USMLE/COMLEX 1 - Valvular Disease

Here are key facts for USMLE Step 1 & COMLEX-USA Level 1 from the Valvular Disease tutorial, as well as points of interest at the end of this document that are not directly addressed in this tutorial but should help you prepare for the boards. See the tutorial notes for further details and relevant links.

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1. Valvular Dysfunction Types

• Stenosis = obstruction of valve orifice.
• Insufficiency/Regurgitation = incomplete closure of valve, leading to backward blood flow.

2. Aortic Stenosis

• Most common valvular disorder in developed countries.
• Caused by calcific degeneration due to hydroxyapatite deposition.
• Risk factors: bicuspid aortic valve, age-related wear, hyperlipidemia, hypertension, atherosclerosis.
• Involves osteoblast-like cells; similar to bone formation.

3. Bicuspid Aortic Valve

• Congenital defect in \~1% of the population.
• Increased risk of aortic stenosis due to greater mechanical stress.
• Associated with Turner syndrome and aortic aneurysms.

4. Aortic Regurgitation

• Often due to aortic root dilation (e.g., from Marfan syndrome or hypertension).
• Leads to volume overload of the left ventricle and widened pulse pressure.
• May be asymptomatic for years but can lead to left ventricular dilation and heart failure.

5. Mitral Valve Prolapse (MVP)

• Most common valvular abnormality in the U.S.
• Often due to myxomatous degeneration of leaflets.
• Causes midsystolic click followed by a late systolic murmur.
• Complications: endocarditis, arrhythmias, stroke due to embolism.

6. Mitral Stenosis

• Strongly associated with rheumatic heart disease.
• Histology: vegetations along the free edge, fusion of chordae tendineae.
• Classic "button hole" or "fish mouth" appearance.
• Results in left atrial dilation and predisposes to atrial fibrillation and thromboembolism.

7. Valve Replacement: Mechanical vs. Bioprosthetic

• Mechanical valves: durable but require lifelong anticoagulation (e.g., warfarin).
• Bioprosthetic valves: less thrombogenic but prone to deterioration.
• Risk of infective endocarditis elevated in both; antibiotic prophylaxis indicated for high-risk procedures.

8. Chordae Tendineae and Papillary Muscle Function

• Crucial for AV valve function.
• Damage can cause functional regurgitation without primary valve disease (e.g., after MI involving papillary muscles).

9. Marfan Syndrome and Aortic Root Dilation

• A connective tissue disorder causing dilation of the aortic root and increasing risk for aortic regurgitation, dissection, and rupture.

10. Endocarditis

• Involves inflammation/infection of heart valves.
• Most common on left-sided valves (mitral > aortic).
• Predisposed by damaged valves, prosthetic valves, and dental procedures (hence need for prophylactic antibiotics).

11. Prosthetic Valve Complications

• Occur in up to 60% of patients within 10 years.
• Include leakage, thromboembolism, and infective endocarditis.

12. Mitral Valve Calcification

• Typically affects annular ring, not leaflets.
• Leads to arrhythmias, stroke, and increased endocarditis risk.

13. Anatomy of Semilunar Valves

• Aortic valve has right coronary, left coronary, and posterior non-coronary leaflets.
• Coronary arteries arise from aortic sinuses near these leaflets.

14. AV Valve Anatomy

• Mitral valve: anterior and posterior cusps.
• Tricuspid valve: anterior, posterior, and septal leaflets.
• Anchored by chordae tendineae to papillary muscles.

15. Role of Valve Annulus

• Fibrous ring anchoring valve to myocardium.
• Pathology here affects valve competence and is a key site for calcification.

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1. Semilunar Valve Components

• Lunule = thin edge of leaflet.
• Nodule of Arantius = thickened center of lunule for tight closure.
• Commissures = leaflet attachments.
• Sinotubular junction = transition from aortic sinus to ascending aorta.

2. Pathophysiology of Valve Degeneration

• Resembles bone formation due to osteoblast-like cells.
• Influenced by mechanical stress and inflammatory factors.

3. Effect of Calcification on Conduction System

• Mitral annular calcification can impair the AV node or bundle of His, causing arrhythmias.

4. Valve Dysfunction from Supporting Structures

• Rupture or dysfunction of chordae tendineae or papillary muscles (e.g., in MI) leads to acute regurgitation.

5. Functional Regurgitation

• Secondary to chamber dilation or wall stress (e.g., in heart failure) rather than primary valve disease.

6. Coronary Arteries and Valve Anatomy

• Originate at aortic sinuses: right and left coronary arteries exit just above corresponding aortic valve cusps.

7. Aortic Valve Leaflets

• Named according to coronary artery relationship: right coronary, left coronary, posterior (non-coronary).

8. Papillary Muscle Anatomy

• Extensions of the ventricular myocardium, important for maintaining valve closure during systole.

9. Infective Endocarditis Prophylaxis

• Indicated in patients with prosthetic valves or prior history of endocarditis undergoing high-risk procedures.

10. Marfan Syndrome

• Mutation in fibrillin-1 gene.
• Affects connective tissue of cardiovascular system (aorta, valves), eyes (lens dislocation), and skeleton.

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1. Rheumatic Fever and Heart Disease

• Caused by immune cross-reactivity (type II hypersensitivity) post-Group A strep pharyngitis.
• Jones criteria: Joints, Carditis, Nodules, Erythema marginatum, Sydenham chorea.
• Late sequela: mitral stenosis.

2. S3 and S4 Heart Sounds

• S3: Associated with volume overload (e.g., in regurgitation, heart failure).
• S4: Associated with stiff ventricles (e.g., hypertrophy, ischemia).

3. Hemodynamics of Valve Disease

• Aortic stenosis: crescendo-decrescendo systolic murmur, radiates to carotids.
• Mitral regurgitation: holosystolic murmur at apex, radiates to axilla.
• Aortic regurgitation: early diastolic murmur, wide pulse pressure.
• Mitral stenosis: diastolic rumble, opening snap.

4. Echocardiography

• Key imaging modality to assess valve structure and function.
• Doppler used to estimate severity of stenosis/regurgitation.

5. Heart Murmur Maneuvers

• Standing/valsalva: decreases preload, accentuates MVP and HOCM murmurs.
• Squatting: increases preload/afterload, reduces MVP murmur.

6. Timeline of Prosthetic Valve Failure

• Mechanical: longer durability, but early thrombosis risk.
• Bioprosthetic: deteriorate over time, often within 10–15 years.