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Ann Thorac Surg 2002;73:813-818
© 2002 The Society of Thoracic Surgeons

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Original article: cardiovascular

The importance of intraoperative angiographic findings for predicting long-term patency in coronary artery bypass operations

^a The Interventional Centre University of Oslo, Oslo, Norway
^b Department of Thoracic Surgery Rikshospitalet, University of Oslo, Oslo, Norway
^c Department of Cardiology Rikshospitalet, University of Oslo, Oslo, Norway
^d Department of Radiology, Rikshospitalet, University of Oslo, Oslo, Norway

Accepted for publication November 1, 2001.

* Address reprint requests to Dr Hol, The Interventional Centre, Rikshospitalet, N-0027 Oslo, Norway
e-mail: per.kristian.hol{at}rikshospitalet.no

	Abstract

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Background. The quality of anastomosis is the cornerstone in coronary artery bypass operations. Intraoperative coronary angiography confirms graft patency with the possibility to revise graft failure. The aim of this study was to describe the lesions found at "on-table" angiography, and to evaluate the significance of these immediate angiographic findings for the long-term patency.

Methods. A total of 57 grafts (42 left internal mammary artery grafts and 15 saphenous vein grafts) in 45 patients who underwent off-pump coronary artery bypass operations were included. On-table angiography was carried out with fixed angiographic equipment installed in the operating room. Follow-up angiographies were performed at 3 months and at 12 months.

Results. The most frequent finding in an on-table angiogram was spasm, which was not present at follow-up. Out of nine kinks, only one developed into a significant stenosis at follow-up. Of 44 grafts that were normal on-table, 37 (84%) were normal at the follow-up. Of 11 grafts with significant lesions on-table, eight (73%) were normal at the follow-up. Five percent of the grafts were revised because of the on-table angiography.

Conclusions. On-table angiograms can be occasionally difficult to interpret because not all findings are important for later patency. Optimal results on-table predict good long-term results with a negative predictive value of 0.84, whereas significant lesions on-table have less impact on the follow-up results because the positive predictive value was only 0.38.

	Introduction

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
The quality of the graft, as well as of the anastomosis, is fundamentally important for the results of coronary artery bypass operations. Although Doppler [1] and transit time flow measurements [2, 3] are exact and reproducible, the ability to detect moderate or even severe stenosis at the anastomotic site is limited [4–6]. Coronary angiography is the most commonly used tool for evaluation of the coronary arteries, both preoperatively and postoperatively. Intraoperative angiography has advantages compared with postoperative catheterization, such as instant confirmation of graft patency and the possibility for immediate revision of graft failure. Intraoperative angiography can be performed with fixed angiographic equipment when an operation is carried out in the catheterization laboratory [7], with a portable C-arm in the operating room [8] or with fixed angiographic equipment installed in the operating room [9]. Fixed installation in the operating room entails that angiography is easily available when needed and gives the opportunity of obtaining multiplanar views of grafts and anastomoses with images of high quality. Our hospital has had such a combined angiography and operating room at the Interventional Centre (Oslo, Norway) since 1996 [10].

The aim of this study was to describe the lesions found at "on-table" angiography in off-pump coronary artery bypass operations, and to compare the intraoperative angiographic findings with angiographic results after 3 and 12 months.

The regional ethical committee approved this study.

	Material and methods

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A total of 57 grafts, 42 left internal mammary artery (LIMA) grafts and 15 saphenous vein grafts, were studied in 45 patients who underwent off-pump coronary artery bypass operations from August 1996 to April 1999 (Table 1). All patients were included after informed consent. There were 41 male and 4 female patients, with a mean age of 63 years (range, 38 to 79 years). In 19 patients with single vessel disease, the LIMA was anastomosed to the left anterior descending artery through a left anterior small thoracotomy operation. In 8 patients the left anterior small thoracotomy operation was combined with concomitant percutaneous transluminal coronary angioplasty or stenting of the circumflex or right coronary artery, a so-called hybrid approach. A total of 27 patients were thus operated on through a thoracotomy. Eighteen patients were operated on through a sternotomy allowing full revascularization, but without the use of cardiopulmonary bypass.

All operations were performed in a combined catheterization and operating room, containing fixed angiographic equipment (Advantx; General Electrical Medical System, Milwaukee, WI). On-table angiography was carried out after closure of the wound while the patient was still on general anesthesia. Catheters (6 French LCB, RCB or IM curve style; Boston Scientific Scimed, Maple Grove, MN) were introduced through a right femoral artery sheath to inject nonionic contrast material (Visipaque 320 mgI/mL, Nycomed, Oslo, Norway) in all grafts.

The angiographies were performed by one member of a team consisting of two radiologists and one cardiologist, and they were evaluated visually by three independent readers. Discrepancies between the readers were settled by consensus. The lesions were defined following FitzGibbon’s classification as normal (less than 50% reduction in diameter), significant (more than 50% reduction in diameter), or occluded [11]. Narrowing of the grafts or coronary arteries that were not present at the preoperative studies, which dissolved partly or completely by injection of nitroglycerin or papaverine, were defined as spasms. Kinking was defined as a sharp angle of the graft presenting a contrast defect. Lesion localization in the most distal end of the graft was called anastomosis proper; lesions in the native coronary artery at the proximal portion of the anastomosis were called heel; and lesions in the native coronary artery at the distal part of the anastomosis were called toe.

A follow-up angiography of all grafts and native coronary vessels was carried out with the same angiographic equipment by the same personnel after 3 months in 44 patients, and after 12 months in 35 patients.

Data of this study are presented as mean, range, or percentages. The sensitivity, specificity, and positive and negative predictive values of intraoperative angiography as predictor of follow-up angiography were calculated on the basis of Table 2. Significant lesions and occlusions in these analyses were grouped together as pathologic findings.

	Results

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

The angiographic findings are summarized in Table 2. Forty-four of 57 grafts (77%) were normal on-table compared with 45 of 57 (79%) at follow-up. Thirteen of 57 grafts (23%) had pathologic findings on-table (11 significant lesions and two occlusions) compared with 12 of 57 (21%) at follow-up (seven significant lesions and five occlusions). The sensitivity and specificity of intraoperative angiography were 0.42 (5 of 12) and 0.82 (37 of 45), respectively, whereas the positive and negative predictive values were 0.38 (5 of 13) and 0.84 (37 of 44), respectively.

Subgroup analyses are shown in Table 3. The most frequent finding on-table was spasm, appearing in 50% of the grafts (Fig. 1). Twenty-four of the 42 LIMA grafts (57%) and 5 of the 15 vein grafts (33%) had spasms on-table. Approximately the same degree of spasms occurred in sternotomy patients as in thoracotomy patients. None of the spasms were found at 3- and 12-month follow-ups. A total of nine kinks (Fig 2) were found in 5 of 42 LIMA grafts (12%) intraoperatively. At 3 months follow-up, five of these nine kinks disappeared (three were unchanged), whereas in one a significant lesion appeared at the site of a kink. Two of 42 LIMA grafts (5%) had a dissection at the distal part of the graft. Of these, one graft was occluded, the other was found open both at 3 and 12 months follow-up (Fig 3).

View larger version (122K): [in this window] [in a new window]   Fig 1. Most frequent finding at on-table angiography was spasm, which can be difficult to distinguish from stenosis of other causes. Spasm was not present at follow-up angiography.

View larger version (117K): [in this window] [in a new window]   Fig 2. A kink demonstrated in the distal part of a left internal mammary artery graft at on-table angiography. A total of nine kinks were found in this study, and no revision was performed. In only one case a significant lesion was found at follow-up in a patient free of angina.

View larger version (117K): [in this window] [in a new window]   Fig 3. One of two left internal mammary artery grafts with dissection at on-table angiography was left untreated. At 12 months follow-up the dissection was still present (arrow) and the graft fully patent.

Ten of 42 LIMA grafts (24%) and 1 of 15 vein grafts (7%) had significant lesions on-table. Of these 11 grafts, eight were normal at 3 months follow-up, whereas three were unchanged. Six of these 11 significant lesions were localized at the anastomosis proper (Fig 4), three in the heel, one in the toe, and one in the graft itself proximal to the distal anastomosis.

View larger version (114K): [in this window] [in a new window]   Fig 4. Significant lesions were most frequently found at the anastomosis proper. Significant lesion on-table was not a good predictor of later patency because 73% disappeared at follow-up.

Three of the 57 grafts (5%) were revised as a consequence of the on-table angiography. Two of the revisions were caused by occluded LIMA grafts. One of these had a dissection distally in the LIMA, and after revision there was still no flow into the left anterior descending artery. The left anterior descending artery was, however, of small caliber, and further attempt of revascularization was not performed. At 3 months follow-up the patient had no angina. At revision of the other occluded LIMA graft, an intimal flap was removed, and the repeated on-table angiography showed a perfect anastomosis. The third graft to be revised was a vein to the obtuse marginal with a 90% stenosis at the anastomosis proper. Strangulation at the distal anastomosis was found at revision, and a perfect graft was demonstrated at the repeat angiography.

The intraoperative angiography added about 30 minutes to the total operative time, up to 60 minutes with a few patients.

At the on-table angiography, 40 of 42 LIMA grafts (95%) and 15 of 5 vein grafts (100%) were patent, giving an overall patency rate of 96% (55 of 57). At the latest of the 3- or 12-month follow-ups, 39 of 42 LIMA grafts (93%) and 13 of 15 vein grafts (87%) were patent, giving an overall patency rate of 91% (52 of 57).

	Comment

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Although some reports of on-table coronary angiography exist [9, 12–15], most of them with the portable C-arm, little is known about the on-table angiographic findings and its significance for later patency.

Our study with a low positive predictive value of 0.38 demonstrated that on-table angiographic findings did not predict poor long-term patency. A normal on-table finding is more predictive of a normal finding at follow-up (negative predictive value, 0.84), although some angiographic changes arise at follow-up.

Multiple factors can cause these changes in angiographic findings. Certain abnormalities in the on-table angiograms, such as spasm, vessel wall edema, thrombus formation, or wall hematoma, may resolve spontaneously, resulting in normal angiograms at the follow-up. The natural progress of the coronary disease itself and intimal hyperplasia can lead to progression of the angiographic findings or appearance of new lesions at follow-up. After operation, lesions can be also caused by sutures that are too tight, as demonstrated in the vein graft that was successfully revised.

The technique of intraoperative angiography is of importance. The accessibility of fixed angiographic equipment in the operating room, and the use of a radiologist or a cardiologist to perform the angiographic examination, provides angiograms of good quality in all patients without procedure-related complications. The disadvantage is the prolongation of the operative time by 30 to 60 minutes.

In an operation through a minithoracotomy the access is limited as compared with an operation through a sternotomy. However, no difference was found between operations performed through a sternotomy and thoracotomy with regard to the number of grafts with spasm, dissection, or intraoperative graft occlusion, and normal intraoperative findings.

Spasm, the most frequent on-table finding in our study, did not always disappear completely after injection of papaverine or nitroglycerin. The snaring sutures can cause a spasm in the coronary arteries close to the anastomosis. Widespread spasm was distinguished from disseminated atherosclerotic disease by performing repeated angiography after injection of papaverine or nitroglycerin or by comparing the on-table angiogram with the preoperative study. A localized spasm can be difficult to distinguish from a stenosis by other causes. A spasm can cause restricted flow and thus increase the possibility of graft occlusion. We did not register any relationship between on-table spasm and later occlusion. The two vein grafts that were normal on-table and occluded after 3 months had both poor run-offs in the native coronary vessel, demonstrating the importance of unrestricted flow for later patency.

Both Izzat and colleagues [13] and Mack and colleagues [15] reported graft revision to be performed in 8% after routine intraoperative angiography. In this study, intraoperative angiography led to a revision of 3 of 57 grafts (5%) and revealed lesions that probably should have been revised. Occluded grafts should always be revised. When to perform graft revision after demonstrating a significant lesion on-table remains to be clarified. Before operating we did not define criteria of when to revise significant lesions, and our material contained too few patients with abnormal grafts to elucidate which would have benefited from graft revision. Lazzara and colleagues [16] reported 2 patients with a kink proximal to the distal anastomosis that was corrected immediately as a consequence of on-table angiography. Our series, with the development of only one significant lesion in 9 patients with kinking, demonstrates that revision might be unnecessary. The one LIMA graft with a dissection on-table and with unobstructed passage of contrast material at 3 and 12 months follow-up, indicated that even dissections may be left untreated, although we would normally make a graft revision after on-table demonstration of such lesions.

Although costly and time-consuming, intraoperative angiography may have a place in surgical coronary revascularization. Transit time flow measurement is a much simpler, less costly, and time-consuming method, but it has limitations in detecting moderate or even severe stenosis at the anastomotic site [4–6]. Evidence-based practice is important when new treatment modalities are implemented, and the only way to obtain evidence is to use all available means. Therefore intraoperative angiography, together with transit time flow measurements, should be used to demonstrate the accuracy in off-pump coronary artery bypass operations. But further studies are needed to correctly interpret on-table angiographic findings and define its role for intraoperative assessment of graft patency. Meanwhile, on-table angiography has to be interpreted with care.

In conclusion, on-table coronary angiography gives valuable information of graft assessment, but can be difficult to interpret because not all findings are of importance for later patency.

	Acknowledgments

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
We thank Kjell Levorstad, MD, PhD, for evaluation of the angiograms, and Nils Heimland for processing of the angiographic images. Financial support was provided in part by a research grant from Haakon and Sigrun Oedegaard Foundation, Oslo, Norway.

	References

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 

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