The Pericardium

First, we imagine the heart and great vessels in context with the diaphragm and lungs.

• The fibrous pericardium forms a loose “bag” around the heart; it is attached to the central tendon of the diaphragm.
• The serous pericardium comprises two layers and a space:
  – The parietal layer lines the fibrous pericardium.
  – The visceral layer, which is the outer covering of the heart; thus, the visceral layer of the pericardium is the epicardium of the heart.
• The pericardial cavity is between the parietal and visceral layers; this small space typically contains less than 50 mL of fluid,which allows for free movement of the heart.
• The pericardium has a limited ability to respond to injury,which is often key to its pathology:
  – In response to injury, the pericardium increases fluid production; this fluid can contain fibrin and inflammatory cells.
  – The pericardium can distend to hold this fluid, but only up to a point.

Pericarditis – Inflammation

• The most common pericardial disease, and, it can lead to others.
• Pericarditis is inflammation (‘itis’) of the pericardium.
  Signs & Symptoms:
• Sharp chest pain, which may radiate to the shoulder.
  – Pain is often relieved upon sitting up or leaning forward.
• Pericardial friction rub, which is often characterized as a squeaking or scratching sound.
• Elevated biomarkers: white blood cells, erythrocyte sedimentation rate (ESR), C-reactive protein, and, in some cases, cardiac troponin.
• ECG changes in 4 stages
  – Can help distinguish pericarditis from myocardial infarction.
  – Stage I: Diffuse concave ST-segment elevation and PR-segment depression, which can be seen in most leads (all except for aVR).

Note that, in myocardial infarction, the ST segments are typically convex and not diffuse.

– Stage II: Normalization of the ST and PR segments, and flattened T-waves.
– Stage III: Inverted T-waves.
Stage IV: T-waves either normalize or persist as inverted waves.

Treatment: Aspirin, NSAIDs, and NSAIDs; corticosteroids may be considered if these drugs fail.

Causes of Pericarditis

Many cases are idiopathic.

Causes of pericarditis vary by population. For example, in richer countries, viral and post-surgical causes prevail; in poorer countries, tuberculosis is a significant cause of pericarditis.

Some causes are associated specific types of pericarditis; for example, some bacteria can cause purulent pericarditis.

• Pathogens, especially HIV, Coxsackie virus, Streptococcus, Staphylococcus, and Tuberculosis, can cause pericarditis. It is thought that many idiopathic cases are caused by viruses.
• Metabolic disorders, such as occurs in kidney failure (uremic pericarditis)
• Autoimmune disorders, particularly Rheumatoid Arthritis and Systemic Lupus Erythematosus
• Cancers, especially of the breast or lung, and Hodgkin lymphoma
• Drugs, including penicillin and some anticoagulants
• Myocardial infarction
• Cardiac surgery or trauma
• Radiation therapy

• Constrictive pericarditis can occur when chronic inflammation leads to fibrosis or calcification of the pericardium.
  – This produces a tough, inelastic shell around the heart that impairs diastolic filling.
  – Impaired diastolic filling can lead to peripheral venous congestion and Kussmaul’s sign
  Kussmaul’s sign is characterized by increased jugular venous pressure during inspiration.

Pericardial Effusion – Fluid accumulation

• Fluid accumulation (in some cases, 100s of mL) in the pericardial cavity.
• Causes of pericardial effusion are similar to, and include, pericarditis.
  – Recall that increased fluid production is one way that the pericardium responds to injury.
• Hemorrhagic effusions can also occur, and tend to result from trauma, myocardial infarctions, and vessel rupture.
• Diagnosis often entails echocardiogram, CT, or MRI, which allows us to see the quantity and location of excess pericardial fluid.
• If pericardial effusion occurs in the absence of pericarditis, the patient may not experience any symptoms.
• Pericardial friction rub may be heard (but not necessarily).
• ECG changes include  tachycardia, electrical alternans, and low QRS voltage.

Cardiac Tamponade – Fluid from effusion impedes filling.

Also called pericardial tamponade

• Occurs when the pressure from the pericardial effusion impedes filling.
  – Recall that the pericardium can distend to hold excess fluid only up to a point; cardiac tamponade occurs when the elastic limit of the pericardium is surpassed, and the accumulating pericardial fluid exerts pressure on the heart.
  – Most likely to occur when fluid accumulates rapidly, but can also occur when a large volume of fluid accumulates over time.
• When the pressures on the heart that impede filling are too high, cardiac tamponade can lead to shock.
• Key clinical indications: tachycardia, high jugular venous pressure, and pulsus paradoxus
  – Pulsus paradoxus is characterized by a 10 mmHg or more drop in arterial blood pressure upon inspiration.
• Treatment: Drainage of the excess fluid from the pericardial cavity.