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Pericardial Effusion in Dogs: Diagnosis & Treatment | VETgirl Veterinary Continuing Education Podcasts

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February 2024

In today’s VETgirl online veterinary CE podcast, we’re going to talk about pericardial effusion – from how to diagnose it, what the clinical signs are, and how to treat it! Most importantly, tune in to learn how to perform a successful pericardiocentesis (well, as best I can teach you via an audio podcast!).

Pericardial effusion is a commonly diagnosed condition in dogs that results from the accumulation of fluid within the pericardial sac, which surrounds the heart. This accumulation of fluid can lead to “pressure on the heart” (in other words, cardiac tamponade), causing decreased FILLING of the heart and secondary decreased cardiac output, eventually resulting in signs of shock. The degree of pressure exerted by the pericardial effusion depends on the volume of the effusion, the rate of fluid accumulation, and the distensibility of the fibrous pericardium.

Pericardial effusion can present in one of two ways, as acute cardiac tamponade, or as a more chronic accumulation of fluid. Acute pericardial effusion often has a small volume of pericardial effusion, let’s say 50 to 100 ml in the pericardial sac, which causes marked intrapericardial pressure and cardiac tamponade. With more chronic cases, there is typically a slower accumulation of pericardial effusion, allowing the pericardial sac to stretch and accommodate a significantly larger amount of fluid before cardiac tamponade results. With chronic cardiac tamponade, we can see signs of heart failure. In most cases, we see right-sided heart failure with pericardial effusion, as right-sided diastolic pressure has to increase only a small amount (from a normal of 5 mm Hg to 10-15 mm Hg) to result in failure [1].

So, what are the clinical signs of pericardial effusion in dogs and who do we see pericardial effusion in? Signs can include lethargy, tachycardia, tachypnea, poor or absent femoral pulses, pulsus paradoxus (when the pulse is stronger during exhalation and weaker on femoral palpation during inhalation), exercise intolerance, weakness, and syncope/fainting. Other clinical signs include decreased appetite, cough, vomiting, abdominal effusion, or even sudden death. If the effusion is chronic, you may also observe hepatomegaly, jugular venous distension, and ascites due to the resultant right-sided congestive heart failure. As for who we see it in? Typically in middle-aged, male, large breed dogs.

What are the typical causes for pericardial effusion? The two most common causes are idiopathic or cardiac neoplasia, with hemangiosarcoma and heart-based tumors being the most common cardiac neoplasias. (Not to forget our feline friends, but pericardial effusion in cats is relatively rare; when we do see it, it is often due to cardiac neoplasia like lymphoma, rare infections like coccidiomycosis, left atrial rupture, trauma or CHF).

Recommended diagnostics can include routine bloodwork including a CBC, chemistry and PT/PTT, radiography, and echocardiography. Radiographs should be limited to a dorsoventral, and possibly lateral view to decrease stress on the dog with cardiac tamponade. Radiographs most commonly reveal an enlarged globoid cardiac silhouette and a dilated caudal vena cava if cardiac tamponade is present. Less commonly, a bulge at the top of the heart can be seen (especially with a heart-based tumor) or pleural effusion may be seen. Don’t forget to look for chest mets.

As for other important diagnostics? An electrocardiogram (ECG) may reveal sinus rhythm, supraventricular tachycardia (SVT), sinus tachycardia, ventricular premature contractions (VPCs) or even electrical alternans (which is due to the heart swinging in the fluid-filled pericardial sac). Echocardiography is highly recommended as the diagnostic test of choice to detect and evaluate the severity of pericardial effusion, as well as providing the ability to perform a diagnostic pericardiocentesis to help determine the underlying cause of the pericardial effusion. On echo, a tumor may be visible and cardiac tamponade may be present (seen as collapsed right atrial and right ventricular walls during systole or diastole).[1]

The choice of treatment for pericardial effusion depends on the dog’s clinical condition, the amount of fluid accumulation, and the underlying cause of the effusion. Dogs with acute cardiac tamponade require urgent treatment as they often present in a critical state with a severely decreased cardiac output, life-threateningly low blood pressure, and signs of decompensatory shock. Emergency treatment generally involves the removal of pericardial fluid through pericardiocentesis. For dogs with chronic pericardial effusion, management may include medical treatment, although this is typically ineffective. Ultimately, the removal of a portion of the pericardial sac, known as a pericardiectomy, may be necessary to prevent fluid accumulation.

To perform a pericardiocentesis, the patient is placed in either sternal or lateral recumbency, typically with the use of sedation for mild chemical restraint, and with the aid of an ECG for monitoring of the patient. Ideally, the patient should also be on concurrent IV fluid therapy, if appropriate based on clinical signs. A local block using 2% lidocaine is also suggested to reduce discomfort for your patient. Medications such as propofol, acepromazine, and inhalant anesthesia should be avoided as they could result in cardiovascular compromise. Unless indicated otherwise by ultrasound guidance, the patient should be prepped by clipping and scrubbing between the 4th and 6th intercostal space on the right side. There is some controversy as to the best side to use but you can ultimately choose whichever side has the best window of approach. (VETgirl was trained on the right side, just saying). In preparation for the procedure, make a small skin stab incision with a No. 11 blade to prevent drag of the catheter through the skin. Also prior to insertion, place side holes in the distal portion of the pericardiocentesis catheter, but avoid making a hole more that 40% of the circumference of the catheter and holes directly opposite each other, both of which can result in catheter weakness.

A 14-gauge, 5-inch catheter works for most medium to large-breed dogs, but you can also use a 16-gauge, 2 ½ inch catheter for smaller dogs. The catheter should enter cranial to the rib to avoid the intercostal vessels and nerves that run along the caudal side of the ribs. Insert the catheter through the skin and thoracic wall until you feel a pop. Once within the pleural space, advance the catheter slowly (1-2 mm at a time) towards the heart, aiming for the opposite scapula (or elbow), while you continuously monitor the patient for discomfort and the ECG for arrhythmias. As you advance the catheter, watch carefully for a flash of pericardial fluid in the hub of the catheter. Typical fluid from the pericardial space will range from red to a port wine color. Once the fluid is seen within the hub of the catheter, the catheter is advanced another 1 to 2 mm to make certain it is best seated within the pericardial space. Remove the stylet and connect an extension set to the catheter at one end and a three-way stopcock on the other. Use a 10 to 20 ml syringe to aspirate the fluid.

VETgirl’s hint? Before removing too much fluid, make sure to place a small sample of the aspirated fluid directly into a red top tube. The red top tube is used to be sure the fluid withdrawn is effusion and not blood from an iatrogenic puncture of a major vessel or the cardiac chamber. Fluid from an effusion will not clot within the first two minutes in the red top tube. On the other hand, if a clot forms within the red top tube, it is a concern for iatrogenic trauma (e.g., cardiac puncture) and the catheter should be removed carefully and quickly. If the fluid is determined to be from the effusion, a sample should also be placed in an EDTA tube for analysis.

After obtaining your sample, a 60-ml syringe can then be used to more rapidly withdraw the effusion (again, once you confirmed the effusion doesn’t clot!). The amount of fluid obtained will vary but may be as much as 1/2 to 1 liter in a large breed dog. Since dogs are often tachycardic on presentation, you should notice a fairly dramatic decrease in heart rate within a few minutes of successful pericardiocentesis. Once fluid is no longer able to be drawn into the syringe, you can remove the catheter. Don’t go too “crazy” trying to get pericardial effusion, as you don’t want to risk puncturing the heart. VETgirl’s tip to remember? You really are just trying to puncture the pericardial sac and remove the effusion, but even when you remove the catheter after you finish the pericardiocentesis, the small hole will help pericardial effusion leak out for a short amount of time each time the heart beats!

Ultimately, prognosis will vary based on whether it was idiopathic in origin or due to secondary neoplasia. If reccurence of pericardial effusion develops, a repeat pericardiocentesis is indicated. A subtotal pericardectomy is recommended after multiple pericardiocentesis procedures are required.

So, what’s the prognosis for pericardial effusion? The prognosis will vary if the pericardial effusion is due to neoplasia. With heart-based tumors, subtotal pericardiectomy is warranted with recurrent pericardial effusion, and survival rates of up to 2 years have been reported. However, if it’s a right atrial mass secondary to hemangiosarcoma, the prognosis is poor to grave due to micrometastasis at the time of diagnosis. It is important that you closely monitor dogs with pericardial effusion as they can develop recurrent effusions or secondary complications, such as fatal arrhythmia, cardiovascular collapse, systemic hypertension, thromboembolism or acute death.

So, what can we take away from this VETgirl podcast? Pericardial effusion in dogs can be a severe and life-threatening condition that requires prompt diagnosis and treatment. In other words, you have to be able to rapidly recognize it! If you have an ultrasound in your clinic, that rapid TFAST ultrasound may be worth it (don’t forget to document and charge for that TFAST!). With proper management, dogs can have a positive prognosis with limited risk of recurrence or secondary complications. Most importantly, don’t be hesitant to perform a pericardiocentesis – it’s scary, but with appropriate preparation, sedation and support, you can do it! It is really crucial to educate pet owners on the importance of regular health checkups and veterinary care to prevent and manage pericardial effusion in their dogs.

References:
1. Kittleson MD. Pericardial effusion in dogs and cats. Merck Manual Veterinary Manual, Accessed November 10, 2023 at https://www.merckvetmanual.com/circulatory-system/various-heart-diseases-in-dogs-and-cats/pericardial-disease-in-dogs-and-cats

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