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Heart Murmurs for ABIM

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Heart Murmurs for the American Board of Internal Medicine Exam
Overview of Heart Murmurs
Heart murmurs are abnormal heart sounds created by turbulent blood flow within the heart or across a valve. They can be classified as systolic, diastolic, or continuous based on their timing in the cardiac cycle.
Normal heart valve pressures
Systolic Murmurs
Aortic Stenosis
  • Mechanism: Stenosis of the aortic valve causes LV outflow obstruction during systole.
  • Auscultation:
    • Location: Right second intercostal space, radiating to the carotids.
    • Sound: Harsh, crescendo-decrescendo (diamond-shaped) systolic ejection murmur.
    • Associated Findings: Diminished, delayed carotid upstroke (pulsus parvus et tardus) and soft S2.
  • Clinical Significance: Symptoms include angina, syncope, and heart failure. Severe cases require valve replacement.
Mitral Regurgitation
  • Mechanism: Incompetent mitral valve allows backflow from LV to left atrium (LA) during systole.
  • Auscultation:
    • Location: Apex, radiating to the axilla.
    • Sound: Holosystolic (pansystolic) murmur, high-pitched and blowing.
    • Associated Findings: S3 heart sound may be present with volume overload in severe regurgitation.
  • Clinical Significance: Causes include mitral valve prolapse (MVP), rheumatic disease, and LV dilation. Severe cases with LV dysfunction require surgical repair or replacement.
Mitral Valve Prolapse (MVP)
  • Mechanism: Prolapse of the mitral valve leaflets into the LA during systole.
  • Auscultation:
    • Location: Apex.
    • Sound: Midsystolic click followed by a late systolic murmur; click and murmur are earlier with maneuvers that decrease LV volume (e.g., standing, Valsalva).
  • Clinical Significance: Usually benign, but severe cases may lead to mitral regurgitation.
Tricuspid Regurgitation
  • Mechanism: Incomplete closure of the tricuspid valve allows backflow from the RV to the RA during systole.
  • Auscultation:
    • Location: Left lower sternal border, increases with inspiration (Carvallo’s sign).
    • Sound: Holosystolic murmur, blowing quality.
  • Clinical Significance: Often secondary to RV dilation, pulmonary hypertension, or left-sided heart disease. Managed with diuretics; surgery is rare but may be indicated in severe cases.
Hypertrophic Obstructive Cardiomyopathy (HOCM)
  • Mechanism: Dynamic LV outflow obstruction due to asymmetric septal hypertrophy.
  • Auscultation:
    • Location: Left sternal border.
    • Sound: Harsh, crescendo-decrescendo systolic murmur that increases with maneuvers decreasing preload (e.g., Valsalva, standing).
  • Clinical Significance: Common cause of sudden cardiac death in young athletes. Managed with beta-blockers, calcium channel blockers, and occasionally surgical myectomy.
Diastolic Murmurs
Aortic Regurgitation
  • Mechanism: Backflow of blood from the aorta into the LV during diastole.
  • Auscultation:
    • Location: Left sternal border (third or fourth intercostal space).
    • Sound: High-pitched, blowing decrescendo murmur.
    • Associated Findings: Widened pulse pressure, bounding pulses, and findings like Corrigan’s pulse (bounding carotid pulse).
  • Clinical Significance: Causes include aortic root dilation, endocarditis, and rheumatic fever. Severe regurgitation with symptoms or LV dysfunction requires valve replacement.
Mitral Stenosis
  • Mechanism: Narrowed mitral valve restricts blood flow from LA to LV during diastole.
  • Auscultation:
    • Location: Apex, best heard in the left lateral decubitus position.
    • Sound: Low-pitched, rumbling diastolic murmur with an opening snap following S2.
  • Clinical Significance: Commonly due to rheumatic fever, causing dyspnea, fatigue, and atrial fibrillation (AF). Percutaneous mitral balloon valvotomy is indicated for severe cases.
Tricuspid Stenosis
  • Mechanism: Narrowing of the tricuspid valve impedes flow from the RA to RV during diastole.
  • Auscultation:
    • Location: Left lower sternal border, increases with inspiration.
    • Sound: Low-pitched, rumbling diastolic murmur with an opening snap.
  • Clinical Significance: Rare, often associated with rheumatic fever and usually occurs with mitral or aortic valve disease.
Pulmonic Regurgitation
  • Mechanism: Backflow from the pulmonary artery to the RV during diastole.
  • Auscultation:
    • Location: Left upper sternal border.
    • Sound: High-pitched, decrescendo murmur (Graham Steell murmur) when due to pulmonary hypertension.
  • Clinical Significance: Commonly secondary to pulmonary hypertension, often managed by treating the underlying condition.
Continuous Murmurs
Patent Ductus Arteriosus (PDA)
  • Mechanism: Persistent opening between the aorta and pulmonary artery allows continuous flow.
  • Auscultation:
    • Location: Left infraclavicular area.
    • Sound: Continuous, “machinery-like” murmur, audible throughout systole and diastole.
  • Clinical Significance: PDA may cause heart failure and pulmonary hypertension if untreated. Closure is achieved with NSAIDs in neonates or surgical ligation if persistent.
Arteriovenous (AV) Fistula
  • Mechanism: Abnormal communication between an artery and a vein creates continuous turbulent flow.
  • Auscultation:
    • Location: Variable, depending on fistula location.
    • Sound: Continuous murmur with a thrill, louder in diastole.
  • Clinical Significance: May cause high-output heart failure if significant. Treated by surgical closure if symptomatic.
Key Points
  • Systolic Murmurs:
    • Aortic Stenosis: Crescendo-decrescendo murmur at the right upper sternal border, radiating to the carotids; associated with delayed carotid pulse.
    • Mitral Regurgitation: Holosystolic murmur at the apex, radiating to the axilla.
    • Mitral Valve Prolapse: Midsystolic click and late systolic murmur; click becomes earlier with maneuvers reducing LV volume.
    • HOCM: Crescendo-decrescendo murmur at the left sternal border, increases with Valsalva.
  • Diastolic Murmurs:
    • Aortic Regurgitation: High-pitched, decrescendo murmur at the left sternal border; associated with widened pulse pressure.
    • Mitral Stenosis: Low-pitched, rumbling murmur at the apex, with an opening snap following S2.
    • Tricuspid Stenosis: Low-pitched murmur at the left lower sternal border, louder with inspiration.
  • Continuous Murmurs:
    • PDA: Continuous “machinery” murmur in the left infraclavicular area.
    • AV Fistula: Continuous murmur with a thrill, commonly associated with high-output failure.
  • Clinical Relevance:
    • Aortic and mitral valve diseases are the most common and may require valve replacement if severe.
    • Murmur changes with maneuvers (e.g., Valsalva, inspiration) help differentiate the type and severity of valve disease.
    • Diagnostic confirmation and severity assessment are done with echocardiography; cardiac catheterization is used selectively.

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