Pericardial disease: Pathology review

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Case study0:00–0:52

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.

Physiology0:52–1:21

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.

Pericarditis1:21–6:49

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 veins of the systemic circulation. One common manifestation of this is jugular venous distention, where the jugular vein that’s relatively close to the heart becomes enlarged and distended.
One fact that you have to remember here is that normally, during inspiration, the jugular venous pressure falls, because blood returns to the right ventricle.
However, in constrictive pericarditis, the right ventricle isn’t as compliant. So, in this case, during inspiration, the jugular venous pressure will paradoxically rise and this is called Kussmaul’s sign.
Also in the body, when blood backs up to the liver and portal circulation, it causes hepatomegaly or liver distention, as well as portal hypertension and ascites, which is the accumulation of fluid in the peritoneal cavity.
Finally, fluid that backs up into the interstitial space in the soft tissues of the legs causes pitting edema, which means that the tissue is visibly swollen and when you apply pressure to it it leaves a “pit” and takes awhile to come back to its original place.
The main symptom of pericarditis, which is extremely high yield, is 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 the lungs expand during inspiration, 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, because less pressure is put on the heart.For diagnosis, the most important clue is that upon auscultation, there’s a pericardial friction rub which is a scratchy, grating, high-pitched rub resembling the sound of leather rubbing against leather.
On ECG, there’s widespread ST segment elevation in several leads. This will help you distinguish it from the myocardial infarction which also presents with chest pain and ST elevation, but in myocardial infarction the ST elevation is only present in the leads that correspond to the infarcted tissue.
Also, for your tests, remember that PR segment depression is a very specific ECG finding in pericarditis. On imaging, pericarditis can show up as an enlarged heart on chest X-ray, and an echocardiogram can show fluid in the pericardium.
In constrictive pericarditis, a CT can detect calcifications and thickening of the pericardium seen in a CT scan. Okay, there’s one more thing to talk about: cardiac tamponade.

Cardiac tamponade6:49–11:37

Pericarditis can lead to pericardial effusion when fluids begins to pool in the pericardial space, and the serous pericardium can’t remove it as quickly as it builds up.
In general, cardiac tamponade can result from pretty much anything that causes rapid accumulation of fluid inside the pericardium.
For example, a stab wound can puncture a blood vessel and fill the pericardium with blood. Even blunt trauma, like a steering wheel getting pushed into your chest during a car crash can lead to tamponade, because the force of the impact causes the rupture of lots of small blood vessels.
Cardiac tamponade can also classically happen a few days after a myocardial infarction, because the weak, infarcted ventricular wall ruptures when it’s exposed to the high ventricular pressures.
Yet another cause is aortic dissection, which is when blood pools in the actual wall of the aorta. If the aortic dissection ruptures through the wall of the aorta and through the fibrous pericardium, blood can spill right into the pericardial cavity, leading to cardiac tamponade.
In any case, when fluid fills the pericardium, it starts putting pressure on the heart itself, preventing it from fully stretching out or relaxing between contractions.
this means that the cardiac chambers can’t fill with blood properly, causing a decrease in cardiac output, so less blood is squeezed out with each heartbeat, leading to hypotension.
In other words, the entry of blood into and out of the heart is obstructed, leading to hypotension, and this is called obstructive shock.
To compensate, the heart rate increases. When a person suffering from cardiac tamponade inhales, the systolic blood pressure sometimes drops.
The reason behind this is that normally, breathing in creates a tiny bit of negative pressure in the heart, pulling in blood from the vena cavas.
This momentarily increases systemic venous return. When that happens, the right heart volumes increases, and the right ventricle expands a bit into the pericardial space, so it doesn’t affect the left heart volume at all.
In cardiac tamponade, during inspiration, the right ventricle can’t move into the pericardial space, so the extra volume pushes the interventricular septum toward the left.
This leads to a reduction in left ventricular diastolic volume, a lower stroke volume, and a drop in systolic blood pressure during inspiration.
A decrease in the systolic pressure of greater than 10 mm mercury is called pulsus paradoxus, and the high yield fact here is that it’s a classic sign of cardiac tamponade, but can also happen with asthma, obstructive sleep apnea, croup and pericarditis.
In cardiac tamponade, the upper heart chambers are also affected: the atria can’t distend enough to accommodate the venous blood returning to the heart.
That blood will have nowhere to go but back into the veins. That’s why you’ll typically see distended jugular veins and Kussmaul sign when you look at the neck of a person with cardiac tamponade.
This is actually part of a triad of symptoms called the Beck’s triad which includes: distended neck veins, hypotension, and distant heart sounds on auscultation.
The last one happens because the fluid build up muffles the normal heart sounds. In cardiac tamponade, classic findings on the ECG include tachycardia, a low QRS complex and electrical alternans, which is when the QRS complexes have different heights.
This happens because the heart moves abnormally within the pericardial cavity which leads to strange reading in the electrodes.
Cardiac catheterization measures the pressure inside the cardiac chamber and in the case of tamponade, the diastolic pressure in all four chambers are equal.
For your exams, it’s important to differentiate cardiac tamponade from tension pneumothorax. Pneumothorax means that there’s air in the pleural space.
This is often caused by injury to the lung or damage to the pleura which can forms a one-way valve, allowing air to go in, but not go out.
The air builds up in the pleural space, causing it to expand and compress the right atrium of the heart and the vena cavae.
This decreases venous return and cardiac output and resulting in hypotension, similar to tamponade. Now, what sets it apart is that, unlike cardiac tamponade, heart sounds are normal, while breath sounds are decreased or absent in the side of the injury, which is also hyperresonant on percussion.
In addition, chest expansion is asymmetrical and the trachea is deviated away from the affected side. And that shift of the trachea as well as the whole mediastinum will be also visible on a chest x-ray.
In terms of treatment, the main goal is to relieve pain, and to treat the underlying cause of inflammation. This is done with NSAIDs or glucocorticoids.

Treatment11:37–12:10

Colchicine, a medication that inhibits neutrophil migration, is also used to decrease the likelihood of recurrent pericarditis.
Constrictive pericarditis may require pericardiectomy which is a surgical removal of the pericardium. For cardiac tamponade, an emergency pericardiocentesis can be done by inserting a needle into the pericardial cavity and draining the excess fluid.
Okay, let’s review! Pericarditis is inflammation of the pericardium and in most cases, it’s idiopathic.

Review12:10–13:38

It can also be caused by viral infections, like a Coxsackie B virus, autoimmune conditions, neoplasia, uremia, radiotherapy, myocardial infarction and Dressler syndrome.
It presents with sharp retrosternal chest pain that gets worse with inspiration and is relieved when sitting up and leaning forward.
The important sign to look for is a friction rub which can be auscultated. ECG changes in pericarditis include ST-segment elevation and PR depression.
Now, sometimes, when the inflammation persists, immune cells can initiate fibrosis of the serous pericardium which can produce an inelastic shell around the heart and this is called constrictive pericarditis.
When pericarditis causes fluid to build up in the pericardial cavity, this is called a pericardial effusion. Finally, when there’s a lot of fluid in the pericardial cavity, it can put pressure on the heart and lower the cardiac output and this is called cardiac tamponade.
It presents with Beck’s triad of hypotension, distended neck veins and distant heart sounds, as well as with a high heart rate and pulsus paradoxus.
ECG in cardiac tamponade shows low-voltage QRS complexes, as well as electrical alternans. Back to our cases.

Summary13:38–14:23

Pamela came in with sharp retrosternal chest pain that gets worse with inspiration and a friction rub has been heard. Both the symptoms and the physical findings are classic clues for pericarditis.
The ECG showed ST-elevation and PR depression and if an echocardiogram is done, it will detect fluid around the heart. This means that Pamela has acute pericarditis.
Thomas came in with severe hypotension, distended next veins and distant heart sounds, which are the three signs in Beck’s triad.
His heart rate was high to compensate for the decreased cardiac output and the ECG showed low-voltage QRS complexes, so he’s got a bad case of cardiac tamponade!