22. DIFFERENTIAL EFFECTS OF CALCIUM CHANNEL ANTAGONISTS IN THE AMELIORATION OF RADIAL ARTERY VASOSPASM
James L. Zellner*, Brian R. Bond, Bruce H. Dorman, Marlina M. Multani, John M. Kratz, Arthur J. Crumbley III*, Fred A. Crawford*, Francis G. Spinale
CT Surgery, Division of CardioThoracic Surgery, Medical University of South Carolina
Charleston, South Carolina, USA
BACKGROUND
Use of radial artery (RA) for coronary artery bypass grafting (CABG) is increasing. Diltiazem (DILT) has traditionally been the calcium receptor antagonist (C-ANT) of choice to reduce the incidence of post-CABG RA vasospasm. Whether C-ANT directly prevent neurohormonally mediated RA vasospasm and are equally protective against this response is unknown. Accordingly, RA segments were taken from patients undergoing elective CABG (n=10) and isometric tension examined in the presence of endothelin (ET;10nM) or norepinephrine (NOR;1
l M).METHODS AND RESULTS
In matched RA, ET or NOR-induced contractions were measured in the presence of DILT (100ng/mL), nifedipine (NIF;50ng/mL), or amlodipine (AMLO;30ng/mL). These C-ANT concentrations were based on clinical blood levels. ET and NOR caused a significant increase in RA developed tension (0.52
± 0.1; 0.59± 0.1g/mg). The percent reduction in RA tension with C-ANT is shown in the Table. DILT did not prevent ET or NOR-mediated RA vasospasm, whereas NIF or AMLO significantly reduced RA vasospasm (*P<0.05).CONCLUSION
These unique results demonstrated that neurohormonal factors which are released post-CABG can cause RA vasospasm, and that C-ANT are not equally effective in abrogating this response. Both NIF and AMLO, which have a higher degree of vascular selectivity and less chronotropic and inotropic effects, appeared to be the most effective in reducing RA vasospasm.
(bar chart)
