Page 102 - Clinical Pearls in Cardiology

90 Clinical Pearls in Cardiology

Fig. 6: Auscultating for S3 and S4

9. What is the significance of S4?
Normally the atrial contraction accounts for only 20%
of the ventricular filling during diastole (80% of the
ventricular filling occurs passively). But in conditions
associated with increased stiffness of the ventricle like
concentric hypertrophy, the atrial contraction acts as
a ‘booster pump’, and accounts for about 40% of the
ventricular filling.
This booster pump action of the atrium results in
augmented blood flow into the left ventricle during late
diastole. This causes sudden tensing of the muscular
wall of left ventricle. This sudden tensing produces the
low pitched S4 (Fig. 7). It may be infrequently heard
in normal young persons. An audible S4 in an elderly
person is almost always pathological. An audible S4
is one of the earliest physical findings of systemic
hypertension.