CARDIAC MURMURS


"Venous hum": Continuous low-pitched murmur caused by collapse of the jugular veins; More prominent with inspiration or diastole

I. Grading of murmurs:

1/6: can only be heard under unusually quiet circumstances, e.g. in a soundproof room
2/6: can barely be heard in the average exam room
5/6: can be heard with chest piece 1/8 inch away from the chest
6/6: can be heard with the unaided ear placed near the chest

II. Differential dx of systolic murmur:

  1. Functional (high-flow) and innocent murmurs
  1. Characteristics that distinguish from murmurs of structural lesions include normal S2 (neither muted nor accentuated or exaggerated splitting) and lack of an enlarged precordial impulse to palpation (source: a handout of obscure origin)
  2. Dx also supported if nl JV pressure and peripheral pulses, Grade II or less, and location at left sternal border (ditto)
  3. Still’s murmur-May arise from vibrations in the chordae tendinae, semilunar valves, or ventricular wall.
  1. Aortic stenosis
  1. Harsh systolic ejection murmur at aortic area transmitted to neck
  2. Can get faint diastolic murmur at aortic area or upper L. sternal border
  3. Can get apical S4
  1. Mitral regurgitation
  1. Apical pansystolic murmur, S1 can be "lost" in the sound of the murmur; often radiates to axilla
  2. Often with S3 gallop
  3. If due to mitral prolapse:
  1. Sometimes a click will be present
  2. Murmur tends to occur earlier in systole with maneuvers that decrease LV size (Valsalva, squatting-to-standing, amyl nitrite inhalation), because in that situation LV reaches size threshold for MV prolapse earlier
  1. Tricuspid regurgitation
  1. Pansystolic murmur at lower left sternal border or subxiphoid region
  2. Often get S3 gallop introducing short early diastolic rumble in same area
  1. Pulmonic stenosis
  2. Hypertrophic cardiomyopathy (IHSS)
  1. Midsystolic or pansystolic murmur; often with S4 gallop
  1. Physiologic peripheral pulmonic stenosis (PPPS)
    1. Systolic murmur which is heard loudest in the axillae bilaterally
    2. Caused by physiologic changes in pulmonary vessels in a newborn
    3. Usually disappears by 9 months of age
  2. VSD
  1. Will often have a thrill along lower left sternal border

III. Differential dx of diastolic murmur:

  1. Mitral stenosis
  1. Diastolic opening snap then rumbling murmur with presystolic accentuation
  2. Splitting of S2 is narrowed
  3. P2 is often louder than normal b/c of pulmonary hypertension
  1. Aortic regurgitation
  1. Decrescendo blowing diastolic murmur heard best at upper L. sternal border
  2. Diastolic rumble ("Austin-Flint" murmur) often heard at apex; possible due to premature closure of anterior leaflet of mitral valve
  3. "Pistol shot" sounds over peripheral arteries
  4. Can get midsystolic ejection murmur at aortic area due to large stroke volume, ending before S2

IV. AN APPROACH TO DIAGNOSIS of SYSTOLIC MURMURS based on data from "Bedside Diagnosis of Systolic Murmurs"; see that article for details on technique

Note: this doesn't help a bit to distinguish pathologically significant murmurs from innocent flow murmurs

  1. REACTION TO INSPIRATION
  1. If no change or decrease, go to B
  2. If increased it's probably PULM. STENOSIS or TRICUSPID REGURG (67% pos. pred. value)
  1. SQUAT-to-STAND, if able
  1. If unable, go to C
  2. If able and no change or decreased, go to D
  3. If able and increased, go to C
  1. PASSIVE LEG ELEVATION
  1. If no change or increased, go to D
  2. If decreased, probably HYPERTROPHIC CARDIOMYOPATHY
  1. TRANSIENT ARTERIAL OCCLUSION
  1. If no change or decreased, probably AORTIC STENOSIS
  2. If increased, probably MITRAL REGURGITATION or VSD (epidemiology favors MR)