General considerations

Auscultation of the heart requires a stethoscope with a bell and a diaphragm. The bell is best for listening to low-pitched sounds such as the murmur of mitral stenosis. The diaphragm filters out such sounds and helps to identify high-pitched sounds such as normal heart sounds and the murmur of aortic regurgitation. The earpieces of the stethoscope should fit comfortably and the tubing should be about 25 cm in length and thick enough to reduce external sound.

Knowledge of the surface anatomy of the heart is helpful in understanding the sites which various murmurs radiate to (Fig. 3.23). A basic knowledge of cardiac physiology is also important (Fig. 3.25). This is further discussed on page 104. Normal heart valves make a sound when they close but not when they open. These sounds are readily heard with a stethoscope.

It is advisable to have a fixed routine for auscultation, especially for the inexperienced. Most clinicians first auscultate at the apex. However, it is easier to start at the base, where the heart sounds are more distinct from each other (the second heart sound is louder and higher pitched). Simultaneous palpation of the carotid pulse may also be helpful; the first heart sound precedes the pulse, the second sound follows it.

Auscultation involves identifying and describing the following:

• the lirst and second heart sound

• extra heart sounds (third and fourth)

• additional sounds, e.g. clicks and snaps

• pericardial rubs

Aorta sys. 90-140 dias. 60-90 mean 70-105

Aorta sys. 90-140 dias. 60-90 mean 70-105

Auscultatory Sequence
Fig. 3.25 Normal resting pressures in mm mercury in the chambers of ttie heart.

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Essentials of Human Physiology

Essentials of Human Physiology

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