Nitroglycerin is superior to diltiazem as a coronary bypass conduit vasodilator.
BACKGROUND
Recent reports of improved radial artery patency have been attributed, in part, to routine use of diltiazem to prevent vasospasm. However, diltiazem is costly, and its use may be associated with negative inotropic and chronotropic side effects. This study compares the vasodilatory properties of diltiazem to those of nitroglycerin.


METHODS
In vitro, with the use of organ chambers, the vasodilatory properties of diltiazem and nitroglycerin were compared in matched segments of radial artery, internal thoracic artery, and saphenous vein that were harvested from the same patients (n = 11). The vasodilatory response of the radial artery to intravenous diltiazem or nitroglycerin was compared in vivo (n = 10) with the use of ultrasonographic measurements of radial artery diameter.


RESULTS
The maximum relaxation of radial artery (100% +/- 4%), internal thoracic artery (96% +/- 4%), and saphenous vein (100% +/- 3%) to nitroglycerin were significantly greater than the response to diltiazem (33% +/- 6%, 22% +/- 7%, and 34% +/- 5%, respectively; P <.001). The thromboxane mimetic, U46619, induced radial artery spasm with a median effective concentration of 3.7 +/- 0.8 nmol/L. Physiologic concentrations of nitroglycerin (0.1+/- micromol/L) significantly inhibited the radial artery response to U46619 (median effective concentration, 6.2 +/- 1.1 nmol/L; P =.046), whereas diltiazem (1 micromol/L) did not (median effective concentration, 3.7 +/- 0.8 nmol/L; P =.64). In vivo, nitroglycerin increased radial artery diameter 22% +/- 3%, which was significantly greater than diltiazem (3% +/- 0.5%; P =.001).


CONCLUSIONS
Nitroglycerin is a superior conduit vasodilator and is more effective in preventing graft spasm than diltiazem. Nitroglycerin should be strongly considered as the drug of choice to prevent conduit spasm after coronary bypass grafting.
Shapira
O M
OM
Department of Cardiothoracic Surgery and Evans Department of Medicine, Boston University School of Medicine, Boston, MA, USA.
Xu
A
A
Vita
J A
JA
Aldea
G S
GS
Shah
N
N
Shemin
R J
RJ
Keaney
J F
JF
D000328:Adult; D017023:Coronary Angiography; D001026:Coronary Artery Bypass; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000601:surgery; D004110:Diltiazem / Q000008:administration & dosage / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D008323:Mammary Arteries / Q000187:drug effects / Q000502:physiology / Q000637:transplantation; D008875:Middle Aged; D005996:Nitroglycerin / Q000008:administration & dosage / Q000627:therapeutic use*; D011183:Postoperative Complications / Q000517:prevention & control; D017534:Radial Artery / Q000000981:diagnostic imaging / Q000187:drug effects / Q000502:physiology* / Q000637:transplantation; D012501:Saphenous Vein / Q000187:drug effects / Q000502:physiology / Q000637:transplantation; D014463:Ultrasonography; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000008:administration & dosage / Q000627:therapeutic use*
D014665:Vasodilator Agents; D004110:Diltiazem; D005996:Nitroglycerin