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Ann Thorac Surg 2004;78:502-505
© 2004 The Society of Thoracic Surgeons

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Original article: cardiovascular

Intraoperative angiography leads to graft revision in coronary artery bypass surgery

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

Accepted for publication December 29, 2003.

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

	Abstract

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
BACKGROUND: Graft anastomosis quality in coronary artery bypass surgery can be assessed by intraoperative angiography. The aim of the present study was to quantify the on-table revision rate initiated by intraoperative angiography.

METHODS: Intraoperative angiography was carried out in 186 patients undergoing coronary artery bypass surgery, with a total of 427 grafts. The operation was performed on-pump in 34%, off-pump through a sternotomy in 49%, and as a minimally invasive direct coronary bypass grafting (MIDCAB) procedure in 17%. The angiography was performed intraoperatively while the patients were still in general anesthesia, with the possibility for on-table revision. Follow-up angiography was carried out after a mean of 346 days.

RESULTS: Eighteen of 427 grafts (4.2%) were revised due to the findings at intraoperative angiography. Revision rate after on-pump surgery was 1.1%, after off-pump through a sternotomy 6.4%, and after MIDCAB 6.5%. In 6 patients the lesions were located at the distal anastomoses and in 12 patients in the conduit. All but one was successfully revised, and at 1-year follow-up all these 17 grafts were patent.

CONCLUSIONS: Intraoperative angiography saves a potential number of grafts that otherwise could have been occluded. An increased implementation of intraoperative quality assessment in coronary artery bypass surgery can lead to improved outcome.

	Introduction

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Long-term graft patency is of fundamental importance in coronary artery bypass surgery. Graft patency is dependent upon the underlying disease, but also on the surgical technique. Intraoperative quality assessment can be performed by electromagnetic flow meters, Doppler, transit time flow meters, thermal imaging, or coronary angiography [1–6]. Coronary angiography is normally not available in the operation theater, however at our institution fixed angiographic equipment was installed in a specially designed operation room in 1996 allowing coronary angiography to be performed intraoperatively [7].

The aim of the present study was to quantify the on-table revision rate in coronary artery bypass surgery initiated by intraoperative angiography.

	Material and methods

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
In the period 1996 to 2003, 186 patients underwent coronary artery bypass grafting in a combined angiographic and operation theater equipped with a digital subtraction angiographic unit (Advantix [General Electrical Medical System, Milwaukee, WI] replaced in 2000 by Angiostar OR [Siemens, Erlangen, Germany]). They were included by random from patients with angina pectoris referred to elective coronary angiography at out institution. The study comprised 152 males and 34 females, with a mean age of 65 years old (38–84 years old) and a total of 427 grafts (Table 1). All surgery was performed with left internal mammary artery (LIMA) anastomosed to left anterior descending (LAD) artery and reversed saphenous vein grafts (SVG) to the other target vessels. Sixty-three patients (34%) had on-pump coronary artery bypass (ONCAB) grafting, 92 patients (49%) off-pump coronary artery bypass (OPCAB) grafting through a median sternotomy; 31 patients (17%) had off-pump minimally invasive direct coronary artery bypass (MIDCAB) procedure with surgical access through a left thoracotomy. In the MIDCAB-group, 21 patients were operated with single LIMA to the LAD coronary artery, in 10 patients combined with percutaneous treatment of other vessels in a hybrid procedure.

In ONCAB surgery a fully heparinized (Duraflo II) system with spiral gold oxygenator (Baxter, Deerfield, IL) was used in all cases. The activated clotting time was maintained above 480 seconds. Bypass management included membrane oxygenators, arterial line filters, nonpulsatile flow of 2.4 L/min per m², a mean arterial pressure greater than 50 mm Hg, and moderate systemic hypothermia.

The on-table angiography was performed after closure of the chest/thoracotomy while the patients were still under general anesthesia, with the possibility for on-table graft revision. The follow-up angiograms were performed on the same angiographic unit. Both the on-table and follow-up angiographic assessments included evaluation of all vein and LIMA grafts, and at the follow-up angiography the assessment included the native coronary arteries as well. The patency grading was evaluated as described by FitzGibbon [8], where grade A was defined as excellent graft with unimpaired run-off, grade B as stenosis reducing the diameter of more than 50% of grafted artery, and grade O as occlusion.

Data were analyzed using the statistical program SPSS (version 10.0 for Windows; Chicago, IL), and expressed as frequency, mean, and standard deviation. The Student's t test was used to compare continuous variables and X-square test to compare categorical variables. Significance was defined as p less than 0.05.

	Results

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Eighteen of 427 grafts (4.2%) were revised due to the findings at intraoperative angiography. The findings are summarized in Table 2. Of the revised grafts, there were 12 LIMA to LAD, two SVG to the diagonal, two SVG to circumflex, and two SVG to the right coronary artery. The overall LIMA and SVG revision rate after ONCAB surgery was 1.1%, after OPCAB 6.4% and after MIDCAB 6.5% (Table 2). A significant lower revision rate was found after on-pump surgery compared to off-pump (OPCAB and MIDCAB) surgery (p < 0.01). In 6 patients the lesions were located at the distal anastomoses and in 12 patients in the conduit. Of the 12 revisions with dysfunction located in the conduit, there were seven LIMA grafts and five SVG. One LIMA graft was constructed on-pump, another LIMA by a MIDCAB procedure, and in the remaining 10 patients (5 LIMA and 5 SVG) surgery was performed off-pump. Of the six revisions with dysfunction located at the distal anastomoses, there were five LIMA grafts and one SVG. One LIMA graft was constructed on-pump, one LIMA graft by a MIDCAB procedure, and in the remaining 4 patients (3 LIMA and 1 SVG) surgery was performed off-pump.

At follow-up of mean 346 days (72–732 days), 148 of 160 LIMA grafts (93%) were patent compared with 169 of 209 vein grafts (81%; p < 0.01). The patency of SVG was significantly poorer compared with patency of the LIMA grafts after OPCAB surgery (p = 0.016; Table 2). No other differences in patency rates were found.

	Comment

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
The observation that 18 of 427 grafts (4.2%) had to be revised due to the findings at the intraoperative angiography clearly demonstrates the importance of intraoperative angiography in coronary artery bypass surgery, because successful correction was performed in all except 1 patient. These grafts would probably otherwise have been occluded.

The revision rate was significantly lower after on-pump surgery (p < 0.01), suggesting that performing coronary artery bypass surgery on a beating heart places greater demands on surgical skills despite the availability of "stabilizers." The "learning curve" associated with the introduction of a new operative procedure could also have played a role, albeit limited, because the revision rate did not change during the course of the study. These findings underline the need for closely on-table quality assessment during introduction of new techniques.

There is a need for quality assessment in coronary bypass surgery to obtain optimal results. This can be achieved by transit time flow measurement, Doppler, thermal imaging, or angiography [1–6]. Of these methods coronary angiography is accepted as the "golden standard" for the assessment of graft patency. It is, however, costly, invasive and frequently not available in the operating room. In 1996 we built an integrated operation theater and angiographic suite allowing coronary angiography to be performed on-table [7]. In addition to allowing percutaneous coronary intervention and surgery to be performed in the same procedure in the hybrid approach, on-table assessment of graft patency can be performed with the state-of-the-art cardiac catheter lab quality images. A team from the catheter lab performed the on-table angiography and this ensured both high image quality and the maintenance of a low complication rate. We had no complication that could be connected to the performance of on-table angiography.

The significance of the results obtained at intraoperative angiography for later patency needs to be documented. In a few articles it is reported that between 27% and 73% of significant lesions found at intraoperative or early postoperative angiography resolved at later follow-up angiography [6, 9, 10]. Some lesions found at on-table angiography may be caused by clots, edema, or intramural hematoma and thus resolve without intervention. Spasm that is quite frequent at on-table angiography [6, 11] may lead to diminished flow and imitate a lesion, but will resolve after the immediate postoperative period, although it may cause graft occlusion. Caution is therefore necessary in interpreting on-table angiography and thus avoiding unnecessary revision. Strict angiographic guidelines for when to revise a graft were therefore difficult to establish. We have revised occluded grafts or grafts that obviously would have occluded. A high number of conduit failures have made us more cautious in graft harvesting and in the quality assessment of the graft to be harvested.

Transit time flow measurement has also been reported to be a good method for on-table graft quality assessment [1–4]. We have, however, previously demonstrated a poor correlation between transit time flow measurement and graft patency as demonstrated by angiography [12]. Transit time flow measurement is performed just after completion of the anastomosis with the chest still open. With closure of the thoracic wall the graft can alter position giving other results at the following on-table angiography. Some of the failures found by intraoperative angiography performed after closure of the chest, as strangulation and kinking, have most likely occurred after the transit time flow measurement. This could partly explain the discrepancy between on-table angiography and transit time flow measurement. Coronary angiography performed after chest closure should be a good indicator of graft patency.

The on-table and intermediate patency rate in this material is in accordance with the literature [6, 9, 10, 13]. Kim and colleagues [14] reported that the patency rate of vein grafts after off-pump surgery was lower than of the arterial grafts and also lower than vein grafts after on-pump surgery, the latter probably due to insufficient anticoagulant therapy in the off-pump group. The follow-up patency rate of the saphenous vein grafts was lower than the patency rate of the arterial grafts after off-pump surgery (p = 0.016), but no difference were found after on-pump surgery. There was no statistically difference between saphenous vein graft patency after on-pump compared to off-pump surgery. Thus there is no statistical evidence to support Kim's hypotheses, but a more aggressive anticoagulation therapy may be indicated after off-pump surgery.

In conclusion, on-table angiography saved a potential numbers of grafts that otherwise would have been occluded, and must be considered a necessary tool in the quality assessment of coronary artery bypass surgery. The introduction of new techniques like off-pump surgery in combination with on-table coronary angiography is useful. In general, graft quality assessment is necessary in coronary bypass surgery to achieve an optimal on-table result.

	Acknowledgments

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Financial support was provided in part by a research grant from Stokbak Heart Foundation, Oslo, Norway.

	References

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 

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