Inflammation around the heart most often affects the pericardium, the thin two-layered sac that surrounds and protects the heart. This condition is called pericarditis, and viruses are the most common trigger. In many cases, a specific cause is never identified. About 30% of people who experience one episode will have a recurrence, typically within 18 months.
Sometimes the inflammation extends deeper into the heart muscle itself, a condition called myocarditis, or involves both layers at once (myopericarditis). The distinction matters because inflammation of the muscle carries more serious long-term risks, including heart failure. Pericarditis, by contrast, is usually self-limiting.
How It Feels
The hallmark symptom is a sharp chest pain behind the breastbone that can radiate to the back, neck, or arms. What sets it apart from a heart attack is how position changes the pain: it typically gets better when you sit up and lean forward, and worsens when you lie flat or take a deep breath. A doctor may hear a scratchy, rubbing sound through a stethoscope, called a friction rub, which is a strong indicator.
When the heart muscle is also involved, symptoms shift. You’re more likely to feel shortness of breath, reduced exercise tolerance, palpitations, or fainting. These signs suggest the inflammation is affecting how well the heart pumps, not just irritating the outer sac.
Viral Infections: The Most Common Cause
The majority of pericarditis cases stem from viral infections. The viruses most frequently responsible include coxsackieviruses A and B, echoviruses, adenoviruses, parvovirus B19, influenza, HIV, Epstein-Barr virus, and cytomegalovirus. In many of these cases, the chest pain shows up a week or two after a respiratory or gastrointestinal illness, and the pericarditis resolves on its own.
COVID-19 added a newer entry to this list. Pericarditis develops in roughly 1.5% of COVID cases. That number sounds small, but the outcomes are notably worse: one study found that six-month mortality was more than double in COVID patients who developed pericarditis compared to matched patients who didn’t (15.5% versus 6.7%).
Bacterial and Fungal Infections
Bacterial pericarditis is less common than viral but tends to be more dangerous. The most frequent bacterial culprits are Staphylococcus, Streptococcus, and Haemophilus species. Tuberculosis is an especially important cause worldwide and can present in many ways, from acute inflammation to large, slowly accumulating fluid collections to chronic scarring that stiffens the sac and restricts the heart’s ability to expand.
People with HIV face a significantly higher rate of bacterial pericarditis than the general population, with infections from atypical bacteria that are otherwise rare. Fungal causes exist too, mainly in people with weakened immune systems.
Autoimmune and Inflammatory Diseases
Your immune system can attack the pericardium as part of a broader autoimmune condition. Lupus is one of the most well-known triggers. Pericarditis occurs in a substantial portion of lupus patients at some point during their illness, sometimes as one of the first recognizable symptoms. Rheumatoid arthritis and scleroderma also carry an elevated risk. In these cases, controlling the underlying autoimmune disease is key to preventing repeated flares of heart inflammation.
In about half of pericarditis cases, no clear cause is found even after testing. These are labeled “idiopathic,” but many are suspected to be viral infections that were never confirmed or low-grade autoimmune reactions the body mounted against its own pericardial tissue.
Inflammation After Heart Injury
The heart’s own healing process can sometimes overshoot. After a heart attack or cardiac surgery, some people develop a delayed inflammatory reaction known as Dressler syndrome. This typically shows up one to six weeks after the initial injury, though symptoms can occasionally appear months later. The pattern is distinctive: you feel like you’re recovering well, then develop new chest pain, fatigue, fever, and malaise weeks after the event.
The mechanism is thought to be an immune response triggered by proteins released from damaged heart tissue. The body essentially mistakes its own healing tissue for something foreign and mounts an attack on the pericardium. This should be considered in anyone who develops persistent fatigue or new chest pain more than two weeks after a heart attack or heart surgery.
Kidney Failure and Metabolic Causes
When the kidneys stop filtering blood effectively, toxic waste products accumulate in the bloodstream. These toxins provoke inflammation in the pericardium, a condition called uremic pericarditis. It’s most common in people with end-stage kidney disease, particularly those who are not yet on dialysis or whose dialysis is inadequate.
The exact toxin responsible hasn’t been pinpointed. It’s likely not the commonly measured waste products (blood urea nitrogen and creatinine) themselves, but other metabolic byproducts that build up alongside them. These toxins trigger the release of inflammatory signals that damage the pericardium and can lead to scarring. The strongest evidence for this theory is practical: increasing the frequency or adequacy of dialysis improves most cases. Factors like malnutrition and low albumin levels in the blood are associated with more severe fluid accumulation around the heart in these patients.
Medications That Can Trigger It
Certain drugs can cause pericardial inflammation or fluid buildup around the heart as a side effect. The medications with the strongest statistical association include hydralazine (used for high blood pressure), dasatinib (a cancer treatment), and mesalazine (used for inflammatory bowel diseases like Crohn’s and ulcerative colitis). Minoxidil, another blood pressure medication, can also cause fluid accumulation around the heart, leading to chest pain and shortness of breath.
The timing varies by drug. Some cause problems within two weeks, while others take a month or longer. The encouraging news is that drug-induced pericarditis typically resolves after the medication is stopped.
Cancer
Cancers that have spread to the chest, particularly lung cancer, breast cancer, and lymphomas, can involve the pericardium directly. Tumor cells may invade the sac or cause it to fill with fluid. Radiation therapy aimed at chest tumors is another recognized cause, sometimes appearing months or even years after treatment.
How It’s Diagnosed
Doctors look for at least two of four criteria: characteristic chest pain, a friction rub heard on exam, specific electrical changes on an EKG, or new fluid around the heart visible on an echocardiogram (ultrasound of the heart). The EKG changes are distinctive. In the early stage, there’s a widespread pattern of upward-curving elevation in the electrical tracing along with depression in another segment, a combination that looks different from the localized changes seen in a heart attack. These electrical patterns evolve through four stages over days to weeks, eventually returning to normal.
When Fluid Becomes Dangerous
The pericardial sac normally contains a small amount of lubricating fluid. When inflammation causes excess fluid to accumulate rapidly, it can compress the heart and prevent it from filling properly. This emergency, called cardiac tamponade, causes low blood pressure, visibly swollen neck veins, and muffled heart sounds. Another telltale sign is a drop in blood pressure of more than 10 mmHg when you breathe in, something a doctor can detect with a blood pressure cuff. Tamponade requires urgent drainage of the fluid.
Recovery and Recurrence
Most people with uncomplicated pericarditis recover fully. The initial episode typically resolves within a few weeks with anti-inflammatory treatment. However, recurrence is a real concern. Among patients with an initially uncomplicated course, about 9% experienced a recurrence over a six-month follow-up in one study. In patients whose first episode was more complicated, the recurrence rate was significantly higher, around 29%. Adding a medication called colchicine to initial treatment has been shown to reduce the odds of recurrence, which is why not receiving it early is considered a risk factor for relapse.
Recurrences follow the same pattern as the original episode: chest pain, possible fever, and fatigue. They can be frustrating but are generally manageable and don’t typically cause lasting heart damage. Most recurrences happen within 18 months of the first episode, and the intervals between flares tend to lengthen over time.