Echocardiographic evaluation is the cornerstone for diagnosing constrictive pericarditis (CP). The fundamental pathophysiology of constriction involves a rigid, non-compliant pericardium that limits total cardiac volume, leading to exaggerated ventricular interdependence and the dissociation of intrathoracic and intracardiac pressures during respiration. Rather than relying on a single finding, a comprehensive evaluation requires integrating structural, M-mode, Doppler, and Tissue Doppler Imaging (TDI) parameters to confirm CP and differentiate it from its primary clinical mimic, restrictive cardiomyopathy.
1. Structural and 2D/M-Mode Findings
Structural findings provide the initial diagnostic clues, though a normal-appearing pericardium on 2D echo does not entirely exclude constriction.
- Respiration-Related Ventricular Septal Shift (Septal Bounce): This is the visual manifestation of exaggerated ventricular interdependence. During inspiration, the drop in intrathoracic pressure increases right ventricular (RV) filling. Because the external rigid pericardium prevents the free wall from expanding outward, the interventricular septum is forced to shift abruptly toward the left ventricle (LV) to accommodate the extra blood volume. The reverse happens during expiration. This “see-saw” or paradoxical septal motion is best captured using real-time 2D imaging (Apical 4-chamber or short-axis views) or M-mode across the septum.
- Pericardial Thickening and Calcification: The pericardium may appear highly echogenic or thickened (>3 mm); however, computed tomography (CT) or magnetic resonance imaging (MRI) offers far superior structural resolution for checking thickness.
- Inferior Vena Cava (IVC) Plethora: Dilatated IVC (≥ 21 mm) with minimal or absent inspiratory collapse (<50%), reflecting significantly elevated right atrial and systemic venous pressures.
2. Doppler Inflow Dynamics (Dissociation of Pressures)
Because the rigid pericardium isolates the heart chambers from normal respiratory changes in intrathoracic pressure, classic “see-saw” variations appear in transmitral and transtricuspid velocities during the respiratory cycle.
- Mitral Inflow (Transmitral E Velocity): During inspiration, as blood is held back in the extra-pericardial pulmonary veins, the transmitral gradient falls. This results in a ≥ 15% to 25% decrease in the peak early diastolic filling velocity (E-wave) during inspiration, with a reciprocal increase during expiration.
- Tricuspid Inflow: Conversely, tricuspid inflow velocity increases substantially during inspiration (>40%) and drops during expiration.
3. Tissue Doppler Imaging (TDI) & “Annulus Reversus”
Tissue Doppler is perhaps the most reliable modality for separating CP from intrinsic myocardial stiffness (RCM). It measures the longitudinal velocity of the mitral annulus during early diastole (e’).
- Preserved or Elevated Medial e‘: In CP, the myocardium itself relaxes normally, but its lateral expansion is constrained by the adjacent rigid pericardium. Consequently, longitudinal compensatory relaxation forces are directed along the septum. This keeps the medial (septal) e’ velocity preserved or even elevated (typically ≥ 8 to 9 cm/s).
- Annulus Reversus: In a normal heart, the lateral mitral annulus moves faster than the medial annulus (lateral e’ > medial e’). In constrictive pericarditis, lateral wall movement is physically tethered by the rigid shell, causing the lateral e’ to drop below the medial e’. This reversal (medial e’ ≥ lateral e’) is highly diagnostic of constriction.
4. Systemic Venous Doppler (Hepatic Veins)
Evaluating hepatic vein flow profiles via pulsed-wave Doppler highlights the baseline volume overload and pressure shifts.
- Expiratory Diastolic Flow Reversal: During expiration, the sudden decrease in RV filling capacity combined with increased abdominal pressure causes a prominent, transient reversal of forward diastolic flow back into the hepatic veins. An expiratory diastolic reversal velocity ratio ≥ 0.79 relative to forward flow is a strong independent predictor of CP.
Diagnostic Criteria: Differentiating CP vs. RCM
The formal diagnostic standard established by the Mayo Clinic Criteria utilizes a combination of these markers to distinguish between constriction and restriction:
| Echocardiographic Parameter | Constrictive Pericarditis (CP) | Restrictive Cardiomyopathy (RCM) |
| Ventricular Septal Shift | Present (Exaggerated interdependence) | Absent (Concordant ventricular filling) |
| Respiratory Mitral E Variation | Present (≥ 15%) | Absent or minimal (<10%) |
| Medial Mitral Annular e’ | Preserved/High (≥ 9 cm/s) | Markedly reduced (<6-7 cm/s) |
| Annulus Reversus (medial e’ ≥ lateral e’) | Present | Absent |
| Hepatic Vein Flow | Prominent diastolic reversal in expiration | Prominent systolic/diastolic reversal in inspiration |
Diagnostic Cluster Yield: The presence of a respiration-related ventricular septal shift combined with either a preserved medial e’ ≥ 9 cm/s or a hepatic vein expiratory diastolic reversal ratio ≥ 0.79 yields a diagnostic sensitivity of 87% and a specificity of 91% for constrictive pericarditis.
References
Welch, T. D., Ling, L. H., Espinosa, R. E., Anavekar, N. S., Wiste, H. J., Lahr, B. D., Schaff, H. V., & Oh, J. K. (2014). Echocardiographic diagnosis of constrictive pericarditis: Mayo Clinic criteria. Circulation: Cardiovascular Imaging, 7(3), 526–534.