Page 109 - Critical Care Nursing Demystified

94 CRITICAL CARE NURSING DeMYSTIFIED

Normal Heart Sounds
The first heart sound, or S1, is the single sound (lub) produced when the mitral
and tricuspid valves close. The second heart sound or S2 (dub) is heard loudest
as the semilunar valves close (see Table 3–4).

NURSING ALERT

Both S1 and S2 are high-pitched and are heard best using the diaphragm of the
stethoscope.

TABLE 3–4 The Two Normal Heart Sounds
S1 S2
Sound Lub Dub
Heart cycle Systole Diastole
Location Apex Base
Closure Mitral/tricuspid valves Aortic/pulmonic Downloaded by [ Faculty of Nursing, Chiangmai University 5.62.158.117] at [07/18/16]. Copyright © McGraw-Hill Global Education Holdings, LLC. Not to be redistributed or modified in any way without permission.

Abnormal Heart Sounds
Abnormal heart sounds are referred to as S3 and S4 or “gallops” when auscul-
tated during tachycardia. They are low-pitched ventricular filling sounds that
can occur during diastole and may be caused by pressure changes, valvular
dysfunctions, and conduction deficits. They are referred to as gallops as they
sound like the hooves of a galloping horse striking the pavement.

NURSING ALERT

S3 and S4 are best heard by placing the bell of the stethoscope over the PMI. These
sounds are rhythmic and mimic a horse galloping when the patient is tachycardic.

The S3 heart sound resembles a dull, low-frequency, thudlike sound, as in
ventricular galloping, for example, “lub-dub, lub-dub,” or “Kentucky, Kentucky,
Kentucky.” A finding of S3 is normal in children and young adults and usually
disappears by the mid-30s. The finding of an S3 gallop in an older adult can
indicate ventricular failure.