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Heart Sounds & Murmurs

Learning Objectives

Core Knowledge & Clinical Reasoning

  • [ ] Identify and interpret S1, S2, S3, S4, and cardiac clicks
  • [ ] Recognize abnormal S2 splitting patterns and their significance
  • [ ] Grade murmurs using the Levine scale
  • [ ] Characterize murmurs by timing, location, radiation, and quality
  • [ ] Correlate auscultatory findings with specific cardiac lesions

Management Decisions

  • [ ] Determine which murmurs require echocardiographic evaluation
  • [ ] Distinguish innocent from pathologic murmurs based on characteristics

Heart Sounds

S1 (First Heart Sound)

  • Mitral and tricuspid valve closure
  • Best heard at apex
  • Usually single
Abnormality Cause
Loud S1 Mitral stenosis, short PR, high output
Soft S1 Long PR, poor LV function, severe MR
Split S1 Usually normal variant; RBBB

S2 (Second Heart Sound) - MOST IMPORTANT

Normal Splitting - A2 (aortic) then P2 (pulmonic) - Increases with inspiration (more RV filling, delayed P2) - Decreases with expiration

Finding Significance
Fixed split ASD (does not vary with respiration)
Wide split RBBB, pulmonary stenosis
Single S2 Severe AS, pulmonary atresia, truncus, TGA
Loud P2 Pulmonary hypertension
Soft P2 Pulmonary stenosis
Paradoxical split LBBB, severe AS

S3 (Third Heart Sound)

  • Early diastole, after S2
  • "Ken-TUC-ky" cadence
  • Normal in children and young adults
  • Pathologic if: heart failure, volume overload

S4 (Fourth Heart Sound)

  • Late diastole, before S1
  • "TEN-nes-see" cadence
  • Always pathologic in children
  • Indicates: decreased ventricular compliance (HCM, HTN)

Clicks

Type Timing Cause
Ejection click Early systole, after S1 Bicuspid AV, pulmonary stenosis
Mid-systolic click Mid systole Mitral valve prolapse

Murmur Evaluation

Timing

Timing Definition Examples
Systolic ejection Crescendo-decrescendo, mid-systolic AS, PS, flow murmurs
Holosystolic Throughout systole, plateau VSD, MR, TR
Diastolic Between S2 and S1 AR, MS, PR
Continuous Through S2, systole + diastole PDA, venous hum, AV fistula

Grading (Levine Scale)

Grade Description
I Barely audible, only in quiet room
II Soft but readily audible
III Moderately loud, no thrill
IV Loud with palpable thrill
V Very loud, audible with stethoscope barely on chest
VI Audible with stethoscope off chest

Location (Where Loudest)

Location Valve Area
RUSB (2nd R ICS) Aortic
LUSB (2nd L ICS) Pulmonic
LLSB (4th L ICS) Tricuspid, VSD
Apex (5th L ICS, MCL) Mitral

Radiation

Radiation Suggests
To carotids Aortic stenosis
To axilla Mitral regurgitation
To back Coarctation, PDA, branch PA stenosis

Quality

Quality Description Example
Harsh/blowing High velocity AS, VSD
Musical/vibratory Low frequency Still's murmur
Rumbling Low frequency, diastolic MS
Machine-like Continuous PDA

Correlating Findings with Conditions

Condition Auscultatory Findings
Large VSD Holosystolic murmur LLSB, may have thrill
ASD Fixed split S2, soft systolic ejection murmur LUSB
PDA Continuous "machinery" murmur left infraclavicular
Aortic stenosis Ejection click + harsh systolic murmur RUSB→carotids
Pulmonary stenosis Ejection click + systolic murmur LUSB
TOF Single S2, systolic murmur LUSB (variable with obstruction)
Coarctation Systolic murmur left back, +/- continuous if collaterals
Heart failure S3 gallop, tachycardia
HCM S4 gallop, systolic murmur LLSB (increases with Valsalva)

Innocent vs Pathologic Murmurs

Innocent Murmur Characteristics (6 S's)

  1. Soft (Grade I-II)
  2. Short (systolic)
  3. Single S2 (normal splitting)
  4. Symptom-free
  5. Size normal (no cardiomegaly)
  6. Sound quality (musical/vibratory, not harsh)

Red Flags for Pathologic Murmur

  • Diastolic murmur (always abnormal)
  • Harsh quality
  • Grade ≥III/VI
  • Associated with thrill
  • Abnormal S2 (fixed split, single, loud P2)
  • Associated symptoms
  • Abnormal pulses or vital signs

Board Pearls

Pearl: Fixed split S2 = ASD

Normal S2 varies with respiration; fixed splitting does not

Pearl: S3 is normal in children; S4 is always abnormal

S4 indicates decreased ventricular compliance (HCM)

Pearl: Ejection click = valve abnormality

Bicuspid aortic valve or pulmonary stenosis

Pearl: Smaller VSD = louder murmur

More turbulence through restrictive defect

Pearl: Diastolic murmurs are ALWAYS pathologic

Even soft diastolic murmurs need echocardiography

Self-Assessment

Q1: On auscultation, you notice that S2 splitting does not change with respiration. What does this suggest?

Answer **Answer**: Atrial septal defect (ASD) **Rationale**: Fixed split S2 (no respiratory variation) is pathognomonic for ASD due to constant LA→RA shunting equalizing RV filling regardless of respiration.

Q2: You hear an S4 gallop in a 12-year-old athlete. Is this normal?

Answer **Answer**: No - S4 is always pathologic in children **Rationale**: S4 indicates decreased ventricular compliance. In an athlete, consider HCM. Unlike S3 (which can be normal in children), S4 is never normal.

Q3: A 5-year-old has a Grade II/VI vibratory murmur at the LLSB that decreases when supine. Normal S2 splitting, no symptoms. What is most likely?

Answer **Answer**: Still's murmur (innocent vibratory murmur) **Rationale**: Still's murmur is vibratory/musical, Grade I-II, at LLSB, changes with position, and has normal heart sounds. No workup needed.

Key Guidelines

2022 AHA/ACC Guideline for Clinical Evaluation of Cardiovascular Disease in Children Circulation. 2022 Systematic approach to auscultation and murmur evaluation in pediatric patients

References

  • Park MK. Pediatric Cardiology for Practitioners, 7th ed.
  • Pelech AN. Pediatr Clin North Am. 1999;46(2):167-88
  • Frank JE, Jacobe KM. Am Fam Physician. 2011;84(7):793-800