Pericarditis in Horses: Inflammation Around the Heart
- See your vet immediately. Pericarditis is inflammation of the sac around the heart and can quickly reduce the heart's ability to fill and pump normally.
- Many horses show vague early signs such as fever, depression, poor performance, reduced appetite, or a fast heart rate before more obvious heart-related signs appear.
- As fluid builds around the heart, horses may develop muffled heart sounds, jugular vein distension, ventral edema under the chest or belly, breathing effort, and weakness.
- Diagnosis usually requires an exam plus echocardiography, bloodwork, and often ultrasound-guided sampling or drainage of pericardial fluid to look for infection or inflammation.
- Treatment options depend on severity and cause. Horses may need anti-inflammatory medication, systemic antimicrobials, hospitalization, repeated pericardial drainage, and close monitoring for cardiac tamponade or constrictive scarring.
What Is Pericarditis in Horses?
Pericarditis is inflammation of the pericardium, the thin sac that surrounds the heart. In horses, this inflammation can cause fluid, fibrin, pus, or blood-tinged material to collect around the heart. When that happens, the heart may not be able to expand normally between beats. In severe cases, pressure around the heart can become an emergency called cardiac tamponade.
This condition is considered uncommon in horses, but it is serious. Reported forms include septic pericarditis linked to infection and idiopathic pericarditis, where no clear cause is found. Some horses improve with prompt treatment, while others develop ongoing inflammation, recurrent fluid buildup, or later scarring that restricts heart function.
For pet parents, the challenge is that early signs are often nonspecific. A horse may seem tired, off feed, feverish, or less willing to work before obvious heart-related signs appear. Because the condition can worsen quickly, any horse with unexplained fever plus weakness, swelling under the chest, or abnormal heart sounds needs urgent veterinary attention.
Symptoms of Pericarditis in Horses
- Fever
- Fast heart rate (tachycardia)
- Muffled or distant heart sounds
- Jugular vein distension or strong jugular pulses
- Ventral edema under the chest, abdomen, or lower body
- Poor performance, exercise intolerance, or tiring easily
- Depression, lethargy, or reduced appetite
- Increased breathing effort or rapid breathing
- Weakness, collapse, or signs of shock
See your vet immediately if your horse has a fast resting heart rate, fever, jugular distension, swelling under the chest, breathing difficulty, weakness, or collapse. Pericarditis can look vague at first, but once fluid around the heart starts affecting circulation, the situation can become life-threatening.
Some horses also have nearby chest disease, such as pleuritis or pneumonia, which can blur the picture. If your horse seems "off" after a recent infection, transport stress, penetrating chest trauma, or a prolonged febrile illness, ask your vet whether heart ultrasound is needed.
What Causes Pericarditis in Horses?
In horses, pericarditis is most often described as either septic or idiopathic. Septic pericarditis means infection is involved. Bacteria may reach the pericardium from the bloodstream, from nearby infection in the lungs or pleural space, or after penetrating trauma to the chest. In some cases, the horse has a history of fever, respiratory disease, abscessation, or another inflammatory condition before heart signs develop.
Idiopathic pericarditis means no clear cause is identified, even after testing. Some of these horses still respond well to treatment, especially when the problem is recognized early and the heart is relieved of excess fluid. A few reports also describe eosinophilic or nonseptic inflammatory forms.
Less common possibilities include extension from pleuropneumonia, neoplasia, hemorrhage into the pericardial sac, or severe systemic infection. Because the cause affects both treatment choices and prognosis, your vet may recommend fluid analysis, bacterial culture, and imaging of the chest in addition to heart-focused testing.
How Is Pericarditis in Horses Diagnosed?
Diagnosis starts with a careful physical exam. Your vet may find tachycardia, muffled heart sounds, jugular distension, ventral edema, fever, weak pulses, or signs of poor circulation. These findings can raise concern for fluid around the heart, but they are not enough to confirm the cause.
The most important test is usually echocardiography, which can show pericardial effusion, fibrin strands, chamber compression, and signs that the heart is struggling to fill normally. Many horses also need bloodwork to look for inflammation, infection, anemia, or organ effects from poor perfusion. Electrocardiography may show low-voltage complexes or electrical alternans in some effusive cases.
If fluid is present, your vet may recommend ultrasound-guided pericardiocentesis to remove some fluid and submit it for cytology and culture. This can help distinguish septic from nonseptic disease and may also provide immediate relief if pressure around the heart is severe. Thoracic ultrasound, chest imaging, and additional infectious disease testing may be used to look for pneumonia, pleural disease, abscesses, or other underlying problems.
Treatment Options for Pericarditis in Horses
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Urgent farm call or clinic exam
- Basic bloodwork and focused ultrasound if available
- NSAID-based anti-inflammatory care directed by your vet
- Systemic antimicrobials when infection is suspected
- Strict stall rest and repeated rechecks
- Referral discussion if fluid is significant or the horse is unstable
Recommended Standard Treatment
- Hospitalization or day-hospital monitoring
- Complete exam, CBC/chemistry, and serial echocardiography
- Thoracic ultrasound and targeted chest evaluation
- IV fluids when appropriate and circulation support
- NSAIDs plus systemic antimicrobials when septic disease is possible
- Ultrasound-guided pericardiocentesis for diagnosis and therapeutic drainage
- Pericardial fluid cytology and bacterial culture
- Activity restriction and follow-up imaging
Advanced / Critical Care
- Referral hospital or equine ICU care
- Continuous cardiovascular monitoring
- Repeated or indwelling-catheter pericardial drainage and lavage when indicated
- Broad-spectrum IV antimicrobials adjusted to culture results
- Serial echocardiography to monitor tamponade, fibrin, and chamber compression
- Management of concurrent pleuropneumonia, sepsis, or heart failure complications
- Longer hospitalization and structured recheck plan after discharge
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Pericarditis in Horses
Bring these questions to your vet appointment to get the most out of your visit.
- Do my horse's signs suggest fluid around the heart, pleural disease, or another cause of fever and swelling?
- Does my horse need an echocardiogram today, and what did it show about fluid, fibrin, or cardiac tamponade?
- Is this more likely to be septic or idiopathic pericarditis based on the exam and test results?
- Should we drain the pericardial fluid now, and what are the benefits and risks of pericardiocentesis in this case?
- What bloodwork, culture, or imaging do you recommend to look for an underlying infection or chest disease?
- What treatment options fit my horse's condition and my budget, and what are the tradeoffs of each approach?
- What warning signs at home mean my horse needs emergency reassessment right away?
- What is the realistic prognosis for survival, comfort, and future athletic function in my horse's specific case?
How to Prevent Pericarditis in Horses
Not every case can be prevented, especially idiopathic forms, but early attention to fever, respiratory disease, chest wounds, and unexplained swelling may reduce the risk of severe complications. Prompt treatment of pleuropneumonia, abscesses, and other systemic infections matters because some septic cases appear to spread from nearby or blood-borne infection.
Good biosecurity, vaccination planning, careful transport management, and fast follow-up for horses that become febrile after shipping or herd outbreaks can also help lower infectious risk. If your horse has a penetrating wound near the chest, that is an emergency even if the surface injury looks small.
After recovery, prevention shifts to monitoring. Your vet may recommend repeat exams and echocardiography because some horses can develop recurrent effusion or delayed constrictive changes months later. A horse that tires easily, develops edema again, or shows a rising resting heart rate should be rechecked promptly.