Pericarditis: etiology. Pathomorphological types
This is the inflammation of the pericardium, the fibrous sac that surrounds the heart. Typically sudden onset of sharp chest pain that is relieved by sitting up. Pain often radiates to shoulders, neck or back. Other symptoms include fever, weakness, palpitation and dyspnea.
Etiology
Common etiology is bacterial or viral (In the developed world, 85% of cases are caused by viruses, while in the developing world Mycobacterium tuberculosis (TB) is a more common etiological factor). Viral causes include coxsackievirus, herpesvirus and mumps. Non-infective etiology includes AI (lupus is common cause), MI, Trauma, uremia, cancer, side effect of drug (e.g. isoniazid, cyclosporine, warfarin, heparin) and aortic dissection.
Pathomorphological types
The pathomorphology of the condition varies based on the etiology:
- In patients with acute viral pericarditis or uremia, exudate is fibrinous, with irregular shaggy pericardial appearance
- In acute bacterial pericarditis the exudate is fibrinopurulent, with ‘frank pus’ areas
- Pericarditis due to malignancy is often associated with shaggy fibrinous exudate and bloody effusion
H&E, fibrinous pericarditis: shaggy pink fibrin projects from the pericardial surface over an inflamed, congested layer.
Image: “Pericarditis fibrinosa” by dr n. med. Krystyna Bielnik, lek. med. Dariusz Młoczkowski, dr n. med. Tadeusz Modrzewski, lek. med. Dorota Snopkowska, , CC BY-SA 3.0, via Wikimedia Commons.
Remember: the types by exudate: serous (viral, SLE, rheumatic fever, uraemia); fibrinous, rough "bread and butter" surfaces (MI, Dressler syndrome, uraemia, rheumatic fever); purulent (bacteria); haemorrhagic (cancer, tuberculosis); caseous (tuberculosis), the type most likely to heal with dense fibrosis and cause constrictive pericarditis.
Pericarditis can resolve without problems, or result in chronic pericarditis, associated with adhesions and fibrotic scars in the pericardial space. This can in turn result in constrictive pericarditis.
Diagnosis and treatment
In uremic pericarditis urea (BUN) and creatinine are increased, but best diagnosis is with ECG, showing saddle shaped ST elevation in all leads except aVR and V1! Note, this is different from MI elevation as the elevation comes out of the S wave, in MI, the elevation comes straight out of the R wave.
On physical examination, there is often evidence of a pericardial friction rub. Complications include pericardial effusion and cardiac tamponade.
Treatment of viral or idiopathic form is with aspirin or NSAIDs, Colchicine can also be added to limit future cases of pericarditis. In bacterial cases, ABs should be given IV. Pericardiocentesis can also be performed to treat pericardial effusion/tamponade.