Heart sounds and murmurs are essential clues in cardiovascular assessment because they connect cardiac anatomy, valve motion, blood flow, and disease. This cheat sheet covers normal heart sounds, extra sounds, murmur timing, murmur location, radiation, and bedside maneuvers. College medical science students need a clear reference because auscultation findings are easiest to learn when timing, valve areas, and clinical causes are organized together.
The core idea is to identify where a sound occurs in the cardiac cycle and then connect that timing to likely valve or ventricular findings. S1 marks closure of the mitral and tricuspid valves, while S2 marks closure of the aortic and pulmonic valves. Systolic murmurs occur between S1 and S2, and diastolic murmurs occur after S2 before the next S1.
Intensity is commonly graded from 1 to 6, and changes with maneuvers such as inspiration, standing, squatting, and handgrip help narrow the diagnosis.
Key Facts
- S1 is produced by closure of the mitral and tricuspid valves and is usually loudest at the apex.
- S2 is produced by closure of the aortic and pulmonic valves and is usually loudest at the base of the heart.
- Systole is the interval from S1 to S2, and diastole is the interval from S2 to the next S1.
- A grade 1 murmur is barely audible, grade 3 is clearly audible without a thrill, grade 4 has a palpable thrill, and grade 6 is audible with the stethoscope off the chest.
- Aortic stenosis is typically a systolic crescendo-decrescendo murmur at the right upper sternal border that radiates to the carotids.
- Mitral regurgitation is typically a holosystolic murmur at the apex that radiates to the left axilla.
- Aortic regurgitation is typically an early diastolic decrescendo murmur along the left sternal border and may become louder with handgrip.
- Inspiration generally increases right-sided heart sounds and murmurs, while expiration often makes left-sided sounds easier to hear.
Vocabulary
- Auscultation
- Auscultation is the clinical act of listening to internal body sounds, such as heart sounds, with a stethoscope.
- Murmur
- A murmur is an extra heart sound caused by turbulent blood flow through a valve, vessel, or abnormal opening.
- Systole
- Systole is the phase of the cardiac cycle when the ventricles contract and eject blood.
- Diastole
- Diastole is the phase of the cardiac cycle when the ventricles relax and fill with blood.
- Thrill
- A thrill is a palpable vibration on the chest wall caused by a loud or turbulent cardiac murmur.
- Radiation
- Radiation describes the direction a murmur sound travels from its point of maximal intensity.
Common Mistakes to Avoid
- Confusing S1 and S2 is wrong because murmur timing depends on knowing which sound starts systole and which sound starts diastole.
- Calling every loud murmur severe is wrong because murmur intensity does not always match disease severity, especially in low-flow states.
- Ignoring radiation is wrong because the path of sound transmission can strongly suggest a lesion, such as aortic stenosis radiating to the carotids.
- Using only one auscultation position is wrong because left lateral decubitus, sitting forward, inspiration, and expiration can reveal sounds that are missed supine.
- Mixing up right-sided and left-sided response to inspiration is wrong because inspiration usually increases venous return to the right heart and makes right-sided murmurs louder.
Practice Questions
- 1 A murmur begins immediately after S1 and stops at S2. Is it systolic or diastolic, and which part of the cardiac cycle does it occupy?
- 2 A murmur is grade 4 out of 6. What physical finding must be present, and how does this differ from grade 3?
- 3 A patient has a crescendo-decrescendo systolic murmur at the right upper sternal border that radiates to the carotids. What valve lesion is most likely?
- 4 Why can changing from standing to squatting alter the loudness of a murmur, and what does that reveal about blood flow and ventricular loading?
Understanding Heart Sounds and Murmurs Reference
Murmurs are made by turbulent blood flow. Smooth flow is usually silent, but blood becomes noisy when it is forced through a narrowed opening, leaks backward through an imperfect valve, or moves unusually fast through a normal structure. The sound pattern gives clues about the changing pressure difference across the valve.
A narrowing usually creates a sound when blood is trying to pass forward through that valve. A leaking valve creates a sound when pressure pushes blood backward. This is why the shape of a murmur matters.
A murmur that grows then fades often reflects flow that rises and falls during ventricular emptying. A murmur that stays similar through contraction suggests a persistent pressure difference.
Extra heart sounds can reveal changes in the ventricle itself. An S3 occurs shortly after the second heart sound, during rapid ventricular filling. In children, teenagers, and some young adults it can be normal because their ventricles relax well and fill quickly.
In an older adult, it may suggest volume overload or heart failure. An S4 occurs just before the first heart sound, when the atrium contracts.
It happens when blood is pushed into a stiff ventricle, such as in long standing high blood pressure or ventricular thickening. An S4 cannot occur in atrial fibrillation because there is no organized atrial contraction.
Good auscultation depends on technique, not only memory. Use the diaphragm of the stethoscope for higher pitched sounds, including many regurgitant murmurs. Use the bell lightly for lower pitched sounds, such as an S3, an S4, or mitral stenosis.
Listening at the apex while the patient lies on the left side can bring low pitched mitral sounds closer to the chest wall. Sitting forward and breathing out can make an aortic regurgitation murmur easier to hear.
A quiet room matters. So does listening for several full cycles rather than deciding after one beat.
Bedside maneuvers work because they change venous return, vascular resistance, or the size of the ventricles. Standing suddenly reduces blood returning to the heart, so most murmurs become softer. Hypertrophic cardiomyopathy becomes louder because its narrowed outflow tract worsens when the left ventricle is less full.
Squatting increases venous return and resistance in the arteries, which usually makes hypertrophic cardiomyopathy softer. Handgrip raises resistance against which the left ventricle pumps. This tends to increase backward flow in mitral regurgitation and aortic regurgitation, while reducing the forward flow murmur of aortic stenosis.
Students should build a fixed listening routine. First find the pulse, since it helps identify systole when the rhythm is regular. Then describe the sound by timing, location, pitch, shape, loudness, and radiation.
Listen for changes with breathing or position before naming a diagnosis. Not every murmur means dangerous heart disease.
Fever, anemia, pregnancy, and exercise can increase blood flow enough to create an innocent flow murmur. Still, a diastolic murmur, a new loud murmur, a murmur with chest pain or fainting, or a murmur linked with heart failure signs needs careful clinical assessment.