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Eur J Cardiothorac Surg 2000;17:294-304
© 2000 Elsevier Science NL

Postoperative radial artery angiography for coronary artery bypass surgery

^a Department of Cardiothoracic Surgery, Suite 3, Melbourne Heart Centre, P.O. Box 2135, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia
^b Department of Anaesthesia, Melbourne Heart Centre, P.O. Box 2135, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia
^c Department of Cardiology, Melbourne Heart Centre, P.O. Box 2135, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia
^d Department of Nuclear Medicine, Melbourne Heart Centre, P.O. Box 2135, Royal Melbourne Hospital, Parkville, Victoria 3050, Australia

Corresponding author. Tel./fax: +61-3-9342-8908
e-mail: alistair.royse{at}nwhcn.org.au

	Abstract

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 
Objective: To compare radial artery (RA) patency with internal mammary artery (IMA) patency for coronary artery bypass surgery in our early experience. Methods: Symptomatic as well as asymptomatic patients with 1 RA coronary graft underwent postoperative angiography. Each anastomosis was considered separately. A string sign referred to a diffusely narrowed conduit, which did not fill the grafted coronary artery, as well as all occluded conduits. The raw value of P was adjusted for the testing of multiple hypotheses (P'). The patency data for each conduit was divided into two parts. ‘Cut-off’ stenosis for a conduit was the lowest dividing coronary stenosis at which a difference in patency rate with P0.05 occurred. Results: One-hundred-and-twenty-nine patients had 137 radial arteries and 157 angiograms. Only the most recent angiogram was analyzed for each patient at 13±0.7 months (n=129). Overall patency for arterial conduit 91% (n=404) was not different from venous conduit 91% (n=42) and patency for RA 90% (n=226) was not different from IMA 92% (n=178), (P'=0.999). Cut-off stenosis for RA was 70% and IMA was 40%. Patent arterial conduit had a mean coronary stenosis of 85% and non-patent conduit 64%, (P'<0.001). Right coronary territory patency was 82 vs. 94% for other territories (P'=0.022). No overall differences in patency were noted for patients with sequential anastomoses, symptoms or coronary disease at the anastomosis at the time of surgery. Reversible ischaemia was detected in the distribution of only two of 14 string signs in patients undergoing sestamibi exercise protocol following angiogram. Conclusion : There were no differences in patency between radial artery and internal mammary artery at 13 months post-operative. Lower coronary stenosis and right coronary territory predicted lower patency. The clinical importance of a string sign remains to be determined.

Key Words: Radial artery • Internal mammary artery • Post-operative angiogram

	1. Introduction

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 
Radial artery use as a coronary graft was stopped in 1974 [1], when post-operative angiography found early patency to be lower than expected. Late angiography of some patients from the early series found patent and disease free radial artery conduits, which had previously been considered occluded [2]. This led to a revival of interest in this conduit with improved early and intermediate patency [3–5].

We have used radial artery in more than 80% of patients undergoing coronary artery bypass graft surgery [6]. It has also been used in sequential and composite grafts [7] where it increases total composite conduit flow [8]. Consequently, use of the radial artery has been central to our attainment of total arterial revascularization.

Short-term clinical outcome of this conduit and these techniques is now investigated. Early and late angiographic outcome for this conduit is important and has been collected in patients, with and without symptoms, and in all configurations of conduit use.

The aim of this paper is to compare radial artery graft patency with that of the internal mammary artery during our early experience. A secondary aim is to consider the significance of narrowed arterial conduit that we refer to as ‘string sign’.

	2. Materials and methods

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 
Angiograms in patients where at least one radial artery was used were included, all other postoperative angiograms being excluded. Where more than one postoperative angiogram was performed on the same patient, the most recent angiogram was analyzed to prevent double counting of findings. Thus, there was only one angiogram per patient analysed. Where the patient underwent re-operation coronary surgery and radial artery used, the conduits pertaining to the original operation were excluded. Where the conduit but not the native coronary artery was injected at the time of the postoperative angiogram, the angiogram was excluded since no assessment of the degree of competitive flow arising from the native coronary circulation could be made.

All were patients of surgeons at the Royal Melbourne Hospital, and most operations and angiograms were performed at Royal Melbourne Hospital. Patients with postoperative symptoms underwent angiography as part of their clinical assessment and their data recorded. Patients without symptoms volunteered for a postoperative angiogram research study approved by the Human Ethics Committee of the Royal Melbourne Hospital. All gave informed consent and all angiograms were performed at Royal Melbourne Hospital. The protocol for this study includes three angiograms at the 6-, 18- and 60-month time frames; but most of these patients had undergone only the first of these angiograms at the time of this report.

2.1. Definitions
Patency was present when the grafted coronary artery filled with angiographic contrast from the conduit. String sign (Fig. 1) was a diffusely narrowed conduit filled with contrast but not seen to opacify the native coronary artery. When a conduit did not fill with contrast at all, it was considered occluded and was included with string sign for the purposes of this analysis. Both of these latter findings were considered together and referred to as a string sign in the analysis. They both imply inadequate coronary artery perfusion via the graft.

View larger version (106K): [in this window] [in a new window]   Fig. 1. String sign in aorta-coronary radial artery to posterior descending artery. The conduit is diffusely narrowed with contrast in the lumen but no opacification of the coronary artery (dotted line).

Autoregulation is a frequently used and loosely defined term. It describes partial narrowing of arterial conduit, but with graft perfusion of the native coronary artery still present. This was believed to represent the ability of arteries to ‘accommodate’ variation in the degree of the competitive flow by vasoconstriction. It was not known if the string sign represented an extreme form of autoregulation.

Sequential anastomosis (Fig. 2), was a side-to-side anastomosis where the conduit continues on to perform one or more further anastomoses. End-side anastomosis, was the anastomosis at the termination of a conduit irrespective of the construction of any previous sequential anastomoses. Pedicled, a conduit that does not take origin from the aorta. Composite, indicated arterial conduits joined together. Where a radial artery is joined to the left internal mammary artery as a Y graft, all distal anastomoses from both conduits are considered as arising from composite conduit. (Since they are also not attached to the aorta, all are also considered to arise from pedicled arterial conduit). An isolated left internal mammary artery is a pedicled but not a composite conduit.

View larger version (120K): [in this window] [in a new window]   Fig. 2. Definitions: Postoperative angiogram illustrating pedicled left internal mammary artery with sequential anastomosis to first diagonal artery and then end-side anastomosis to left anterior descending artery. A line represents an aorta-coronary conduit to the left anterior descending artery. Radial artery is joined to the left internal mammary artery as a composite arterial graft; and both conduits are therefore also pedicled since neither are attached to the aorta. LIMA, left internal mammary artery.

2.2. Other methods
Since many conduits were used for sequential anastomoses, the conduit segment supplying each coronary anastomosis was considered separately, as the behaviour of each segment may vary depending on differences in the degree of competitive flow at each anastomosis. Thus, the proximal and distal segments of the same conduit were analysed separately in the case of one sequential and one end- side anastomosis being performed from that conduit.

Coronary stenosis was recorded as a continuous scale by cardiologist observer in increments of 5% stenosis. The stenosis affecting an anastomosis was taken to be the most severe stenosis present in the coronary tree between the aorta and that anastomosis. The exact size of the stenosis was not measured nor was edge detection software used. All data was recorded on a custom database written by the principal author. Where an ‘intermediate artery’ was present it was included with the circumflex coronary territory.

Comparison between conduits was performed for arterial conduit only.

Some patients with string sign at angiography volunteered for stress technetium 99m sestamibi (mibi) study. Exercise protocol was according to a standardised bicycle format. Where the patient was unable to exercise adequately, a dipyridamole protocol was used with supplementary exercise on a bicycle prior to injection. Approximately 250 MBq of mibi was injected at rest and single photon emission computed tomography performed after 45 min. Following the stress protocol, a further 750 MBq approximately of mibi was administered 2 min prior to the completion of exercise. Images were then acquired from 30 to 60 min later. A Multispect 3 gamma camera (Siemens, Chicago, IL), was used to acquire 43 views at 18 s per view from 2 heads over 120°. A 64x64 matrix size was utilised. Image reconstruction used a Butterworth labelled filter with a 0.4 cut-off and displayed in a standard fashion. Stress images were gated to assess left ventricular function. The nuclear physician was blinded to the results of angiography. Analysis of rest and stress images was by semi-quantitative means utilizing 20 standard segments [9]. Defects were recorded as normal, infarct (a fixed defect) and reversible ischaemia. The presence of reversibility was assessed qualitatively.

2.3. Statistical analyses
Dichotomous variables were analysed using Fisher's exact test and continuous variables by the unpaired t-test (SPSS V9.0, SPSS Inc., Chicago, IL). To determine relative significance of analysed factors affecting patency, the exact binomial test for the null hypothesis that the odds ratio (OR)=1 was used (StatXact V3.1, Cytel Software Corporation, Cambridge, MA). Where appropriate, the raw value of P was corrected for multiple hypothesis testing (P') according the Ryan–Holm step-down Bonferroni procedure [10]. Statistical significance was considered present if the two-sided P or P'0.05. Continuous variables are expressed as mean±1 standard error.

	3. Results

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 
One-hundred-and-twenty-nine patients in whom 1 radial arteries had been used for coronary artery bypass surgery underwent 157 postoperative angiograms. In these patients, 137 radial arteries were used. The most recently performed angiogram for each patient was analyzed (n=129) at 13.0±0.7 (range 0.1–42.1) months. No gastroepiploic or inferior epigastric arteries were used. Of earlier angiograms excluded, the only finding of relevance was the presence of a radial artery string sign that was later found to be patent.

Two patients had injection of the conduit but not the native coronary arteries and were excluded since no assessment of competitive flow affecting the conduit could be made. One of these patients had a subsequent angiogram for symptoms related to progression of an ungrafted native coronary artery and this latter angiogram is included in this series, being the most recent.

Since many patients received sequential grafting with radial and internal mammary arteries, each distal anastomosis was considered separately (n=446). Of these, 42 were venous conduit and 404 arterial. The patency for venous conduit was 90.5% and arterial conduit was 91.1%, (P=0.781). The remainder of the analysis will consider arterial conduit only (Table 1). Patency for radial artery (90.3%) (22 string signs) was not different from internal mammary artery (92.1%) (14 string signs), (P'=0.999).

The reasons for grafting coronary arteries with stenosis of <50% were not recorded. The surgeons were not subject to any specific unit or research protocol. In some cases differences in preoperative angiogram interpretation by the surgeons may have occurred. One radial artery was grafted to the left ventricular branch of right coronary artery in error, rather than to the posterior descending artery, and that patient represented with postoperative symptoms. However, it is considered that most internal mammary arteries grafted in this fashion were done so in the setting of severe double vessel disease and ‘borderline’ left anterior descending disease. Most radial arteries used in this setting were to vessels in the circumflex territory as sequential grafts using pedicled (Y graft) radial arteries and appear to have been performed where the right coronary artery territory has been severely stenosed; all of these sequential grafts were found to be patent.

The right coronary artery territory had a lower patency rate (81.9%) than for the other two territories (93.9%) P'=0.022 (Table 1), but this was not due to differences in severity of coronary stenosis (Table 3). In this territory, pedicled radial artery appeared to have a lower patency than aorta-coronary radial artery but the difference was not significant after adjustment (Table 4). The coronary stenosis for pedicled radial artery in this territory was 83.2±2.5%, (n=56) and for aorta-coronary radial artery 89.1±2.1%, (n=35), (P=0.107). Patency in both the circumflex and left anterior descending territories was not different from the remaining territories of the heart (Table 1).

In the presence of occluded coronary arteries (i.e. absence of competitive flow), patency for pedicled radial artery was 100% in all coronary territories. Patency for aorta-coronary radial artery was 100% in the right territory (P'=0.999) and 94.4% in the circumflex territory, (P=0.078). There were no aorta-coronary radial artery grafts in the left anterior descending territory.

For comparisons involving only the left anterior descending territory, only composite arterial conduit had reduced patency 89.4% compared to non-composite 100%, (P'=0.042), but composite conduit was grafted to coronaries of lesser stenosis 79.8±2.3%, (n=92) compared to non-composite conduit 86.3±1.8%, (n=80), (P=0.034). There were no other significant differences in any of the comparisons in the other coronary territories.

Sequential anastomoses for all arterial conduits were associated 95.9% patency compared to end-side anastomoses 89.0%, (P'=0.330) (Table 1); and 96.5 vs. 86.5%, respectively, (P=0.019, P'=0.152) for radial artery conduit. When examining anastomotic method in conduit comparison subsets, there were no differences noted (Table 5). Radial artery sequential anastomoses were mostly performed in the circumflex territory (n=73) (86%) and few in the right coronary territory (n=6) (7%) or the left anterior descending territory (n=6) (7%), (P<0.001). Most of the radial artery sequential anastomoses in the circumflex territory arose from a composite origin (n=60) (82%).

Ten patients with 14 postoperative string signs underwent mibi protocol. No evidence of reversible ischaemia was detected in the distribution of 11 string signs and infarction noted in the distribution of one string sign. Reversible ischaemia was noted for a further two string signs, of which one radial artery was grafted to a 40% stenosed posterolateral branch of the right coronary artery rather than to the occluded posterior descending artery. A radial artery was grafted to a 70% stenosed marginal artery in the case of the other reversible defect. Coronary stenosis for these string signs was 56±5% (range 20–80%), (n=14).

The comparisons examined in this paper are not independent and so multivariate logistic regression analysis is not possible. In order to determine degree of importance of these factors we have calculated the odds ratio and P-value by exact means, for dichotomous variables. The most important variable appeared to be lesser coronary stenosis (Table 1). Next the right coronary territory had lower patency than the other two coronary territories with OR=0.3. There were no other factors that attained statistical significance after adjustment for multiple hypothesis testing. There appeared to be a large difference in patency between pedicled internal mammary artery and aorta-coronary internal mammary artery but this did not attain significance, possibly related to the small sample size of aorta-coronary internal mammary artery. There were no differences where the coronary artery was diseased at the anastomosis at surgery; but 13 months may not be sufficient time for progression of native coronary disease to occur.

Specifically, there were no differences noted between the radial artery and internal mammary artery for any of the analyses.

	4. Discussion

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 
In 129 patients we found no difference in patency rates between the radial artery 90.3% and internal mammary artery 92.1% at 13±0.7 months postoperatively (P'=0.999). Patency rates may be affected by a number of factors. The degree of coronary stenosis, conduit used, coronary territory, methods of anastomosis, pedicled or composite origin, the presence of atheroma at the site of anastomosis at the time of surgery and the presence of symptoms as an indication for angiography have been examined. Unfortunately, the distribution of these factors was not uniform and so no single factor can be examined in isolation.

Grafting coronary arteries of lesser stenosis was the most important factor in the rate of string sign (Table 1). Whilst this is not a surprising finding, the coronary stenosis at which a significant increase in rate of string sign (‘cut-off stenosis’) was lowest for the internal mammary artery and pedicled arterial conduit as shown in Table 2. The concept of cut-off stenosis is intended to replicate the clinical decision making processes. These data would suggest that internal mammary artery and pedicled arterial conduit are more resistant to the effects of lesser coronary stenosis. Cut-off stenosis should, however, not be misinterpreted. It does not imply all conduits are not patent if grafted to a stenosis less than that stated in Table 2, nor does it imply absence of string sign for greater stenosis. Nor should excessive importance be placed on these findings since the influences of other factors analyzed in this paper may affect these data.

Our patency rates for all conduit are slightly lower than for previous reports [2,4,5,11–13], but we did not exclude patients from this series if grafting was performed to coronary arteries of moderate stenosis. When we introduced radial artery, our grafting criteria did not change, and we continued to graft coronary arteries of <70% stenosis with arterial conduit. As confidence grew with sequential grafting, we occasionally grafted coronary arteries of <50% stenosis with sequential anastomoses if the termination of this conduit was to a coronary artery of moderate or severe stenosis. It is a common clinical dilemma for surgeons where one coronary artery of 40–70% stenosis is present, with severe stenoses in other coronary territories. Should the surgeon graft these vessels or not? Most previous angiographic reports have selected radial artery grafted to severely stenosed lesions only.

This series did not record the reasons for grafting vessels of moderate or minor stenosis. There may have been differences in angiogram interpretation and there was one instance of erroneous coronary branch selection at surgery. The left anterior descending territory grafting may have been influenced by the notion that the ‘LIMA to LAD’ graft is particularly important, and grafted in the setting of severe non left anterior descending disease even when the left anterior descending disease was not severe. We found that 50% of these grafts remained patent. Most grafts to minor stenosed vessels in the circumflex territory appear to have been with pedicled (composite or Y graft) radial artery as a sequential anastomosis; and where the conduit ended on a severely stenosed vessel in the right coronary artery territory. We found that all six such sequential anastomoses remained patent.

Coronary stenosis assessed by a clinical observer has limitations including subjectivity. Our knowledge of valve surgery and of Bernoulli's theorem, would indicate that the cross sectional area of the lesion with some influence from variations in resistance distal and proximal to the lesion in the form of peak and mean trans-lesion gradients are far more important than percentage stenosis – something not measured by angiography. Thus, the amount of blood flowing through a stenosis will be less for a small coronary artery than for a larger coronary artery with the same percent stenosis. Is the stenosis in the smaller coronary artery therefore ‘more flow limiting’?

There were no significant differences in the degree of coronary stenosis for the comparisons analyzed (Table 3). For patent conduit, sequential anastomoses were performed to coronary arteries of lesser stenosis than for end-side anastomoses 80 vs. 87%, (P'=0.013). There were no differences in patency noted between conduits according to anastomosis method (Table 5).

Our harvest technique and perioperative management of radial artery has been previously reported [6]. Use of postoperative calcium channel antagonists was not analyzed. We have no objective evidence of clinical benefit with these agents.

It is widely believed that all conduits retain higher patency when grafted to the left anterior descending territory. In this series patency of left anterior descending territory was 94 vs. 89% for other territories (Table 1), but the difference was not significant (P'=0.738). The circumflex territory also had high patency but not different from the other territories. Indeed, the key finding was that grafts to the right coronary territory had a lower patency (P'=0.022). This territory is supplied by the termination of a long length of aorta-coronary conduit or pedicled conduit, where there may have also been prior sequential anastomoses along its length (the ‘steal’ phenomenon). Pedicled radial artery appeared to retain a lower patency in this territory than aorta-coronary radial artery, but this was not significant after adjustment (P'=0.133), (Table 4). It is possible that conduits grafted to the right coronary territory are more vulnerable to factors that affect conduit flow as analysed in this paper. In the circumflex territory, pedicled radial artery appeared to retain a higher patency 98.6%, than aorta-coronary radial artery 88.9%, but this was not significant after adjustment (P'=0.672), (Table 4). Most sequential anastomoses in this territory were performed using pedicled radial artery.

The concept that the ‘LIMA to LAD’ graft is the key to coronary surgery may be challenged by parts of these data. Where analysis was restricted to the left anterior descending territory (Table 4), the patency of pedicled left internal mammary artery 93.8% was not higher than for other conduit 100%. Composite arterial conduit did have a lower patency 89.4% than non-composite conduit 100%, (P'=0.042), but was also grafted to lesser coronary stenosis 80 vs. 86%, (P=0.034).

This raises an interesting theoretical consideration. Is it possible that the pressure at any particular point within a composite arterial conduit is lower than for the corresponding non-composite conduit to the same coronary anastomosis; or indeed for a pedicled compared to an aorta-coronary conduit? Arterial conduit may have varying susceptibility to the effects of competitive flow arising from the native coronary circulation. When we considered pedicled (or composite) and aorta-coronary radial artery in the absence of competitive flow (occlusion of the coronary arteries and thus coronary blood flow was entirely graft dependent) there was 100% patency for all pedicled radial arteries. Aorta-coronary radial artery had 100% patency in the right coronary territory and 94% patency in the circumflex territory. With progression of native coronary disease over time (reduced competitive flow) and if arterial conduit does not develop graft atherosclerosis, is it possible that we will see improved conduit patency in the longer term?

Another consideration is whether composite conduit has greater vasoreactivity. Conduit vasoreactivity has been regarded as a non-desirable feature, but preserved reactivity could also be viewed as improved conduit preservation during surgery, which intuitively should be desirable. This particularly relates to free arterial conduits. Construction of the composite conduit usually occurs immediately following radial artery harvest with rapid re-establishment of blood flow into the conduit. This results in a shorter ischaemic time for the radial artery used in a composite conduit compared to use as an aorta-coronary conduit.

The clinical importance of a string sign is currently unknown. We found that 12 of 14 string signs did not have evidence of reversible ischaemia in the distribution of the string sign at mibi protocol stress testing. The coronary stenosis was 56±5% (n=14), suggesting that in some patients, the string sign may be a physiologic vasoconstriction in response to competitive flow from the native coronary circulation. Thus, the angiographic and clinical results may be disparate. We are also unsure if a string sign is a reversible phenomenon. We did see one reversal of radial artery string sign from first to latest angiogram; but the first angiogram was excluded from this series and that conduit was analysed as being patent. There are other reports of reversal of string sign or occlusion [4,5,14–17] including the important report of Acar [2] where this finding stimulated the renewed interest in radial artery.

The series has potential bias in that both symptomatic and asymptomatic patients were included. It would be expected that the patency rate in the symptomatic group would be lower than for those without symptoms and, therefore, also lower overall patency. There was, however, no global (Table 1), nor conduit specific difference in patency between these two groups (Table 6). Thus, inclusion of symptomatic patients may not have introduced much bias.

Surgeons may consider not grafting coronary arteries where atheroma is present, particularly if the artery is diffusely diseased. This is usually because of the impression that late conduit patency will be poor as a consequence of progression of this native coronary disease which will either stenose the anastomosis or alternatively stenose the coronary artery adjacent to the anastomosis. We were able to assess patency according to whether the coronary artery was diseased or normal at the anastomosis at surgery. There was no global (Table 1), or subset difference noted (Table 7). The time to latest angiogram was 13 months and not different for patent or non-patent conduit or for subset comparisons. These data do not yet answer the question of whether disease present at the anastomosis predicts lower late patency, as 13 months may not be sufficient time for progression of native coronary disease to occur. For patients enrolled in our research study, angiograms will continue to be performed as late as 60 months post-operative.

We cannot predict the time course of string sign formation from these data. To do so would require frequent serial angiograms rather than the latest angiogram for each patient as for this series. Also, analysis must assume that the string sign occurred on the day of angiogram, rather than it occurring at a variable time prior to the angiogram.

It is not possible to provide a simple guide to factors predicting arterial conduit patency from these data. There is inter-relationship between the factors analysed, and perhaps there are additional factors not analysed such as technical errors of grafting. An attempt was made to rank these factors in order of relative importance (Table 1) by the application of the exact binomial test for the null hypothesis that the odds ratio=1. This test is applicable to dichotomous variables and so cannot be used with the continuous variables of coronary stenosis and duration post operation. Greater coronary stenosis would appear to be the most important factor predicting patency. This does not, however, answer the clinical question of whether a particular coronary artery in a particular patient with a moderate stenosis should, or should not be grafted. Surgeons need to balance the higher risk of reduced conduit patency rate with the risk of recurrence of angina or infarction from progression of native coronary disease. Individual patient variation makes prediction almost impossible; but it is important to appreciate that lower coronary stenosis is associated with a reduced rate of patency–not absence of patency.

After correction for multiple hypothesis testing, only grafting the right coronary territory remained as an additional significant factor. In the view of the authors, this is probably a reasonable assessment of the importance of these factors; but others may see this as excessively harsh adjustment of significance. Thus raw P and adjusted P' values are presented for completeness.

	5. Conclusion

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 
There were no differences in patency between radial artery and internal mammary artery. Lower coronary stenosis and right coronary artery territory predicted lower arterial conduit patency. The clinical importance of a string sign remains to be determined.

	Acknowledgments

 
The authors wish to acknowledge Dr John Ludbrook (Biomedical Statistical Consulting Pty Ltd.) for his statistical analysis and manuscript review. We thank Mrs Karen Groves for data collation, Dr Paul Soeding for manuscript review and members of the cardiothoracic surgery unit, Royal Melbourne Hospital. Grant assistance from Getz Bros. and Co. (Aust.) Pty Ltd., the Royal Australasian College of Surgeons and the Lew Carty Foundation is gratefully acknowledged.

	Footnotes

 
Presented at the 13th Annual Meeting of the European Association for Cardio-thoracic Surgery, Glasgow, UK, September 5–8, 1999.

	Appendix A. Conference discussion

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 
Dr R. Dion (Brussels, Belgium): Didn't you see more cases of ‘string sign’ with the radial artery graft than with the internal thoracic artery graft?

Dr Royse: The percentage patency for internal mammary artery was 92% and 90% for radical artery, and that was not significantly different.

Dr Dion: But was a ‘string sign’ regarded as a patent sign?

Dr Royse: No, patency was the absence of string sign or occlusion.

Dr Dion: So a string sign was not patency?.

Dr Royse: It was considered not patent.

Dr Dion: Thus a ‘string sign’ was not.

Dr V. Gulielmos (Dresden, Germany): I would like to know, how do you choose the right graft for the right coronary artery, because you used 40 or 42 vein grafts. How do you make your choice?

Dr Royse: The series included both symptomatic and asymptomatic research patients. In terms of the surgeon deciding what graft to use, there was no unit protocol whatsoever. Conduit selection was entirely left to the surgeon's own discretion, and we are simply providing you with the analysis of the angiograms we encountered.

Dr Gulielmos: I am sorry to insist. I would like to know about your personal opinion, how do you personally make your choice of using a radial artery to which coronary vessel or a vein graft to which coronary vessel?

Dr Royse: I use vein grafts in about 1% of my patients and I use the composite Y graft technique in about 90–95% of my patients. So in a triple-vessel coronary patient, for example, they would get a Y graft operation and the right coronary would be grafted with the pedicled radial artery. On the other hand, if the patient needed a single graft to the right coronary artery, such as an aortic valve replacement and single graft, then I would probably use an aorta-to-coronary radial artery in that instance.

Dr D. Hoffman (New York, NY): I seem to be harping on spasm. We have done over 600 radials now with very satisfactory results, using them as independent grafts directly from the aorta, and I would like to ask you, we have switched recently from diltiazem orally in the post-operative period after an intravenous infusion to just using nitrate. What are using?

Dr Royse: Intraoperatively we vasodilate the radial artery using topical and intraluminal papaverine (1 mg/ml) just as we would for an internal mammary artery. We do not use perioperative vasodilators other than low-dose nitrates. Indeed, about 60% or more of our patients will get vasoconstrictors, noradrenaline or metaraminol to support blood pressure if they are getting a low peripheral vascular resistant state. Some years ago we started using calcium channel antagonists orally commencing 1–2 days post-operatively and continued for 3–6 months. We are not convinced by the efficacy of these drugs. We have seen no objective data that use of these agents is of value, but we have continued to use them, perhaps given that there are few side effects. We haven't yet taken the step of formally stopping it.

Dr Hoffman: Indeed, there is in vivo and in vitro evidence that the calcium channel blockers are not effective, and that is what has persuaded us.

Dr J. Pomar (Barcelona, Spain): Do you think there is any relation between the size of the grafts and the patency, because the tendency or the trend is to use a larger caliber graft for sequential grafting just not to unload and maybe can account for that also?

Dr Royse: I am not sure that the conduit size per sé plays much importance, since the flow reserve of the conduit is great, but I think the coronary size and lesion severity probably makes quite a deal of difference to the competitive flow that can come through a lesion. We all know from our experience of valve surgery and from the Bernoulli theorem that the cross sectional area of a stenotic lesion is really the most important determinant of flow. So if you had a 70% lesion of the small coronary artery as opposed to a 70% lesion of the large coronary artery, it may well be that the influence (‘significance’) of competitive flow is different.

Dr Vanermen (Aalst, Belgium): When we talk about degree of stenosis, we do something like ‘lumenology’. Well, a lot of cardiologists will tell you that there is no relation between fractional flow reserve and the kind of lumenology we do. Have you got data on fractional flow reserves of the degrees of stenosis that you were describing?

Dr Royse: We did not have the ability early in the series and we haven't pursued the possibility of quantitative coronary measurements, if that is what you are referring to. We did not perform any intracoronary pressure measurements.

Dr Vanermen: It is not, no. Cardiologists will tell you that sometimes a 30% stenosis on the right, what we would describe as a 30% stenosis, is less significant in terms of fractional flow reserve than a coronary stenosis that we would describe as being 80%. So I wonder whether the degree of stenosis can by very predictive as far as string sign or patency is concerned.

Dr Royse: Absolutely. that is the key finding of this paper, and indeed with virtually the other angiographic papers. The most powerful influence on string sign formation is lowered coronary stenosis, and the mechanism by which that causes a string sign is always assumed and almost certainly is the increased translesion coronary flow as a consequence of that. This translates to a higher coronary pressure distal to the lesion which competes with pressure within the graft (greater ‘competitive flow’, higher fractional flow reserve).

	References

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion 5. Conclusion Appendix A. Conference... References

 

1. Carpentier A. Discussion of: Geha AS, Krone RJ, McCormick JR, Baue AE. Selection of coronary bypass: anatomic, physiological and angiographic considerations of vein and mammary artery grafts. J Thorac Cardiovasc Surg 1975;70:429-430.
2. Acar C., Jebara V., Portoghese M., Beyssen B., Pagny J., Grare P., Chachques J., Fabiani J., Deloche A. Revival of the radial artery for coronary artery bypass grafting. Ann Thorac Surg 1992;54:652-659.[Abstract]
3. Calafiore A., Di Giammarco G., Teodori G., D'Annunzio E., Vitolla G., Fino C., Maddestra N. Radial artery and inferior epigastric artery in composite grafts: improved midterm angiographic results. Ann Thorac Surg 1995;60:517-523.[Abstract/Free Full Text]
4. Acar C., Ramsheyi A., Pagny J.Y., Jebara V., Barrier P., Fabiani J.N., Deloche A., Guermonprez J.L., Carpentier A. The radial artery for coronary artery bypass grafting: clinical and angiographic results at five years. J Thorac Cardiovasc Surg 1998;116:981-989.[Abstract/Free Full Text]
5. Possati G., Gaudino M., Alessandrini F., Luciani N., Glieca F., Trani C., Cellini C., Canosa C., Di Sciascio G. Midterm clinical and angiographic results of radial artery grafts used for myocardial revascularization. J Thorac Cardiovasc Surg 1998;116:1015-1021.[Abstract/Free Full Text]
6. Royse A., Royse C., Shah P., Williams A., Kaushik S., Tatoulis J. Radial artery harvest technique, use and functional outcome. Eur J Cardio-thorac Surg 1999;15:186-193.[Abstract/Free Full Text]
7. Royse A., Royse C., Raman J. Exclusive Y graft operation for multivessel coronary revascularisation. Ann Thorac Surg 1999;68:1612-1618.[Abstract/Free Full Text]
8. Royse A., Royse C., Groves K., Yu G. Blood flow in composite arterial grafts and effect of native coronary flow. Ann Thorac Surg 1999;68:1619-1622.[Abstract/Free Full Text]
9. Kiat H., Maddahi J., Roy L.T., Van Train K., Friedman J., Resser K., Berman D.S. Comparison of technetium 99m methoxyisobutylisonitrile and thallium 201 for evaluation of coronary artery disease by planar and tomographic methods. Am Heart J 1989;117:1-11.[Medline]
10. Ludbrook J. Multiple comparison procedures updated. Clin Exp Pharmacol Physiol 1998;25:1032-1037.[Medline]
11. Calafiore A., Teodori G., Di Giammarco G., D'Annunzio E., Angelini R., Vitolla G., Maddestra N. Coronary revascularization with the radial artery: new interest for an old conduit. J Card Surg 1995;10:140-146.[Medline]
12. da Costa F., da Costa I., Poffo R., Abuchaim D., Gaspar R., Garcia L., Faraco D. Myocardial revascularization with the radial artery: a clinical and angiographic study. Ann Thorac Surg 1996;62:475-479.[Abstract/Free Full Text]
13. Bhan A., Gupta V., Choudhary S.K., Sharma R., Singh B., Aggarwal R., Bhargava B., Sharma A.V., Venugopal P. Radial artery in CABG: could the early results be comparable to internal mammary artery graft?. Ann Thorac Surg 1999;67:1631-1636.[Abstract/Free Full Text]
14. Aris A., Borras X., Ramio J. Patency of internal mammary artery grafts in no-flow situations. J Thorac Cardiovasc Surg 1987;93:62-64.[Abstract]
15. Dincer B., Barner H. The ‘occluded’ internal mammary artery graft: restoration of patency after apparent occlusion associated with progression of coronary disease. J Thorac Cardiovasc Surg 1983;85:318-320.[Medline]
16. Yamaguchi A., Kitamura N., Irie H., Ko T., Kimura S., Shuntoh K. A case report of disappearance of free internal thoracic artery graft stenosis. Nippon Kyobu Geka Gakkai Zasshi 1994;42:2272-2277.[Medline]
17. Hata M., Shiono M., Orime Y., Hata H., Yagi S., Tsukamoto S., Kimura S., Sezai A., Kashiwawzaki S., Choh S., Negishi N., Sezai Y. Spontaneous recanalization of postoperative severe graft stenosis: what is the cause and prognosis of the ‘string sign’ in the internal thoracic artery?. Ann Thorac Cardiovasc Surg 1999;5:52-55.[Medline]

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