Is vitamin C superior to diltiazem for radial artery vasodilation in patients awaiting coronary artery bypass grafting?
OBJECTIVE
We aimed to measure the vasodilating effects of vitamin C on the radial arteries of healthy subjects and to assess whether vitamin C is superior in this regard to diltiazem, a commonly used vasodilator in coronary artery bypass using radial conduits.


METHODS
In a case-control study (study 1) oral single-dose vitamin C (2 g) was given to 15 healthy nonsmokers and 15 matched otherwise healthy smokers. In a randomized double-blind study (study 2) oral single-dose vitamin C (2 g, n = 15) and diltiazem (180 mg, n = 15) were compared in preoperative patients with coronary artery disease. We examined the dilation of the radial artery with high-resolution ultrasonography and measurement of the lumen surface and color Doppler images of the nondominant radial artery just before and 2 hours after drug administration.


RESULTS
In study 1 both smokers and nonsmokers showed a significant increase in the lumen surface at 2 hours compared with at baseline (P <.001 and P =.013, respectively). The increase was larger in smokers (median, 37.5% vs 14.3%; P =.004). In study 2 both groups showed statistically significant increases in the lumen surface at 2 hours compared with at baseline (P <.001 and P =.008 for vitamin C and diltiazem, respectively). Vitamin C achieved a larger increase than diltiazem (median, 33.3% vs 18.2%; P =.016). In multivariate modeling the increase in lumen surface was independently predicted by use of vitamin C over diltiazem (+21.2%, P =.007), diabetes mellitus (+14.5%, P =.085), increased cholesterol (+26.2%, P =.001), and smoking history (+20.8%, P =.017).


CONCLUSIONS
Vitamin C is a potent acute vasodilator in both smokers and nonsmokers and is superior to diltiazem in preoperative coronary patients who need protection from vasospasm of the radial conduit.
Drossos
George E
GE
Department of Cardiothoracic Surgery, University of Ioannina School of Medicine, Ioannina, Greece.
Toumpoulis
Ioannis K
IK
Katritsis
Demosthenes G
DG
Ioannidis
John P A
JP
Kontogiorgi
Persephone
P
Svarna
Eugenia
E
Anagnostopoulos
Constantine E
CE
D000328:Adult; D000368:Aged; D001205:Ascorbic Acid / Q000494:pharmacology / Q000627:therapeutic use*; D016022:Case-Control Studies; D001026:Coronary Artery Bypass / Q000379:methods*; D003327:Coronary Disease / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology / Q000601:surgery; D048909:Diabetes Complications; D004110:Diltiazem / Q000494:pharmacology / Q000627:therapeutic use*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000150:complications; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010865:Pilot Projects; D011237:Predictive Value of Tests; D017534:Radial Artery / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000503:physiopathology / Q000637:transplantation*; D012907:Smoking / Q000009:adverse effects / Q000188:drug therapy* / Q000503:physiopathology; D018615:Ultrasonography, Doppler, Color; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology / Q000627:therapeutic use*
D014665:Vasodilator Agents; D004110:Diltiazem; D001205:Ascorbic Acid