Feeds:
Posts
Comments

Posts Tagged ‘s 3 and s4 gallop’

Third heart sound is a unique heart sound  because its   perfect physiology  to hear it  in the young  ,  while the same may denote  serious LV dysfunction in patients with myocardial disease.

It is a low pitched  early diastolic sound usually correspond to  the end of rapid filling phase.The mechanism of genesis of this sound has been debated for many years .(Still I think it is unsettled !)

We know genesis of intracardiac sound is contributed  by three factors

  • The blood flow
  • The valve motion
  • The myocardial contractile and  relaxyl  property

The above  three is collectively  called cardio-hemic system . When this system vibrates heart sounds are generated .In  the genesis of S3 all the three may be important . The only difference is ,  in physiological S3 the valvular and hemic component play a major role . In pathological S3 the  myocardial component has a pivotal  role .The distended LV facilitates chest wall impact during the rapid filling phase . It is now  accepted  LV S3 is  generated outside the LV  . It  was proved elegantly by Shaver et all with sound recording on either side of  LV /Chest wall.

It is to be emphasized  the mechanism of genesis of S3 is diagonally opposite in  physiology vs  pathological  S3 in some conditions . Rapid AV filling  can  rarely be  responsible for pathological  S3  associated with severe LV dysfunction , while chest wall  impact can contribute in both physiological as well as pathological S 3 .

 One can understand the complexity of genesis of  S 3  , as  there are  too many  determinants  that contribute in  varying degree of acoustics.

Factors determining the intensity of S3 is complex 

  1. Age,
  2. Atrial pressure,
  3. Rapidity of  flow across the atrio-ventricular valve,
  4.  Rate of early  diastolic relaxation 
  5.  Distensibility of the ventricle,
  6.  Blood  volume,
  7. Ventricular cavity size,
  8.  Diastolic momentum of the  heart,
  9. Degree of contact (coupling) with the chest wall, thickness
  10. Character of the chest wall
  11.  The position of the  patient.

 

It is ironical, pathological   S3 which is a  diastolic  sound  though ,  still  its genesis  is largely  determined by the systolic function of the heart .This mystery is partially solved as we recognise  now ,  LV S3 is equally common in  severe degrees of diastolic dysfunction. In fact ,  while we were studying the relationship  of LVS3 in DCM  , it  has strongly predicted the  presence of   severe restrictive pattern in them .

 

 

 Reference

1.Multimedia of S3

http://www.inovise.com/learn/s3causes.html

2.Importance of  S3 in cardiology NEJM 2001 article

http://www.nejm.org/doi/pdf/10.1056/NEJMoa010641

3.Chest wall impact theory of S3  by Shaver

Shaver JA, Salerni R. Auscultation of the heart. In: Hurst, ed. Heart. 8th ed. New York, NY: McGraw-Hill, Inc; 1994:291.

Read Full Post »