My notes on this include the following :
Pericarditis is the inflammation of the pericardium. It is one of the frequent conditions found in swine at slaughter. The agents causing pericarditis include viruses, mycoplasma, bacteria, fungi and other microorganisms. It is a common complication of enzootic pneumonia due to secondary invasion with E. coli.
Pericarditis can occur secondary to heart infections, systemic infections, or result from metastases of neoplasms arising in remote sites. In swine, fibrinous pericarditis is associated with hog cholera, erysipelas and Glasser's disease. Inflammation of pericardium is also observed in pasteurellosis, porcine enzootic pneumonia and streptococcal infection in suckling pigs. Primary pericarditis occurs rarely and is of viral origin.
So given that's it's common, I wouldn't particularly worry.