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J Thorac Cardiovasc Surg 2003;126:1671-1672
© 2003 The American Association for Thoracic Surgery

Letters to the editor

Lack of evidence for vitamin C as acute vasodilator

^a Wales Heart Research Institute, University of Wales College of Medicine, Cardiff, United Kingdom

To the Editor:

We read with interest the article by Drossos and colleagues.¹ They measured radial artery diameter before and after acute oral administration of vitamin C (2 g) in two separate studies. Study one was a comparison in healthy subjects comparing nonsmokers with smokers; study two was double-blind comparison with diltiazem.

The article raises several issues that we believe require clarification by the authors. First, the article does not contain any data on the diameter measurements. This is important, because previous studies^2,3 that used the same dose of vitamin C did not show any acute effect on the baseline (unstimulated) diameter, at the same time showing an improvement in endothelial vasomotor function. Our own observations are also consistent with this. By showing an increase in the lumen surface area, derived from diameter changes, Drossos and colleagues¹ implied that vitamin C produces endothelium-independent dilatation.

Second, Drossos and colleagues¹ presented their data as lumen surface area. Why was this chosen? Also, was it derived from r²? This also was not made clear in the article.

Third, the results were actually presented as percentage change of lumen surface area. With this approach, any small change in measured diameter would be magnified by conversion to lumen surface area and further magnified by analysis of percentage change. Was the change in diameter statistically significant?

Finally, despite the larger increase in lumen surface area seen with vitamin C than with diltiazem, there did not appear to be any effect on blood pressure. Did Drossos and colleagues¹ see a change in heart rate and blood pressure in the vitamin C group? If not, why not?

References

1. Drossos GE, Toumpoulis IK, Katritsis DG, Ioannidis JP, Kontogiorgi P, Svarna E, et al. Is vitamin C superior to diltiazem for radial artery vasodilation in patients awaiting coronary artery bypass grafting? J Thorac Cardiovasc Surg. 2003;125:330–335[Abstract/Free Full Text]
   
2. Levine GN, Frei B, Koulouris SN, Gerhard MD, Keaney JF, Vita JA. Ascorbic acid reverses endothelial vasomotor dysfunction in patients with coronary artery disease. Circulation. 1996;93:1107–1113[Abstract/Free Full Text]
   
3. Raitakari OT, Adams MR, McCredie RJ, Griffiths KA, Stocker R, Celermajer DS. Oral vitamin C and endothelial function in smokers: short term improvement, but no sustained beneficial effect. J Am Coll Cardiol. 2000;35:1616–1621[Abstract/Free Full Text]
   

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Madhavan, A. Articles by Goodfellow, J. Search for Related Content PubMed PubMed Citation Articles by Madhavan, A. Articles by Goodfellow, J. Related Collections Cardiac - pharmacology