Heart Sound medicine ug
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Heart Sounds - Complete UG Medicine Guide
Sources: Guyton & Hall Medical Physiology, Fuster & Hurst's The Heart 15th Ed., Harrison's Principles of Internal Medicine 22E, Harriet Lane Handbook 23rd Ed., Goldman-Cecil Medicine
Overview
Normal cardiac auscultation produces the classic "lub-dub" sound pattern. These sounds arise from valve closure and associated blood/wall vibrations.
Auscultation Areas
| Area | Location | Best For |
|---|---|---|
| Mitral (Apex) | 5th ICS, midclavicular line | S1, S3, S4, MR, MS |
| Tricuspid | 5th ICS, left parasternal | S1, TR |
| Pulmonary | 2nd ICS, left parasternal | P2, splitting of S2, PS |
| Aortic | 2nd ICS, right parasternal | A2, AS |
| Accessory Aortic (Erb's point) | 3rd ICS, left parasternal | AR |
Technique note: Use the diaphragm for high-pitched sounds (S1, S2, most murmurs); use the bell (light pressure) for low-pitched sounds (S3, S4, mitral diastolic rumble). Always auscultate in three positions: supine, sitting, and left lateral decubitus.
The Four Heart Sounds
S1 - First Heart Sound ("Lub")
- Timing: Beginning of systole (ventricular contraction)
- Cause: Closure of mitral (M1) and tricuspid (T1) valves; M1 precedes T1
- Best heard: Apex / left lower sternal border (LLSB)
- Quality: Low-pitched, longer (~0.14 sec), dull
- Normal splitting: M1-T1 split can be heard at LLSB - this is physiologic
Intensity changes of S1:
| Loud S1 | Soft S1 |
|---|---|
| Short PR interval (preexcitation, tachycardia) | Prolonged PR interval (1st degree AV block) |
| Pliable mitral stenosis | Calcified/immobile MS leaflets |
| Hyperdynamic states (fever, thyrotoxicosis) | Poor LV contractility / severe LV dysfunction |
| Thin chest wall | Obesity, emphysema, pericardial effusion |
| - | Atrial fibrillation (variable intensity) |
S2 - Second Heart Sound ("Dub")
- Timing: End of systole
- Cause: Closure of aortic (A2) and pulmonary (P2) valves
- Best heard: Left upper sternal border (LUSB)
- Quality: Higher-pitched, shorter (~0.11 sec) than S1 due to tauter semilunar valves
Physiologic (Normal) Splitting of S2
During inspiration: increased venous return → prolonged RV ejection → P2 delayed → A2-P2 gap widens (audible split)
During expiration: gap narrows → single S2
Types of Abnormal S2 Splitting
| Type | Character | Causes |
|---|---|---|
| Wide (persistent) splitting | Split heard in both inspiration and expiration; widens more on inspiration | RBBB, pulmonary stenosis, pulmonary hypertension (delayed P2); MR, VSD, early A2 closure |
| Fixed splitting | Wide split that does NOT change with respiration | ASD, PAPVR (equalised RV/LV preload changes) |
| Paradoxical (reversed) splitting | Split heard in expiration, disappears on inspiration | LBBB (delayed A2), severe AS, HOCM, WPW type B, RV pacing |
| Single S2 | No audible split | Pulmonary HTN (loud P2 merges), severe PS/AS (absent P2 or A2), TGA, TOF, pulmonary atresia, aortic atresia, truncus arteriosus |
P2 loudness clues:
- Loud P2 = pulmonary arterial hypertension (if heard at apex = severe PAH)
- Diminished/absent P2 = severe valvular PS, COPD/emphysema, TOF
- Loud A2 = systemic hypertension, syphilitic aortitis
- Diminished A2 = calcific aortic stenosis (important severity marker)
S3 - Third Heart Sound (Ventricular Gallop / "Ken-tuc-KY")
- Timing: Early diastole (beginning of middle third); follows S2 by ~0.12-0.16 sec
- Cause: Rapid ventricular filling phase - blood rebounding off ventricular walls
- Quality: Low-pitched, soft; heard with the bell at the apex in left lateral decubitus
- Rhythm: "S1 - S2 - S3" = "lub-dub-ta" = Protodiastolic gallop
| S3 - Physiologic (Normal) | S3 - Pathological |
|---|---|
| Children, adolescents, young adults (<40 yrs) | Adults >40 yrs |
| Athletes | LV systolic failure (dilated cardiomyopathy, CCF) |
| Pregnancy, high-output states | Large VSD, severe MR, severe AR |
| - | Right-sided S3 in RV failure (heard at LLSB, increases with inspiration) |
S4 - Fourth Heart Sound (Atrial Gallop / "TEN-nes-see")
- Timing: Late diastole (presystole); just before S1
- Cause: Forceful atrial contraction into a non-compliant (stiff) ventricle
- Quality: Low-pitched; heard with the bell at the apex (left lateral decubitus)
- Rhythm: "S4 - S1 - S2" = "ta-lub-dub" = Presystolic gallop
- S4 is ALWAYS pathological (never normal in adults)
- Absent in atrial fibrillation (no atrial contraction)
Causes of S4:
- LV hypertrophy (HTN, HCM, AS)
- Acute MI (stiff, ischemic ventricle)
- Diastolic dysfunction (Grade I)
- Restrictive cardiomyopathy
- Right-sided S4: RV hypertrophy, pulmonary hypertension, pulmonic stenosis
Summary Diagram - Added Heart Sounds
A = S4 atrial/presystolic gallop | B = Split S1 (M1-T1) | C = Ejection click (EC) | D = Split S2 (A2-P2) | E = Opening snap (OS) | F = S3 third heart sound | G = Midsystolic click (SC)
Additional Sounds
Ejection Clicks (Systolic)
- Occur just after S1 (early systole)
- High-pitched, best with diaphragm
- Causes: Stenosis or dilation of semilunar valves
- Aortic ejection click - aortic stenosis, bicuspid aortic valve, aortic root dilation (does NOT change with respiration)
- Pulmonary ejection click - pulmonary stenosis, pulmonary HTN, idiopathic PA dilation (DECREASES with inspiration - unique among right-sided sounds)
Midsystolic Click
- Mid-to-late systole
- Best heard at apex
- Cause: Mitral Valve Prolapse (MVP) - click moves earlier with standing/Valsalva (decreased preload), later with squatting (increased preload)
Opening Snap (OS) - Diastolic
- High-pitched snap just after S2 in early diastole
- Cause: Mitral stenosis (pliable, non-calcified leaflets snapping open)
- Also in tricuspid stenosis (rare)
- S2-OS interval: shorter interval = more severe MS (higher LA pressure)
- Absent when leaflets are calcified and immobile
Pericardial Knock
- Early diastolic sound (like loud S3)
- Cause: Constrictive pericarditis - abrupt cessation of ventricular filling by rigid pericardium
Tumor Plop
- Mid-diastolic sound
- Cause: Left atrial myxoma prolapsing through mitral valve; mimics OS but timing varies with position
Quick Memory Table
| Sound | Timing | Best Heard | Cause | Significance |
|---|---|---|---|---|
| S1 | Beginning systole | Apex | MV + TV closure | Normal |
| S2 | End systole | LUSB | AV + PV closure | Normal |
| S3 | Early diastole | Apex (bell) | Rapid filling / volume overload | Physiologic in young; CCF in old |
| S4 | Late diastole (pre-S1) | Apex (bell) | Forceful atrial contraction | Always pathologic; not in AF |
| EC | Early systole | LUSB/Apex | Semilunar valve disease | AS, PS, MVP |
| Midsystolic click | Mid systole | Apex | MVP | Varies with preload |
| OS | Early diastole | Apex/LLSB | MS (pliable leaflets) | Rheumatic MS |
| Pericardial knock | Early diastole | LLSB | Constrictive pericarditis | Loud early diastolic sound |
Grading of Heart Murmurs (Levine Scale)
| Grade | Description |
|---|---|
| I | Barely audible (very experienced examiner, quiet room) |
| II | Soft but readily heard |
| III | Moderately loud; NOT associated with thrill |
| IV | Loud; associated with palpable thrill |
| V | Very loud; audible with stethoscope barely touching chest |
| VI | Audible with stethoscope off the chest |
Grades I-II: soft murmurs | Grades IV-VI: always associated with thrill (from Grade IV onwards)
- Guyton & Hall Textbook of Medical Physiology, p.289 | Fuster & Hurst's The Heart 15th Ed., pp.88-92 | Harrison's Principles of Internal Medicine 22E | Harriet Lane Handbook 23rd Ed., pp.223-224 | Goldman-Cecil Medicine
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