title: Assessment of renal artery stenosis severity by pressure gradient measurements.
abstract: OBJECTIVE
  The purpose of this study was to define "significant" renal artery stenosis (i.e., a stenosis able to induce arterial hypertension).
  
  
  BACKGROUND
  The degree of renal artery stenosis that justifies an attempt at revascularization is unknown.
  
  
  METHODS
  In 15 patients, transstenotic pressure measurements were obtained before and after unilateral stenting. After stenting, graded stenoses were created in the stented segment by progressive inflation of a balloon catheter. Stenosis severity was expressed as the ratio of distal pressure (P(d)) corrected for aortic pressure (P(a)). Balloon inflation pressure was adjusted to create 6 degrees of stenosis (P(d)/P(a) from 1.0 to 0.5, each step during 10 min). Plasma renin concentration was measured at the end of each step in the aorta and in both renal veins.
  
  
  RESULTS
  For a P(d)/P(a) ratio >0.90, no significant change in plasma renin concentration was observed. However, when P(d)/P(a) became <0.90, a significant increase in renin was observed in the renal vein of the stenotic kidney, finally reaching a maximal increase of 346 +/- 145% for P(d)/P(a) of 0.50 (p = 0.006). These values returned to baseline when the stenosis was relieved. In addition, plasma renin concentration increased significantly in the vein from the non-stenotic kidney (p = 0.02).
  
  
  CONCLUSIONS
  In renal artery stenoses, a P(d)/P(a) ratio of 0.90 can be considered a threshold value below which the stenosis is likely responsible for an up-regulation of renin production and, thus, for renovascular hypertension. These findings might contribute to better patient selection for renal angioplasty.
authors.affiliation: Cardiovascular Center Aalst, OLV Clinic, Aalst, Belgium. bernard.de.bruyne@olvz-aalst.be
authors.forename: Bernard
authors.initials: B
authors.lastname: De Bruyne
authors.forename: Ganesh
authors.initials: G
authors.lastname: Manoharan
authors.forename: Nico H J
authors.initials: NH
authors.lastname: Pijls
authors.forename: Katia
authors.initials: K
authors.lastname: Verhamme
authors.forename: Juraj
authors.initials: J
authors.lastname: Madaric
authors.forename: Jozef
authors.initials: J
authors.lastname: Bartunek
authors.forename: Marc
authors.initials: M
authors.lastname: Vanderheyden
authors.forename: Guy R
authors.initials: GR
authors.lastname: Heyndrickx
mesh_terms: D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D002404:Catheterization / Q000379:methods; D005260:Female; D006801:Humans; D006978:Hypertension, Renovascular / Q000175:diagnosis / Q000503:physiopathology; D008297:Male; D012078:Renal Artery Obstruction / Q000175:diagnosis* / Q000503:physiopathology*; D012720:Severity of Illness Index; D018615:Ultrasonography, Doppler, Color / Q000379:methods