Definition

Abnormally high volume of fluid within the pericardial sac; cardiac tamponade refers to the clinical syndrome that results from reduced cardiac output due to mechanical compression of the heart.

Pathophysiology

Accumulation of effusion exceeds the elastic capabilities of the pericardial sac resulting in elevated intrapericardial pressure. Cardiac tamponade occurs when intrapericardial pressure exceeds cardiac diastolic filling pressures. The compliant right atrium and right ventricle normally have the lowest filling pressures and are thus predominantly affected. The resultant reduction in cardiac venous return diminishes cardiac output. In animals with chronic pericardial disease, low cardiac output activates compensatory mechanisms that lead to fluid accumulation, typically manifested as right-sided CHF. Animals with acutely developing effusions typically exhibit signs of weakness or collapse.

Systems Affected

• Cardiovascular-signs of low cardiac output and CHF
• Hepatobiliary-chronic passive congestion with mildly to moderately high liver enzymes
• Renal/Urologic-prerenal azotemia
• Respiratory-tachypnea or pleural effusion

Incidence/Prevalence

Pericardial disorders comprise approximately 8% of the canine cardiology caseload at referral institutions.

Geographic Distribution

Increased incidence of coccidioidomycosis-induced effusive constrictive pericarditis in the southwestern United States, Mexico, and Central and South America.

Signalment

Signs

Causes

• Neoplasia-hemangiosarcoma, heart base tumor, thyroid adenoma or adenocarcinoma, mesothelioma, metastatic neoplasia, and lymphoma (especially cats)
• Idiopathic-pericarditis (benign hemorrhagic effusion vs. effusive constrictive pericarditis with pericardial fibrosis)
• Coagulopathy-intoxication with vitamin K antagonist rodenticide, other coagulopathies
• CHF (especially cats)
• Infection-feline infectious peritonitis, coccidioidomycosis, bacterial pericarditis
• Congenital disorders-pericardioperitoneal diaphragmatic hernia, intrapericardial cysts
• Left atrial tear or cardiac trauma
• Pericardial foreign body

Risk Factors

• Cardiac neoplasia
• Advanced chronic valvular disease
• Coagulopathy

Differential Diagnosis

• CHF secondary to other causes (e.g., valvular disease, cardiomyopathy, congenital heart disease), hepatic failure, abdominal neoplasia with hemorrhage, protein-losing nephropathy or enteropathy, Budd-Chiari-like syndrome.
• Other causes of ascites (e.g., hepatic failure, hypoproteinemia, intra-abdominal neoplasia, and hemorrhage)-characteristically result in remarkable abnormalities on CBC and biochemistry profile, with a lack of jugular venous distention. Jugular vein examination can be helpful in differentiating these conditions from heart failure.

CBC/Biochemistry/Urinalysis

• CBC-usually normal; anemia possible in animals with hemangiosarcoma, lymphoma, or coagulopathy; red cell morphology may be abnormal; may see thrombocytopenia in animals with neoplasia or DIC.
• Biochemistry profile-often normal; may see mild to moderately elevated liver enzymes (in animals with chronic passive hepatic congestion), mild azotemia (typically prerenal), hypoproteinemia, and mild electrolyte abnormalities (e.g., hyponatremia, hypochloremia, and hyperkalemia).
• Urinalysis-usually normal with normal renal concentrating ability unless a diuretic has been administered.

Other Laboratory Tests

• Elevated serum concentrations of cardiac troponin I (cTnI) have been demonstrated in dogs with pericardial effusion, especially in those with hemangiosarcoma.
• Clotting times (e.g., activated partial thromboplastin time and one-stage prothrombin time)-prolonged in animals with vitamin K antagonist rodenticide intoxication or DIC.
• Pericardial fluid analysis, although limited in diagnostic sensitivity and specificity, may be helpful in identifying certain neoplastic etiologies (e.g., lymphoma) or infectious causes.
• Feline infectious peritonitis testing or feline leukemia virus testing may be useful in cats.

Imaging

Diagnostic Procedures

Pathologic Findings

• Pathologic findings will vary based on the underlying cause of pericardial effusion.
• Small cardiac masses may be identified that were not visible on antemortem testing.
• Dogs with left atrial tears will have advanced mitral endocardiosis with thickened and irregular mitral and/or tricuspid valve leaflets, left atrial enlargement and endocardial jet lesions, and possible ruptured chordae tendinae.

Appropriate Health Care

Cardiac tamponade warrants immediate pericardiocentesis; if uncomfortable with performing pericardiocentesis, referral to individuals with competence in this technique is strongly advised. Repeated pericardiocentesis may be needed; surgery may be indicated in selected dogs. Pericardiocentesis is rarely required in the cat.

Nursing Care

Unless the patient has marked dehydration, fluids are generally not required or recommended for chronic pericardial effusion. Mild volume expansion may be useful in selected animals with acute pericardial effusion. Administer oxygen to dogs with tachypnea or signs of hemodynamic instability.

Activity

Cage rest, followed by exercise restriction

Diet

N/A

Client Education

Clients should be informed that pericardial effusions are typically recurrent in nature, though the prognosis may vary greatly depending on the underlying cause. Clients should be educated about the importance for close monitoring for recurrent effusion and warned of the potential for sudden death.

Surgical Considerations

• Pericardiectomy may be useful in the treatment of pericardial effusion accompanying heart base tumors and prolongs survival; this may also be considered for palliation of right atrial hemangiosarcoma but it is unknown whether it has any impact on survival.

• If idiopathic-may respond to pericardiocentesis; pericardiectomy is indicated for recurrent effusion.
• Right auricular appendage masses may be treated surgically but resection alone without adjuvant chemotherapy is unlikely to significantly prolong survival.
• Thoracoscopy allows for partial pericardiectomy with reduced risk and reduced postoperative pain.

Drug(s) Of Choice

• Drugs should not be used in place of pericardiocentesis.
• Diuretics-may help reduce ascites but can lead to progressive azotemia and patient weakness; generally not advised.
• Vitamin K-indicated for patients with rodenticide anticoagulant intoxication.
• Appropriate antibiotics are indicated in animals with infectious pericarditis.
• Chemotherapy-may be useful to treat effusion caused by lymphoma; partially effective in the treatment of atrial hemangiosarcoma and generally ineffective for heart-base tumor; adjuvant doxorubicin-based chemotherapy following right atrial mass resection has been shown to increase survival times but dogs rarely survive more than 6 months postoperatively.

Contraindications

Digitalis, vasodilators, and angiotensin- converting enzyme inhibitors-reported to be relatively or absolutely contraindicated.

Precautions

Diuretic administration often leads to exacerbation of weakness and azotemia.

Alternative Drug(s)

• Intracavitary chemotherapy may be attempted to treat mesothelioma.
• Anti-inflammatories or colchicine may be useful in selected dogs with idiopathic pericardial effusion.
• Additional immunosuppressives or intracavitary chemotherapy can be considered for recurrent effusions, especially in cases with recurrent pleural effusion after pericardiectomy.

Patient Monitoring

• ECG-advised during first 24 hours as pericardiocentesis often leads to ventricular arrhythmias.
• Pericardial effusion may recur at any stage; examination and echocardiography at 10–14 days and every 2–4 months recommended to detect recurrent idiopathic pericardial effusion.

Possible Complications

• Hypotension or shock.
• Pneumothorax, arrhythmias, and myocardial perforation or coronary laceration secondary to pericardiocentesis.

Expected Course and Prognosis

• Right atrial hemangiosarcoma-poor; tumor is highly malignant, usually not resectable at the time of diagnosis; may respond transiently to adriamycin-based chemotherapy; the benefit of palliative pericardiectomy is unproven.
• Chemodectoma-fair; slow-growing tumor, late to metastasize; pericardiectomy often resolves clinical signs; may respond to chemotherapy or radiation therapy;survival of up to 3 years has been reported following pericardiectomy alone.
• Prognosis is good with idiopathic pericardial effusion; approximately 50% of cases resolve after one or two pericardiocenteses; pericardiectomy is often curative in persistent cases.

Associated Conditions

Hemangiosarcoma of the spleen

Age-Related Factors

• Idiopathic pericardial effusion may be more common in middle-aged to elderly dogs.
• Hemangiosarcoma and heart-base tumors are more common in elderly dogs.

Zoonotic Potential

Coccidioidomycosis

Synonyms

• Cardiac tamponade
• Pericardial tamponade
• Pericarditis

See Also

• Anticoagulant Rodenticide Poisoning
• Atrial Wall Tear
• Chemodectoma
• Coccidioidomycosis
• Feline Infectious Peritonitis
• Hemangiosarcoma, Heart
• Myocardial Tumors

Abbreviations

• CHF = congestive heart failure
• cTnI = cardiac troponin I
• DIC = disseminated intravascular coagulation
• ECG = electrocardiogram
• PPDH = pericardioperitoneal diaphragmatic hernia

Client Education Handout Available Online