AssessmentsPericardial disease: Pathology review
USMLE® Step 1 style questions USMLE
A 35-year-old woman is brought to the emergency department following a motor vehicle accident. At the scene, she was in severe pain and pointed to her chest. Soon after arrival, the patient loses consciousness. Temperature is 37.0°C (98.6°F), pulse is 120/min, respirations are 22/min, and blood pressure is 75/55 mmHg. On physical examination, there are multiple lacerations over the torso and face. Significant bruising is noted over the chest. Neck veins are distended. On chest auscultation, lung fields are clear bilaterally and heart sounds are weak. Echocardiography is obtained and shows a large pericardial effusion. Which of the following sets of hemodynamic parameters are most likely to be seen in this patient?
Contributors:Megan Gullotto, MSMI, Victoria Cumberbatch, Sam Gillespie, BSc, Yifan Xiao, MD, Anca-Elena Stefan, MD
Two people came to the emergency department. One of them is 55 year old Pamela who has sharp retrosternal chest pain that gets worse when she breathes in. On chest auscultation, a friction rub can be heard. The other person is 43 year old Thomas, who had been in a car accident and now presents severe hypotension and on physical examination, his neck veins are distended, his heart rate is really high. On chest auscultation there’s barely audible heart sounds. An ECG was ordered for both individuals. Pamela had ST-segment elevation in several leads and also PR depression, while Thomas has low-voltage QRS complexes.
Okay, based on what we know about the individuals, we can assume that both suffer from pericardial disease. But first, a bit of physiology. 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. The space between the two layers is the pericardial cavity 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 large vessels don’t get pinched shut.
Now for pericardial disease, we should start by talking about inflammation in the pericardium, which is called pericarditis. People who develop pericarditis are also at risk of developing a pericardial effusion where the inflammation causes fluid to accumulate around the heart.
Pericarditis is in most cases idiopathic. It can also be due to a viral infection, like Coxsackie B virus. Pericarditis can also be seen in autoimmune diseases, like rheumatoid arthritis or systemic lupus erythematosus, because the immune system attacks our own tissues, including the pericardium. For your exams, other high yield causes include myocardial infarction and Dressler syndrome which occurs several weeks after a myocardial infarction. Basically, when heart cells die in a myocardial infarction, it attracts white blood cells to the area, leading to massive inflammation that also involves the serous pericardium. Another cause is uremia, which is when blood levels of urea gets really high and this usually happens due to kidney failure. The high levels of urea irritate the serous pericardium, making it secrete a thick pericardial fluid that’s full of fibrin strands and white blood cells. Cancers like lung cancer and lymphoma can also lead to pericarditis, due to metastasis that reach the pericardium, irritating it. Finally, there’s radiation therapy that can also lead to pericarditis.
Now, inflammation of the pericardium causes the fluid and immune cells in tiny blood vessels in the fibrous and serous pericardium to leak into the interstitium of those layers, making the layer itself a bit thicker and more boggy; think of how a piece of dry sponge thickens as it soaks up fluid.
Now, sometimes, when the inflammation persists, immune cells can initiate fibrosis of the serous pericardium which can produce an inelastic shell around the heart, making it hard for the chambers to expand and this is called constrictive pericarditis. For your tests, remember that the most common cause of constrictive pericarditis in high- and middle-income countries is idiopathic or viral infection, while in lower-income countries, it’s tuberculosis. In a test question, it might often also appear as a consequence of chest radiotherapy. Now, both ventricles can’t fully expand and fill with blood. So, from the left ventricle, all that blood backs up into the lungs, specifically in the pulmonary veins and capillary beds which can increase the pressure in these vessels. This leads to fluid moving from the blood vessels to the interstitial space causing pulmonary edema, or congestion. In the alveoli of the lungs, all the extra fluid makes oxygen and carbon dioxide exchange a lot harder, and therefore patients have dyspnea or trouble breathing. And from the right ventricle, blood accumulates in the