The pericardium is a sac that covers the heart and the roots of the great vessels.
The pericardium has two layers, an inner serous layer and an outer fibrous layer, and the space between the two layers is the pericardial cavity.
The pericardial cavity is normally filled with about 50 mL of serous fluid that cushions the heart from any kind of external jerk or shock - like a shock absorber.
The pericardium also fixes the heart to the mediastinum, to prevent it from twisting, so that the big vessels don’t get pinched shut.
Pericardial disease is inflammation of the pericardium due to a variety of causes - from infections, to autoimmune disorders, cancer, and trauma.
In pericarditis, the pericardium is inflamed and irritated.
If the inflammation leads to the accumulation of excess fluid in the pericardial sac then it’s called a pericardial effusion, and in its worst form, that extra fluid can cause tamponade physiology.
Finally, there’s constrictive pericarditis, which is where the inflammation is chronic and leads to fibrosis.
In pericarditis, the two inflamed layers of the pericardium rub against one another every time the heart beats. This causes severe, sharp retrosternal chest pain, that radiates to the neck, shoulders, and back, and it typically happens with each breath during inspiration.
That’s because in inspiration the lungs expand, filling the thoracic cavity and compressing the pericardium.
The pain typically worsens when a person is supine and improves when a person is sitting upright and leaning forward.
Upon auscultation, there’s a pericardial friction rub, which is a scratchy, grating, high-pitched rub resembling the sound of leather-on-leather rubbing against each other.
On ECG, there’s widespread ST segment elevation in several leads, which distinguishes it from the ST elevation in myocardial infarction which is only present in the leads that correspond to the infarcted tissue.