Transcript for Pericardial disease
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.
Also, a very specific ECG finding in pericarditis is PR segment depression.
Pericarditis also causes generalized inflammation, so there’s often an elevated white blood cell count, ESR, and CRP.
In addition, it’s important to obtain troponins to rule out conditions like a myocardial infarction.
Since pericarditis can lead to pericardial effusion, a transthoracic echocardiography is used to look for a pericardial effusion.
In addition, it can be used to look for wall motion abnormalities, which are widespread in acute pericarditis, but limited to the area of infarct in a myocardial infarction.
Diagnosis of acute pericarditis is based on having the typical chest pain, a friction rub on auscultation, suggestive ECG findings, and evidence of a pericardial effusion.
Most cases of acute pericarditis are uncomplicated and self limited. And most of the time, there’s no clear cause identified or it’s thought to be viral pericarditis, like from coxsackie virus, and supportive treatment is given to ease the pain and inflammation.
Nonsteroidal anti inflammatory drugs, or NSAIDs, like ibuprofen or aspirin, usually work for pain relief. If NSAIDs aren’t enough, they may be combined with colchicine, which inhibits neutrophil motility and has an anti-inflammatory effect.
In some cases of acute pericarditis, corticosteroids may be used to calm the inflammation, but use of corticosteroids is a risk factor for recurrence. So, they should only be used if NSAIDs and colchicine aren’t sufficient.
Finally, if there’s an underlying cause for the pericarditis, then it should be treated.
For example, if there’s a cancer of a surrounding tissue or organ like a lymphoma, lung, breast, or esophageal tumor, then in some cases chemotherapy can be injected directly into the pericardial sac.
Similarly, if the underlying cause is a bacterial or tuberculosis infection, then antibiotics can help treat the pericarditis.
In a pericardial effusion, the pericardial sac can fill up with up to 200 mL of fluid acutely, and over a liter of fluid if it accumulates slowly.
Small effusions may be asymptomatic unless they’re associated with pericarditis, whereas a large effusion may cause symptoms of cardiac tamponade. That’s where the fluid around the heart prevents the ventricle from relaxing enough to accept blood - lowering cardiac output and causing hemodynamic compromise, which can ultimately lead to shock.
But timing matters, and if the effusion occurs rapidly enough, then even 100 mL can cause cardiac tamponade.
Cardiac tamponade is life-threatening and causes Beck's triad, which is hypotension due to the impaired cardiac output, jugular venous distention due to blood backing up, and muffled heart sounds on auscultation because of the extra fluid between the heart and the stethoscope.
In fact, larger effusions can cause Ewart's sign, which is dullness to percussion over the left subscapular area due to compression of the left lung base.
On ECG, a large effusion can cause low voltages across many of the leads due to the increased distance from the chest leads.
It can also cause electrical alternans, which is where the readings shift from heartbeat to heartbeat due to the heart jiggling around a bit within the effusion.
And in cardiac tamponade, classic ECG findings include sinus tachycardia and a low QRS complex voltage.
On an X-ray, of a heart with a large pericardial effusion, you can see a silhouette that pools to the bottom of the heart and gives a classic “water bottle” sign, and a large pericardial effusion of at least about 200 mL causes cardiomegaly.
That’s a large cardiac shadow which blurs out the distinction between the arch of the aorta and the left ventricle.
Echocardiography is the main diagnostic tool used in the evaluation of pericardial effusion, showing the excess fluid creating an echo-free space between the two pericardial layers.
Echocardiography gives a very clear picture on the extent of the effusion, which is directly proportional to the separation between the layers.
The effusion can be small, moderate, or large.
For circumferential pericardial effusions, a pericardial effusion that has less than 10 mm of pericardial separation in diastole is small, and corresponds to a fluid volume of 50 to 100 mL; 10 to 20 mm of separation is moderate, and corresponds to a fluid volume of 100 to 500 mL; and greater than 20 mm separation is large, and corresponds to a fluid volume greater than 500 mL.
Additionally, on an echocardiogram, a pericardial effusion makes the heart looks like it’s dancing within the pericardium.