Pericardium Step 1

The pericardium is a dual-layered membrane that surrounds the heart and the origins of the major blood vessels. It plays a crucial role in protecting the heart, maintaining its position, and reducing friction during cardiac cycles.

Anatomy of the Pericardium

The pericardium consists of two main layers:

1. Fibrous Pericardium

• The outermost layer, composed of dense, irregular connective tissue.
• It is inelastic, preventing overexpansion of the heart.
• Function: Anchors the heart to nearby structures (sternum, diaphragm, and great vessels).
• Attachments:
  • Superiorly: Merges with the tunica adventitia of the great vessels.
  • Inferiorly: Attached to the central tendon of the diaphragm.
  • Laterally: Connects to the pleura.
  • Anteriorly: Attached to the sternum via the sternopericardial ligaments.

2. Serous Pericardium

• A thin, double-layered membrane that secretes lubricating fluid.
• Composed of:
  • The parietal layer covers the interior surface of the fibrous pericardium.
  • Visceral layer (Epicardium) – Closely adheres to the heart, forming its outermost layer.

3. Pericardial Cavity

• A potential space between the parietal and visceral layers, containing 10-50 mL of pericardial fluid.
• Function:
  • Lubricates the heart to reduce friction during contractions.
  • Enables unrestricted motion of the heart within the pericardial sac.

Functions of the Pericardium

1. Mechanical Protection: Shields the heart from external trauma and infections.
2. Prevention of Overexpansion: Limits excessive dilation of the heart, especially during volume overload.
3. Lubrication: Pericardial fluid minimizes friction between the heart and surrounding structures.
4. Fixation of the Heart: Helps maintain the heart’s position in the thorax.

Blood Supply and Innervation

Blood Supply

• Arterial:
  • Internal thoracic artery (pericardiacophrenic branch)
  • Musculophrenic artery
  • Thoracic aorta branches
• Venous Drainage:
  • Pericardiacophrenic veins → Brachiocephalic veins
  • Azygos venous system

Innervation

• Sensory: Phrenic nerve (C3–C5) – Responsible for pericardial pain, often referred to the shoulder.
• Autonomic:
  • Sympathetic fibers regulate vasomotor function.
  • Parasympathetic input from the vagus nerve.

Clinical Conditions Related to the Pericardium

1. Pericarditis (Inflammation of the Pericardium)

• Causes:
  • Infections: Viral (Coxsackievirus B, influenza), bacterial (TB, pneumococcal).
  • Autoimmune diseases: Rheumatoid arthritis, SLE.
  • Post-myocardial infarction (Dressler’s syndrome).
• Symptoms:
  • Sharp, pleuritic chest pain, worsens with lying down, improves when sitting forward.
  • Pericardial friction rub – High-pitched, scratchy sound on auscultation.
  • ECG: Diffuse ST-elevations and PR depressions.
• Treatment:
  • NSAIDs (e.g., ibuprofen, aspirin) + colchicine.
  • Treat underlying cause.

2. Pericardial Effusion (Excess Fluid in the Pericardial Cavity)

• Can be due to infections, malignancies, renal failure, or trauma.
• Symptoms: Muffled heart sounds, dyspnea.
• Diagnosis: Echocardiography (gold standard).
• Treatment:
  • Small effusions: Monitor.
  • Large/symptomatic effusions: Pericardiocentesis.

3. Cardiac Tamponade (Compression of the Heart Due to Fluid Accumulation)

• Medical Emergency!
• Symptoms (Beck’s Triad):
  1. Hypotension
  2. Muffled heart sounds
  3. Jugular venous distension (JVD)
• Other signs: Pulsus paradoxus (exaggerated drop in BP during inspiration).
• Diagnosis: Echocardiography – Shows right ventricular collapse during diastole.
• Treatment: Urgent pericardiocentesis.

4. Constrictive Pericarditis (Chronic Pericardial Thickening and Fibrosis)

• Causes:
  • Tuberculosis (common worldwide).
  • Radiation therapy.
  • Post-cardiac surgery.
• Symptoms:
  • Right heart failure (JVD, peripheral edema, ascites).
  • Kussmaul’s sign: JVD increases with inspiration (opposite of normal).
  • Pericardial knock: Early diastolic sound due to abrupt cessation of ventricular filling.
• Diagnosis: CT/MRI showing thickened pericardium (>4 mm).
• Treatment: Pericardiectomy (surgical removal of pericardium).

Imaging and Diagnosis

• Echocardiography: First-line for detecting effusions and tamponade.
• CT/MRI: Best for evaluating pericardial thickening (constrictive pericarditis).
• ECG: Helpful in pericarditis (ST elevation, PR depression).

Key Takeaways

• The pericardium is a double-layered sac that protects the heart and provides lubrication.
• Pericardial effusion and cardiac tamponade can be life-threatening and require urgent intervention.
• Pericarditis presents with chest pain, pericardial friction rub, and diffuse ST elevation.
• Constrictive pericarditis leads to right-sided heart failure and requires surgical pericardiectomy.