USMLE/COMLEX 1 - Heart Murmurs

Here are key facts for USMLE Step 1 & COMLEX 1 from the Hypertension Overview 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. Murmurs are due to turbulent blood flow across abnormal valves (stenosis or regurgitation). 2. Systolic murmurs include:

• Aortic stenosis
• Mitral regurgitation
• Mitral valve prolapse

3. Diastolic murmurs include:

• Aortic regurgitation
• Mitral stenosis

4. Holosystolic murmur heard best at the apex, radiates to axilla. 5. Pathophysiology:

• Regurgitant flow from LV to LA during systole
• Increased LA pressure → pulmonary congestion
• Elevated v-wave on LA pressure tracing

6. Common causes: MVP (in younger), rheumatic fever, ischemic heart disease (papillary muscle rupture). 7. Early diastolic, decrescendo murmur best heard at left sternal border. 8. Pathophysiology:

• Blood flows back from aorta to LV during diastole
• Widened pulse pressure
• High systolic, low diastolic aortic pressures
• Corrigan's sign: bounding pulse or “water-hammer pulse”

9. Complication: LV dilation and heart failure. 10. Systolic crescendo-decrescendo murmur at right 2nd intercostal space, radiates to carotids. 11. Pathophysiology:

• Fixed obstruction of LV outflow → pressure overload
• LV concentric hypertrophy
• Reduced systolic aortic pressure

12. Symptoms: Syncope, Angina, Dyspnea (SAD). 13. Pulsus parvus et tardus: weak, delayed pulse. 14. Opening snap followed by low-pitched diastolic murmur heard best at apex, in left lateral decubitus. 15. Pathophysiology:

• Obstructed LA to LV flow during diastole
• Elevated LA pressure, LA hypertrophy → atrial fibrillation
• Decreased LV filling → reduced CO

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16. MR:

• Elevated preload, reduced afterload
• Volume overload → eccentric hypertrophy

17. AR:

• Increased stroke volume, increased preload
• Elevated systolic, low diastolic → increased pulse pressure

18. MS:

• High LA pressure → pulmonary edema
• Decreased aortic pressure and stroke volume

19. AS:

• High LV pressure, normal/low aortic pressure → pressure gradient across valve
• Atrial pressure may also rise due to increased afterload

20. MR and AS → systolic murmurs (between S1 and S2). 21. MS and AR → diastolic murmurs (after S2). 22. VSD and tricuspid regurgitation also cause holosystolic murmurs like MR. 23. MVP: Mid-systolic click + systolic murmur that increases with Valsalva or standing (decreased preload). 24. AS murmur increases with squatting (increased preload). 25. AR has a “blowing” early diastolic quality, especially with patient leaning forward.

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• Increased preload (squatting, leg raise) intensifies most murmurs except MVP and HOCM.
• Decreased preload (Valsalva, standing) softens most murmurs but intensifies MVP and HOCM.

• Chronic MR and AR lead to eccentric hypertrophy and eventual left-sided heart failure.
• MS can cause atrial fibrillation and stroke risk due to LA enlargement and stasis.

• Rheumatic fever → MS, MR
• Aging and calcification → AS
• Connective tissue disorders (e.g., Marfan) → MVP, AR