What is the difference between constrictive and restrictive cardiac physiology in terms of diagnosis and treatment?

Differentiating Constrictive Pericarditis from Restrictive Cardiomyopathy

Constrictive pericarditis and restrictive cardiomyopathy are distinct conditions with different pathophysiologies, requiring different treatments, with pericardiectomy being the definitive treatment for constrictive pericarditis while restrictive cardiomyopathy typically requires medical management.

Pathophysiology

Constrictive Pericarditis

• Definition: A condition where the pericardium becomes thickened, fibrotic, and often calcified, limiting cardiac filling
• Mechanism: External compression of the heart by rigid pericardium
• Causes:
  • Idiopathic/viral (42-49%)
  • Post-cardiac surgery (11-37%)
  • Post-radiation therapy (9-31%)
  • Tuberculosis (common in developing countries)
  • Connective tissue disorders (3-7%)
  • Other causes: malignancy, trauma, uremia 1

Restrictive Cardiomyopathy

• Definition: Impaired ventricular filling due to myocardial disease with normal or reduced ventricular volumes and normal wall thickness
• Mechanism: Intrinsic myocardial stiffness limiting diastolic function
• Causes:
  • Amyloidosis (most common in Western countries)
  • Sarcomeric protein gene mutations
  • Metabolic disorders
  • Infiltrative diseases 1

Diagnostic Features

Clinical Presentation

Both conditions present with:

• Signs of right heart failure
• Elevated jugular venous pressure
• Hepatomegaly
• Ascites
• Peripheral edema
• Kussmaul sign (paradoxical increase in jugular venous pressure during inspiration) 1

Key Diagnostic Differences

Imaging Findings

Feature	Constrictive Pericarditis	Restrictive Cardiomyopathy
Pericardial thickness	Typically thickened (>3mm) or calcified (though normal in ~20% of cases)	Normal (<3mm)
Septal motion	"Septal bounce" - abnormal motion of interventricular septum	No septal bounce
Ventricular configuration	Tube-like configuration of ventricles	Normal ventricular configuration
Atrial size	Biatrial enlargement	Biatrial enlargement
Myocardial thickness	Normal	May be increased

Echocardiographic Findings

Feature	Constrictive Pericarditis	Restrictive Cardiomyopathy
Respiratory variation	Marked respiratory variation (>25%) in mitral inflow velocities	Minimal respiratory variation (<25%)
Tissue Doppler	e' velocity >8.0 cm/s	e' velocity <8.0 cm/s
Propagation velocity (Vp)	>45 cm/sec	<45 cm/sec
E/A ratio	>2, short deceleration time	>2, short deceleration time
[1]

Hemodynamic Findings

Feature	Constrictive Pericarditis	Restrictive Cardiomyopathy
Ventricular pressures	Equalization of LV and RV diastolic pressures (within 5 mmHg)	LVEDP exceeds RVEDP by ≥5 mmHg
Pressure waveform	"Dip and plateau" or "square root" sign in both ventricles	"Dip and plateau" pattern may be present
RV systolic pressure	Usually <50 mmHg	Often >50 mmHg
Ventricular interdependence	Marked (systolic area index >1.1)	Less prominent
[1,2]

Diagnostic Approach

Initial Evaluation

• Transthoracic echocardiography (Class I recommendation) 1
• Chest X-ray (frontal and lateral views) to assess for pericardial calcifications (Class I recommendation) 1

Advanced Imaging

• CT and/or CMR to assess:
  • Pericardial thickness and calcifications
  • Degree and extension of pericardial involvement
  • Myocardial characterization (for restrictive cardiomyopathy) 1

Invasive Assessment

• Cardiac catheterization when non-invasive methods are inconclusive (Class I recommendation)
• Endomyocardial biopsy may be useful to identify specific causes of restrictive cardiomyopathy and avoid unnecessary thoracotomy 3

Treatment Approach

Constrictive Pericarditis

• Definitive treatment: Pericardiectomy for chronic permanent cases
• Medical therapy may be appropriate in:
  1. Specific etiologies (e.g., tuberculous pericarditis) to prevent progression
  2. Transient constriction (10-20% of cases) - anti-inflammatory drugs
  3. Advanced cases when surgery is contraindicated - supportive care 1

Restrictive Cardiomyopathy

• Primary approach: Medical management of heart failure symptoms
  • Diuretics for congestion
  • Heart rate control to optimize LV filling
  • Anticoagulation for all patients with atrial fibrillation
• Device therapy: ICD for patients with sustained ventricular arrhythmias causing hemodynamic instability (Class I recommendation)
• Advanced therapy: Heart transplantation for eligible patients with progressive disease 1

Prognosis

Constrictive Pericarditis

• Pericardiectomy mortality: 6-12%
• Complete normalization of cardiac hemodynamics: ~60% of patients
• Prognosis worsens with delayed surgery 1

Restrictive Cardiomyopathy

• Poor long-term prognosis
• In children: 5-year survival ~68%
• Risk factors for mortality: NYHA functional class, left atrial size, male sex 1

Clinical Pitfalls and Caveats

1. Normal pericardial thickness does not exclude constrictive pericarditis - present in up to 20% of surgically proven cases 1

2. Mixed constrictive-restrictive physiology can occur, making diagnosis challenging

3. Transient constrictive pericarditis may resolve with anti-inflammatory therapy - look for elevated CRP and imaging evidence of pericardial inflammation 1

4. Pericardiectomy contraindications: myocardial atrophy and perimyocardial fibrosis 4

5. Respiratory variation in mitral inflow may be reduced in patients with elevated left atrial pressures, even in constrictive pericarditis 1

6. Endomyocardial biopsy should be considered before thoracotomy to avoid unnecessary surgery in patients with restrictive cardiomyopathy 3