Cardiac Auscultation II: Heart Murmurs

Question 1

Genesis of Cardiac Murmurs

• Cardiac murmurs
• Reynolds number
• Turbulence
• Normal conditions
• Primary variable affecting Reynolds number

Answer 1

• Cardiac murmur
  
  • Sound generated by turbulent flow
• Reynolds number
  
  • Re = ( ρ * V * D ) / η
  • ρ = fluid density
  • η = fluid viscosity
  • V = flow velocity
  • D = tube diameter
• Turbulence
  
  • When Renylods number > critical value
• Normal conditions
  
  • Blood density, blood viscosity, & cardiac geometry remain constant
• Primary variable affecting Reynolds number
  
  • Velocity of blood flow

Question 2

Characterization of Murmurs

Answer 2

• Intensity
  
  • Loud or soft
• Timing
  
  • Systole or diastole
• Location
  
  • Aortic, pulmonic, tricuspid, or mitral
• Radiation
  
  • To suprasternal notch, axilla, or posteriorly

Question 3

Loudness/Intensity of Systolic & Diastolic Murmurs

Answer 3

• Systolic murmurs
  
  • 1/6: barely audible
  • 2/6: quiet but clearly audible
  • 3/6: easily audible
  • 4/6: easily audible w/ palpable thrill
  • 5/6: audible w/ stethoscope barely on chest wall
  • 6/6: audible w/ stethoscope off chest wall
• Diastolic murmurs
  
  • 1/4: barely audible
  • 2/4: faint but clearly audible
  • 3/4: easily audible
  • 4/4: loud

Question 4

Systolic Murmurs

Answer 4

• Systolic ejection murmurs
  
  • Generation
    
    • Turbulent flow across the A2 or P2 outflow tracts
  • Contour
    
    • Crescendo-decrescendo or diamond-shaped
    • Mirrors the acceleration fo blood flow across the valve during systolic ejection
  • Intensity
    
    • Varies w/ stroke volume or the contractile state of the ventricle
    • Increase during exercise & w/ inotropic agents
    • Augmented w/ longer RR intervals following premature ventricular contractions (PVCs)
  • Stroke volume
    
    • Affected by changes in diastolic filling time
    • Longer diastolic filling time –> larger stroke volume
  • Onset
    
    • Separated from S1 by the period of isovolumic contraction
    • Can’t be appreciated on auscultation
• Halo- or Pan-systolic murmurs
  
  • Generation
    
    • Flow from a high pressure chamber to a low pressure chamber
    • Ex. mitral & tricuspid regurgitation, ventricular septal defects
  • Contour
    
    • Rectangular or plateau
  • Onset
    
    • Begins w/ S1 and may continue up to & through S2
    • Not associated w/ a period of isovolumic contraction

Question 5

Classification of Systolic Murmurs based on Physiologic Mechanism of Production

Answer 5

Question 6

Common Causes of Systolic Ejection Murmurs

Answer 6

• Forward flow across a normal outflow tract
  
  • Innocent murmur
• Antegrade flow across an obstructed left or right ventricular outflow tract
  
  • Aortic or pulmonic stenosis
  • Sub-valvular membranes
  • Hypertrophic obstructive cardiomyopathy
• High flow states related to coexisting medical conditions
  
  • Thyrotoxicosis
  • Anemia
• High antegrade flow across a non-stenotic valve related to recirculated volume
  
  • Intracardiac shunts
  • Significant valvular insufficiency or regurgitation
• Forward flow into a dilated great vessel
  
  • Uncommon

Question 7

Characteristics of Systolic Ejection Murmurs

Answer 7

Question 8

Effect of Exercise & Isoproterenol on LV Ejection Dynamics

Answer 8

Question 9

Effect of Stroke Volume on LV Ejection Dynamics

Answer 9

Question 10

SEM: The “Innocent” Murmur

Answer 10

• Common physiologic finding in up to 50% of children
• Intensity < grade 3
• Ends before S2
• Normal physiological splitting of S2
• Absence of associated diastolic or systolic ejection sounds
• Absence of latered physiologic conditions that can increase cardiac output
  
  • Anemia, thyrotoxicosis, high fevers
  • Structural heart disease
  • Abnormal carotid pulse contour

Question 11

Differential Diagnosis of the Innocent Murmur

Answer 11

• Innocent cardiac murmur: diagnosis of exclusion
• High output / flow states
• Atrial septal defect
• Mitral valve prolapse
• Mild valvular aortic stenosis
• Mild valvular pulmonic stenosis
• Hypertrophic cardiomyopathy

Question 12

SEM: Aortic & Pulmonic Stenosis

• Contour of aortic & pulmonic stenosis murmurs
• Mild vs. worsening valvular stenosis
• A2 & P2 in aortic vs. pulmonic stenosis
• Calcified valve leaflets in aortic vs. pulmonic stenosis

Answer 12

• Contour of aortic & pulmonic stenosis murmurs
  
  • Diamond-shaped (systolic ejection) murmurs
  • Decrease valve orifice –> increase ventricular ejection time –> increase SEM intensity & duration
• Mild vs. worsening valvular stenosis
  
  • Mild valvular stenosis: systolic ejection click may be appreciated if the valve leaflets are pliable & noncalcified
  • Worsening valvular stenosis: SEM –> later peaking –> delayed A2 or P2 onset
• A2 & P2 in aortic vs. pulmonic stenosis
  
  • Aortic stenosis: narrowing of the S2 split
  • Pulmonic stenosis: widening of the S2 split
• Calcified valve leaflets in aortic vs. pulmonic stenosis
  
  • S2 becomes quieter & more muffled
  • Aortic steonsis: outflow tract obstruction –> decreased cardiac output –> decreased antegrade stroke volume –> decreased SEM intensity
  • Pulmonic stenosis: crescendo-decrescendo murmur may continue beyond & approach P2

Question 13

SEM: Atrial Septal Defect

• In the absence of pulmonary hypertension
• Auscultatory findings
  
  • Increased flow across the pulmonic outflow tract
  • If left to right shunt is sufficiently large
  • Increased pulmonic valve ejection time

Answer 13

• In the absence of pulmonary hypertension
  
  • Congenital hole in the atrial septum
  • –> LA pressure > RA pressure
  • –> increased blood from from the LA to the right-sided cardiac chambers
  • –> increased antegrade flow across tricuspid & pulmonic valves
• Auscultatory findings
  
  • Increased flow across the pulmonic outflow tract
    
    • Hear early peaking SEM at the LUSB
  • If left to right shunt is sufficiently large
    
    • Hear diastolic flow murmur across the tricuspid valve
  • Increased pulmonic valve ejection time
    
    • Hear wide fixed S2 splitting
    • Related to increased forward stroke volume across the pulmonic valve & decreased impedance in the pulmonary vascular bed

Question 14

SEM: Hypertrophic Obstructive Cardiomyopathy (HOCM)

• Hypertrophic obstructive cardiomyopathy
• Systolic anterior motion of the mitral valve (SAM)
• Resulting SEM
• S4
• Pansystolic murmur of mitral regurgitation

Answer 14

• Hypertrophic obstructive cardiomyopathy
  
  • Abnormal thickening of the ventricular septum
  • –> abnormal anterior motion of the anterior mitral valve leaflet during systole
• Systolic anterior motion of the mitral valve (SAM)
  
  • Creates a dynamic obstruction in the LV outflow tract
  • Increases in severity as the diameter of the LV decreases
• Resulting SEM
  
  • Mirrors the severity of the dynamic LVOT gradient
  • –> late-peaking SEM heard at the LLSB & the cardiac base w/ radiation to the suprasternal notch
• S4
  
  • May be present due to a late diastolic “atrial kick” into a stiff noncompliant LV
• Pansystolic murmur of mitral regurgitation
  
  • May be appreciated due to the abnormal coaptation of the mitral valve leaflets during ventricular systole

Question 15

Pan- or Holo-systolic Murmurs (HSMs)

• General
• Conditions you can hear this with
• Auscultatory findings
• Intensity

Answer 15

• General
  
  • Produced by retrograde blood flow from a high pressure chamber to a low pressure chamber
• Conditions you can hear this with
  
  • Mitral regurgitation
  • Tricuspid regurgitation
  • Ventricular septal defects
• Auscultatory findings
  
  • High pitched
  • “Blowing” quality
  • Rectangular contour
• Intensity
  
  • Good correlation b/n the intensity of the regurgitant murmur & the severity of regurgitant flow

Question 16

With arterial vasodilation, a mitral regurgitation murmur would most likely…

Answer 16

Decrease in intensity

Question 17

Paradoxical splitting of the S2 may be associated w/ which of the following conditions:

• Congenital pulmonic stenosis
• Atrial septal defect
• Moderate aortic stenosis
• RBBB
• LBBB

Answer 17

LBBB

• Paradoxical splitting occurs when A2 and P2 are abnormally separated
• With inspiration, see the split narrow instead of widen
• A2 migrates beyond P2, so with inspiration, A2 and P2 get closer
• LBBB: LV contracts later than normal, so A2 migrates beyond P2

Question 18

Which of the following auscultatory findings is most specific for the presence of severe mitral stenosis?

• Presence of a holosystolic murmur
• Presystolic accentuation of a diastolic murmur
• Presence of an S4
• Narrow S2 opening snap interval
• Presence of an S3

Answer 18

Presystolic accentuation of a diastolic murmur

Question 19

Effect of Changes in Afterload on Murmur of Mitral Regurgitation

• Mitral regurgitation
• Intensity
• Interventions that increase systemic / LV pressure (increase the pressure gradient)…
• Interventions that decrease systemic / LV pressure (decrease the pressure gradient)…

Answer 19

• Mitral regurgitation
  
  • Retrograde flow across the mitral valve from the high pressure LV into the low pressure LA
• Intensity
  
  • Influenced by the pressure gradient driving retrograde flow across the valve
  • Unlike SEMs, pansystolic murmurs vary less w/ changes in RR intervals & alternations in ventricular contractility
• Interventions that increase systemic / LV pressure (increase the pressure gradient)…
  
  • Increase MR murmur intensity
  • Ex. handgrip, squatting, & vasoconstrictor drugs like phenylephrine
• Interventions that decrease systemic / LV pressure (decrease the pressure gradient)…
  
  • Decrease MR murmur intensity
  • Ex. vasodilator drugs like amyl nitrite

Question 20

Mitral Regurgitation Related to Mitral Valve Prolapse

• Mitral valve prolapse
• Auscultatory findings

Answer 20

• Mitral valve prolapse
  
  • Abnormally thickened, elongated, & floppy mitral valve
  • Causes mitral regurgitation
• Auscultatory findings: mid-systolic click
  
  • Redudant leaflets reach their elastic limits
  • Imperfect coaptation of mitral valve leaflets –> crescendo mitral regurgitant murmur
  • Timing & intensity are affected by loading conditions of the heart

Question 21

Ventricular Septal Defects (VSDs)

• General
• Intensity
• Location

Answer 21

• General
  
  • Congenital or acquired
  • Characterized by holosystolic murmurs related to blood flow from the high pressure LV to the lower pressure RV
• Intensity
  
  • Inversely related to the size of the defect
  • Smaller defect –> louder murmur
  • Larger defect –> quieter murmur
• Location
  
  • Varies depending on the location of the VSD
  • High pressure gradient driving flow –> murmur heard throughout precordium
  • Palpable thrills frequently present

Question 22

Diastolic Murmurs (DM)

• Diastolic rumble
• Aortic or pulmonic regurgitation
• Difference b/n daistolic & systolic murmurs

Answer 22

• Diastolic rumble
  
  • Turbulent antegrade flow across the mitral or tricuspid valves
  • Low-pitched murmur
• Aortic or pulmonic regurgitation
  
  • Retrograde flow across the aortic & pulmonic valves
  • High-pitched murmur
• Difference b/n daistolic & systolic murmurs
  
  • Diastolic murmurs are always indicative of a pathological condition

Question 23

Classification of Diastolic Murmurs Based on Physiological Mechanism of Production

• Diastolic rumbles are associated with…
• Diastolic regurgitant murmurs are associated with…

Answer 23

• Diastolic rumbles are associated with…
  
  • Turbulent antegrade flow across a stenotic (anatomically narrowed) mitral or tricuspid valve
  • Austin-Flint murmur: physiological impingement of mitral valve diastolic excursion by a severe aortic regurgitation
  • High volume antegrade flow across the mitral or tricuspid valve
    
    • Associated w/ an intracardiac shunt (ASD or VSD) or significant AV valve regurgitation
• Diastolic regurgitant murmurs are associated with…
  
  • Incompetency of the semi-lunar (aortic & pulmonic) valves
  • Dilation of the aorta or pulmonary artery

Question 24

Characteristics of a Diastolic Rumble vs. Semilunar Valve Regurgitant Murmur

• Diastolic rumbles related to mitral stenosis
  
  • Onset
  • Auscultation
  • Contour
• Aortic & pulmonic regurgitant murmurs
  
  • Onset
  • Auscultation

Answer 24

• Diastolic rumbles related to mitral stenosis
  
  • Onset
    
    • Separated from S2 by a period equivalent to the isovolumic relaxation time/period
  • Auscultation
    
    • Heard at the LLSB & the apex
    • Louder in early diastole during the rapid passive filling phase of the LV
  • Contour
    
    • Decrescendos in mid diastole, then crescendos in late diastole w/ the atrial “kick”
• Aortic & pulmonic regurgitant murmurs
  
  • Onset
    
    • Begin immediately after S2 & decrescendo to S1
    • Closely mirror the aortic to LV pressure gradient
  • Auscultation
    
    • Heard at the cardiac base

Question 25

Diastolic Flow Murmurs Related to Increased Flow

Answer 25

* Increased flow across anatomically normal valves --\> diastolic flow murmurs * Most commonly seen in patients w/ intracardiac shunts (ex. ASDs or VSDs) * Increased intravalvular blood flow is related to recirculated blood volume from the shunt * Similar findings can be seen w/ recirculated blood volume related to severe mitral or tricuspid regurgitation

Question 26

Diastolic Murmurs: Auscultatory Findings Associated with Intracardiac Shunt

Answer 26

* Atrial septal defects & no pulmonary hypertension * Blood is shunted from the LA to the RA --\> increased diastolic flow across the tricuspid valve * --\> soft tricuspid valve diasotle flow rumble * Blood volume is ejected across the pulmonic valve * --\> SEM & wide fixed S2 splitting * Ventricular septal defects * Blood flows from the high pressure LV to the lower pressure RV * --\> pan- or holo-systolic murmur * Recirculated blood volume courses through the pulmonary vascular bed into the LA & across the mitral valve * --\> mitral diastolic flow rumble

Question 27

Auscultatory Findings Associated w/ Patent Ductus Arteriosus (PDA)

Answer 27

* Aortic pressure \> pulmonary pressure during both systole & diastole * Persistent congenital left to right shunt across the PDA from the aorta to the pulmonary artery * --\> continuous murmur in the left infraclavicular region or the left 2nd intercostal space * Left to right shunt increases pulmonary venous return into the LA & across the mitral valve * --\> mitral diastolic flow rumble

Question 28

Auscultatory Findings Associated w/ Severe MR & TR

Answer 28

* Antegrade flow of the recirculated regurgitant volume across the AV valves * --\> diastolic flow rumbles * Large LA blood volume in early diastole * --\> S3 * Tricuspid valve pathology * Respiratory variation of the systolic & diastolic murmurs

Question 30

Aortic & Pulmonic Regurgitant Murmurs * Aortic regurgitation * Aortic regurgitation auscultation * Harvey's sign * Afterload vs. aortic regurgitation * Pulmonic valve regurgitation

Answer 30

* Aortic regurgitation * Retrograde flow across an incompetent aortic valve * Aortic regurgitation auscultation * Blowing high-pitched decrescendo diastolic murmur * Heard at the 3rd & 4th intercostal spaces * Harvey's sign * Aortic regurgitation due to dilation of the aortic root * Murmur heard along the right parasternal border * Afterload vs. aortic regurgitation * Maneuvers that affect afterload: hand grip or amyl nitrate * Increase aortic diastolic pressure --\> increase aortic regurgitant murmur intensity * Decrease aortic diastolic pressure --\> decrease aortic regurgitant murmur intensity * Pulmonic valve regurgitation * Graham Steell murmur: associated w/ pulmonary hypertension & a dilated pulmonary artery

Question 31

Other Heart Sounds * To-fro murmurs * Continuous murmurs * Continuous venous hum * Mammary souffle

Answer 31

* To-fro murmurs * Aortic stenosis + aortic regurgitation * Crescendo-decrescendo SEm + decrescendo diastolic murmur * Continuous murmurs * Caused by arterial to venous shunts (ex. PDAs, arterial-to-venous fistulas) * Characterized by flow that begins in systole & continues through S2 into diastole * Continuous venous hum * Associated w/ high cardiac output & rapid venous return * Heard in the right supraclavicular fossa in children & pregnant women * Terminated by compression of the JVP * Mammary souffle * Associated w/ cardiac output & rapid venous return * Related to increased flow in mammary artery & veins * Heard in pregnant & lactating females * Terminated by compression of the stethoscope against the chest wall