What is done with the pericardium after the surgery?

Pathology inspects. The pericardium, once removed, is sent to pathology for routine histologic examination, in order to determine any abnormal appearance, and what might be the specific disease process causing that appearance. Special stains for tumor types and other diseases can be done as well, as can cultures for infectious organisms.
Stays in place. The only time the pericardium is removed is if it is constricting the heart. During open heart surgery the pericardium (sac around the heart) is opened to get to the heart and then usually closed back up (sewn together). Some surgeons will leave it open and just close the chest wall. Sometimes a piece of pericardium is used to patch a hole in the heart.