Overview
This lecture covers the fundamentals of heart sounds, including S1, S2, extra heart sounds (S3, S4), murmurs, stethoscope use, auscultation positions, and tips for distinguishing heart sounds relevant to nursing assessments.
Purpose and Basics of Heart Sounds
- Heart sounds assess the closure of heart valves and give insight into cardiac function.
- Four main heart valves: tricuspid, mitral (AV valves); aortic, pulmonic (SL valves).
- S1 ("lub") is caused by closure of AV valves; best heard at the apex.
- S2 ("dub") is caused by closure of SL valves; best heard at the base.
Heart Anatomy and Blood Flow
- Blood flows from vena cava → right atrium → tricuspid valve → right ventricle → pulmonic valve → pulmonary artery.
- Oxygenated blood returns via pulmonary vein → left atrium → bicuspid (mitral) valve → left ventricle → aortic valve → aorta.
- Diastole is relaxation (chambers fill); systole is contraction (blood is pumped out).
Stethoscope Use
- Diaphragm (large side): hears high-pitched sounds (S1, S2, regurgitant murmurs).
- Bell (small side): hears low-pitched sounds (S3, S4, mitral stenosis murmurs).
- Inch the chest piece along the chest rather than lifting to preserve rhythm audibility.
- Reduce background noise and ensure proper earpiece fit for accurate auscultation.
Patient Positioning for Auscultation
- Start with patient lying or sitting; use diaphragm for S1 and S2.
- Place patient in left lateral position and use bell at apex for S3, S4, and mitral murmurs.
- Sit patient up, lean forward, and exhale to better hear aortic and pulmonic murmurs.
Auscultation Landmarks and Sequence
- Use mnemonic: All Patients Take Medicine (Aortic, Pulmonic, Tricuspid, Mitral).
- Aortic: 2nd right intercostal space, sternal border (S2).
- Pulmonic: 2nd left intercostal space, sternal border (S2).
- Erb's Point: 3rd left intercostal space.
- Tricuspid: 4th left intercostal space, sternal border (S1).
- Mitral (apex): 5th left intercostal space, midclavicular line (S1, point of maximal impulse).
Distinguishing S1 and S2
- S1 is louder at the mitral (apex), S2 is louder at the aortic/pulmonic (base).
- Correlate S1 with QRS complex (R wave) on EKG or carotid pulse.
Extra Heart Sounds and Murmurs
- S3 occurs just after S2 (ventricular filling vibration, seen in heart failure/fluid overload).
- S4 occurs just before S1 (atrial kick against resistant ventricles).
- Murmurs are blowing/swishing sounds due to turbulent blood flow from valve/chamber defects, graded I (barely audible) to VI (loudest with thrill).
Key Terms & Definitions
- S1 — First heart sound ("lub"), closure of AV valves.
- S2 — Second heart sound ("dub"), closure of SL valves.
- Diastole — Heart relaxation and chamber filling.
- Systole — Heart contraction and blood ejection.
- Murmur — Abnormal heart sound due to turbulent flow.
- Thrill — Palpable vibration over the heart due to loud murmur.
- Point of Maximal Impulse (PMI) — Location at apex (mitral area) where heart's impulse is strongest.
Action Items / Next Steps
- Take the online quiz on heart sound theory at registernursern.com.
- Practice auscultating heart sounds using correct landmarks and techniques.
- Watch the next video on performing heart sound assessment with a live patient.