Overview
This lecture covers the proper techniques for cardiac assessment using a stethoscope, including auscultation sites, expected and extra heart sounds, and relevant clinical implications.
Stethoscope Use for Cardiac Assessment
- The stethoscope diaphragm (larger side) is used with heavy pressure to hear high-pitched sounds.
- The stethoscope bell (smaller side) is used with light pressure to hear low-pitched sounds.
- Some stethoscopes have a tunable diaphragm that adjusts sound by varying pressure.
- Familiarize yourself with your specific stethoscope model and its features.
Cardiac Auscultation Sites
- Auscultate the heart at five locations: aortic, pulmonic, Erb's point, tricuspid, and mitral areas (APETM mnemonic).
- Aortic: 2nd intercostal space, right sternal border.
- Pulmonic: 2nd intercostal space, left sternal border.
- Erb's Point: 3rd intercostal space, left sternal border (hear all heart sounds equally here).
- Tricuspid: 4th intercostal space, left sternal border.
- Mitral (point of maximal impulse): 5th intercostal space, left midclavicular line.
Expected and Extra Heart Sounds
- S1 ("lub") is caused by closure of the mitral and tricuspid valves.
- S2 ("dub") is caused by closure of the aortic and pulmonic valves.
- S3 is an extra sound indicating fluid overload, often associated with heart failure and rapid ventricular filling in early diastole.
- S4 is an extra sound due to poor ventricular compliance, commonly found in patients with a history of myocardial infarction.
- Murmurs are whooshing sounds from turbulent blood flow due to faulty or leaky heart valves.
- Pericardial friction rub is a squeaky, rubbing sound caused by inflamed pericardial layers rubbing against each other, seen in conditions like pericarditis or post-heart surgery.
Key Terms & Definitions
- Diaphragm (stethoscope) — Larger side used with heavy pressure for high-pitched sounds.
- Bell (stethoscope) — Smaller side used with light pressure for low-pitched sounds.
- Auscultation — Listening to internal body sounds, typically heart or lungs.
- Erb's Point — 3rd intercostal space, left sternal border; all heart sounds are equally audible.
- S1/S2 — Normal heart sounds from valve closures ("lub dub").
- S3/S4 — Extra heart sounds indicating pathology (fluid overload or poor compliance).
- Murmur — Abnormal heart sound from turbulent blood flow.
- Pericardial Friction Rub — Squeaky sound from inflamed pericardial surfaces.
Action Items / Next Steps
- Practice identifying heart sounds at each auscultation site on yourself or a peer.
- Review the APETM mnemonic and site locations.
- Understand the characteristics and causes of extra heart sounds and murmurs.