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?