Pericardial effusion is the acute or chronic accumulation of fluid in the pericardial space (between the parietal and the visceral pericardium) and is often associated with a variety of underlying disorders. The fluid can be either bloody (e.g., following aortic dissection) or serous (usually idiopathic). As the pericardium is rather stiff, the capacity of the pericardial space is limited. In chronic effusion, the pericardium can stretch to a certain degree, accommodating slightly more fluid. In the acute setting, however, the added volume quickly exceeds the maximum capacity of the pericardial space. In both cases, the end result is often cardiac tamponade: compression of the heart that can lead to a life-threatening reduction in cardiac output. Pericardial effusion is initially asymptomatic, but cardiac tamponade has a distinct clinical presentation, including hypotension, tachycardia, jugular venous congestion, and pulsus paradoxus. Echocardiography is the most important diagnostic procedure and usually reveals an anechoic pericardial space. Treatment depends on hemodynamic stability: unstable patients require quick pericardial fluid drainage, through either pericardiocentesis or surgery, whereas in stable patients, treatment focuses on the underlying disease.
- Pericardial effusion: an accumulation of fluid in the pericardial space between the parietal and visceral pericardium. May be acute or chronic.
- Cardiac tamponade: a pathophysiological process whereby elevated intrapericardial pressure from a pericardial effusion causes compression of the heart (especially the right ventricle) 
- Serous or serosanguinous pericardial effusion 
Cardiac tamponade: pericardial fluid collection (e.g., bloody or serous) → ↑ pressure in the pericardial space → compression of the heart (especially of the right ventricle due to its thinner wall) → interventricular septum shift toward the left ventricle chamber → ↓ ventricular diastolic filling → ↓ stroke volume (and venous congestion) → ↓ cardiac output and equal end-diastolic pressures in all 4 chambers 
- Initially asymptomatic in most cases
- Shortness of breath, especially when lying down (orthopnea)
- Retrosternal chest pain
- Can cause compressive symptoms
- Apical impulse is difficult to locate or nonpalpable.
- Ewart sign: dullness to percussion at the base of the left lung with increased vocal fremitus and bronchial breathing due the compression of lung parenchyma by the pericardial effusion 
- Critically unstable patients and patients in cardiac arrest with suspected cardiac tamponade: start immediate treatment (i.e., pericardiocentesis).
- In all other patients, confirm the diagnosis with echocardiography. (either TTE or focus-assessed transthoracic echocardiography [FATE]).
- Laboratory studies and analysis of the pericardial fluid can be used in the investigation of the underlying etiology.
- Indication: all patients with suspected pericardial effusion
- Procedure: TTE (gold standard) or focused-assessed transthoracic echocardiography
- Allows for the detection of: 
- Findings supportive of pericardial effusion
Findings supportive of cardiac tamponade 
- Chamber collapse
- Swinging motion of the heart
- Inspiration: decrease in LV filling
- Exhalation: increase in LV filling and decrease in RV filling
- Blood flow changes during inspiration
- Hepatic vein and inferior vena cava plethora
Findings in pericardial effusion
- Normal in smaller effusions
- Low voltage; complexes and electrical alternans in larger effusions
- Findings in cardiac tamponade 
Chest x-ray: not required to diagnose pericardial effusion but often performed to exclude other causes of dyspnea 
- PA view findings
Lateral view findings
- Posterior inferior bulge sign: a change in the silhouette of the heart due to a pericardial effusion that collects in the posterior-inferior pericardiac recess and expands the pericardium 
- Pericardiac fat pad sign: a > 2 mm soft-tissue stripe between the epicardiac fat and the anterior mediastinal fat that may be visible anterior to the heart 
- Further imaging 
Investigation of the underlying etiology
Pericardiocentesis with pericardial fluid analysis 
- Indication: etiology of the effusion is unclear 
- Cell count
- Gram stain and culture
- Acid-fast bacilli
- Glucose level: < 60–80 mg/dL suggestive of malignant, parapneumonic, or tuberculous effusions, or connective tissue disease.
- Protein level: > 6.0 g/dL is associated with purulent, parapneumonic, and tuberculous effusions.
- LDH: Isolated pericardial fluid LDH elevation of > 300 units/dL suggests malignant effusion.
- Interpretation 
|Interpretation of pericardial fluid samples|
|Fluid type||Appearance||Etiology |
|Purulent || || |
Laboratory studies and specific investigations 
- CBC: leukocytosis if infection or inflammation
- CRP, ESR: elevated in infection or inflammation
- Creatinine kinase: elevated in myocarditis, rhabdomyolysis
- BMP: elevated BUN in uremic pericarditis
|Investigation of underlying etiology in pericardial effusion|
|Suspected etiology||Additional investigations to consider|
|Uremic pericardial effusion|| |
In cardiac tamponade, the mainstay of treatment is urgent decompression of the heart. In pericardial effusion, treatment is focused on management of the underlying cause with a more limited role for pericardial fluid drainage.
- Urgent pericardiocentesis
- Hemodynamic support
- Subsequent management
- Monitoring: : Serial pulsus paradoxus measurement
Small pericardial effusions may resolve with treatment of the underlying cause. In an uncertain diagnosis or with larger effusions that are causing symptoms, pericardial fluid drainage should be performed.
Pericardial fluid drainage
- Indications 
- Procedure: ultrasound, CT, or fluoroscopy guidance recommended for planned pericardiocentesis 
- Description: : a pericardial incision for continual drainage from the pericardial space into the pleural cavity
- Indications: : commonly used for reaccumulating effusions and in a palliative setting for effusions due to underlying malignancy 
- Consult cardiology immediately.
- Confirm the diagnosis with echocardiography if the patient is stable (proceed directly to pericardiocentesis if not)
- Urgent pericardiocentesis in patients with cardiac tamponade
- Continuous telemetry
- If the patient is hypotensive, consider cautious IV fluid use.
- Consult cardiothoracic surgery for surgical drainage if pericardiocentesis is unsuccessful or if hemopericardium or purulent effusion are suspected.
- Serial pulsus paradoxus measurement
- Transfer to ICU/CCU.
- Avoid anesthetic agents and positive pressure ventilation.