USMLE Cardiovascular 12: Murmurs Explained (starts at 11:00), Endocardits and Rheumatic Fever

Want to support the channel? Be a patron at:   / lymed   *Correction: Handgrip during murmurs decreases forward moving murmurs (stenosis), but increases the sound of regurg/VSD. Welcome to LY Med, where I go over everything you need to know for the USMLE STEP 1, with new videos every day. Follow along with First Aid, or with my notes which can be found here: https://www.dropbox.com/sh/xisbr5u8re... This video will be on valvular pathologies and heart murmurs. We'll start with infective endocarditis. This effects the endocardium, the lining of the valves and leads to vegetations. We have high virulence bugs like in Staph aureus which causes acute symptoms and loves the mitral valve. The exception is in IV drug users as this effects the tricuspid valve. Lower virulence strains include viridans strep which can only effect damaged valves. Think of this in patients that underwent dental procedures. Some important bugs include Group D strep (Strep gallolyticus) which is seen in patients with colon cancer. Do a colonoscopy for these patients! Another bug includes strep epidermidis which effects prosthetic valves due to their biofilms. Know the physical exam findings of IE which include your osler nodes, janeway lesions, splinter hemorrhages and more! You can have sterile endocarditis which is seen in hypercoagulabe states and cancer, as well as lupus SLE. This is called Libman Sacks endocarditis which effects both sides of the valve. Our next topic is rheumatic fever, a complication of strep throat! This is strep pyogenes or group A beta hemolytic strep. This is due to antibodies against strep (type II hypersenstivity) and this attacks M protein which can attack our own proteins that look like it (we call it molecular mimicry). THis can lead to chorea, migratory polyarthritis, pancarditis, erythema marginatum, and painful nodules. Since we are in our CVS block, lets talk about the pancarditis. When it destroys your endocardium, it can affect the valves leading to mitral regurgitation and stenosis later, myocarditis and death, and pericarditis. You can see granulomas on biopsy as aschoff bodies and anitschkow cells. You can also do lab findings to confirm the diagnosis with anti-streptolysin O and anti-DNAse b titers. Let's finally talk about heart murmurs. Valves open do two things - open and close. If they cant open, that's stenosis. If they can't close we call that regurgitation. In systole, your aortic and pulmonary valves open and your mitral and tricuspid valves close. If there's a problem here we get systolic murmurs. In aortic stenosis, think elderly patients with syncope or younger patients with bicuspid aortic valves. It sounds like a crescendo decrescendo murmur that radiates to the carotids. In mitral and tricuspid regurgitation, blood will leak through. Know mitral valve prolapse, in which the valve is floppy. This is heard as a mid-systolic click and murmur. This is associated with CT disorders and Marfans due to myxomatous degeneration. Last one is ventricular septal defects - VSD. In systole you'll hear blood moving through the VSD and this is seen in children. In diastole: your aortic and pulmonary valves close and your mitral and tricuspid open. In closure problems, you get aortic regurgitation, which raises pulse pressure. You get bounding pulses, head bobbing and LHF. In mitral and tricuspid stenosis theres a mid diastolic snap. The shorter the interval to the snap, the more severe. Our last murmur is the PDA. This is a continuous murmur in the left infraclavicular area. Associated with prematurity and congenital rubella. How do you tell murmurs apart? Well listen to the different areas of the heart and maneuvers! Let's discuss some maneuvers. If you increase the preload of your right heart by inspiration, this increases the intensity of right heart murmurs. Increasing preload in general like in hand grip and squatting which increases all murmurs. Decrease preload like in standing up or valsalva maneuver which decreases murmurs. Mitral valve prolapse click occurs later in increased preload. The click occurs earlier in decreased preload. In hypertrophic cardiomyopathy, this is the opposite of everything else! Done!