The vibration of valves and ventricular walls during the second phase of ventricular filling when the atria contracts, produces the?

Appeared in: DSSSB - 29 August 2019 (Shift-1)

Explanation

The fourth heart sound (S4) is a low-frequency sound that occurs in late diastole, just before S1.
It is generated by the forceful contraction of the atria (the 'atrial kick') pushing blood into a non-compliant or stiff ventricle.
This forceful movement of blood causes vibrations in the ventricular walls and valves, which are heard as the S4 sound.
S4 is often referred to as an 'atrial gallop' and is typically considered an abnormal finding in adults, often indicating underlying cardiac pathology like ventricular hypertrophy or ischemia.

Option B: The second heart sound (S2) is a high-pitched sound caused by the closure of the aortic and pulmonic (semilunar) valves at the end of ventricular systole, not by atrial contraction.
Option C: The first heart sound (S1) is caused by the closure of the mitral and tricuspid (atrioventricular) valves at the beginning of ventricular systole.
Option D: The third heart sound (S3) is caused by the rapid, passive filling of the ventricles in early diastole. It is not associated with atrial contraction, which happens later in diastole.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Physiology of Heart Sounds as background academic context rather than a clinical decision trigger.
Auscultating for an S4 is a key nursing assessment skill. Its presence can be an early indicator of serious cardiac conditions like uncontrolled hypertension, aortic stenosis, or heart failure, prompting the need for further evaluation and intervention.
Nurses must be able to differentiate S4 from other sounds like S3 or a split S1, as the underlying cause and management differ. S4 is a low-pitched sound best heard with the bell of the stethoscope at the cardiac apex with the patient in the left lateral decubitus position.
What if? If the patient was a young, healthy athlete, an S4 sound would still be considered abnormal and require investigation. This contrasts with an S3 sound, which can sometimes be a normal physiological finding ('physiological S3') in children and trained athletes.

How to Approach the Question

First, identify the key physiological events described in the question: 'vibration of... ventricular walls' and 'when the atria contracts'.
This points to an event driven by the 'atrial kick'.
Next, recall the causes of the four main heart sounds.
S1 ('lub') is from the closure of the atrioventricular (AV) valves at the start of systole.
S2 ('dub') is from the closure of the semilunar valves at the end of systole.
S3 is associated with rapid, passive ventricular filling in early diastole.

Concept Tested & Keywords

Concept Tested: Physiology of Heart Sounds
Stem keywords: vibration, ventricular walls, ventricular filling, atria contracts
Lead-in keywords: produces the

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E6 Physiology Guyton 4SAE Part 2A p. 12-13

E6 Medicine Harrison 22e Part 1 p. 1906-1908

Practise the full DSSSB - 29 August 2019 (Shift-1)

Attempt every question from this paper in a timed mock, then review the full solution for each one.