Click here to read this article as a CME activity
Ann Thorac Surg 2009;88:1404-1409. doi:10.1016/j.athoracsur.2009.06.010
© 2009 The Society of Thoracic Surgeons
Original Articles: Adult Cardiac
Choice of Conduit for the Right Coronary System: 8-Year Analysis of Radial Artery Patency and Clinical Outcomes Trial
Ignatius E. Hadinataa,
Philip A.R. Hayward, MRCP, FRCSb,
David L. Hare, MBBS, FRACPa,c,
George S. Matalanis, MBBS, FRACSb,
Siven Seevanayagam, MBBS, FRACSb,
Alexander Rosalion, MBBS, FRACSb,
Brian F. Buxton, FRACS, FRCSd,*
a University of Melbourne Medical School, Parkville, Melbourne, Australia
b Department of Cardiac Surgery, Austin Hospital, Heidelberg, Melbourne, Australia
c Department of Cardiology, Austin Hospital, Heidelberg, Melbourne, Australia
d Victorian Heart Centre, Richmond, Victoria, Australia
Accepted for publication June 4, 2009.
* Address correspondence to Prof Buxton, Department of Cardiac Surgery, Austin Hospital, Heidelberg, Victoria, 3084, Australia (Email: brianbuxton{at}ozemail.com.au).
| ADULT CARDIAC SURGERY:
The Annals of Thoracic Surgery CME Program is located online at http://cme.ctsnetjournals.org. To take the CME activity related to this article, you must have either an STS member or an individual non-member subscription to the journal.
|
 |
Abstract
|
|---|
Background: Previous reports have supported the use of bilateral internal thoracic arteries to revascularize the left coronary circulation. If this becomes standardized practice, the optimal conduit for the right coronary system remains to be established. Our objective is to compare the performance of the radial artery versus the saphenous vein when used to graft the right coronary artery or its branches during an 8-year period after primary coronary artery bypass graft surgery.
Methods: The Radial Artery Patency and Clinical Outcomes study is a randomized controlled trial comparing radial artery, saphenous vein, and free right internal thoracic artery. Of the 621 patients enrolled in the study, 465 patients received a graft to the right coronary artery or its branches. The retrospectively compiled database was used to establish patency rates and clinical events among these patients.
Results: Absolute graft patency rates were as follows: radial artery, 86.9% of 68 (95% confidence interval, 76.6% to 93.1%); and saphenous vein, 81.2% of 197 (95% confidence interval, 75.1% to 86.1%). Noninferiority tests show that absolute radial patency to saphenous patency is at least 0.9526 (p = 0.025). Kaplan-Meier estimates of angiographic outcomes show no significant difference (log rank p = 0.22). Cardiac events in the right coronary territory occurred in the radial artery group (1.79%) versus the saphenous vein group (4.93%; p = 0.26). Overall mortality was 8.03% in the radial artery group versus 12.5% in the saphenous vein group (p = 0.23).
Conclusions: The radial artery patency is at least comparable to that of the saphenous vein when grafted to the right coronary artery or its branches. The paucity of clinical events in both grafts is notable. Selection of best conduit may therefore be made according to other factors.
Coronary artery bypass grafting remains an excellent treatment for multivessel obstructive coronary disease with low rates of reintervention and excellent long-term survival and freedom from angina. Graft patency lies at the heart of its procedural success and durability, and our understanding of the interplay between conduit, target, and disease burden continues to develop. Recognition of the differences in size, territory of runoff, and local flow characteristics between different coronary targets make generalizations about the relative qualities of individual conduits somewhat misleading. In particular, the left and right coronary systems enjoy distinct physiologic flow patterns, and (possibly as a result or quite separately) different patterns of atheromatous disease, which, for example, may account for poorer patency of an in situ right internal thoracic artery (ITA) grafted to the right coronary artery (RCA) compared with a left-sided target. Selection of the optimal conduit for the RCA or its branches cannot therefore simply be extrapolated from data arising from left-sided or mixed targets.
The past decade has seen several publications of data supporting the use of bilateral in situ ITA grafting [1–4]. Based on evidence from these studies, and the meta-analysis from Taggart [5], we and others have adopted a policy of bilateral ITA grafting for the left coronary system. The true superiority of bilateral ITA technique remains to be clarified by the Arterial Revascularisation Trial [6], which randomized patients to receive either bilateral ITA or single ITA to the left coronary circulation, but the excellent patency rates and responsiveness to vasodilators and endogenous nitric oxide of these gold standard conduits may well confirm the affirmation by Lytle and colleagues [7] that two is better than one.
The remaining clinically relevant question is which conduit to use for the right coronary circulation. Although good overall patency for radial artery (RA) and saphenous veins (SV) have been described, these are largely observational studies and their results vary greatly [8, 9]. The results of the two randomized controlled trials investigating these conduits are yet to be published [10, 11], but overall outcomes might not be relevant to the RCA when trial grafts have been used to graft the largest non–left anterior descending coronary artery target (usually an obtuse marginal or other left-sided target [12]). We have sought to address this question by analysis of the clinical and angiographic outcomes in patients enrolled in one of these trials who received either an RA or an SV graft to the RCA territory.
Apart from the patency of the conduit, there are many other patient factors to consider such as donor site injury. The RA harvest has been found to be relatively safe with only a small minority of patients experiencing problems (eg, donor site hematoma, finger tip ischemia, dysesthesia, and scar hypersensitivity) related to its harvest [13–15]. The SV harvest may suffer similar adverse effects such as pain and impaired wound healing [16], and a study by Hata and associates [17] found that RA harvest outperformed SV harvest in terms of patient concern (5.2% versus 7.4%) and discomfort (5.2% versus 11.9%). Nonetheless, these adverse events are rare and minor enough to be of secondary consideration to graft patency and cardiac clinical events.
|
Material and Methods
|
|---|
This is a retrospective study of a subgroup of patients enrolled in the Radial Artery Patency and Clinical Outcomes (RAPCO) trial. The RAPCO trial is a randomized controlled trial that assigned 621 patients to either RA, SV, or free right ITA for the largest coronary target other than the left anterior descending coronary artery. All of the RAPCO patients consented to the randomized surgery, follow-up angiogram, and annual clinical follow-up for 10 years after surgery. The RAPCO protocol was approved by the Austin Hospital Human Research Ethics Committee (project no. H95/086). The latest amendment to the RAPCO protocol (approval dated December 3, 2008, project no. H2006/02690) included this retrospective study as a substudy within RAPCO, therefore allowing access to the database and annual clinical follow-up.
The study design of RAPCO has been detailed elsewhere [18]. Briefly, RAPCO randomized patients into two trial arms. The first trial arm included people younger than 70 years of age (<60 years if diabetic) who were randomized to receive either RA or free right ITA to the largest coronary target other than the left anterior descending coronary artery. The second trial arm enrolled patients aged at least 70 years of age (
60 years if diabetic) who were randomized to receive either RA or SV to a similar target. All patients received the gold standard in situ left ITA to left anterior descending coronary artery graft. Further SV (or occasionally an RA) was used for any subsequent grafts.
The SV was used for grafting only if it was without varices, gross wall thickening, or atherosclerosis. The harvesting of the SV was performed through an open technique with minimal conduit handling or distention. The vein was fumigated with papaverine or milrinone, then stored in the same solution of papaverine or milrinone with 50% blood.
The RA was only used for grafting if it measured more than 2 mm and satisfied the conditions for RA harvesting. The RA was removed through an open technique and harvested as a pedicle with the collateral vein, with branches divided between hemostatic clips. Meticulous dissection was performed without touching the RA. The wound was irrigated with a solution of either papaverine or milrinone. The RA was dilated with intraluminal papaverine or milrinone 1 mmol after the distal end of the RA was clipped. The dissection was continued up to the level of the bifurcation of the brachial artery or 2 cm below the elbow, at which site the RA was again separated from the veins and clipped proximally. The RA was stored at room temperature in a solution of 50% heparinized blood and 50% papaverine in Ringer's lactate solution until implantation. Vasopressors were avoided strictly in the perioperative period. Milrinone with aggressive filling was used when inotropic support was required. Postoperatively, patients were treated for 3 months with oral amlodipine.
Each patient was followed up yearly for 10 years after surgery. Study angiograms were scheduled between 0 and 10 years according to another random assignment. Major end points of this study were angiographic patency of the RCA graft, death, and cardiac events (postoperation acute myocardial infarction, angioplasty, and reoperation). Angiograms are reported by 3 independent observers, and grafts are deemed to have failed if there is occlusion, string sign, or greater than 70% stenosis.
This analysis included all RAPCO patients who received a graft to the RCA, posterior descending artery, or left ventricular branch of the RCA using either an RA or SV. Patients receiving a free right ITA to the right system were excluded as this conduit is now reserved for left-sided grafting. Further, we excluded those who received both an RA and an SV to two right coronary system branches as this confounds comparison of clinical outcomes.
|
Results
|
|---|
A total of 416 patients were eligible for inclusion in the study. Among 205 exclusions, 156 did not receive a graft to the RCA territory, 45 received only a right ITA to the RCA territory, and 4 received both RA and SV to the RCA territory. Mean duration of follow-up among the 416 included patients was 8.2 years (95% confidence interval = 7.9 – 8.4 years). The distribution of RCA targets among these patients were 74%, 14%, and 12% for the posterior descending artery, RCA, and left ventricular branch of the RCA, respectively. Because RAPCO has not completed its follow-up yet, angiographic data were available for 255 RCA territory grafts rather than the entire cohort. Figure 1
summarizes the recruitment summary.
View larger version (57K):
[in this window]
[in a new window]
|
Fig 1. Recruitment summary. (RA = radial artery; RAPCO = Radial Artery Patency and Clinical Outcomes; RCA = right coronary artery; RITA = right internal thoracic artery; SV = saphenous vein.)
|
|
The baseline demographics for the two groups are similar (Table 1), except for age. The SV group is significantly older by 3.2 years (p = 0.001), inevitably by RAPCO trial design. The cholesterol profile for each group is also similar (Table 2), with the exception of postoperative cholesterol, with the RA group being 0.21 mmol/L higher than the SV group (p = 0.02). However, both groups had a significant fall in cholesterol between the operative and postoperative periods (paired Student's t test of preoperative versus postoperative cholesterol for each group; p < 0.0001).
Mortality is depicted in Table 3. There was no significant difference in overall mortality in either group, being 7.76% in the RA group versus 12.3% in the SV group (p = 0.23). Nonfatal cardiac events are summarized in Table 4, and are not significantly different at 1.79% in the RA group versus 4.93% in the SV group (p = 0.26).
Absolute angiographic patency rates of the two groups do not differ: 59 of 68 RA grafts to the RCA were patent, an absolute patency rate of 86.9% (95% confidence interval, 76.6% to 93.1%). By comparison, 160 of 197 SV grafts to the RCA were patent, an absolute patency rate of 81.2% (95% confidence interval, 75.1% to 86.1%). Mean clinical follow-up and angiographic times for each graft are shown in Table 5. A noninferiority test with 97.5% confidence found that RA patency to SV patency was at least 0.9226 (p = 0.025, one-tailed). Kaplan-Meier estimates of graft patency rates are shown in Figure 2. Estimated graft patency at 6 years is 90.2% for RA versus 79.6% for SV, with no significant difference (log rank p = 0.22).
The univariate analysis of the risk factors used for calculations of adjusted estimates of graft patency is shown in Table 6. In the whole group, degree of native vessel stenosis is not a significant risk factor for graft failure (hazard ratio, 1.0; p = 0.92). However, it is only a significant risk factor in the RA group (hazard ratio, 0.96; p = 0.047). Among 47 RA grafts, 18 had stenosis in the native RCA vessel, compared with 64 of 88 SV grafts. The RA patency when grafted on native vessels with medium stenosis (
80% stenosis) versus those grafted to a coronary vessel of severe stenosis (>80% stenosis) was 64.7% (95% confidence interval, 41.16% to 82.8%) versus 93.3% (95% confidence interval, 77.63% to 99.2%; p = 0.02).
The actual patency rates for patients exhibiting the risk factors for coronary heart disease is shown in Table 7
(RA group) and Table 8
(SV group), while their cholesterol profiles are shown in Table 9
(RA group) and Table 10
(SV group). These tables show that patency rates for patients who exhibit the risk factors for coronary heart disease are not different from their healthy counterparts for the RA and SV groups.
|
Comment
|
|---|
The merits of using bilateral ITA to graft the left coronary system has been proposed by Lytle and Loop [1], although this remains to be clarified by a randomized controlled trial such as the ongoing Arterial Revascularisation Trial [6]. We have adopted this policy already based on data from Lytle ad Loop [1] and from Taggart's meta-analysis [5] and thus sought to identify the optimal conduit for the right coronary system.
Our finding of no differences in the angiographic profile or major clinical outcomes of the RA compared with the SV when grafted to the RCA system at a mean of 8 years after surgery affords surgeons some flexibility in selecting an appropriate conduit to supplement the ITA-based revascularization. This decision may be based on other factors such as anticipated quality of conduit based on clinical preoperative examination, comorbidity such as peripheral vascular disease, which might impact on the conduit harvest site, and anticipated length of conduit required. Furthermore, this equivalent outcome means that if bilateral ITA is not achievable in a given patient, a single RA may be reserved for left-sided revascularization without compromising the outcome of the RCA graft.
The absolute patency rates reported here (83.6% RA and 76.5% SV) are lower than the latest reported patency rates of RAPCO patients (90% for RA; and 82% SV on a 5-year average follow-up [12]), and there are several possible explanations for this. It may reflect both a longer mean duration of follow-up, with a later drop off in patency. Second, the RCA was likely a smaller target artery and had a smaller territory of runoff than the majority of the RAPCO study grafts, most of which were directed to the left side (indicating that the RCA was thought by the surgeon to be a lower-order target). We have reported previously superior patency in study grafts versus nonstudy grafts [12]. Finally, we have demonstrated that competitive flow in native vessel stenosis of at least 80% is a significant risk factor in RA graft failure on the right side, which may be more frequent a problem than on the left side, thereby reducing mean RA patency to the RCA territory.
Furthermore, unlike in the main trial analyses of protocol-directed angiography results, we have included a mix of both protocol-directed and symptom-directed angiography. This in part explains why patency rates presented here are lower than reported elsewhere from the RAPCO data set, as symptom-directed studies may underestimate overall patency rates [10].
It is not clear whether longer follow-up will highlight a difference in outcomes with these two conduits when grafted to the RCA territory. The patency rates achieved beyond 8 years already are better than reported in historical series that represent a mixture of left- and right-sided targets, and it seems likely that excellence of secondary prevention and careful operative handling has already improved outcomes of SVs to these smaller targets, such that a significant advantage of an arterial graft, if it exists, may not be demonstrable without very large numbers of patients. Nonetheless, it may be that further vein graft atherosclerotic disease might progress beyond a decade of follow-up, even if slowed by secondary prevention measures. It is equally possible however that progression of native disease or aortic disease might compromise free arterial grafts, so these randomized patients will need to remain under annual review, if possible beyond the time frame of the trial.
As patients are presenting with greater comorbidities that may influence the choice of conduit (eg, peripheral vascular disease or deteriorating renal function, which may require hemodialysis), the finding that comparable cardiac outcomes may be achieved allows surgeons to select RA or SV for the RCA system with greater than 80% stenosis according to other patient factors. Nonetheless, the trend toward superior patency of RA, if confirmed by larger numbers when all RAPCO patients have received an angiogram, may give preference to an RA conduit when indicated and feasible.
|
Acknowledgments
|
|---|
The following participants are acknowledged: surgeons, including Jai Raman, MD, PhD; cardiologists, including Mark Horrigan, MBBS, FRACP; and research and editorial staff, including Mardi Malone, Margaret Shaw, Sandra Picardo, Deidre Toia, and Andrew Stewart.
|
References
|
|---|
- Lytle BW, Loop FD. Superiority of bilateral internal thoracic artery grafting: it's been a long time comin' Circulation 2001;104:2152-2154.[Free Full Text]
- Endo M, Nishida H, Tomizawa Y, Kasanuki H. Benefit of bilateral over single internal mammary artery grafts for multiple coronary artery bypass grafting Circulation 2001;104:2164-2170.[Abstract/Free Full Text]
- Lytle BW, Blackstone EH, Loop FD, et al. Two internal thoracic artery grafts are better than one J Thorac Cardiovasc Surg 1999;117:855-872.[Abstract/Free Full Text]
- Buxton BF, Komeda M, Fuller JA, Gordon I. Bilateral internal thoracic artery grafting may improve outcome of coronary artery surgery: risk-adjusted survival Circulation 1998;98(19 Suppl):II-1-II-6.
- Taggart DP. Bilateral internal mammary artery grafting: are BIMA better? Heart 2002;88:7-9.[Free Full Text]
- Taggart DP, Lees B, Gray A, et al. Protocol for the Arterial Revascularisation Trial (ART). A randomised trial to compare survival following bilateral versus single internal mammary grafting in coronary revascularisation [ISRCTN46552265]. Trials 2006;7:7.[Medline]
- Lytle BW, Blackstone EH, Sabik JF, Houghtaling P, Loop FD, Cosgrove DM. The effect of bilateral internal thoracic artery grafting on survival during 20 postoperative years Ann Thorac Surg 2004;78:2005-2014.[Abstract/Free Full Text]
- Georghiou GP, Vidne BA, Dunning J. Does the radial artery provide better long-term patency than the saphenous vein? Interact Cardiovasc Thorac Surg 2005;4:304-310.[Abstract/Free Full Text]
- Mussa S, Choudhary BP, Taggart DP. Radial artery conduits for coronary artery bypass grafting: current perspective J Thorac Cardiovasc Surg 2005;129:250-253.[Free Full Text]
- Buxton BF, Raman JS, Ruengsakulrach P, et al. Radial artery patency and clinical outcomes: five-year interim results of a randomized trial J Thorac Cardiovasc Surg 2003;125:1363-1371.[Abstract/Free Full Text]
- Fremes SE. Multicenter radial artery patency study (RAPS). Study design. Control Clin Trials 2000;21:397-413.[Medline]
- Hayward PA, Buxton BF. Contemporary coronary graft patency: 5-year observational data from a randomized trial of conduits Ann Thorac Surg 2007;84:795-799.[Abstract/Free Full Text]
- Sudhakar CB, Forman DL, Dewar ML, Shaw RK, Fusi S. Free radial artery grafts: surgical technique and results Ann Plast Surg 1998;40:408-412.[Medline]
- Royse AG, Royse CF, Shah P, Williams A, Kaushik S, Tatoulis J. Radial artery harvest technique, use and functional outcome Eur J Cardiothorac Surg 1999;15:186-193.[Abstract/Free Full Text]
- Tatoulis J, Buxton BF, Fuller JA, Royse AG. Total arterial coronary revascularization: techniques and results in 3,220 patients Ann Thorac Surg 1999;68:2093-2099.[Abstract/Free Full Text]
- Kayacioglu I, Camur G, Gunay R, et al. The risk factors affecting the complications of saphenous vein graft harvesting in aortocoronary bypass surgery Tohoku J Exp Med 2007;211:331-337.[Medline]
- Hata M, Raman J, Matalanis G, et al. Post harvest wound infection and patient's perception: comparative study between radial artery and saphenous vein harvest sites Ann Thorac Cardiovasc Surg 2002;8:97-101.[Medline]
- Hayward PA, Hare DL, Gordon I, Buxton BF. Effect of radial artery or saphenous vein conduit for the second graft on 6-year clinical outcome after coronary artery bypass grafting. Results of a randomised trial. Eur J Cardiothorac Surg 2008;34:113-117.[Abstract/Free Full Text]
Top
Abstract
Introduction
