Most cases of pericarditis are triggered by a viral infection, though the inflammation of the sac surrounding your heart can also result from autoimmune diseases, kidney failure, chest trauma, heart surgery, cancer, and certain medications. In many cases, doctors never identify a definitive cause, and these are labeled “idiopathic,” which essentially means the culprit was likely a virus that cleared before testing could catch it.
Viral Infections Are the Most Common Cause
Viral infection is the leading trigger of acute pericarditis. The most common culprits are influenza and coxsackievirus B, and cases tend to follow seasonal epidemic patterns. What typically happens is a respiratory or gastrointestinal virus spreads through the body and inflames the pericardium, the thin two-layered sac that surrounds and protects the heart. You might notice pericarditis symptoms a week or two after what seemed like an ordinary cold or flu.
COVID-19 has added to this picture. A study published in The Lancet found that a COVID-19 diagnosis was associated with a 3.5-fold higher risk of developing myocarditis or pericarditis in the first week after infection. That elevated risk persisted, at a lower level, for more than 12 months. In absolute terms, the risk remained small: roughly 2 extra cases per 100,000 people over six months compared to those without a diagnosis.
Bacterial, fungal, and parasitic infections can also cause pericarditis, though these are far less common in developed countries. Tuberculosis remains an important cause in parts of Africa and Asia.
After a Heart Attack or Heart Surgery
Pericarditis can develop as a reaction to heart tissue injury. This happens in two distinct patterns. The first is early inflammation, appearing within days of a heart attack or cardiac procedure, caused by direct irritation of the pericardium from damaged tissue nearby.
The second pattern, known as Dressler syndrome, is a delayed immune response that shows up two to eight weeks after a heart attack. Your immune system, primed by the initial heart damage, essentially overreacts and attacks the pericardium. Dressler syndrome has become rare in the modern era of rapid heart attack treatment, though it was reported in about 5% of heart attack patients before clot-clearing therapies became standard.
A related condition, post-pericardiotomy syndrome, affects 10 to 40% of patients who undergo cardiac surgery. It typically appears days to several weeks after the operation. The wide range in that estimate reflects differences in how strictly doctors define the condition, but it’s common enough that cardiac surgeons watch for it routinely.
Autoimmune Diseases
When your immune system chronically attacks your own tissues, the pericardium can become collateral damage. Lupus is the most well-studied example. Data from the University of Toronto Lupus Clinic found that about 20% of lupus patients developed pericarditis at some point during their disease course. Rheumatoid arthritis, scleroderma, and other connective tissue disorders carry similar risks, though at lower rates.
In autoimmune pericarditis, the inflammation tends to recur. Managing it usually means controlling the underlying disease rather than treating the pericardium in isolation.
Kidney Failure
Advanced kidney disease can cause a form called uremic pericarditis. When your kidneys can no longer filter waste effectively, toxic metabolites build up in the blood alongside elevated levels of urea and creatinine. This buildup appears to irritate and inflame the pericardium, though the exact mechanism isn’t fully understood. Increased blood vessel permeability and oxidative stress from high levels of free radicals likely play a role.
Uremic pericarditis can develop in people with severe kidney failure who haven’t started dialysis, but it also occurs in patients already on dialysis if their treatment isn’t adequately clearing waste. It’s one of the signs that kidney disease has reached a critical stage or that a dialysis regimen needs adjustment.
Cancer
Cancer can cause pericarditis either by spreading directly to the pericardium or by triggering an immune-mediated inflammatory response. Lung cancer is the most frequent source of pericardial metastases, followed by breast cancer, melanoma, and lymphomas. The cancer cells can seed the pericardial tissue and cause inflammation, fluid buildup, or both.
In some cases, the pericarditis isn’t from the cancer itself but from its treatment. Radiation therapy directed at the chest, particularly for breast cancer or lymphoma, can damage the pericardium. This may happen during treatment or emerge months to years later as radiation-induced fibrosis gradually thickens and stiffens the sac.
Medications and Vaccines
A surprisingly long list of medications can trigger pericardial inflammation. The mechanism varies: some drugs cause a lupus-like immune reaction, others are directly toxic to pericardial tissue, and for some the pathway remains unclear.
- Blood pressure medications: Hydralazine, minoxidil, and methyldopa have all been linked to pericarditis.
- Antibiotics and anti-infectives: Isoniazid (used for tuberculosis), certain tetracycline-type antibiotics, and penicillin are reported triggers.
- Cancer drugs: Immune checkpoint inhibitors, certain chemotherapy agents, and targeted therapies like some leukemia drugs carry pericarditis as a known side effect.
- Antipsychotics: Clozapine is the most commonly implicated, along with related medications like quetiapine and olanzapine.
- Anti-inflammatory drugs: Paradoxically, some drugs used to treat inflammatory bowel disease can themselves cause pericarditis.
Vaccines, including those for hepatitis B, varicella, and COVID-19, have been associated with pericarditis as a rare complication. The COVID-19 mRNA vaccines drew particular attention for this, though the absolute risk remains very low and the cases are typically mild and self-resolving.
Chest Trauma
A direct blow to the chest, whether from a car accident, a fall, or a sports injury, can inflame the pericardium. Both penetrating injuries (like a stab wound) and blunt force trauma can trigger it. What’s notable is that post-traumatic pericarditis can develop even when there are no obvious signs of cardiac injury on initial evaluation. The inflammation may appear days to weeks after the trauma, making it easy to miss the connection if you aren’t aware of it.
Why Many Cases Go Unexplained
Despite this long list of known triggers, a large proportion of pericarditis cases end up classified as idiopathic. Standard blood tests and imaging often can’t pinpoint a specific virus or cause, and extensive testing isn’t always worthwhile when the treatment approach would be the same regardless. Most experts believe the majority of these idiopathic cases are viral in origin, with the virus having already been cleared by the time symptoms appear and testing begins.
Recurrent pericarditis, where inflammation keeps coming back after an initial episode, affects roughly 15 to 30% of people. Recurrence doesn’t necessarily mean a new trigger each time. Instead, the immune system can become sensitized after the first episode and repeatedly inflame the pericardium on its own, creating a cycle that sometimes requires longer-term immune-targeted treatment to break.