Heart Sound

HEART SOUND

Q. 1

First heart sound occurs during the period of:

 A

Isovolumetric relaxation

 B

Isotonic relaxation

 C

Isovolumetric contraction

 D

Isotonic contraction

Q. 1

First heart sound occurs during the period of:

 A

Isovolumetric relaxation

 B

Isotonic relaxation

 C

Isovolumetric contraction

 D

Isotonic contraction

Ans. C

Explanation:

First heart sound is a low, slightly prolonged lub caused by vibrations set up by the sudden closure of mitral or tricuspid valves at the start or ventricular systole and it occurs during the period of Isovolumetric contraction.

Ref: Medical Physiology: Principles for Clinical Medicine, 3rd Ed, Page 247 By Rodney Rhoades, David R. Bell, Ph.D

Q. 2

Which of the following is true about fourth heart sound ‘S4’ :

 A

Can be heard by the unaided ear

 B

Frequency is greater than 20 Hz

 C

Heard during ventricular filling phase

 D

Heard during ventricular ejection phase

Q. 2

Which of the following is true about fourth heart sound ‘S4’ :

 A

Can be heard by the unaided ear

 B

Frequency is greater than 20 Hz

 C

Heard during ventricular filling phase

 D

Heard during ventricular ejection phase

Ans. C

Explanation:

C i.e. Heard during ventricular filling

  • It is a low pitched presystolic sound which can almost never be heard with a stethoscope (& ear) because of its weakness and very low frequency – usually 520 cycles/ second (1-1,)Q. It is caused by in thrushing of blood into ventricles (ventricular fillingQ, which initiates vibration) when the atria contractsQ.
  • S4, sometime becomes audible, when atrial pressure is very high or ventricle is stiff (diminished ventricular compliance) increasing the resistance to normal filling. When audible it is best heard with bell of stethescope, at left ventricular apex in left lateral position and accentuated by exercise (isotonic or isometric) in the supine position.
  • Pathologically S4 may be seen in

Pulmonary stenosis & hypertension (right S4)

Aortic stenosis & systemic hypertension

Ischemic heart disease – HOCM – Mitral regurgitation

Advanced age (physiological)

Feature

1st heart sound

2″ heart sound

3rd heat sound

4th heart sound

Character

Low pitched (frequency)

slightly prolonged “lub”

Shorter high

pitched “dup”

Soft low pitched weak

rumbling

Arterial heart sound

Duration

0.14 second

0.11 sec

0.1 sec

‑

Frequency

25-45 Hz

50 Hz

 

< 20 HzQ

Cause

Sudden closure of mitral

& tricuspid valves

Closure of aortic &

pulmonary valves

Rapid ventricular

fillingQ d/t inthrushing

of blood from atria

Ventricular fillingQ d/t atrial

contraction causing inthrushing of

blood

Timing

Start of ventricular

systole

Just after end of

ventricular systole

Begining of middle third

of diastole

Immediately before 1st heart

sound (presystolic)

Heard

Si & S2 can be heard with stethoscope

S3 & S4 can not be heard by stethoscope (ear)Q. S3 oftenly and

Sa sometimes can be recorded in phonocardiorgam


Q. 3

First heart sound is soft in all, except:

 A

Short PR interval

 B

Ventricular septal defect

 C

Mitral regurgitation

 D

Calcified valve

Q. 3

First heart sound is soft in all, except:

 A

Short PR interval

 B

Ventricular septal defect

 C

Mitral regurgitation

 D

Calcified valve

Ans. A

Explanation:

Answer is A (Short PR interval)

Short PR interval is associated with a Loud S,.

SI is produced as a result of closure of AV valves.

In short PR interval mitral leaflets are at a greater distance from neutral as decreased interval between atrial contraction and ventricular systole does not allow them to return towards neutral before the ventricular contraction 


Q. 4

Reverse splitting of first heart sound in heard in (select two correct options):

 A

RBBB

 B

LBBB

 C

Tricuspid stenosis

 D

AR

Q. 4

Reverse splitting of first heart sound in heard in (select two correct options):

 A

RBBB

 B

LBBB

 C

Tricuspid stenosis

 D

AR

Ans. B

Explanation:

Answer is B (LBBB)

Left Bundle Branch Block, and Atrial myxoma are causes of reverse splitting of First Heart Sound (Si).

First heart Sound (S1) and Splitting

First heart sound (MITI) is produced by closure of Mitral valve (M1) and closure of Tricuspid valve (T1)

The mitral valve closes slightly before the Tricuspid valve (M1 –> TI) 

This normal splitting (physiological splitting) cannot be detected by auscultation because both components are low pitched and separated only by 20-30 ms.

Therefore splitting of first heart sound, whenever audible is considered pathological.


Q. 5

Paradoxical splitting of second heart sound is seen in?

 A

RBBB

 B

ASD

 C

LBBB

 D

VSD

Q. 5

Paradoxical splitting of second heart sound is seen in?

 A

RBBB

 B

ASD

 C

LBBB

 D

VSD

Ans. C

Explanation:

Answer is C (LBBB)

Left Bundle Branch Block (LBBB) is typically associated with Reversed or Paradoxical Splitting of S2

Paradoxical splitting of second heart sound is caused by delayed A2 or early P2. Left Bundle Branch Block (LBBB) is associated with delayed Aortic closure (delayed A2) due to delayed electrical activation of the left ventricle.

ASD and RBBB are associated with a wide physiological (non-paradoxical) split of second heart sound due to delayed pulmonic closure (Delayed P2) while VSD is associated with a wide physiological (non-paradoxical) split second heart sound from early aortic closure (Early A2).


Q. 6

Wide-split second heart sound is seen in (select two options) –

 A

ASD

 B

LBBB

 C

Pulmonary Stenosis

 D

a and c

Q. 6

Wide-split second heart sound is seen in (select two options) –

 A

ASD

 B

LBBB

 C

Pulmonary Stenosis

 D

a and c

Ans. D

Explanation:

Answer is A, C (ASD, Pulmonary Stenosis)

ASD and pulmonic stenosis are associated with wide splitting of second heart sound due to associated delayed closure of pulmonic valve.


Q. 7

Single second heart sound is seen in (select three options):

 A

TOF

 B

Pulmonary arterial hypertension

 C

Pulmonary atresia

 D

a and c

Q. 7

Single second heart sound is seen in (select three options):

 A

TOF

 B

Pulmonary arterial hypertension

 C

Pulmonary atresia

 D

a and c

Ans. D

Explanation:

Answer is A, C (TOF, Pulmonary Atresia)

TOF, Pulmonary Atresia and severe pulmonic stenosis are associated with single S2 as one component of S2 is either absent or inaudible in these conditions.


Q. 8

The first heart sound is due to: 

September 2005

 A

AV valves closure

 B

Closing of aortic and pulmonary valves

 C

Opening of AV valves

 D

Opening of aortic and pulmonary valves

Q. 8

The first heart sound is due to: 

September 2005

 A

AV valves closure

 B

Closing of aortic and pulmonary valves

 C

Opening of AV valves

 D

Opening of aortic and pulmonary valves

Ans. A

Explanation:

Ans. A: AV valves closure


Q. 9

Wide split fixed 2nd heart sound is heard in :

March 2005

 A

Normal individuals

 B

Left bundle branch block

 C

ASD

 D

VSD

Q. 9

Wide split fixed 2nd heart sound is heard in :

March 2005

 A

Normal individuals

 B

Left bundle branch block

 C

ASD

 D

VSD

Ans. C

Explanation:

Ans. C: ASD

Fixed splitting denotes absence of significant variation of the splitting interval with respiration, such that the separation of A2, and P2, remains unchanged during inspiration and expiration.

Atrial septal defect, with either normal or high pulmonary vascular resistance, is the classic example of fixed splitting of the second sound.

The fixed nature of the split is due to approximately equal inspiratory delay of the aortic and pulmonic components, indicating that the two ventricles share a common venous reservoir. Respiratory splitting of the second sound immediately returns to normal following surgical repair of an atrial septa] defect, although the pulmonic closure sound may remain delayed for weeks or months.

Severe right heart failure can lead to a relatively fixed split. This occurs because the right ventricle fails to respond to the increased volume produced by inspiration and because the lungs are so congested that impedance to forward flow from the right ventricle barely falls during inspiration.

In anomalous pulmonary venous return without atrial septal defect, fixed splitting is not usually seen despite the simultaneous inspiratory delay in aortic and pulmonic closure



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