Cardiac Auscultation II: Heart Murmurs Flashcards
1
Q
Genesis of Cardiac Murmurs
- Cardiac murmurs
- Reynolds number
- Turbulence
- Normal conditions
- Primary variable affecting Reynolds number
A
- 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
2
Q
Characterization of Murmurs
A
- Intensity
- Loud or soft
- Timing
- Systole or diastole
- Location
- Aortic, pulmonic, tricuspid, or mitral
- Radiation
- To suprasternal notch, axilla, or posteriorly
3
Q
Loudness/Intensity of Systolic & Diastolic Murmurs
A
- 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
4
Q
Systolic Murmurs
A
- 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
- Generation
- 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
- Generation
5
Q
Classification of Systolic Murmurs based on Physiologic Mechanism of Production
A
6
Q
Common Causes of Systolic Ejection Murmurs
A
- 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
7
Q
Characteristics of Systolic Ejection Murmurs
A
8
Q
Effect of Exercise & Isoproterenol on LV Ejection Dynamics
A
9
Q
Effect of Stroke Volume on LV Ejection Dynamics
A
10
Q
SEM: The “Innocent” Murmur
A
- 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
11
Q
Differential Diagnosis of the Innocent Murmur
A
- 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
12
Q
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
A
- 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
13
Q
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
A
- 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
- Increased flow across the pulmonic outflow tract
14
Q
SEM: Hypertrophic Obstructive Cardiomyopathy (HOCM)
- Hypertrophic obstructive cardiomyopathy
- Systolic anterior motion of the mitral valve (SAM)
- Resulting SEM
- S4
- Pansystolic murmur of mitral regurgitation
A
- 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
15
Q
Pan- or Holo-systolic Murmurs (HSMs)
- General
- Conditions you can hear this with
- Auscultatory findings
- Intensity
A
- 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