Welcome to the all-new Vetlearn

  • Vetlearn is becoming part of NAVC VetFolio.
    Starting in January 2015, Compendium and
    Veterinary Technician articles will be available on
    NAVC VetFolio. VetFolio subscribers will have
    access to not only the journals, but also:
  • Over 500 hours of CE
  • Community forums to discuss tough cases
    and networking with your peers
  • Three years of select NAVC Conference
  • Free webinars for the entire healthcare team

To access Vetlearn, you must first sign in or register.


  Sign up now for:
Become a Member

Compendium July 2007 (Vol 29, No 7)

Canine Pericardial Effusion: Diagnosis, Treatment, and Prognosis

by Scott Shaw, John E. Rush, DVM, MS, DACVIM (Cardiology), DACVECC

    CETEST This course is approved for 2.0 CE credits

    Start Test


    Most cases of pericardial effusion can be diagnosed with a thorough physical examination. Physical examination findings may include muffled heart sounds, pulsus paradoxus, and jugular venous distention. Radiographs may show a globoid cardiac silhouette. Echocardiography is reliable in diagnosing pericardial effusion. Pericardiocentesis is indicated for the emergency treatment of pericardial tamponade. Pericardiectomy may improve survival in some dogs. The prognosis varies greatly, depending on the underlying cause.

    Pericardial effusion can result in life-threatening clinical signs and commonly requires emergency care. This article focuses on the diagnosis, treatment, and prognosis of dogs with pericardial effusion.



    The history of a dog with pericardial effusion varies, depending on whether the effusion is acute or chronic. Dogs with chronic pericardial effusion typically have signs secondary to right-sided heart failure, including lethargy, exercise intolerance, respiratory difficulty, weight loss, and abdominal distention. These signs may be progressive as the ability of the pericardium to stretch is exceeded. Dogs with acute pericardial effusion typically present with a history of acute collapse or weakness secondary to decreased cardiac output.1 Collapse sometimes occurs shortly after physical exertion, and syncope may also be noted.

    Physical Examination

    Although no single physical examination finding is pathognomonic of pericardial effusion, a combination of several classic findings is highly indicative of the diagnosis. A combination of muffled heart sounds, jugular venous distention, and poor pulse quality or pulsus paradoxus should result in a very high index of suspicion for the presence of pericardial effusion, particularly in middle-aged or older large-breed dogs. Other physical examination findings may include tachycardia, hepatomegaly, ascites, and tachypnea or dyspnea.

    Jugular venous distention occurs secondary to increased right atrial filling pressures. All dogs with pericardial tamponade have jugular venous distention. Dogs with thick haircoats may require hair clipping to allow detection of jugular venous distention. Many dogs with pericardial effusion have muffled heart sounds resulting from attenuation of the sound by the effusion, but affected dogs can also have normal heart sounds.

    Pulsus paradoxus is an exaggerated pattern of change in arterial pressure during respiration and is characterized by a fall in blood pressure during inspiration. This occurs when the normal negative inspiratory pressure is transmitted to the pericardium and right atrium, resulting in augmentation of right atrial and ventricular filling during inspiration. This shifts the interventricular septum toward the left ventricle. Because the degree of cardiac distention is limited by the effusion, left ventricular filling is decreased with a resultant decrease in stroke volume during the next cardiac cycle. This change can be identified as a weak pulse during inspiration with a stronger pulse during expiration.2 Pulsus paradoxus can best be detected in dogs that are breathing slowly while laterally recumbent. It may not be detected in all affected dogs that are standing or panting.

    Laboratory Testing

    Mild anemia may occur secondary to blood loss or to anemia associated with chronic disease. A mild increase in the leukocyte count also frequently occurs.3 Nucleated erythrocytes, schistocytes, or acanthocytes may occur in dogs with pericardial effusion, especially those with hemangiosarcoma. The results of serum chemistry analysis are generally within normal limits except for mild increases in the blood urea nitrogen and/or creatinine levels in patients with prerenal azotemia, which may develop because of decreased cardiac output. Mild hyponatremia, hypochloremia, and hyperkalemia occur in some cases, especially in dogs with considerable ascites due to a decrease in effective circulatory volume. Dogs with pericardial effusion secondary to uremic pericarditis have marked increases in their blood urea nitrogen and creatinine levels.3 In general, changes in the hemogram reflect the underlying disease process.

    A coagulation screen should be conducted when clinically indicated based on historical or other physical examination findings to rule out anticoagulant rodenticide toxicosis. Dogs with coagulopathy due to anticoagulant rodenticide toxicosis typically have markedly prolonged bleeding times.

    Titers for Coccidioides immitis should be conducted in dogs from endemic areas. Positive titers highly suggest a fungal cause of pericardial effusion.

    One report4 found that cardiac troponin I levels are more elevated in dogs with pericardial effusion caused by hemangiosarcoma than in dogs with pericardial effusion resulting from other causes. Further studies are required to confirm the findings and elucidate the degree of troponin I elevation that is consistent with a diagnosis of hemangiosarcoma.


    Mild to severe enlargement of the cardiac silhouette is commonly observed on thoracic radiographs. The size of the cardiac silhouette increases in conjunction with the chronicity of the effusion and the associated fluid volume. The cardiac silhouette frequently appears globoid or rounded. Pleural effusion may be present, and the caudal vena cava may be enlarged secondary to right-sided congestive heart failure.5 In addition, the edges of the cardiac silhouette may be very "sharp" due to decreased motion artifact from cardiac contraction6 (Figure 1). Some dogs may also show evidence of metastatic disease. Abdominal radiography may reveal hepatomegaly or decreased abdominal detail due to ascites, either of which may occur secondary to right-sided congestive heart failure caused by pericardial effusion.


    Sinus tachycardia is a frequent electrocardiographic finding. Ventricular premature contractions occur less frequently; however, they are common during or after pericardiocentesis. In dogs, low-voltage QRS complexes (<1 mV) in all limb leads may occur because of increased electrical impedance caused by pericardial effusion. Low-voltage QRS complexes have been reported3 in approximately 50% of dogs with pericardial effusion. Electrical alternans occurs in 6% to 60% of cases1,3 (Figure 2). Electrical alternans is characterized by a cyclic change in R-wave amplitude (e.g., 1:1, 2:1) caused by the motion of the heart in the pericardial sac. A normal electrocardiogram does not rule out pericardial effusion.


    Echocardiography is considered the "gold standard" for establishing a diagnosis of pericardial effusion. From the right parasternal view, an echo-free space is evident between the pericardial sac and epicardium (Figure 3). In some cases, a left parasternal view may allow better visualization of the right side of the heart, which may aid in identifying right atrial masses. A fluid volume as small as 10 to 15 ml can be detected using ultrasonography. Dia­stolic collapse of the right atrium or ventricle can be detected and is diagnostic of pericardial tamponade. Although echocardiography cannot provide a definitive diagnosis, in many diseases, the location and appearance of a mass are sufficiently consistent to allow strong assumptions to be made regarding its origin. A cavitated, soft tissue mass arising from the right atrium is almost certainly a hemangiosarcoma (Figures 4 and 5 ). A mass arising from and encircling the ascending aorta is likely a heart-base tumor. Transthoracic two-dimensional echocardiography reportedly has an 80% sensitivity for a diagnosis of cardiac masses.7 In most cases, clinicians with basic ultrasonographic skills can readily identify pericardial effusion. However, visualization and definitive identification of masses often require an exhaustive echocardiographic examination from both sides of the thorax and a higher level of echocardiographic skill.

    Fluid Analysis

    Analysis of fluid obtained from pericardiocentesis is rarely helpful in establishing the cause of pericardial effusion. The effusion typically has a hemorrhagic appearance despite the underlying cause. One study8 of 50 dogs with pericardial effusion found that cytologic examination could not reliably distinguish between pericardial effusion due to neoplasia and that due to other causes. The use of pericardial fluid pH as a marker of malignancy has also been suggested.9 However, reports10,11 have found that pH cannot be accurately used to identify the underlying cause in most cases. Fluid analysis may be diagnostic in cases of infection or lymphosarcoma; therefore, although cytologic evaluation has a low diagnostic yield, we still recommend it when a mass that is not consistent with hemangiosarcoma is observed.



    Pericardiocentesis is indicated as an emergency treatment of cardiac tamponade (see box). Cases of pericardial effusion that do not demonstrate clinical or echocardiographic signs consistent with cardiac tamponade may not require pericardiocentesis. Reported complications associated with pericardiocentesis include ventricular premature contractions, laceration of the coronary artery, and sudden death.12 Some cases of idiopathic pericardial effusion resolve after one or more pericardiocenteses.13 Most authors do not recommend long-term diuretic therapy to aid the resolution of ascites because diuretics can result in a decrease in preload with a resultant catastrophic decrease in cardiac output if cardiac tamponade recurs.14

    Surgical Treatment

    Pericardiectomy can be a definitive treatment of idiopathic pericardial effusion and a palliative treatment of malignant pericardial effusion.3 When pericardial effusion recurs after one or more therapeutic pericardiocenteses, surgical treatment becomes an option. Surgery may be used to remove the pericardium and obtain a biopsy specimen or resect a mass of uncertain origin. Surgery is also an option for the management of traumatic pericardial effusion. Because of the poor long-term prognosis for affected patients, many owners decline surgery when a right atrial mass is detected using echocardiography or pulmonary metastasis is detected using thoracic radiography. Cases of peritoneopericardial diaphragmatic hernia (PPDH) can be definitively treated using surgery. In other cases, the goal is to allow drainage of the pericardial fluid into the pleural space, which allows superior lymphatic drainage and may reabsorb the accumulating effusion, and to prevent the recurrence of cardiac tamponade.

    Traditional surgical approaches include median sternotomy or right lateral thoracotomy. Subtotal pericardiectomy can be performed with either approach. The advantages of open thoracotomy include complete removal of the pericardium below the level of the phrenic nerve, accurate identification of masses arising from the right atrium, and the ability to excise the right auricular appendage when the mass is isolated to that part of the heart.15,16

    Thoracoscopic pericardiectomy is available to treat recurrent pericardial effusion. Thoracoscopic pericardiect­omy offers the advantage of a decreased morbidity rate compared with that associated with traditional thoracotomy. Disadvantages of thoracoscopic pericardiectomy include the inability to visualize the entire right atrium and perhaps unfounded concerns that the relatively small pericardial window created may close over time.17,18

    The use of percutaneous balloon pericardiotomy to manage pericardial effusion has also been described.19,20 It offers the advantage of being minimally invasive and may be useful in patients with a poor long-term prognosis resulting from previously identified neoplasia. The main disadvantages of this technique include the inability to obtain a tissue biopsy specimen and the possible recurrence of pericardial effusion due to closure of the pericardial window. Because the heart is not directly visualized, it may be more predisposed to serious complications than when other techniques are used.

    Adjuvant Therapies

    Chemotherapy may be useful in some cases of malignant pericardial effusion. Intracavitary chemotherapy has been used to treat malignant mesothelioma. There is little information on the efficacy of chemotherapy to treat malignant pericardial effusion.


    The prognosis for dogs with pericardial effusion varies greatly, depending on the underlying cause. Congenital PPDH generally has a favorable prognosis. The prognosis for dogs with pericardial effusion secondary to hemangiosarcoma is generally poor, with the average duration of survival reportedly being 1 to 3 months.16,21,22 Many dogs initially respond to pericardiocentesis, but signs recur shortly after effusion recurs. Because aortic body tumors are slow growing, the prognosis for dogs with these tumors can be fair to good (129 days without pericardiectomy; 661 days with pericardiectomy).23 Dogs with mesothelioma that is treated using pericardiectomy may also have a fair to good prognosis. The mean duration of survival after a diagnosis of mesothelioma and subsequent pericardiectomy is reportedly 13.6 months, with 80% of patients surviving 1 year and 40% surviving 2 years.24 The prognosis for pericardial effusion due to other types of neoplasia is generally poor to guarded.

    Infectious pericardial effusion has a guarded to good prognosis and typically requires a combination of surgical pericardiectomy and antimicrobial or antifungal therapy.25

    Fluid from pericardial effusion secondary to congestive heart failure rarely accumulates in a large enough volume to require pericardiocentesis, and the prognosis is dictated by the severity of the underlying heart disease. Dogs with rupture of the left atrium secondary to myxomatous degeneration have a poor prognosis resulting from the severity of the underlying heart disease and the high likelihood of recurrence. In the short term, affected dogs may respond to aggressive therapy for heart failure.

    Constrictive pericarditis should be treated using pericardiectomy and therapy directed toward the underlying cause if one is identified. The long-term prognosis for dogs with constrictive pericarditis is guarded; six of nine dogs did not survive the perioperative period in one study.26

    Idiopathic pericardial effusion has a good to excellent prognosis. It may spontaneously resolve after one or more therapeutic pericardiocenteses or require surgical pericardiectomy. In one study,13 50% of patients were alive 1,500 days after the initial diagnosis. Another study16 reported a 72% survival rate after 18 months. In general, surgical pericardiectomy using one of the discussed techniques is indicated in dogs with chronic pericardial effusion.


    Pericardial effusion can result in cardiac tamponade, which requires emergency pericardiocentesis. The prognosis associated with pericardial effusion varies greatly, depending on the underlying cause. Surgical or thoracoscopic pericardiectomy can be used as definitive or palliative treatment of pericardial effusion.


    *A companion article on pathophysiology and cause begins here.

    See Key Points box.

    Downloadable PDF

    1. Smith F, Rush J: Diagnosis and treatment of pericardial effusion, in Kirk R, Bonagura J (eds): Current Veterinary Therapy XIII. Philadelphia, WB Saunders, 1999, pp 772-777.

    2. Shoemaker W: Pericardial tamponade, in Grenvik A (ed): Textbook of Critical Care. Philadelphia, WB Saunders, 2000, pp 1097-1101.

    3. Berg R, Wingfield W: Pericardial effusion in the dog: A review of 42 cases. JAAHA 20:721-730, 1984.

    4. Shaw SP, Rozanski EA, Rush JE: Cardiac troponins I and T in dogs with pericardial effusion. J Vet Intern Med 18(3):322-324, 2004.

    5. Lehmkuhl L, Bonagura J, Biller D, Hartman W: Radiographic evaluation of caudal vena cava size in dogs. Radiol Ultrasound 38:94-100, 1997.

    6. Root C, Bahr R: The heart and great vessels, in Thrall D (ed): Textbook of Veterinary Diagnostic Radiology, ed 2. Philadelphia, WB Saunders, 1994, pp 316-317.

    7. Thomas W, Sisson D, Bauer T, Reed J: Detection of cardiac masses in dogs by two-dimensional echocardiography. Vet Radiol 25:65, 1984.

    8. Sisson D, Thomas W, Ruehl W, Zinkl J: Diagnostic value of pericardial fluid analysis in the dog. JAVMA 184:51-54, 1984.

    9. Edwards N: The diagnostic value of pericardial pH determination. JAAHA 32:63-66, 1996.

    10. Fine D, Tobias A, Jacob K: Use of pericardial fluid pH to distinguish between idiopathic and neoplastic effusions. J Vet Intern Med 17:525-529, 2003.

    11. de Laforcade AM, Freeman LM, Rozanski EA, Rush JE: Biochemical analysis of pericardial fluid and whole blood in dogs with pericardial effusion. J Vet Intern Med 19(6):833-836, 2005.

    12. Martin M: Pericardial disease in the dog. J Small Anim Pract 53:381-385, 1999.

    13. Gibbs C, Gaskell C, Darke P, Wotton P: Idiopathic pericardial haemorrhage in dogs: A review of fourteen cases. J Small Anim Pract 23:483-500, 1982.

    14. Bouvy B, Bjorling D: Pericardial effusion in dogs and cats, part 1. Normal pericardium and causes and pathophysiology of pericardial effusion. Compend Contin Educ Pract Vet 13:417-424, 1991.

    15. Berg R: Pericardial disease and cardiac neoplasia. Sem Vet Med Surg Small Anim 9:185-191, 1994.

    16. Aronsohn M, Carpenter J: Surgical treatment of idiopathic pericardial effusion in the dog: 25 cases (1978-1993). JAAHA 35(6):521-525, 1999.

    17. Jackson J, Richter K, Launer D: Thoracoscopic partial pericardiectomy in 13 dogs. J Vet Intern Med 13:529-533, 1999.

    18. Dupre G, Corlouer J, Bouvy B: Thoracoscopic pericardiectomy performed without pulmonary exclusion in 9 dogs. Vet Surg 30:21-27, 2001.

    19. Cobb M, Boswood A, Griffin G, McEvoy F: Percutaneous balloon pericardiotomy for the management of malignant pericardial effusion in two dogs. J Small Anim Pract 37(11):549-551, 1996.

    20. Sidley J, Atkins C, Keene B, DeFrancesco T: Percutaneous balloon pericardiotomy as a treatment for recurrent pericardial effusion in six dogs. J Vet Intern Med 16(5):541-546, 2002.

    21. Ware W, Hopper D: Cardiac tumors in dogs: 1982-1995. J Vet Intern Med 12:95-103, 1999.

    22. Brown N, Patnaik A, MacEwen E: Canine hemangiosarcoma: Retrospective analysis of 104 cases. JAVMA 186:56-58, 1985.

    23. Vicari E, Brown D, Holt D, Brockman D: Survival times of and prognostic indicators for dogs with heart-base masses: 25 cases (1986-1999). JAVMA 219:485-487, 2001.

    24. Dunning D, Monnet E, Orton C, Salman M: Analysis of prognostic indicators for dogs with pericardial effusion: 46 cases (1985-1996). JAVMA 212:1279-1280, 1998.

    25. Aronson L, Gregory C: Infectious pericardial effusion in five dogs. Vet Surg 24:402-407, 1995.

    26. Thomas W, Reed J, Bauer T, Breznock E: Constrictive pericarditis disease in the dog. JAVMA 184(5):546-553, 1984.

    References »

    NEXT: Canine Pericardial Effusion: Pathophysiology and Cause

    CETEST This course is approved for 2.0 CE credits

    Start Test


    Did you know... Most secondary systemic hypertension is caused by renal, cardiac, and endocrine diseases.Read More

    These Care Guides are written to help your clients understand common conditions. They are formatted to print and give to your clients for their information.

    Stay on top of all our latest content — sign up for the Vetlearn newsletters.
    • More