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How accurate is the TR jet derived Pulmonary artery systolic pressure ?

Posted Feb 21 2012 11:50am

Measuring TR peak velocity is the most popular  method to assess pulmonary arterial  pressure.It is  universally  believed  TR jet predicts the systolic PA pressure fairly accurately. By all means it is  a wrong perception.

At best ,  it has only 40% correlation with cath  derived PAP  . In other words cardiologist are fooled by TR jet more often than not ! Here is an  elegantly done study  from American  Journal of  Respiratoty and critical care medicine  in  patients  who had undergone lung transplantation . It compared  systolic PAP derived from  Doppler vs cardiac  cath.

The accuracy of DE in assessing sPAP. DE estimation of sPAP was designated as accurate when the measurement was within 10 mm Hg of the actual measurement by cath Overestimation and underestimation designate a discrepancy of greater than 10 mm Hg above or below the cath-measured value, respectively. Analysis was performed separately for those patients without [PH (−)and with [PH (+)PH defined by cath"

Important observations about TR jet derived PAP

  • Over estimation is the key error.
  • Error of  under -estimation  less common .
  • Over estimation often occur in normal persons
  • Under estimation more frequent in patients with PAH.

(The above study documents  over estimation of 10mmhg  in systolic PAP in 50 out of  100 patients )

Final message

Nothing is perfect in science ,  especially in medical science.  In spite of the limitations  of  TR  jet  , it   will remain the corner stone in the hemodynamic evaluation of right heart pressures . (Forget for the moment . . . the umpteen variables  in  the modified Bernolui equation  , flow acceleration , viscous friction etc )

It is prudent ,  cardiologists  are expected to be aware of this harsh  fact  and  should be meticulous in tracing TR jet and  reduce the error.

One controversial  but logical  suggestion  would be  to drop the ritual of adding  empirical  RA pressure   5- 10mmhg  over the TR  jet  while  calculating PAP , as there is   60 %  error  of  over-estimation  that naturally occur with TR jet. 

Reference


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