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Posts Tagged ‘mechansim of systolic murmur in pulmonary arterial hypertension ?’

A short systolic murmur over pulmonary area (ie Left second inter coastal space ) is listed among 6 other auscultatory  feature  of pulmonary arterial hypertension.Though it is an accepted sign  many would question  the existence of such a murmur or its relevance in PHT.

Why does it occur  ?

Acoustics  principle  tells us whenever  velocity of blood  flow exceeds a critical point(Raynolds number*) in a specific anatomical territory , a  turbulent zone is created  and  a murmur could be generated .This is why many physiological situations like pregnancy, anemia, and some benign outflow murmurs occur.

 

In pulmonary hypertension , three things are thought to contribute for the murmur generation

  1. Dilated pulmonary artery  promotes Raynauld turbulence
  2. Increased flow velocity (This is correlated with pulmonary artery acceleration time in Doppler)
  3. RV contractility  (A normally functioning   RV is required to generate the murmur .Once RV dysfunction sets the  murmur of pulmonary hypertension usually disappear , of course a TR murmur may appear and confuse the picture )

Reference

* Reynolds number is a way to predict under ideal conditions when turbulence will occur. The equation for Reynolds number is:

Reynolds number(Where v = mean velocity, D = vessel diameter, ρ = blood density, and η = blood viscosity )

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