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) 
- Hemopericardium: accumulation of blood in pericardial space
- 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 → ↓ systemic venous return (preload) → ↓ 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 
- Beck triad
- Tachycardia, pulsus paradoxus
- Pallor, cold sweats
- Left ventricular failure
- Symptoms of right heart failure
- Obstructive shock, cardiac arrest (presenting as ) 
- Unstable patients with suspected tamponade: Do not delay treatment for extensive diagnostic workup; proceed directly with .
- In all other patients, confirm the diagnosis with echocardiography (either TTE or FAST).
- Laboratory studies and analysis of the pericardial fluid can be used in the investigation of the underlying etiology.
- Indication: diagnosis and monitoring of all patients with suspected pericardial effusion and/or tamponade 
- Procedure: TTE (gold standard) or focused-assessed transthoracic echocardiography
- Allows for the detection of: 
- Findings supportive of pericardial effusion: Can be identified using POCUS (See “Subxiphoid view" of the “FAST scan.”)
Echocardiographic 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 (See “IVC ultrasound.”)
Epicardial fat can be mistaken for pericardial fluid on echocardiography. However, unlike fluid, it tends to be brighter, moves along with the myocardium, and does not collect in dependent regions. 
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
Pericardial fluid analysis 
- Indication: pericardial effusion of unclear etiology 
- Procedure: Pericardial fluid is obtained via diagnostic pericardiocentesis.
- 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|
- Unstable patients: Identify and urgently, if present.
- Stable patients
- Treat the underlying cause, e.g., , .
- Provide supportive care, e.g., pain management
- Consult cardiology urgently if cardiac tamponade is suspected (See “Management of cardiac tamponade”).
- Consult cardiothoracic surgery if surgical is indicated.
- If pericardiocentesis is performed, admit patients to hospital ward or observation unit for postprocedure monitoring, serial examination, and .
Surgical pericardial fluid drainage (e.g., pericardiotomy and pericardiectomy) is commonly performed for patients with traumatic, purulent, loculated, rapidly reaccumulating, or malignant effusions. 
Pericardial fluid drainage 
- Performed as a temporizing measure for hemodynamically unstable patients with cardiac tamponade
- Can relieve symptoms for large chronic or recurrent effusions
- Consider specialist referral for patients at high risk of reaccumulating pericardial fluid, e.g., for indwelling catheter or pericardiectomy
- See “Pericardiocentesis” for details.
Pericardiotomy: the creation of an opening in the pericardium to allow continuous drainage of pericardial fluid (externally or into the pleural space) 
- Surgical pericardiotomy (pericardial window): A surgical incision is made in the pericardium. 
- Percutaneous balloon pericardiotomy: A transthoracic needle introduces a balloon-tipped catheter into the pericardial space which is progressively dilated to create an opening wide enough for continuous drainage.
- Complications: The mortality rate varies from 8–19%, depending on the underlying etiology. 
- pericardial effusion, effusion due to constrictive pericarditis, or purulent pericarditis  : performed as definitive management for refractory
Rapid evaluation of unstable patients
- Use pericardial effusion (see the “Subxiphoid view” of the “ ” for the technique). to confirm the presence of a
- Suspect tamponade in patients with suggestive clinical features and/or bedside imaging findings.
- ≥ 70% of patients have ≥ 1 of the following: 
- Beck's triad is poorly sensitive for tamponade and it is very rare for all elements to be present 
- < 50% of patients have low voltage QRS complexes on ECG. 
- Obtain an urgent bedside echocardiogram to evaluate for .
- Evaluate the need for immediate pericardial fluid drainage.
- Consult a cardiologist and/or cardiothoracic surgeon and consider using a scoring system to help determine when urgent pericardiocentesis is advised and when it can safely be deferred. 
The most common underlying causes of cardiac tamponade are cardiac interventions (e.g., PCI, pacemaker implantation), malignancy, infectious or inflammatory pericarditis, mechanical complications of MI, and aortic dissection. 
Cardiac arrest due to suspected cardiac tamponade
See also “Cardiac arrest and cardiopulmonary resuscitation.”
- Nontraumatic cardiac arrest 
Urgent pericardial fluid drainage
- Perform pericardiocentesis under echocardiographic (or fluoroscopic) guidance without delay in unstable patients unless indications for immediate surgery are present. 
- Do not delay immediate surgical management in patients with a low likelihood of successful pericardiocentesis due to immediate reaccumulation of pericardial fluid, for example in: 
- Refer for surgical management if pericardiocentesis is unsuccessful, e.g., due to difficult conditions 
- Establish IV access with two large-bore IV lines (peripheral or central).
- Cautious fluid resuscitation (only in hypovolemic patients) 
- Inotropic support: dobutamine 
- Avoid anesthetic agents and positive pressure ventilation. 
- See “mechanical ventilation is unavoidable. ” for the management approach if
- 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.