Heart Parts: Pericardial Effusion

Imagine trying to take deep breaths wearing a jacket four sizes too small

February 4, 2019 (published)
Photo courtesy of DepositPhotos

Less readily diagnosed and more easily missed than hemoabdomen, pericardial effusion is medicalese for a buildup of fluid in the sac around the heart. Heart failure is basically a buildup of fluid in bad places because the heart can’t move it around and deliver oxygen.

Most people know the earth is about 2/3 water – but did you know that our bodies and those of our pets are also mostly water? Fluid is crucial for life and how fluid is handled is one of the body’s main priorities and the main way of staying alive. When fluid goes where it shouldn’t, bad things happen.

Another little-known fact is that the heart is surrounded by a thin but rather tough membrane called the pericardium. Peri is the Latin root meaning “around” and cardium refers to the heart itself. This sac normally contains a small amount of fluid that helps lubricate the heart muscle as it beats. However, sometimes this small amount of fluid can increase. A little extra fluid is no big deal, but a large volume of fluid developing rapidly can impair the pumping action of the heart and result in heart failure. The pericardial sac doesn’t stretch easily, so it becomes like a straitjacket around the heart. Imagine trying to take really deep breaths while wearing a jacket four sizes too small and you’ll have some idea how the heart can struggle when pressure builds up from extra fluid in the pericardial sac. You can breathe out, no problem, but breathing in is no fun, right?

The most common way the fluid builds up and causes problems is similar to the cause of hemoabdomen: a ruptured tumor. Dogs are prone to developing tumors on a part of the heart called the auricle, which, along with the rest of the heart, is located inside the pericardial sac. The tumors that develop on the auricle tend to be nasty, aggressive cancerous growths known as hemangiosarcomas. When hemangiosarcomas arise in the spleen or liver and rupture, a hemoabdomen develops. When one grows on the auricle and begins to bleed, the normally small volume of fluid in the sac increases quickly and results in the poor heart trying to "breathe in" while wearing a tiny jacket.

There are a couple of other conditions that can cause the pericardial fluid volume to increase, but in dogs a ruptured tumor is one of the most common. (Cat’s don’t have hearts, only a tiny glistening black jewel that holds all the secrets of the vast universe, so they’re nearly immune to this condition.) (Nearly.) The constant movement of the heart, coupled with the tendency of these tumors to bleed when jostled, means that a small tumor can produce a lot of blood in a teeny tiny short amount of time.

What happens when these tumors bleed? As the amount of blood inside the sac rises, pressure on the outside of the heart increases and it loses the ability to pump blood because it can’t fill itself up properly. It can still push the little bit of blood out, but blood struggles to get back into the heart from the body. Oxygen delivery to the body drops off, blood pressure drops and the patient goes into shock. Imagine the poor old heart, struggling inside its tiny little coat, while the rest of the body is wondering where all the life-giving blood and oxygen went. Dogs with pericardial effusion have pale gums, low body temperature, low blood pressure and are unable to stand up. If the situation isn’t recognized and corrected rapidly, organ failure, unconsciousness, and death can occur quickly.

One of the most important things in diagnosing pericardial effusion is to think of it as a possibility. It’s not a common condition, so realizing it’s a possible cause of unexplained collapse is vital to making the right call in time. It usually strikes older, large-breed dogs (it’s quite rare in cats, even those with hearts) and dogs with German shepherd or golden retrievers in their mix are especially prone to it. If I ever see a 10-year-old German Shepherd who’s suddenly collapsed at home, hemoabdomen and pericardial effusion are the top two things that come to mind.

Many of the signs seen with pericardial effusion, such as collapse, pale gums and low blood pressure, are similar to those seen with hemoabdomen. There are a few tests we can rely on to quickly make a diagnosis and start treatment. Ultrasound is particularly useful, as you can see the fluid around the heart (and sometimes the tumor itself), which confirms the diagnosis. X-rays and an EKG can sometimes also be helpful in figuring out what’s going on.

How do you treat a patient with pericardial effusion? With a very large needle. Someone wise once said “There is no body cavity that can’t be reached with a good, strong arm and a 14-gauge needle” and that’s true when it comes to treating this condition.

Once the diagnosis is confirmed, or strongly suspected, draining the fluid around the heart is important. Giving IV fluids is also helpful as this gives the heart something to pump around, but removing the fluid that’s strangling the heart is job #1. Usually (but not always) done with ultrasound guidance, a large needle or catheter is inserted between the ribs and into the distended sac around the heart in a procedure known as pericardiocentesis – and it’s quite rewarding to perform. We usually use a local anesthetic and perhaps mild sedation to make sure the patient is comfortable and doesn’t move, although I had one memorable patient who picked the exact moment I started draining the fluid to jump off the table and land on the needle.

He did fine.

Pericardiocentesis almost immediately reduces the pressure around the heart, allowing it to fill up again like normal and deliver life-sustaining oxygen to the body. Patients are often immediately better – for a time.

What does the future look like for these patients?

One of the saddest things about cases of cancerous pericardial effusion is that the outcome is often not good in the long term, despite the fact that the pericardiocentesis may have saved their life and made them dramatically better rapidly. Since the underlying cause of this condition is often a nasty cancer, many patients either experience a recurrence of the bleeding (sometimes within a few hours) or spread of the cancer to other parts of the body. Pericardial effusions not caused by cancers often respond to just the draining and the dogs do great. So, we have to figure out what is causing the effusion to have a good idea of the likely outcome.

All is not always lost, however. There are new therapies for cancer, and more are being developed every day. That same patient who hopped off the table and onto the needle lived for another 2 years with the help of surgery, chemotherapy and radiation. Obviously, that’s not for everyone, but he had a really good quality of life for some time.

This is definitely one of those “but he was fine yesterday, doc” kinds of diseases. It strikes quickly and dramatically, often without any warning. In that respect, it is similar to hemoabdomen. Owners are often dumbfounded at how fast things can go from he’s fine to he’s dying, and in many cases the time afforded by the pericardiocentesis is most useful for owners to come to terms with the gravity of the situation.

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