Pericardial Effusion

Etiology

The etiology of pericardial effusion varies widely and can be divided into several categories:

• Infectious: Pericardial effusion may be caused by viral, bacterial, fungal, or parasitic pathogens. 
• Inflammatory/rheumatologic: Numerous autoimmune disorders, including systemic lupus erythematosus, rheumatoid arthritis, and Sjogren syndrome, can cause a pericardial effusion.
• Neoplastic: Metastatic disease and primary cardiac tumors can cause pericardial effusions. Lung cancer is the most common cause of malignant pericardial effusion.
• Trauma: Blunt, penetrating, and iatrogenic injury to the myocardium, aorta, or coronary vessels can lead to the accumulation of blood within the pericardial sac.
• Cardiac: Pericardial effusion can arise after a myocardial infarction (referred to as Dressler syndrome), cardiac surgery, or cardiac wall rupture.
• Vascular: A type A aortic dissection can be complicated by cardiac tamponade.
• Idiopathic: Many cases of pericardial effusion are idiopathic.
• Other: This category includes radiation, chronic kidney disease, renal failure, congestive heart failure, cirrhosis, hypothyroidism leading to myxedema, ovarian hyperstimulation syndrome, and drug-induced.[5]

Pericardial effusion has diverse etiologies that may be identified with good clinical evaluation and appropriate use of diagnostic examinations. Understanding these varied origins is crucial for effective treatment.

Epidemiology

Pericardial effusion can occur across all ages and populations.[6] The effusion's predominant etiology varies by demographic characteristics such as age, geography, and comorbidities. Data regarding the prevalence and incidence of pericardial effusions is limited. Viral pericarditis leading to effusion is the most common cause in the developed world. In developing areas, pericardial effusion due to Mycobacterium tuberculosis is quite prevalent. Bacterial and parasitic etiologies are less common.

Multiple malignant neoplasms can cause noninflammatory pericardial effusions. A malignant etiology is present in 12% to 23% of patients with pericardial effusion. In patients with human immunodeficiency virus, pericardial effusion is reported in 5% to 43%, depending on the inclusion criteria, with 13% having moderate to severe effusion. A pediatric study revealed that postcardiac surgery (54%), neoplasia (13%), renal (13%), idiopathic or viral pericarditis (5%), and rheumatologic (5%) were the major underlying etiologies of pericarditis and pericardial effusions in children.[7][8][9]

Pathophysiology

Pericardial effusion is an acute or chronic fluid accumulation within the pericardial space. Effusion can be transudative, exudative, or sanguineous. The pericardium has limited elasticity, and in acute settings, only 100 to 150 mL of fluid is necessary to cause cardiac tamponade. The fluid accumulation increases pressure in the pericardial sac, leading to the compression of the heart, especially the right heart, which has a thinner wall. Impaired diastolic filling of the right heart causes venous congestion. Reduced left ventricular diastolic filling results in decreased stroke volume.

Tachycardia and increased contractility are the initial compensatory responses, mediated by adrenergic stimulation to maintain cardiac output. However, blood pressure and cardiac output eventually decline.[10] In chronic settings, pericardial effusion may reach 1 to 2 liters before causing cardiac tamponade, provided the fluid accumulates gradually and the parietal pericardium has time to stretch and accommodate the increase.[11][12][13]

History and Physical

The clinical presentation of pericardial effusion ranges from being a clinically irrelevant, incidental finding to becoming a life-threatening cardiac tamponade. This wide variation is mainly due to the variable accumulation rate of the pericardial fluid. Acute accumulation may cause impaired cardiac filling and decreased cardiac output with as little as 100 mL of fluid. In contrast, chronic and slow accumulation may lead to significant effusions of 1 to 2 liters that produce no significant hemodynamic effects. 

In patients with pericardial effusion due to pericarditis, patients often present with chest pain and dyspnea, with symptoms improving while sitting upright and worsening while lying flat due to the inflamed pericardium contacting adjacent structures. Patients may also present with symptoms not specific to pericardial effusion, including dyspnea, edema, and fatigue. Other essential history elements include recent illnesses, malignancy, tuberculosis and vaccination status, autoimmune disorders, chronic kidney disease, renal failure, congestive heart failure, hypothyroidism, and liver disease.

Pericardial effusion leading to pericardial tamponade should be on the differential for patients in cardiac arrest or with vital sign abnormalities, including hypotension and tachycardia. The classic Beck triad, comprising hypotension, jugular venous distension, and muffled heart sounds, is only found in a minority of patients.[14] Other physical exam findings unique to pericardial effusion include the Ewart sign, characterized by dullness to percussion at the base of the left inferior scapular border, tubular breath sounds, and egophony.

The physical examination of patients suspected of having cardiac tamponade should include an evaluation for pulsus paradoxus, a drop in systolic blood pressure of more than 10 mm Hg during inspiration. This drop occurs because the expanding right ventricle collapses the left ventricle, causing the interventricular septum to bow and compress the left heart, leading to decreased filling, reduced stroke volume, and lower systolic blood pressure. While history and physical examination are critical components of the evaluation for pericardial effusion and cardiac tamponade, the standard of care now includes additional modalities such as echocardiography to confirm the diagnosis.

Evaluation

Several tests can help evaluate a suspected pericardial effusion. Most cases require a combination of multiple diagnostic modalities to accurately determine the cause and extent of pericardial effusion. The chest radiograph may not directly identify a pericardial effusion. The heart may appear boot-shaped in the presence of significant, chronic effusion, and radiology may comment on a "water bottle sign" or a water bottle-shaped heart. Pulmonary edema, pulmonary vessel engorgement, or pleural effusion may also be evident on chest radiographs, but none are sensitive or specific for pericardial effusion.

The electrocardiography (ECG) findings vary from normal to non-specific ST-segment changes for small effusions. The ECG may demonstrate electrical alternans for large effusions or tamponade, which is a specific but not sensitive finding. "Electrical alternans" refers to QRS complexes of varying heights corresponding to a back-and-forth motion of the heart within the pericardial sac as it swings on its anchored base during the cardiac cycle. The ECG may show PR depression or diffuse ST elevation if the pericardial effusion is due to pericarditis.

Transthoracic (TTE) or transesophageal echocardiography (TEE) is the diagnostic modality of choice when evaluating for pericardial effusion. Echocardiography dynamically assesses pericardial effusion size and detects signs of cardiac tamponade physiology. Pericardial effusion is identified as anechoic fluid surrounding the heart. In hemopericardium with a clot, pyogenic effusions, or exudative effusions, a hypoechoic clot or debris may be visible within the anechoic pericardial fluid.

Numerous criteria are used for diagnosing cardiac tamponade by TTE or TEE. Right atrial free-wall collapse or inversion during systole, right ventricular free-wall collapse during diastole, increased septal bowing into the left ventricle during inspiration and the right ventricle during exhalation, a dilated inferior vena cava without respiratory variation in a spontaneously breathing patient in sinus rhythm, and increased flow across the mitral valve during exhalation and the tricuspid valve during inspiration all potentially indicate intrapericardial pressures greater than intracardiac pressures and potential pericardial tamponade. Notably, some echocardiography findings are sensitive but not specific to cardiac tamponade, while others are specific but not sensitive.[15] Pericardial effusion may also be identified on computed tomography or magnetic resonance imaging of the chest or heart. However, these modalities are less important than echocardiography in evaluating pericardial effusion.[16][17][18]

Treatment / Management

Pericardial effusion treatment ranges from watchful waiting to emergent intervention and depends largely on the suspected etiology. Small effusions without hemodynamic compromise may be monitored with serial echocardiography or deemed insignificant enough to require no further follow-up. Large effusions may receive a diagnostic pericardiocentesis to evaluate the etiology or drained to provide symptomatic relief if the patient has associated symptoms such as dyspnea, chest discomfort, pulmonary or lower extremity edema, or decreased exercise tolerance.

Effusions that accumulate rapidly or grow large enough to cause hemodynamic instability or collapse require emergent management at the bedside, cardiac catheterization lab, or operating room. Drainage techniques include needle pericardiocentesis via a subxiphoid or anterior thoracic approach, with or without pericardial drain placement for serial evacuation, percutaneous balloon pericardiotomy, emergent thoracotomy with pericardiotomy, and surgical pericardial window via subxiphoid approach, anterior minithoracotomy, or video-assisted thoracoscopic surgery. The intervention chosen is based on the etiology of the pericardial effusion, the patient's clinical status at the time of the intervention, and the expected clinical course.[19][20]

Of note, patients with large pericardial effusions with underlying ventricular dysfunction have a risk of developing pericardial decompression syndrome (PDS) after pericardiocentesis. PDS is an infrequent, life-threatening complication following an uncomplicated pericardial evacuation for cardiac tamponade physiology.[21] PDS is characterized by paradoxical hemodynamic instability or pulmonary edema following an otherwise uncomplicated pericardial drainage. Physicians should be familiar with prevention strategies for PDS and offer vulnerable patients very close clinical monitoring, especially those undergoing pericardial drainage for large malignant effusions for suspected tamponade.

A sensible plan would be to avoid drainage of large quantities of pericardial fluid in a single attempt, especially in large pericardial effusions. The optimal approach involves removing enough pericardial fluid to relieve cardiac tamponade physiology, guided by hemodynamic or echo-Doppler monitoring. Subsequently, prolonged pericardial drainage may be used for gradual fluid removal until daily drainage falls below 30 to 50 mL, indicating resolution.[22]

Differential Diagnosis

The differential diagnosis of pericardial effusion includes the following conditions:

• Acute pericarditis
• Cardiac tamponade
• Cardiogenic pulmonary edema
• Constrictive pericarditis
• Dilated cardiomyopathy
• Effusive-constrictive pericarditis
• Myocardial infarction
• Pulmonary embolism

Correct diagnosis and management require careful clinical evaluation and appropriate diagnostic testing.

Prognosis

Pericardial effusion can either occur as an isolated finding or be associated with specific underlying conditions such as autoimmune, neoplastic, or metabolic diseases. Echocardiography is crucial for diagnosing, measuring, and serially assessing the hemodynamic impact of effusions on cardiac diastolic function. Advanced imaging techniques like computed tomography and cardiac magnetic resonance imaging should be utilized when initial tests are inconclusive.

Patient management should follow the 2015 European Society of Cardiology Guidelines for pericardial diseases, prioritizing the presence of hemodynamic compromise and suspicion of malignant or purulent pericarditis as the first step. The second step involves measuring C-reactive protein serum levels, followed by investigations for conditions known to be associated with pericardial effusion. The third step considers the size and duration of the effusion. Treatment should be individualized based on these factors.

The prognosis of chronic pericardial effusions largely depends on the underlying cause. Recent data suggests that individuals with idiopathic, chronic (lasting over 3 months), large (exceeding 2 cm), and asymptomatic pericardial effusions generally have a benign prognosis, and vigilant monitoring is often more reasonable and cost-effective than routine drainage, which was previously recommended.[23]

Complications

A recent study compared pericardiocentesis to pericardial window in dealing with pericardial effusion. The procedural success rate was 100% for pericardial window and 95% for pericardiocentesis, though this difference was not statistically significant (p-value equals 0.22). Patients who underwent a pericardial window had a longer hospital stay of more than 7 days than those who underwent pericardiocentesis (47% vs 17%, p-value equals 0.007).

However, the 30-day reaccumulation rate of pericardial fluid was significantly higher in the pericardiocentesis than in the pericardial window group (34% vs. 0%, p-value is less than or equal to 0.001). Additionally, patients undergoing a pericardial window experienced a higher number of complications, including major bleeding and infection (p-value is less than or equal to  0.001). Mortality between the 2 procedures is not significantly different (p-value equals 0.75).[24]