reversus) 4
   • Prominent hepatic vein expiratory diastolic flow reversals (reversal ratio ≥0.79) 3
   • E/A ratio >2 with short deceleration time 1

Diagnostic Algorithm

1. First-line assessment: Transthoracic echocardiography with respiratory monitoring 1

   • Look for ventricular septal shift with respiration
   • Measure mitral inflow velocities during respiration
   • Assess tissue Doppler velocities at medial and lateral mitral annulus
   • Evaluate hepatic vein flow patterns

2. Mayo Clinic Diagnostic Criteria 3, 4:

   • Highest diagnostic accuracy when combining:
     • Ventricular septal shift + medial e' ≥9 cm/s (sensitivity 87%, specificity 91%)
     • Adding hepatic vein expiratory diastolic reversal ratio ≥0.79 increases specificity to 97% but reduces sensitivity to 64%

3. Special considerations:

   • In atrial fibrillation, all criteria except mitral inflow velocity variation remain valid 3
   • Transesophageal echocardiography may be superior to TTE for assessing pericardial thickening 1

Differentiation from Restrictive Cardiomyopathy

Feature	Constrictive Pericarditis	Restrictive Cardiomyopathy
Septal motion	Respiratory septal shift/bounce	Absent
Medial e' velocity	Preserved/increased (≥9 cm/s)	Reduced (<8 cm/s)
Respiratory variation	Marked variation in mitral inflow	Minimal variation
Medial-to-lateral e' ratio	≥0.91 (annulus reversus)	<0.91

Prognostic Value

• Post-pericardiectomy normalization of Doppler findings correlates with symptomatic improvement 5
• Persistence of restrictive Doppler features after pericardiectomy suggests poor functional outcome 5
• In effusive-constrictive pericarditis, echocardiography can identify patients who may not require pericardiectomy, as many resolve with conservative management 6

Pitfalls and Limitations

• Pericardial fat pads may be mistaken for pericardial effusion but typically show some internal echoing 7
• The descending aorta may be mistaken for posterior effusion; rotating the probe into a transverse plane can resolve this confusion 7
• Echocardiography alone cannot accurately assess pericardial thickness; CT or MRI is needed for definitive evaluation 1
• No single echocardiographic sign is diagnostic; a combination of findings is required 1
• Normal echocardiographic findings do not completely exclude the diagnosis, particularly in early or localized disease

When constrictive pericarditis is suspected but echocardiographic findings are equivocal, cardiac CT or MRI should be performed to assess pericardial thickness and calcification, followed by cardiac catheterization if necessary 1.