Auscultation of Heart Valves: Clinical Anatomy

The Five Classic Auscultatory Areas

Key concept: Auscultatory areas do NOT correspond to the anatomical location of the valves. They are the sites on the chest wall where sounds from each valve are best conducted and heard.

Why Sounds Are Heard Where They Are

• Aortic stenosis murmur: heard at the base (right 2nd ICS) and radiates to the carotid arteries
• Mitral regurgitation murmur: heard at the apex and radiates to the left axilla
• Aortic regurgitation murmur: heard along the left sternal border (3rd-4th ICS) when caused by valve disease; when caused by aortic root dilation, it may be more audible along the right sternal border
• Tricuspid regurgitation: can radiate to the right sternal border; increases with inspiration (Carvallo's sign)

Technique

1. Sitting up, leaning forward - best for aortic regurgitation and pericardial rubs; base of heart sounds
2. Supine - standard for most heart sounds
3. Left lateral decubitus - brings the apex closer to the chest wall; best for mitral murmurs (especially the low-pitched MS rumble) and S3/S4 gallops

• Diaphragm (firm pressure): high-pitched sounds - most murmurs, S1, S2, aortic regurgitation, ejection clicks, opening snaps
• Bell (light pressure): low-pitched sounds - S3, S4, mitral stenosis diastolic rumble, vascular bruits. If excessive pressure is applied to the bell, it acts like a diaphragm and low-pitched sounds are lost

Heart Sounds and Their Valve Origins

S1 (First Heart Sound)

• Produced by closure of the mitral and (to a lesser extent) tricuspid valves - marks the end of diastole/start of systole
• Louder in mitral stenosis (when leaflets are mobile)
• Softer in mitral regurgitation (poor leaflet coaptation)

S2 (Second Heart Sound)

• Produced by closure of the aortic valve (A2) followed by the pulmonic valve (P2)
• Physiologic splitting: On inspiration - increased RV filling delays P2, causing audible splitting (A2 then P2). On expiration - both coincide and S2 is single
• Fixed splitting: A2-P2 interval unchanged with respiration - seen in atrial septal defect and right bundle branch block
• Paradoxical splitting: S2 splits on expiration and becomes single on inspiration - delayed A2 (e.g., severe AS, HOCM, LBBB)
• Loud A2: systemic hypertension
• Soft/absent A2: severe calcific aortic stenosis
• Loud P2: pulmonary hypertension

Opening Snap

• High-pitched sound in early diastole - heard before rapid filling begins
• Mitral opening snap: heard best at the apex
• Tricuspid opening snap: left 3rd-4th ICS
• Distinguished from a loud P2 by its longer interval from S2 and its location

S3 (Third Heart Sound)

• Low-pitched sound in early diastole - corresponds to rapid ventricular filling
• Normal in children and young adults; pathological after age ~40
• Causes: mitral regurgitation (increased filling volume), heart failure (elevated filling pressures)
• Left ventricular S3: heard at the apex with the bell
• Right ventricular S3: heard at the 4th ICS, left parasternal border with the bell

S4 (Fourth Heart Sound)

• Low-pitched sound in late diastole - from atrial contraction against a stiff ventricle
• Nearly ubiquitous in hypertension, heart failure, ischemic heart disease

Murmur Characteristics at Each Valve

Aortic Stenosis (AS)

• Harsh systolic ejection murmur, late-peaking
• Best heard at the right 2nd ICS, radiates to carotids
• Gallavardin phenomenon: high-frequency components radiate to apex and can mimic MR
• Louder and later-peaking = more severe
• Decreases with standing/Valsalva; increases with squatting

Aortic Regurgitation (AR)

• High-pitched, blowing diastolic murmur, begins immediately after A2
• Best heard at the left sternal border (3rd-4th ICS), with patient sitting up and leaning forward in deep exhalation
• Duration correlates better with severity than intensity
• Austin Flint murmur: a mid-to-late diastolic low-pitched rumble at the apex in severe AR (AR jet impinging on the mitral valve)

Mitral Stenosis (MS)

• Low-pitched diastolic rumble with pre-systolic accentuation (in sinus rhythm)
• Best heard at the apex, with patient in left lateral decubitus, using the bell
• Preceded by an opening snap
• Louder S1 when leaflets remain mobile

Mitral Regurgitation (MR)

• High-pitched, blowing pansystolic murmur
• Best heard at the apex, radiates to the left axilla
• Intensity unaffected by beat-to-beat variation (unlike AS)

Tricuspid Regurgitation (TR)

• Pansystolic murmur at the lower left sternal border (tricuspid area)
• Increases with inspiration (Carvallo's sign) - distinguishes TR from MR

Pulmonic Stenosis (PS)

• Systolic ejection murmur at the left 2nd ICS
• Often preceded by an ejection click

Murmur Grading (Levine Scale)

Prosthetic Valve Sounds

• All mechanical valves produce a crisp high-pitched closing click
• Older ball-cage and tilting-disk prostheses also produce an opening click
• Newer bileaflet valves are typically silent on opening
• Any regurgitant murmur from a prosthetic valve is pathological (paravalvular leak, leaflet dysfunction)
• Normal prostheses have an intrinsic mild ejection murmur (aortic/pulmonic position) or a soft diastolic rumble (mitral/tricuspid position)

Auscultation of Heart Valves - Summary

5 Auscultatory Areas

Heart Sounds - Origins

Key Murmurs

3 Patient Positions

• Supine - standard
• Left lateral decubitus - mitral murmurs, S3/S4
• Sitting, leaning forward - aortic regurgitation, pericardial rub

Stethoscope

• Diaphragm - high-pitched sounds (most murmurs, S1, S2, AR)
• Bell (light pressure) - low-pitched sounds (S3, S4, MS rumble)

Murmur Grading

• I-III: no thrill | IV-VI: thrill present | Grade VI heard without stethoscope