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Yvonne Viens, SGM, Research Institute, St. Vincent Mercy Medical Center, 2222 Cherry St, MOB2, Ste 1250, Toledo, OH 43608
(Email: anoar_zacharias{at}mhsnr.org).
We appreciate Nezic and colleagues' observations [1] addressing issues related to our recent article [2]. They raised questions regarding methodology in related randomized and observational studies showing the superior results of the radial artery (RA) graft compared with the saphenous vein (SV) graft.
We previously reported graft patency data based on symptom-driven repeat angiography comparing survival of patients receiving RA vs SV grafts, both in association with a left internal thoracic artery (LITA) graft to the left anterior descending coronary artery (LAD) [3]. From that study [3], Nezic and colleagues did not note a particularly pertinent comparison; specifically, the patency comparison derived from the subcohort of restudied patients that received both RA and SV grafts. This risk-matched comparison, with each patient serving as his or her own control, showed an SV failure rate of 41% that was significantly greater than the 29.3% observed for RA (p = 0.039) [3]. Importantly, these results are based on a liberal graft failure definition (> 75% stenosis) and included all RA showing string sign, which would unfavorably affect the RA patency rate. Other investigators have also taken this approach because thrombolysis in myocardial infarct flow (TIMI) is in part a subjective assessment and to a great extent difficult to quantify, so a rational comparative analysis can be undertaken. The long term results of RA grafts with string sign and TIMI 1 and 2 flows are not uniform. There have been reports of resolution of the string sign in patients where the stenosis of the grafted coronary artery became severe.
In the revascularization plus coronary endarterectomy study [4], although the patients were not matched and a small difference in the incidence of risk factors was documented, it is to be expected that this variation would tend to have a greater implication in patient survival than in graft patency, primarily in a short-term follow-up. There were twice as many reoperations, a higher incidence of triple-vessel disease, and a greater number of grafts per patient in the RA population. Yet, postoperative results, including death, were similar in both groups.
The study by Desai and colleagues [5] is a well-designed randomized trial that provided substantial information regarding the superiority of the RA graft compared with the SV graft. This group reported that the presence of angina at 12 months postoperatively was not associated with the incidence of radial string sign overall. Nearly 50% of their patients with a string sign had a TIMI flow 3 and no symptoms of coronary insufficiency. Only the patients with TIMI 1 flow had documented angina at 12 months postoperatively. The authors' methodology a priori considered grafts with string sign to be patent and, hence, it would be a protocol deviation to consider them as occluded vessels at analysis.
In a recent single-center prospective randomized study, Collins and colleagues [6] reported that 5-year patency rates for RA (98.3%) were similar to those observed for ITA grafts but significantly superior to the patency rates for SV (86.4%; p = 0.04). An interesting observation in the study was the frequent occurrence of occlusive disease in the body of the patent SV graft at 5 years, which was absent in the RA grafts.
The reported response of the RA graft to different physiologic events, such as competitive flow, and the positive changes in surgical indications and techniques will continue to have a favorable effect in the long term patency of the RA.
Finally, although one expects that improved graft patency will be associated with better long-term outcomes, it is important not to overlook the currently accumulating evidence of superior survival results when the RA is used as a second arterial conduit as opposed to using SV grafts [2–4].
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