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Interact CardioVasc Thorac Surg 2007;6:298-302. doi:10.1510/icvts.2006.149914
© 2007 European Association of Cardio-Thoracic Surgery
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Institutional report - Cardiac general

Frequent change of procedure during coronary artery bypass surgery suggests insufficient preoperative diagnostic strategy{star}

Rozy Eckardta,*, Bo Juel Kjeldsena, Per Thayssenb, Werner Vachc, Torben Haghfeltb, Poul F. Høilund-Carlsend and LarsIb Andersena

a Department of Cardiothoracic Surgery, Institute of Clinical Research, Odense University Hospital, 5000 Odense C, Denmark
b Department of Cardiology, Odense University Hospital, Odense, Denmark
c Department of Statistics, University of Southern Denmark, Odense, Denmark
d Department of Nuclear Medicine, Odense University Hospital, Odense, Denmark

Received 8 December 2006; received in revised form 26 January 2007; accepted 30 January 2007

{star} The study was supported with a grant from the Danish Heart Foundation.

*Corresponding author. Tel.: +45 6541 2408; fax: +45 6591 6935.

E-mail address: rozy.eckardt{at}ouh.fyns-amt.dk (R. Eckardt).


   Abstract
Top
 Abstract
1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Conclusion
 Acknowledgements
 References
 
We sought to evaluate how often and in what way surgeons change peroperatively their preoperative coronary artery bypass grafting strategy and to what degree these changes affect postoperative graft patency. A series of 109 patients with stable angina pectoris and at least one occluded coronary artery participated. The surgeon filled in a questionnaire pertaining to the planned localization and number of grafts. These estimates were compared to procedures actually performed and with the angiographic outcome six months after bypass surgery. Planned and actually inserted grafts disclosed a discrepancy in 22% of the patients, resulting in a lower or higher number of grafts than pre-operatively estimated. The difference in shift rates between the three sites, left anterior descending, left circumflex, and right coronary artery, was significant (P=0.014). Patency rates were highest when only preoperatively planned grafts were inserted. When shifts occurred, no matter in which direction, it resulted in a decreased patency rate of the inserted grafts. This finding was significant for LAD (P=0.037). Our findings might indicate the necessity of future studies with the use of scintigraphy or fractional flow reserve as physiological adjuncts to angiography for more targeted revascularization.

Key Words: Coronary disease; Revascularization; Graft patency


   1. Introduction
Top
 Abstract
 1. Introduction
2. Materials and methods
 3. Results
 4. Discussion
 5. Conclusion
 Acknowledgements
 References
 
The indication for coronary artery bypass graft surgery (CABG) and the consideration of precise grafting strategy are generally based on symptoms and information derived from coronary angiography (CA). Surgeons assess preoperatively which coronary arteries might be possible to graft on the basis of the ‘eye-balled’ diameter of the diseased coronary artery, the degree of stenosis, and the estimated functional importance of the myocardial area affected by the narrowing of the relevant coronary artery [1]. The surgeons' experience is essential when predicting which arteries should be grafted and the effect of revascularization on vessel perfusion, symptoms, and possible improvement of left ventricular contractile function as reflected by left ventricular ejection fraction (LVEF). During CABG it is yet not possible to measure blood flow in different regions of the myocardium, unless the area is grafted [2, 3]. Despite a well-planned preoperative grafting strategy based on CA, surgeons might change the procedure during the operation, a phenomenon which has never been elucidated.

The purpose of our study was to compare the preoperatively planned grafting strategy in a selected group of patients with ischemic heart disease scheduled for CABG with the grafting procedures actually performed and with the angiographic outcome six months after CABG.


   2. Materials and methods
Top
 Abstract
 1. Introduction
 2. Materials and methods
3. Results
 4. Discussion
 5. Conclusion
 Acknowledgements
 References
 
2.1. Study population

From January 2002 to January 2003 and from January 2004 to April 2005, we prospectively included consecutive patients referred for first time isolated CABG. At six months post surgery, clinical examination and follow-up CA to elucidate graft patency were undertaken.

During the two periods, a total of 163 patients were eligible (Fig. 1). Fifty-four of the patients did, for personal reasons, not want to participate (non-participants), leaving 109 patients as participants. Seventeen of these dropped out before the six-month follow-up CA, leaving 92 patients for before-and-after analysis.


Figure 1
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  		Fig. 1. Flowchart illustrating patient eligibility.

 
The clinical indications for surgery were mainly: angina pectoris and angiographic data that indicated estimated prognostic effect of surgery, progress in symptoms not relieved sufficiently by medication and without possibility of percutaneous coronary intervention, and/or relapse of symptoms after previous angioplasty. The study protocol was approved by the local scientific ethical committee and all enrolled subjects gave written informed consent before inclusion.

2.2. Questionnaire

All twelve cardiac surgeons performing CABG participated in the study by filling-in a preoperative questionnaire on the day of surgery. The surgeons were asked about their expectations with respect to the grafting strategy and results of the surgical intervention based on the preoperative CA. In particular, they should indicate how many grafts he/she expected to insert in each of the three main coronary arteries.

2.3. Coronary revascularization/surgical procedure (CABG)

The criteria for grafting were the generally accepted guidelines that were followed by all 12 cardiac surgeons [4]. Standard operative procedures [5] were performed.

2.4. Coronary angiography (CA)

Selective coronary angiography was undertaken through the femoral approach ad modum Judgkin using Seldinger technique [6]. A significant stenosis was defined as a luminal diameter reduction of 50%. All angiograms were interpreted separately by an experienced cardiologist blinded to clinical data and patient identification.

Graft patency was defined for each region as an open sufficient graft with TIMI flow 2–3 [7] to the receiver-vessel. If a myocardial region was supplied with more than one graft, e.g. left anterior descending (LAD) and a diagonal branch, the patency of the graft to the main coronary artery (LAD, LCx or RCA (right coronary artery)) was considered as the most important. Assessment of patency was performed only for the grafted vessels.

2.5. Graft strategy analysis

The planned number of grafts for each region (as indicated in the questionnaire), were compared to what had actually been done, both overall and stratified by region. More or fewer grafts inserted than expected were denoted as upward- or downward shifts. Rates of patency were compared between the three regions and in dependence on the discrepancy between planned and performed number of grafts.

2.6. Statistical analysis

Continuous variables were expressed as mean value±S.D., and categorial variables were presented as counts and percentages. Continuous data were compared using the Wilcoxon rank sum test. Categorial data were compared using the {chi}2-test with Yates correction and Fisher's exact test when appropriate. Statistical significance was defined as a P<0.05 (two-tailed). Statistical Package for Social Sciences 14.0 was used for analysis. Agreement was expressed in raw percentages and {kappa}-values [8].


   3. Results
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
4. Discussion
 5. Conclusion
 Acknowledgements
 References
 
3.1. Study population

Table 1 summarizes the demographic and angiographic data for patients with follow-up, the drop-outs, and the non-participants. The group of non-participants differed from the participants in that fewer had hypercholesterolemia, their chest pain was less severe, and all were in NYHA class I or II. Otherwise their demographics were in general rather similar to those of the participants. In the follow-up group, the rates of single-, double- and multivessel disease were 11%, 23%, and 66%, respectively. Patients with previous PCI comprised 20%. A little more than half of the follow-up patients were in NYHA class I compared to almost all non-participants, 49% had CCS class III angina vs. 30% of non-participants, and 62% had a normal LVEF compared to 35% of the non-participants. Two percent had a severely reduced LVEF (<30%), and 61%, 34%, and 5%, respectively, had low, intermediate or high estimated operative mortality risk according to EuroSCORE [9].


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  		Table 1 Demographic data of patients with follow-up, drop-outs and the non-participants

 
3.2. Number of grafts

Table 2 and Fig. 2 show the surgeons' preoperatively predicted number of grafts compared with the number of grafts inserted for each region. Overall, in the 327 cases, agreement between the estimated and the actual number of grafts was present in 78%. The agreement was highest for RCA followed by LCx and LAD (87%, 74%, and 73%, respectively).


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  		Table 2 Expected vs. inserted number of grafts (n=109 patients)

 

Figure 2
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  		Fig. 2. Expected vs. inserted number of grafts in different groups (n=109). Group 1: Grafts planned but not inserted; Group 2: Grafts planned and inserted; Group 3: Grafts not planned but inserted. Expected vs. inserted number of grafts in different regions (n=109). Abbreviations: LAD, left anterior descending; LCx, left circumflex; RCA, right coronary artery.

 
For LCx a preoperative ‘overestimation’ of grafts was present (downward shifts 19 and upward shifts 9). In contrast, we observed for LAD (9 vs. 20) and for RCA (5 vs. 9) a preoperative ‘underestimation’ of the number of grafts, but none of the differences in the individual vessels were significant. However, the difference in shift rates in all three sites (LAD, LCx and RCA) were significant (P=0.014). None of the differences (shifts) in number of grafts within a region in the single patient were larger than 1.

3.3. Graft patency

Rates of graft patency are shown in Table 3. Follow-up angiography revealed a tendency of higher patency rates in the region of LAD (91%) compared to RCA (80%) and LCx (78%). Peroperative changes in graft strategy resulted in: planned but not inserted grafts (group 1), planned and inserted grafts (group 2), and inserted but not planned grafts (group 3). There was a tendency of a lower patency rate in the regions of LAD and LCx with group 1 and group 3 grafts. Hence, patency rates were highest when only preoperatively planned grafts were inserted during the operation. When shifts occurred, no matter in which direction, it resulted in a decreased patency rate of the inserted grafts. The results were, however, only significant for LAD.


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  		Table 3 Patency of grafts six months after surgery (n=92). Group I: Grafts preoperatively planned but not inserted; Group 2: Grafts preoperatively planned and inserted; Group 3: Grafts preoperatively not planned but inserted. Displayed are only patencies of grafted vessels

 

   4. Discussion
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
5. Conclusion
 Acknowledgements
 References
 
Our study demonstrated a discrepancy between the preoperatively planned grafting strategy based on CA and the actual number of grafts inserted. We found that the myocardial region supplied by the LAD was consistently grafted with more grafts than preoperatively estimated. In contrast, the region supplied by the LCx was grafted with fewer grafts than predicted. Ultimately, we found a significantly lower patency rate of not planned but inserted grafts, and for planned but not inserted grafts, compared to planned and inserted grafts to the LAD region. A similar tendency was seen in the region of LCx, but was absent in the region of RCA.

A substantial number of patients with follow-up were in NYHA class I, CCS class I–II, and around one-third had a moderately compromised left ventricular function, while only two patients had a severely reduced LVEF, suggesting a selected, low-risk population. However, the clinical characteristics, angiographic features and the mortality risk expressed by EuroSCORE [9] of our study population resembled other studies, except for the age which was somewhat higher than earlier described [10–12]. The latter might be explained by more effective antianginal and prophylactic medical treatment policy and/or differences in PCI strategy, especially as an early aggressive treatment in patients with acute coronary syndrome [13, 14].

Analysis of the data from the surgeons' prediction of outcome (Table 2 and Fig. 2) visualizes a certain degree of ambiguity when predicting the number of grafts needed. When focusing on the expected number of grafts, the agreement was highest for RCA followed by LCx and LAD. LAD was the ‘leading’ shift-artery, suggesting that surgeons are more in doubt when planning grafting of LAD than other main arteries.

The surgeons' predictions were based on visually judged CA performed by cardiologists (eye-balling). As there is a subjective element to visually judged CA analysis, some patients might preoperatively have been incorrectly categorized and this may, at least in part, account for some of the changes from expected to actually inserted number of grafts. However, there may be several other important explanations of the change in grafting strategy. Firstly, surgeons may consider the LAD region as being more essential than other regions, and, thus, when in action, they may tend to supply the diagonals anyhow although this was preoperatively predicted unnecessary. Secondly, the better luminal diameter of the diagonals compared with the branches of the LCx may invite grafting. Thirdly, grafting of the diagonals is ‘geographically’ easier than grafting the marginals. Ultimately, an individual variation in the perception of indication and number of grafts needed cannot be neglected.

In cases in which preoperatively planned number of grafts were in agreement with actually inserted grafts (see Table 3), patency was higher than in cases of preoperatively ‘under-’ or ‘overestimation’ of grafts. However, this result was only significant when changes occurred in the grafting of LAD, which might be explained by the severity of stenosis in the recipient native coronary artery. Even though the surgeons followed the generally accepted guidelines for grafting, some of the stenoses in the grafted vessels or the additional preoperatively not planned grafts might be non flow limiting, e.g. borderline significant stenosis and, therefore, with a higher tendency of occlusion.

Our results cannot be regarded as representative for all patients with chronic coronary artery disease and as representative for all CABG operations. We considered it a strength that twelve cardiac surgeons with each of their skills and approaches participated in this trial aiming at elucidating if the planned procedures were in line with the actually performed ones. Our results do not depict the practice of a single surgeon, but of the ‘average’ surgeon of a single department. In the analysis of patency, only grafts actually performed could be evaluated. Hence, all cases in which a surgeon planned a graft without inserting it were not included in the analysis.

When is a CABG sufficiently prepared? Angiographic visualization of the arteries seems a relatively poor representative of coronary anatomy. Quantitative CA is equally insufficient, provides no functional parameters and is routinely not performed. What is left is the surgeons' experience (and intuition) when predicting the effect of revascularization on perfusion, symptoms, and possible improvement of left ventricular contractile function. The decision of surgery, the grafting-strategy, and the outcome may be significantly improved if the interpretation of angiographic information could be based on functional assessment of ischemia. It appears that improvement in angina is directly related to improvement in perfusion following angioplasty or CABG [15]. Future studies should elucidate the potential benefits of more tailored surgical revascularization, not only on tissue perfusion per se, but also on outcome in terms of alleviation of angina and, importantly, improvement of left ventricular function.


   5. Conclusion
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Conclusion
Acknowledgements
 References
 
This kind of evaluation raises the question of whether it is sufficient to base the diagnostic set-up of patients scheduled for CABG on history and CA alone. Our findings call for future studies evaluating the potential benefits of additional preoperative physiological measurements as adjuncts to CA.


   Acknowledgements
Top
 Abstract
 1. Introduction
 2. Materials and methods
 3. Results
 4. Discussion
 5. Conclusion
 Acknowledgements
References
 
The authors are grateful for funding by the Danish Heart Foundation and the Cardiothoracic Fund, University Hospital of Odense, Denmark.


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

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