Response to Letter Regarding Article, “Impact of Patient and Target-Vessel Characteristics on Arterial and Venous Bypass Graft Patency: Insight From a Randomized Trial”
We thank Spence and colleagues for their letter about our article.1 They raise the interesting possibility of confounding as an explanation for our finding that radial graft patency was reduced among patients with peripheral vascular disease. Specifically, patients with severe peripheral vascular disease are much more likely to undergo diagnostic coronary angiography through the radial artery. Spence et al hypothesize that cannulation might damage the artery before harvesting for bypass surgery and thereby reduce its long-term patency.
In fact, no patients who had follow-up to 1 year in our trial2 received a radial artery graft after that same artery had been cannulated for diagnostic coronary angiography. During the recruitment phase of our trial (1996 to 2001), radial artery access for diagnostic coronary angiography was uncommon at the centers involved in this study except in cases of severe peripheral vascular disease, which in turn was a prespecified exclusion criteria.2
Study centers were also advised against harvesting a radial artery used for diagnostic coronary angiography. In cases in which radial artery catheterization for angiography was performed, this was done via the radial artery in the dominant arm, typically on the right side, and the nondominant (left) arm was used to harvest the radial artery graft.
We do not have information on the use of radial arteries catheterized for arterial line monitoring preoperatively and did not exclude such cases; however, the majority of recruited patients had stable angina, and almost all had well-preserved ventricular function. Hence, we surmise that the number of affected patients would be very small. We conclude that the adverse results seen with peripheral vascular disease are very unlikely to be confounded by other interventions.
On a related point, we strongly discourage catheterization via the nondominant (left) radial artery because this may be used as a bypass conduit. Clinical studies have shown radial artery spasm occurs in >11% of patients after sheath insertion,3 and severe vasomotor dysfunction is observed for up to 9 weeks thereafter.4 Radial artery diameter remains reduced up to 1 year after catheterization.5 Given these documented effects of radial artery catheterization, it remains our clinical practice to perform diagnostic angiography via the dominant radial artery (right) and to use the nondominant radial artery (left) as a bypass graft. This may be particularly prudent in the current era in which the increasing proportion of urgent and emergent cases has dramatically shortened the interval between catheterization and surgery. From a practical perspective, accessing the right radial artery is generally easier in a typical cardiac catheterization laboratory, where the viewing monitors are on the patient’s left side.
Sources of Funding
This work was supported by grant MT-13883 from the Canadian Institutes of Health Research.
Desai ND, Naylor CD, Kiss A, Cohen EA, Feder-Elituv R, Miwa S, Radhakrishnan S, Dubbin J, Schwartz L, Fremes SE; Radial Artery Patency Study Investigators. Impact of patient and target-vessel characteristics on arterial and venous bypass graft patency: insight from a randomized trial. Circulation. 2007; 115: 684–691.