HEART SOUNDS — COMPLETE NURSING NOTES
Adult Health Nursing | Cardiovascular System | NORCET 12
Learn the mechanism of normal and abnormal heart sounds, S1–S4, auscultation areas, splitting, murmurs, clinical assessment and high-yield examination points.
Concept-Based Notes Clinical Correlation Original SVG Diagrams 25 MCQsLearning Objectives
- Explain the origin of the first, second, third and fourth heart sounds.
- Differentiate systole from diastole using heart sounds.
- Identify the standard cardiac auscultation areas.
- Understand physiological and pathological splitting of S2.
- Recognize common heart sounds associated with cardiac disorders.
- Apply heart sound knowledge to nursing assessment and NORCET-style questions.
Table of Contents
- Introduction to Heart Sounds
- Mechanism of Heart Sound Production
- Heart Sounds and Cardiac Cycle Diagram
- First Heart Sound — S1
- Second Heart Sound — S2
- Splitting of Heart Sounds
- Third Heart Sound — S3
- Fourth Heart Sound — S4
- Areas of Cardiac Auscultation
- Heart Murmurs
- Important Abnormal Heart Sounds
- Nursing Assessment and Clinical Approach
- Mnemonics and High-Yield Revision
- 25 MCQs Interactive Test
1. Introduction to Heart Sounds
Heart sounds are audible vibrations produced mainly by cardiac structures and blood flow during the cardiac cycle. They are assessed through auscultation using a stethoscope.
In a normal adult, two principal heart sounds are usually heard:
- S1 — “Lub”: associated with closure and vibration of the mitral and tricuspid valve apparatus at the beginning of ventricular systole.
- S2 — “Dub”: associated with closure and vibration of the aortic and pulmonary valve apparatus at the end of ventricular systole and the beginning of ventricular diastole.
Normal sequence
Simplified schematic: S1 marks the beginning of ventricular systole; S2 marks the beginning of ventricular diastole.
2. Mechanism of Heart Sound Production
Heart sounds are closely related to pressure changes, valve movement and vibrations during the cardiac cycle.
| Event | What happens? | Associated sound |
|---|---|---|
| Ventricular pressure rises above atrial pressure | Mitral and tricuspid valves close. | S1 |
| Ventricular pressure falls below aortic and pulmonary artery pressure | Aortic and pulmonary valves close. | S2 |
| Rapid passive ventricular filling | Ventricular filling produces low-frequency vibrations. | S3, when audible |
| Atrial contraction | Blood enters the ventricle and produces vibrations in a stiff ventricle. | S4, when present |
3. Diagram: Heart Sounds and Cardiac Cycle
Illustrative schematic only. The amplitude, timing and presence of sounds vary with the patient and recording method.
4. First Heart Sound — S1 (“Lub”)
S1 occurs at the beginning of ventricular systole. It is primarily associated with closure and vibration of the mitral and tricuspid valve apparatus.
Characteristics of S1
- Timing: Beginning of ventricular systole.
- Valves: Mitral (M1) and tricuspid (T1).
- Pitch: Relatively low-pitched compared with S2.
- Duration: Generally longer than S2.
- Best heard: Near the cardiac apex, especially around the mitral area.
- Relationship to pulse: Occurs near the beginning of the ventricular ejection period and around the start of the palpable arterial pulse, although exact timing varies.
Factors affecting S1 intensity
| Finding | Possible explanation |
|---|---|
| Loud S1 | May occur when AV valve leaflets are still widely separated at the onset of ventricular systole, such as in some cases of mitral stenosis with mobile leaflets. |
| Soft S1 | May occur with mitral regurgitation, reduced leaflet mobility, prolonged PR interval or impaired ventricular contractility. |
| Variable S1 intensity | May be heard in atrial fibrillation because the timing between atrial and ventricular activation varies. |
5. Second Heart Sound — S2 (“Dub”)
S2 occurs at the end of ventricular systole and marks the beginning of ventricular diastole. It is associated with closure of the semilunar valves.
- A2: Aortic valve closure.
- P2: Pulmonary valve closure.
- Pitch: Usually higher-pitched and shorter than S1.
- Best heard: At the base of the heart, particularly the aortic and pulmonary areas.
A2 versus P2
| Feature | A2 | P2 |
|---|---|---|
| Valve | Aortic valve | Pulmonary valve |
| Location | Right second intercostal space, sternal border | Left second intercostal space, sternal border |
| Usual sequence | Usually closes first | Usually closes slightly after A2 |
| Respiratory effect | Relatively less affected by inspiration | Often delayed during inspiration in healthy individuals |
6. Splitting of Heart Sounds
Splitting means that components of a heart sound are heard separately rather than as one sound. The most clinically important example is splitting of S2.
A. Physiological splitting of S2
During inspiration, increased venous return to the right ventricle can prolong right ventricular ejection and delay P2. At the same time, changes in left ventricular filling can bring A2 slightly earlier. The separation between A2 and P2 therefore becomes more audible.
Conceptual diagram, not an ECG or diagnostic recording.
B. Types of S2 splitting
| Type | Pattern | Clinical association |
|---|---|---|
| Physiological | Splitting increases with inspiration and narrows with expiration. | Normal finding in many healthy individuals. |
| Wide | A2 and P2 are separated more than expected; the separation may increase further during inspiration. | May occur with delayed right ventricular emptying, such as right bundle branch block or pulmonary stenosis. |
| Fixed | Little respiratory variation in the separation of A2 and P2. | Classically associated with atrial septal defect (ASD). |
| Paradoxical (reversed) | P2 occurs before delayed A2; splitting may be heard during expiration and narrow during inspiration. | May occur with left bundle branch block or severe aortic stenosis. |
• Fixed split S2 → Think ASD.
• Paradoxical split → Think delayed A2.
• Normal inspiration → Wider A2–P2 separation.
7. Third Heart Sound — S3
S3 is a low-frequency sound heard during early diastole, shortly after S2, during rapid ventricular filling.
Mechanism
As blood rapidly enters the ventricle, vibrations of the ventricular walls, blood and supporting structures can produce S3.
Clinical significance
- May be physiological in children, adolescents, young adults and during pregnancy.
- In an older adult, a new S3 may suggest increased ventricular filling pressures or volume overload.
- It can be associated with heart failure, especially when accompanied by dyspnea, edema or other evidence of congestion.
- It may occur in some conditions with increased flow or ventricular dilation.
Where and how to hear S3
- Left-sided S3 is often best heard at the apex with the patient in the left lateral position.
- Use the bell lightly because S3 is low-pitched.
- Right-sided S3 may be more audible near the lower left sternal border and can become more prominent with inspiration.
Mnemonic: “Ken-tuc-ky” is often used to represent the cadence of S3.
8. Fourth Heart Sound — S4
S4 is a low-frequency sound heard in late diastole, immediately before S1. It is associated with atrial contraction forcing blood into a stiff or poorly compliant ventricle.
Common associations
- Left ventricular hypertrophy.
- Long-standing hypertension with a stiff ventricle.
- Aortic stenosis.
- Myocardial ischemia or other conditions that reduce ventricular compliance.
S4 generally requires an effective atrial contraction. It is usually absent in atrial fibrillation because coordinated atrial contraction is lacking.
- Best heard: At the apex for a left-sided S4, using the bell lightly with the patient in the left lateral position.
- Timing: Late diastole, immediately before S1.
- Mnemonic: “Ten-nes-see” is often used to represent the cadence of S4.
S3 = rapid ventricular filling, early diastole.
S4 = atrial contraction against a stiff ventricle, late diastole.
S3 versus S4
| Feature | S3 | S4 |
|---|---|---|
| Timing | Early diastole, after S2 | Late diastole, before S1 |
| Mechanism | Rapid ventricular filling | Atrial contraction into a stiff ventricle |
| Typical association | Volume overload or ventricular dysfunction; may be physiological in young people | Reduced ventricular compliance, such as LV hypertrophy |
| Atrial contraction required? | No | Generally yes |
| In atrial fibrillation | Can be present | Usually absent |
9. Areas of Cardiac Auscultation
The standard auscultation areas are surface landmarks where sounds from particular valves are heard most clearly. They do not represent the exact anatomical positions of all four valves.
Illustrative surface-landmark diagram. The patient's anatomy and clinical circumstances may affect the optimal examination site.
| Area | Location | Main sounds assessed |
|---|---|---|
| Aortic | 2nd right intercostal space, right sternal border | Aortic valve sounds; aortic murmurs |
| Pulmonic | 2nd left intercostal space, left sternal border | Pulmonary valve sounds; S2 splitting |
| Erb's point | 3rd left intercostal space, left sternal border | Useful for assessing certain murmurs, including aortic regurgitation |
| Tricuspid | Lower left sternal border, usually around the 4th–5th intercostal space | Tricuspid valve sounds and murmurs |
| Mitral / apex | Usually 5th left intercostal space near the midclavicular line in adults | S1, mitral murmurs and apical S3/S4 |
Bell versus diaphragm
| Stethoscope part | Best for |
|---|---|
| Diaphragm | Higher-pitched sounds, including many murmurs and most routine heart sounds. |
| Bell | Low-pitched sounds such as S3, S4 and the low-pitched rumble of mitral stenosis. Apply lightly; firm pressure can make the bell function more like a diaphragm. |
10. Heart Murmurs
A heart murmur is a prolonged sound caused by turbulent blood flow. Unlike the short, discrete S1 and S2 sounds, a murmur is usually heard between or across heart sounds.
Classification by timing
| Type | Timing | Examples / associations |
|---|---|---|
| Systolic murmur | Between S1 and S2 | Aortic stenosis, mitral regurgitation, tricuspid regurgitation, ventricular septal defect |
| Diastolic murmur | After S2 and before the next S1 | Aortic regurgitation, mitral stenosis |
| Continuous murmur | Extends through systole and diastole | Patent ductus arteriosus is a classic example |
Common murmur patterns
| Condition | Typical murmur description | Common examination clue |
|---|---|---|
| Aortic stenosis | Crescendo–decrescendo systolic ejection murmur | Often radiates to the carotid arteries |
| Mitral regurgitation | Holosystolic murmur | Often best heard at the apex and may radiate to the axilla |
| Tricuspid regurgitation | Holosystolic murmur | Often louder with inspiration |
| Mitral stenosis | Low-pitched mid-diastolic rumble | May have an opening snap if the valve is sufficiently mobile |
| Aortic regurgitation | Early diastolic decrescendo murmur | Often best heard along the left sternal border with the patient leaning forward during expiration |
| Patent ductus arteriosus | Classically continuous, machinery-like murmur | Clinical findings depend on the size of the ductus and hemodynamic effect |
How to describe a murmur
Use a structured assessment:- Timing: systolic, diastolic or continuous.
- Location: where it is loudest.
- Radiation: whether it travels to another area.
- Intensity: grade I–VI for systolic murmurs when appropriate.
- Pitch and quality: high/low, blowing, harsh, rumbling or musical.
- Response to maneuvers: changes with respiration, position or other maneuvers.
- Associated findings: pulse, blood pressure, symptoms and other heart sounds.
11. Important Abnormal Heart Sounds
| Finding | Possible association | Clinical significance |
|---|---|---|
| Opening snap | Often associated with mitral stenosis | Occurs after S2 when a sufficiently mobile stenotic valve opens. |
| Ejection click | May occur with certain abnormal semilunar valves or great-vessel conditions | Interpret with other findings; not all valve disorders produce a click. |
| Pericardial friction rub | Pericarditis | Often scratchy or grating; may have multiple components and can vary with position. |
| Pericardial knock | Constrictive pericarditis | An early diastolic sound related to abrupt limitation of ventricular filling. |
| Summation gallop | May occur when S3 and S4 merge at a high heart rate | More likely when diastole is shortened. |
Pericardial friction rub versus heart sounds
A pericardial friction rub is produced by inflamed pericardial surfaces rubbing against each other. It is not a valve-closure sound. It may be heard best with the diaphragm along the left sternal border while the patient leans forward, and it may vary over time.
12. Nursing Assessment and Clinical Approach
Preparation before auscultation
- Perform hand hygiene and explain the procedure.
- Provide privacy and expose only the chest area necessary for assessment.
- Position the patient comfortably, usually supine or with the head of the bed elevated.
- Ensure a quiet environment and warm the stethoscope if needed.
- Assess heart rate, rhythm, blood pressure, respiratory status and relevant symptoms.
Systematic auscultation
- Identify the aortic, pulmonic, Erb's point, tricuspid and mitral areas.
- Listen for S1 and S2 at each site.
- Assess rate and rhythm; determine whether sounds are regular or irregular.
- Identify extra sounds such as S3, S4, clicks, snaps or rubs.
- Listen for murmurs and describe their timing, location, intensity and radiation.
- Repeat with the patient in a suitable position when clinically indicated.
- Document findings clearly and report significant new abnormalities.
When to escalate urgently
- Acute chest pain or suspected acute coronary syndrome.
- Severe or sudden shortness of breath.
- Syncope or near-syncope, particularly with exertion.
- Hypotension, altered mental status or signs of shock.
- New cyanosis, severe hypoxemia or rapidly worsening clinical status.
Documentation example
Document only findings actually assessed. If an abnormality is present, describe its timing, location, quality and associated patient symptoms rather than recording only “abnormal heart sounds.”
13. Mnemonics and High-Yield Revision
Mnemonic 1: S1 and S2
S1 = AV valves close = start of systole.
S2 = semilunar valves close = start of diastole.
Mnemonic 2: S3 and S4
S3 = “Fill” — rapid ventricular filling in early diastole.
S4 = “Atrial kick” — atrial contraction into a stiff ventricle in late diastole.
Mnemonic 3: Valve auscultation areas
Move across the upper chest and then down toward the apex:
- Aortic — 2nd right intercostal space.
- Pulmonic — 2nd left intercostal space.
- Erb's point — 3rd left intercostal space.
- Tricuspid — lower left sternal border.
- Mitral — apex.
APETM is a useful sequence mnemonic.
Rapid revision table
| Exam clue | Best answer |
|---|---|
| Beginning of ventricular systole | S1 |
| Beginning of ventricular diastole | S2 |
| Closure of mitral and tricuspid valves | S1 |
| Closure of aortic and pulmonary valves | S2 |
| Rapid ventricular filling | S3 |
| Atrial contraction into a stiff ventricle | S4 |
| Fixed splitting of S2 | Classically ASD |
| Paradoxical splitting of S2 | Delayed A2 |
| Low-pitched S3 or S4 | Use the bell lightly |
| High-pitched sounds and many murmurs | Use the diaphragm |
| Early diastolic decrescendo murmur | Aortic regurgitation |
| Low-pitched mid-diastolic rumble | Mitral stenosis |
| Holosystolic murmur radiating to axilla | Mitral regurgitation |
| Systolic ejection murmur radiating to carotids | Aortic stenosis |
14. Interactive MCQ Test — Heart Sounds
Question 1 of 25
Instructions: Select one best answer for each question. Use Previous and Next to navigate. Submit the test to view your score and explanations. Each correct answer carries 1 mark.
Final Takeaway
For heart sound questions, first determine whether the sound occurs during systole or diastole. Then connect the timing to the mechanism: AV valve closure (S1), semilunar valve closure (S2), rapid ventricular filling (S3), or atrial contraction into a stiff ventricle (S4). Use the patient's symptoms and other findings to guide clinical interpretation.
For nursing and NORCET exam preparation.