Pericardial cysts are uncommon and represent approximately 5% of thoracic cysts. Most of these are asymptomatic and usually detected incidentally. However, in case of chest trauma, they can rupture leading to hemodynamic compromise. In addition, large cysts may sometimes compress the heart leading to tamponade-like physiology or present with acute cough and chest pain.
Here are some images from a patient who suffered multiple stab wounds to the chest, shared by Dr. Jones. The first image looks pretty normal: no pericardial effusion & heart pump function looks good. However, as more deeper images are obtained, a cystic structure appears adjacent to the right atrium = pericardial cyst. This is actually the commonest location. A CT scan confirmed the diagnosis.
On echo, pericardial cyst may be confused with a loculated pericardial effusion; but the presence of a thin wall separating the cyst from the main pericardial space distinguishes the two. If it is difficult to view clearly on trans-thoracic echo, TEE can help.