USMLE Cardiovascular 11: Pericardial Diseases (Pulsus Paradoxus) and Cardiomyopathies

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  / lymed   *Mistake: Eccentric hypertrophy adds in series, and concentric adds in parallel.

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In our previous videos, we discussed some things like cardiac tamponade, fibrinous pericarditis and Dressler syndrome. These were diseases of the pericardium. This video will explore the pericardium in more detail. Your pericardium is a sack that surrounds your heart and is made up of the visceral pericardium parietal pericardium and the fibrous pericardium. In between is pericardial fluid. Lets talk about some diseases.
The first one is pericarditis which can be seen in Coxsackie B virus, uremia seen in chronic kidney disease (CKD), as well as those discussed in previous videos. Physical examination shows sharp chest pain worse on inspiration and lying down. Relief when leaning forward. Auscultation will show friction rub and ECG will show ST elevations. Another pericardial disease is cardiac tamponade. This is when blood leaks into the pericardial space and compresses the heart equalizing the diastolic pressure. This makes it difficult to fill and leads to hypotension, distended neck veins and distant heart sounds and pulsus paradoxus.

Our next topic is cardiomyopathies. This is pathology dealing with the heart muscles. Just to preface it, you have sarcomeres that help your heart contract. You can recruit more in parallel, which thins out the heart and we call this eccentric hypertrophy. We can also put more sarcomere in series, thickening it and leading to concentric hypertrophy. So back to our cardiomyopathies.
1) Dilated: some insult leads to eccentric hypertrophy and dilation of the heart leading to inability to contract. We call this systolic dysfunction. This is seen in coxsackie, alcohol, wet beriberi, doxorubicin, and postpartum women. Physical exam findings include S3 heart sound and regurgitation murmur.
2) Hypertrophic cardiomyopathy: concentric hypertrophy, this is seen in mutations in b-myosin heavy chain which leads to a thickened heart wall in disarray. This can lead to arrhythmias and sudden death in young athletes. On auscultation you'll hear a S4 and a HCM murmur. Treat by stopping sports, beta blockers and an ICD.
3) Restrictive and Infiltrative cardiomyopathy: this can be deposition by amyloidosis and hemochromatosis, sarcoidosis, Loffler syndrome, and fibrosis. This can't fill with blood and thus diastolic dysfunction.
Done!