What is the difference between constrictive (constrictive cardiomyopathy) and restrictive (restrictive cardiomyopathy) cardiomyopathy and how do I diagnose one over the other?

Distinguishing Constrictive Pericarditis from Restrictive Cardiomyopathy

The critical distinction is that constrictive pericarditis involves pericardial disease causing external compression of the heart, while restrictive cardiomyopathy involves intrinsic myocardial disease causing increased ventricular stiffness—this matters because constriction is surgically curable whereas restriction requires medical management or transplantation. 1, 2

Key Pathophysiologic Difference

Constrictive pericarditis results from a rigid, scarred pericardium that prevents normal ventricular filling by external constraint, creating ventricular interdependence where filling of one ventricle directly impairs filling of the other. 1, 2

Restrictive cardiomyopathy results from intrinsic myocardial disease—either interstitial fibrosis, infiltration (amyloid, sarcoid), storage material accumulation (hemochromatosis), or endomyocardial fibrosis—causing increased myocardial stiffness without significant external constraint. 1, 3

Clinical Presentation Overlap

Both conditions present identically with:

• Dyspnea from elevated diastolic pressures 1
• Prominent fluid retention and signs of right heart failure 1
• Fatigue and weakness from impaired cardiac output reserve 1
• Kussmaul sign (paradoxical rise in jugular venous pressure with inspiration) 1
• No cardiomegaly on chest X-ray 1

Diagnostic Algorithm

Step 1: Echocardiography (First-Line)

Findings favoring constrictive pericarditis:

• Septal bounce (ventricular interdependence) 1
• Respiratory variation of mitral peak E velocity >25% 1
• "Annulus reversus": septal e' velocity higher than lateral e' velocity (opposite of normal) 4
• Tissue Doppler: peak e' >8.0 cm/s (relatively preserved) 1

Findings favoring restrictive cardiomyopathy:

• Lateral e' higher than septal e' (normal pattern maintained) 4
• Tissue Doppler: peak e' <8.0 cm/s (markedly reduced) 1, 4
• Massive biatrial enlargement with normal/small ventricles 1, 4
• Markedly increased left atrial volume index >50 mL/m² 4
• E/e' ratio >14 4

Step 2: CT or Cardiac MRI (Second-Line)

CT findings:

• Pericardial thickness >3.0 mm strongly suggests constriction 1
• Pericardial calcification is virtually diagnostic of constriction 1
• Normal pericardial thickness (<3.0 mm) favors restriction but does not exclude constriction 1

Cardiac MRI findings:

• Late gadolinium enhancement patterns identify specific causes of restriction (amyloid shows diffuse subendocardial or transmural enhancement; sarcoid shows patchy mid-wall or subepicardial enhancement) 1
• Real-time cine imaging demonstrates ventricular interdependence in constriction 1

Step 3: Cardiac Catheterization (When Non-Invasive Testing Inconclusive)

Hemodynamic findings favoring constrictive pericarditis:

• RVEDP and LVEDP are equal (within 5 mmHg) 1
• RVEDP <1/3 of RVSP 1
• RV systolic pressure typically <50 mmHg 1
• Systolic area index >1.1 (ventricular interdependence) 1
• Prominent respiratory variation in ventricular filling 4

Hemodynamic findings favoring restrictive cardiomyopathy:

• LVEDP exceeds RVEDP by ≥5 mmHg at rest or with exercise 1
• RV systolic pressure often >50 mmHg (pulmonary hypertension) 1, 4
• RVEDP >1/3 of RVSP 1
• Less pronounced respiratory variation 4
• Both show "dip and plateau" or "square root" sign 1, 4

Step 4: Additional Diagnostic Tests for Restrictive Cardiomyopathy Etiology

When restriction is confirmed, identify the specific cause:

• Tc-99m-PYP or Tc-99m-DPD scintigraphy for cardiac amyloidosis (high specificity) 1
• FDG-PET for cardiac sarcoidosis (89% sensitivity, 78% specificity) 1
• Endomyocardial biopsy when non-invasive testing is inconclusive—demonstrates amyloid deposition, iron overload, eosinophilic infiltration, or fibrosis 1, 5
• Genetic testing for familial restrictive cardiomyopathy (troponin I, troponin T, desmin mutations) 1

Critical Pitfalls to Avoid

Transient constriction can occur during resolution of acute pericarditis and mimics permanent constriction—look for elevated CRP and pericardial inflammation on CMR contrast enhancement, which suggests reversibility with anti-inflammatory therapy. 1

Effusive-constrictive pericarditis shows persistent elevation of right atrial pressure (>10 mmHg or failure to fall by 50%) after pericardiocentesis, distinguishing it from pure tamponade. 1

Mixed phenotypes exist—some patients have elements of both hypertrophic and restrictive physiology, particularly in infiltrative diseases like amyloidosis. 3

No single test is definitive—the diagnosis requires integration of multiple modalities, and when uncertainty persists after comprehensive non-invasive evaluation, cardiac catheterization is indicated. 1, 2

Therapeutic Implications

For constrictive pericarditis: Pericardiectomy is curative, with better outcomes when performed early before advanced disease develops. 1, 6

For restrictive cardiomyopathy: Disease-specific therapy exists only for amyloidosis (chemotherapy, stem cell transplant) and iron overload (chelation); otherwise, treatment is supportive with diuretics and heart rate control to optimize filling, with cardiac transplantation as definitive therapy in appropriate candidates. 1, 3