title: Differential effects of calcium channel antagonists in the amelioration of radial artery vasospasm.
abstract: BACKGROUND
  Radial artery (RA) is being used for coronary artery bypass grafting (CABG) with greater frequency. However, RA is prone to post-CABG vasospasm, which may be neurohormonally mediated. Use of the calcium channel antagonist diltiazem has been advocated as a strategy to reduce post-CABG RA vasospasm. However, whether and to what degree different calcium channel antagonists influence neurohormonally induced RA vasoconstriction remains unknown.
  
  
  METHODS
  RA segments were collected from patients undergoing elective CABG (n = 13), and isometric tension was examined in the presence of endothelin (10 nM) or norepinephrine (1 microM). In matched RA, endothelin- or norepinephrine-induced contractions were measured in the presence of diltiazem (277 nM), amlodipine (73 nM), or nifedipine (145 nM). These concentrations of calcium channel antagonists were based upon clinical plasma profiles.
  
  
  RESULTS
  Endothelin and norepinephrine caused a significant increase in RA-developed tension (0.54+/-0.1 and 0.68+/-0.1 g/mg, respectively; p<0.05). Amlodipine or nifedipine significantly reduced RA vasoconstriction in the presence of endothelin (30+/-6% and 41+/-9%, respectively; p<0.05) or norepinephrine (27+/-8% and 53+/-9%, respectively; p<0.05), whereas diltiazem did not significantly reduce RA vasoconstriction.
  
  
  CONCLUSIONS
  These results demonstrate that neurohormonal factors released post-CABG can cause RA vasoconstriction, and that calcium channel antagonists are not equally effective in abrogating that response. Both amlodipine and nifedipine, which have a higher degree of vascular selectivity, appear to be the most effective in reducing RA vasoconstriction.
authors.affiliation: Division of Cardiothoracic Surgery, Medical University of South Carolina, Charleston, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Bond
authors.forename: J L
authors.initials: JL
authors.lastname: Zellner
authors.forename: B H
authors.initials: BH
authors.lastname: Dorman
authors.forename: M M
authors.initials: MM
authors.lastname: Multani
authors.forename: J M
authors.initials: JM
authors.lastname: Kratz
authors.forename: A J
authors.initials: AJ
authors.lastname: Crumbley
authors.forename: F A
authors.initials: FA
authors.lastname: Crawford
authors.forename: F G
authors.initials: FG
authors.lastname: Spinale
mesh_terms: D017311:Amlodipine / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D001026:Coronary Artery Bypass; D004110:Diltiazem / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009543:Nifedipine / Q000494:pharmacology*; D017534:Radial Artery; D014661:Vasoconstriction / Q000187:drug effects*
chemical_list: D002121:Calcium Channel Blockers; D017311:Amlodipine; D004110:Diltiazem; D009543:Nifedipine