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Here's your practical revision on Pulse & Heart Sounds, straight from Guyton & Hall and Ganong's:
Pulse & Heart Sounds - Physiology Practical Revision
ARTERIAL PULSE
The pulse is a pressure wave that travels along arterial walls when blood is ejected into the aorta during systole. Key points:
- The wave travels at ~4 m/s in the aorta, ~8 m/s in large arteries, ~16 m/s in small arteries (faster in older/stiffer arteries)
- The pulse is felt at the radial artery (wrist) about 0.1 s after peak systolic ejection into the aorta
- Pulse strength = pulse pressure (systolic - diastolic), NOT mean pressure
- Pulse is weak/thready in shock
- Pulse is strong/bounding when stroke volume is large (e.g., exercise, aortic regurgitation)
Dicrotic Notch
A small oscillation in the falling phase of the pulse wave, caused by vibrations when the aortic valve snaps shut. It is visible on a recorded pressure trace but NOT palpable at the wrist.
Special Pulse Patterns
| Pulse Type | Condition | Feature |
|---|---|---|
| Corrigan / Water-hammer pulse | Aortic regurgitation | Very strong, forceful |
| Thready pulse | Shock | Weak, rapid |
| Pulsus paradoxus | Cardiac tamponade | Drops >10 mmHg on inspiration |
HEART SOUNDS
The Normal "Lub-Dub"
| Sound | Name | Cause | Timing | Duration |
|---|---|---|---|---|
| "Lub" | S1 (First) | Closure of mitral + tricuspid (AV) valves | Start of systole | ~0.14 sec |
| "Dub" | S2 (Second) | Closure of aortic + pulmonary (semilunar) valves | End of systole | ~0.11 sec |
Mnemonic: "MiTral" = S1 at the Middle of Thump; Aortic + Pulmonary = S2 = end of pump
- S1 is lower pitch (less taut AV valves, larger, looser ventricles)
- S2 is higher pitch (tauter semilunar valves, stiffer arterial walls)
- Audible range: 40-520 cycles/sec
S3 - Third Heart Sound
- Heard in the middle third of diastole
- Caused by: blood rushing from atria into ventricles, reverberating off ventricular walls ("blood sloshing in a bag")
- Very low frequency - often below audible range
- Normal in children, adolescents, young adults
- Pathological (S3 gallop) in older adults - indicates systolic heart failure
S4 - Fourth Heart Sound
- Occurs with atrial contraction (just before S1)
- Caused by: inrush of blood from contracting atria into a stiff, non-compliant ventricle
- Frequency ~20 Hz or less - rarely heard with stethoscope
- S4 gallop = common in LV hypertrophy, older patients with decreased ventricular compliance
AUSCULTATION AREAS
| Area | Location | Best for |
|---|---|---|
| Aortic | Right 2nd intercostal space, sternal border | Aortic valve (S2) |
| Pulmonic | Left 2nd intercostal space, sternal border | Pulmonary valve (S2) |
| Tricuspid | Left lower sternal border (4th-5th ICS) | Tricuspid valve (S1) |
| Mitral (Apex) | 5th ICS, midclavicular line | Mitral valve (S1), loudest |
Note: Auscultation areas are NOT directly over the valves - sounds are transmitted along blood flow direction.
QUICK PRACTICAL TIPS
- S1 > S2 at the apex (mitral area); S2 > S1 at the base (aortic/pulmonic areas)
- S1 coincides with the carotid pulse - use this to time sounds
- Normal heart rate at rest: 60-100 bpm
- Normal pulse rhythm: regular
- Check pulse for: rate, rhythm, volume, character, vessel wall condition
Good luck tomorrow! Let me know if you want to go over murmurs, ECG, or blood pressure next.
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