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Understanding Heart Sounds and Murmurs

Mar 7, 2025

Heart Sounds and Heart Murmurs Lecture Notes

Introduction

  • Heart sounds and murmurs are complex but high-yield topics for exams like USMLE and COMLEX.
  • Tests may give visual sound amplitude depictions or audio files requiring interpretation.
  • Understanding normal and abnormal heart sounds is crucial.

Normal Heart Sounds

  • S1 (Lub): occurs at the beginning of systole; mitral and tricuspid valves closing.
  • S2 (Dub): occurs at the beginning of diastole; aortic and pulmonic valves closing.
  • Cardiac cycle:
    • Systole: between S1 and S2.
    • Diastole: between S2 and the next S1.
  • Audio Representation: Normal heart sounds are rhythmic - Lub-Dub, Lub-Dub.

Splitting of Heart Sounds

  • Physiology: S2 split into A2 (aortic) and P2 (pulmonic), affected by breathing.

Types of Splitting

  1. Wide Splitting

    • Occurs due to delayed right ventricle emptying (e.g., pulmonic stenosis, right bundle branch block).
    • During inhalation, P2 separates further from A2.

  2. Fixed Splitting

    • A2 and P2 are evenly spaced regardless of breathing.
    • Associated with atrial septal defect (ASD) causing left-to-right shunt.

  3. Paradoxical Splitting

    • Occurs due to delayed aortic valve closure (e.g., aortic stenosis, left bundle branch block).
    • Reversed order of A2 and P2 during exhalation; inhalation renormalizes it.

High-Yield Heart Murmurs

Aortic Stenosis

  • Description: Systolic, crescendo-decrescendo ejection murmur.
  • Associations: Pulsus parvus et tardus, syncope, angina, dyspnea; age-related calcification, bicuspid aortic valve.
  • Audio: Harsh, peaks then drops off sound during systole.

Mitral and Tricuspid Regurgitation

  • Description: Holosystolic, high-pitched blowing murmur.
  • Associations:
    • Mitral: Post-MI, infective endocarditis.
    • Tricuspid: Intravenous drug use, right-sided heart failure.
  • Audio: Continuous, high-pitched murmur from S1 to S2.

Mitral Valve Prolapse

  • Description: Late systolic crescendo murmur with a mid-systolic click.
  • Associations: Connective tissue disorders (Marfan, Ehlers-Danlos), infective endocarditis.
  • Audio: Notable mid-systolic click followed by crescendo.

Ventricular Septal Defect (VSD)

  • Description: Holosystolic, harsh-sounding murmur.
  • Associations: Genetic disorders (Down Syndrome, trisomies), torch infections.
  • Audio: Harsh murmur throughout systole.

Aortic Regurgitation

  • Description: Early diastolic, high-pitched blowing decrescendo murmur.
  • Associations: Chronic conditions (bicuspid valve), acute infective endocarditis.
    • Signs: Water hammer pulse, De Musset sign (head bobbing).
  • Audio: Loud at onset, tapers off during diastole.

Mitral Stenosis

  • Description: Diastolic opening snap followed by a delayed diastolic rumble.
  • Associations: Rheumatic fever, left atrial myxoma as mimickers.
  • Audio: Opening snap post-S2, followed by rumble.

Patent Ductus Arteriosus

  • Description: Continuous, machine-like murmur throughout systole and diastole.
  • Associations: Congenital rubella, premature infants.
  • Treatment: Prostaglandins to keep it open, indomethacin to close it.

These notes cover the essentials of normal heart sounds, splitting, and various types of heart murmurs, crucial for understanding the pathology and preparing for medical exams.

Full transcript