Constrictive Pericarditis vs Restrictive Cardiomyopathy

Definition

The differentiation of constrictive pericarditis (CP) from restrictive cardiomyopathy (RCM) is one of the most challenging diagnostic problems in cardiology. Both conditions present with right-sided heart failure, elevated and equalized diastolic pressures across all four cardiac chambers, and a dip-and-plateau ("square root sign") pattern on ventricular pressure tracings. The distinction is critical because CP is surgically curable (pericardiectomy) while RCM is not.

Key Concepts

Aetiology and Context

• Common causes of CP in the modern era: previous cardiac surgery, chest radiation (often with mixed myo-pericardial disease), viral pericarditis, and idiopathic — patients who have had both radiation and prior surgery frequently have a combination of pericardial and myocardial disease sources/hemodynamics-circ-2012 high
• RCM causes: amyloidosis (most common in adults), haemochromatosis, sarcoidosis, endomyocardial fibrosis, Fabry disease, glycogen storage disorders sources/rhc-hf-ehj-2025 high

Clinical Presentation

• Both: signs of biventricular failure, elevated JVP with Kussmaul sign, pulsus paradoxus (more prominent in tamponade than CP), peripheral oedema, ascites
• CP: early diastolic knock (rapid filling sound); pericardial calcification on imaging (not always present)
• RCM: biatrial enlargement, elevated BNP/NT-proBNP, more severe pulmonary hypertension typical

Echocardiographic Differentiation

• CP: septal bounce (interventricular septal motion reversal with respiration); mitral E velocity varies >25% with respiration; tissue Doppler e' relatively preserved (>8 cm/s) despite high E/e' (annulus reversus)
• RCM: no septal bounce; no respiratory variation in mitral E velocity; markedly reduced e' (<8 cm/s) reflecting myocardial disease; prominent hepatic venous diastolic flow reversal during expiration
• CMR: pericardial thickening >3–4 mm and/or enhancement supports CP; myocardial fibrosis/LGE supports RCM sources/rhc-hf-ehj-2025 high

Cardiac Catheterization — Haemodynamic Criteria

Old Criteria (Low Specificity — Rarely Sufficient Alone)

• Absolute PA pressure elevation, ratio of RVEDP to RVSP, and difference between LVEDP and RVEDP were all used historically but have low specificity and are rarely diagnostic in an individual patient sources/hemodynamics-circ-2012 high
• Both CP and RCM share: early rapid filling (prominent y-descent), dip-and-plateau morphology, equalization of diastolic pressures (RVEDP = LVEDP within ~5 mmHg), and elevation of RAP:PAWP ≥0.5 sources/rhc-hf-ehj-2025 high

Current Criteria — Respiratory Ventricular Interaction

The key discriminating finding is whether ventricular filling is discordant or concordant during the respiratory cycle:

Constrictive Pericarditis — Ventricular Discordance:

• The rigid pericardium dissociates intrathoracic from intracardiac pressure transmission
• During inspiration: intrathoracic pressure falls but cardiac pressure is not transmitted → the driving pressure from pulmonary veins to LV decreases → ↓ LV filling → ↓ LV systolic pressure
• The fixed total cardiac volume within the rigid pericardium means ↓ LV filling simultaneously enhances RV filling (ventricular interaction enhanced)
• Result: During inspiration, RV pressure rises while LV pressure falls — discordance sources/hemodynamics-circ-2012 high

Restrictive Cardiomyopathy — Ventricular Concordance:

• No pericardial constraint; intrathoracic-intracardiac pressure coupling is preserved
• During inspiration: both LV and RV filling pressures fall together
• Result: Both LV and RV pressures fall during inspiration — concordance sources/hemodynamics-circ-2012 high

Practical measurement (high-fidelity manometer-tipped catheters preferred):

• Simultaneous RV and LV pressure tracings during spontaneous respiration
• Measure the systolic pressure area under the curve over multiple respiratory cycles
• CP: discordance index (RV area increases as LV area decreases) reliably differentiates from RCM sources/rhc-hf-ehj-2025 high

Volume Loading

• In diuretic-treated patients with relatively normal diastolic pressures, volume loading may be needed to unmask the classic haemodynamic findings of both conditions sources/hemodynamics-circ-2012 high

Severe Right Heart Failure Caveat

• Severe RV systolic/diastolic dysfunction or severe TR can produce elevated equalized diastolic pressures and mild respiratory discordance — can mimic CP
• Careful examination of LV and RV diastolic pressure respiratory changes helps differentiate these conditions from true constrictive pericarditis sources/hemodynamics-circ-2012 high

Cardiac Tamponade vs Constrictive Pericarditis

• Tamponade: blunted early diastolic rapid filling (x-descent prominent, y-descent absent or blunted); intracardiac volume compression by pericardial fluid dominates
• CP: prominent y-descent = rapid early diastolic filling due to high driving pressure followed by abrupt cessation (rigid pericardium)
• Effusive-constrictive pericarditis: after pericardiocentesis, diastolic pressures remain elevated AND prominent y-descent (early rapid filling) emerges → indicates underlying pericardial constriction → requires pericardiectomy sources/hemodynamics-circ-2012 high

Management

• CP: Pericardiectomy is curative in suitable patients; results best with complete decortication; post-radiation cases have worse outcomes due to mixed myocardial damage
• RCM: Treat underlying cause where possible (e.g., ERT/chaperone therapy for Fabry, ATTR stabilisers for amyloidosis); symptom management; often progresses to cardiac transplantation

Contradictions / Open Questions

• Mixed pericardial and myocardial disease (common after radiation or prior surgery) can present with intermediate haemodynamics — neither pure discordance nor concordance; diagnosis requires integration of CMR, haemodynamics, and clinical context sources/hemodynamics-circ-2012 high
• No large RCT defines the optimal diagnostic workup strategy (catheterization vs CMR vs combined)
• The threshold discordance ratio for diagnosing CP at catheterization varies by institutional method; high-fidelity catheters required for reliable tracings

Connections

• Related to concepts/Right-Heart-Catheterization
• Related to entities/RCM
• Related to entities/Heart-Failure
• Related to entities/ATTR-Amyloidosis
• Related to entities/Anderson-Fabry-Disease
• Related to entities/Pulmonary-Hypertension

Sources

• sources/hemodynamics-circ-2012
• sources/rhc-hf-ehj-2025