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Correspondence

Reply

Division of Cardiac Surgery, University of Ottawa Heart Institute, 40 Ruskin St, Ste 3401, Ottawa, Ontario, K1Y 4W7 Canada

(Email: akulik{at}ottawaheart.ca).

To the Editor:

We thank Pai and colleagues [1] for their interest and insightful comments about our manuscript that described the clinical safety and efficacy of radial artery treatment with phenoxybenzamine during coronary artery bypass graft surgery [2]. Our study compared perioperative myocardial injury and adverse cardiac events in 311 patients who received radial artery grafts treated with phenoxybenzamine with 387 patients who received radial artery grafts treated with verapamil and nitroglycerin (VG solution). Treatment of radial artery grafts with phenoxybenzamine was safe and was associated with a reduction in perioperative myocardial injury and adverse cardiac events [2].

As Pai and colleagues noted [1], we used the dose of phenoxybenzamine (2 mg/mL) that was first reported by Taggart and coworkers in 2000 [3]. Specifically, each phenoxybenzamine-treated radial artery was irrigated and incubated in a solution containing 100 mg of phenoxybenzamine in 50 mL of heparinized blood for 15 minutes. Before anastomosis, each phenoxybenzamine-treated artery was internally and externally irrigated with heparinized saline solution. We have used this phenoxybenzamine treatment technique for radial artery grafts since 2001.

While the endothelial cell viability data presented by Pai and colleagues [1] is intriguing, we believe their results have limited clinical applicability and we disagree with their interpretation of the data. First, it is difficult to correlate the in vitro experimental methods of cultured radial artery endothelial cells to the in vivo conditions of a systemically perfused radial artery conduit consisting of endothelial cells, an intact basement membrane, and supporting vascular cells. Second, the methods reported by Pai and colleagues [1] were unclear about the 30-minute phenoxybenzamine treatment of cultured radial artery endothelial cells. In particular, suboptimal pH conditions can lead to major viability losses in cell culture, and phenoxybenzamine is a highly acidic solution. For our clinical methods, we buffer phenoxybenzamine in autologous heparinized blood to prevent cellular injury. Third, the data reported by Pai and colleagues suggest that phenoxybenzamine is toxic to radial artery endothelial cells, and the authors conclude that "lower doses of phenoxybenzamine would benefit...potentially the long-term patency of the graft." However, in our experience phenoxybenzamine is safe for clinical use, and to our knowledge there is no evidence that phenoxybenzamine (at any dose) affects either short- or long-term radial artery graft patency. Phenoxybenzamine attenuates human radial artery vasoconstriction to adrenergic stimuli in a dose-dependent manner, and lower doses are less effective in inhibiting radial artery vasoconstriction in organ bath studies [4]. It is currently unknown whether a dose of less than 2 mg/mL would reduce its purported clinical effect of inhibiting perioperative radial artery vasospasm.

We thank Pai and colleagues for their interest in studying the effect of phenoxybenzamine on cultured radial artery endothelial cells. At this time, however, we believe that the data presented by the authors is insufficient to warrant discontinuation or alteration in our phenoxybenzamine treatment protocol. Nevertheless, we share with them the view that additional studies are needed to evaluate the potential benefits and limitations of phenoxybenzamine use with radial artery grafts.

	References

Top References

 

1. Pai RK, Conant AR, Dihmis WC. Treatment with phenoxybenzamine may lead to loss of endothelial viability in radial artery(letter) Ann Thorac Surg 2008;86:350-351.[Free Full Text]
2. Kulik A, Rubens FD, Gunning D, et al. Radial artery graft treatment with phenoxybenzamine is clinically safe and may reduce perioperative myocardial injury Ann Thorac Surg 2007;83:502-509.[Abstract/Free Full Text]
3. Taggart DP, Dipp M, Mussa S, Nye PC. Phenoxybenzamine prevents spasm in radial artery conduits for coronary artery bypass grafting J Thorac Cardiovasc Surg 2000;120:815-817.[Free Full Text]
4. Corvera JS, Morris CD, Budde JM, et al. Pretreatment with phenoxybenzamine attenuates the radial artery's vasoconstrictor response to alpha-adrenergic stimuli J Thorac Cardiovasc Surg 2003;126:1549-1554.[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 Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Alexander Kulik Fraser D. Rubens Marc Ruel Permission Requests Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Kulik, A. Articles by Ruel, M. Search for Related Content PubMed Articles by Kulik, A. Articles by Ruel, M. Related Collections Related Article