The document discusses the fourth heart sound, also known as S4. S4 occurs as a result of forceful atrial contraction and is a low-pitched sound heard just before the first heart sound. It can be confused with a split S1 sound but firm pressure with a stethoscope distinguishes the two. Left-sided S4 is best heard during expiration while right-sided S4 is best heard during inspiration. Common causes of a left-sided S4 include hypertension, hypertrophic cardiomyopathy, and ischemic heart disease, while causes of a right-sided S4 include pulmonary hypertension and pulmonary stenosis.

1. ‫الرحمن‬ ‫هللا‬ ‫بسم‬‫الرحیم‬

2. Fourth Heart Sound
SIGNIFICANCE AND CAUSES

3. Fourth Heart Sound
 Fourth heart sound (S4) occurs as a result of forceful atrial contraction ("atrial
kick"). It is a low-pitched sound heard in pre-systole (late diastole; before first
heart sound). It is absent in atrial fibrillation
 S4 may be confused with spilt S1. Firm pressure by the diaphragm of
stethoscope eliminates S4 but not split S1.
 S4 is always abnormal.
 A fourth heart sound arising from the left side is known as "left-sided fourth
heart sound" and the one arising from right side as "right-sided fourth heart
sound".
 Left-sided S4 is best heard during expiration with the patient in the left lateral
position.
 Right-sided S4 is best heard during inspiration.

4. Causes of Fourth Heart Sound
Left-sided S4 Right-sided S4
• Systemic hypertension
• Hypertrophic cardiomyopathy
• ischemic heart disease
(especially acute myocardial
infarction)
• Acute mitral regurgitation
• Anemia, thyrotoxicosis and
AV fistulae
• Right ventricular hypertrophy
due to
• Pulmonary hypertension
• Pulmonary stenosis