Impact of sequential grafting of the internal thoracic or right gastroepiploic arteries on multiple coronary revascularization

Cardiovascular Surgery, Vol. 8, No. 5, pp. 386–392, 2000  2000 The International Society for Cardiovascular Research. Published by Elsevier Science Ltd All rights reserved. Printed in Great Britain 0967–2109/00 $20.00

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Impact of sequential grafting of the internal thoracic or right gastroepiploic arteries on multiple coronary revascularization M. Ochi, K. Yamada, Y. Ishii, H. Ogasawara, M. Fujii, T. Yajima, S. Kanno and S. Tanaka Department of Surgery II, Cardiovascular Surgery, Nippon Medical School, 1-1-5 Sendagi Bunkyoku, Tokyo, 113-8603, Japan Objective. The aim of the study is to clarify the efficacy of the sequential anastomotic technique of the arterial conduits for multiple coronary revascularization. Background. The internal thoracic artery (ITA) is now widely accepted as a durable conduit for myocardial revascularization. The right gastroepiploic artery (GEA) has been developed as a third in situ arterial graft with an outcome similar to that of the ITA. Material and method. One hundred and forty five consecutive patients (116 male, 29 female, mean age 60.4 yr) who received sequential grafting of either the ITA or GEA or both were retrospectively analysed. Results. Sequential anastomoses were performed in 121 in situ left ITAs, 36 in situ GEAs and 12 composite right ITAs. No in situ right ITA was anastomosed sequentially. Two to six vessels (mean 3.8) were revascularized for each patient. Of the total 543 bypassed vessels, 432 (79.6%) were reconstructed with the arterial grafts. In 85 patients with quadruple bypass or more, the arterial grafts were able to reconstruct 266 out of 360 (74.0%) target vessels. Seventy one patients (49.0%) were revascularized without venous grafts. The arterial grafts could revascularize 293 out of 310 vessels (94.5%) in the LAD 苲 Diagonal region, 83 out of 113 (73.4%) in the distal RCA or Cx region. There were no cardiac events responsible for the arterial grafts in the follow up period. Conclusion. In light of our experience, multiple revascularization with in situ arterial sequential grafts is feasible. Aggressive application of this technique provides patients requiring multiple coronary revascularization with favorable long-term results.  2000 The International Society for Cardiovascular Research. Published by Elsevier Science Ltd. All rights reserved Keywords: internal thoracic artery, right gastroepiploic artery, sequential anastomoses

Introduction It is generally accepted that the use of the internal thoracic artery (ITA) for myocardial revascularization provides better results than that of saphenous vein grafts because of higher patency rates and a lower mortality and morbidity [1–4]. Several reports have shown that the use of bilateral ITAs further

Correspondence to: Masami Ochi M.D.

386

decreases the recurrence of angina and reoperations [5–7]. The right gastroepiploic artery (GEA), on the other hand, has been developed as a third in situ arterial graft and has been proven to be a reliable alternative to the saphenous vein graft with mid-term patency and an outcome similar to that of the ITAs [8–13]. Over the last seven years, our revascularization has been based on the following strategies: use of as many in situ arterial grafts as possible to the left anterior descending artery (LAD) and diagonal or to CARDIOVASCULAR SURGERY

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the Ramus intermedius branch region which is the most important part of the coronary system, and to the distal part of the circumflex artery (Cx) or right coronary artery (RCA) where vein grafts are not reliable for patency. In order to achieve this goal, sequential anastomotic techniques have been aggressively applied whenever possible. Veins were used as the graft of choice for the proximal segment of the Cx or RCA. Increased numbers of grafted vessels with in situ arterial grafts, of which the characteristics and longterm outcome are well-defined, can be expected to provide a better postoperative cardiac status. The aim of this study was to clarify the efficacy of the technique for multiple coronary revascularization by analyzing 145 consecutive patients who underwent coronary artery bypass grafting (CABG) with in situ arterial sequential grafting.

Material and methods Among 520 patients who underwent isolated CABG from March 1991 to May 1998, there were 145 patients (28.0%) who received sequential graftings of either the in situ left ITA (LITA) or GEA or both. They consisted of 116 male and 29 female patients with an age ranging from 29 to 77 yr old (mean age, 60.4 yr). Thirty nine patients had double-vessel disease and 106 triple-vessel disease. Twenty one patients had a left main trunk lesion. One hundred and twenty six patients underwent elective and 19 patients urgent surgery. Acute myocardial infarction had been complicated in 12 patients. Seventy one patients were diabetic (Table 1). None of the in situ right ITAs (RITA) were anastomosed sequentially because of anatomical reasons. Instead, sequential anastomoses were constructed with a composite-RITA by attaching its proximal end to the side wall of the LITA in some patients. None of the other free arterial conduits, such as the radial artery or inferior epigastric artery, were used in this series.

Operative technique The ITA was primarily semi-skeletonized with a little fat and accompanying veins along its entire length. On the left side, the mediastinal fat pad was always dissected bluntly off the median aspect of the pleura to the level of the phrenic nerve to make a deep sulcus between the pleura and the pericardium so that the LITA could take the shortest course to the coronary artery without compression of the lung. The pleural cavity was entered if necessary. The GEA was dissected as a pedicle along the greater curvature of the stomach from the pylorus to the point where its pulsation became weaker. The artery was brought into the pericardial cavity anterior to the pylorus through a small opening on the diaphragm just above the left lobe of the liver. No standards for the free flow of the arteries for the sequential grafts were instituted. Selective or semi-selective angiography of the GEA was performed in all patients in order to evaluate the adequacy of the size of this artery for the sequential grafting. In performing sequential anastomoses of the GEA, the diameter of the distal end of the artery at the presumed anastomosis must be no smaller than 2 mm on the angiogram. In the ITAs, however, only the length of the artery was our concern for the sequential grafting. No vasodilating agents were administered routinely in the arteries unless a spasm was suspected. In performing sequential anastomoses, the proximal side-to-side anastomosis was constructed first. All of the proximal anastomoses were constructed so that the graft was attached to the coronary artery longitudinally (paralel anastomosis). Unlike a venous graft, the so-called ‘diamond anastomosis’, in which the graft is attached to the coronary artery perpendicularly, was not employed to avoid ‘gull wing’ deformity. The length of the arteriotomy of the graft for the side-to-side anastomosis was a little longer than that of the coronary artery. Anastomosis was carried out with a single 8-0 Prolene (Ethicon, Inc., Somerville, NJ) continuous suture with the aid of four times magnification. Further details of the techniques of the sequential anastomoses have been described previously [14].

Table 1 Patients characteristics

Statistical method

Age Male:female Vessels involved

The cardiac event-free curve is expressed according to the Kaplan–Meier method. In calculating the cardiac event-free rates, the following parameters were included; acute myocardial infarction, recurrence of angina and requirement of PTCA or re-CABG.

Diabetes IABP AMI Urgency

29–77 (mean 60.4) 116:29 Double Triple LMT 71 7 12 19

39 106 21

LMT: left main trunk lesion; IABP: intra-aortic balloon pump; AMI: acute myocardial infarction

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Results There were three operative deaths. The causes of death were pre-existing infection or respiratory fail387

Impact of sequential grafting on multiple coronary revascularization: M. Ochi et al.

Figure 1 The number of patients in accordance with the number of bypassed vessels

ure, none of which were related to the surgical technique. Two to six vessels with a mean of 3.8 vessels were revascularized for each patient (Figure 1). All the arterial grafts were used as an in situ graft except for 28 free RITAs which were used by attaching the proximal end of the artery either to the side wall of the LITA to make a composite graft (compositeRITA, 24 patients) or directly to the ascending aorta (4 patients). Sequential anastomoses were performed in 121 LITAs, 36 GEAs and 12 composite-RITAs (Table 2). Triple sequential anastomoses were performed in 4 LITAs and 4 GEAs. In the LITA sequential grafting, the distal anastomosis was to the LAD in 115 patients. Of the total 543 bypassed vessels, 432 (79.6%) were reconstructed with the arterial grafts (Figure 2). In 85 patients with quadruple bypass or more, the arterial grafts were able to reconstruct 266 out of 360 (74.0%) target vessels.There were 71 patients (49.0%) who were revascularized without venous grafts. In this group of patients, the LITA was utilized in all patients. The GEA was utilized in 39 patients and contributed to triple to hexatuple bypass as well (Figure 3). Regarding how the arterial grafts contribute to the

Figure 2

The number of vessels revascularized by each graft

revascularizaion of three different areas, Figure 4 illustrates the grafts revascularizing the vessels in the three different regions. In the LAD 苲 diagonal region, 293 out of 310 vessels (94.5%) were revascularized with the arterial grafts. Venous grafts were used in only 17 vessels in this area. Similarly, in the distal RCA or CX region, 83 out of 113 vessels (73.4%) were revascularized with the GEA (77 vessels) and the composite-RITA (6 vessels). In contrast, in the proximal segment of the RCA or CX, the arterial grafts revascularized 57 out of 120 vessels (41.8%). With a follow up period from 3 to 86 months, there were two patients with recurrent angina, both of which were attributed to failure of the venous

Table 2 The number of the arterial grafts Total in situ LITA GEA RITA

145 67 40

145 67 12

composite

seq.

nonseq.

24

121 36 12*

24 31 28

seq.: sequential; non-seq.: nonsequential; *all were composite-RITA

388

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Figure 3 Revascularization without a saphenous vein graft

Figure 4 Grafts revascularizing vessels in three different areas. See text for detail. Diag.: diagonal branch; Intermed.: ramus intermedius branch

grafts, and were successfully treated with percutaneous balloon angioplasty. Acute myocardial infarction or reoperation was not observed (Figure 5).The cardiac event-free rate in the follow-up period was 96.2%. Postoperative angiographic evaluation was obtained in 67 patients, revealing that all the arterial grafts including 79 sequential grafts (LITAs, 52, GEAs, 22, composite-RITAs, 5) were widely patent and working well (Figures 6 and 7), while the patency of the venous grafts was 92.3% (36/39). The so-called ‘thinning phenomenon’, probably CARDIOVASCULAR SURGERY

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Figure 5 A Kaplan–Meier analysis showed that the cardiac event-free rate at maximum 84 months postoperatively was 96.2%. There were two patients with recurrent angina, which were attributed to failure of the saphenous vein grafts

Figure 6 An angiogram of a patient with the LITA sequential graft as well as the composite-RITA sequential graft at 24 months postoperatively. Small arrows indicate the LITA to the diagonal and the LAD anastomoses. Large arrows indicate the composite-RITA to the proximal Cx and the distal Cx anastomoses

due to a flow competition between the coronary artery, was noticed in the distal segment of the sequential GEA in three patients, whereas none of the sequential LITAs showed such a phenomenon.

Discussion The main advantage of the ITA and GEA is their incomparable long-term patency when they are used in an in situ situation. Over the last 7 yr, in an effort to generate more extensive usage of the arteries in 389

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Figure 7 An angiogram of a patient with the GEA sequential graft at 7 yr postoperatively. Arrows indicate the GEA to distal RCA and distal Cx anastomoses

patients with multiple vessel disease, we have used them by performing sequential anastomoses whenever possible. More recently the RITA has been utilized as a free graft by attaching the proximal end of the artery to the side wall of the LITA to form a composite graft to make it possible to construct the sequential anastomoses with the RITA. Several reports have shown that this type of conduit can offer better revascularization for multiple vessel disease [15–18]. Although it is rather technically demanding, the sequential anastomotic technique provides the possibility of complete revascularization with in situ arterial grafts [13, 19–21]. In this series, 71 patients (49.0%) were revascularized without venous grafts. Among these patients, 25 patients had more than four branches revascularized with only arterial grafts. Two patients were revascularized even in six branches with in situ arterial grafts [22]. As shown in Figure 4 94.5% of the vessels in the diagonal to LAD region were revascularized with the in situ LITAs, RITAs and composite-RITAs. Similarly, in the distal segment of the RCA or Cx, 73.5% (83/113) were revascularized by the GEA or composite-RITA. Overall, 432 of 543 vessels (79.6%) in the total 145 patients were revascularized with the ITAs and the GEA. In 132 patients with more than triple grafting, 78.5% (406/517) of bypassed vessels could be revascularized with the arterial grafts, and even in 86 patients with more than quadruple grafting, 74.7% (281/376) could be revascularized with the arterial grafts. These results indicate that aggressive utilization of the sequential grafting technique can provide even patients with multiple vessel disease with possibility of complete revascularization with only in situ arterial grafts. Meanwhile, there are some factors which influence 390

the performance of arterial sequential anastomoses. First, the size of the arteries, i.e. the length and the luminal diameter, is one of major factors, especially for the GEA. Since the GEA ranges widely in size when compared to the ITA, sequential anastomoses of the artery is not always possible. In addition, the evidence indicates that there is a difference in flow capacity between the ITA and the GEA [23, 24]. In the sequential anastomoses, the GEA has to be long enough to reach the distal anastomotic site. The diameter of the GEA at the distal anastomosis can be much smaller than at the proximal anastomosis. Diminished diameter of the distal end of the GEA can result in flow competition between the coronary artery. Sequential anastomoses of the GEA should only be constructed when the adequacy of the length and luminal diameter is first confirmed (Figure 8). On the other hand, several reports indicate that the ITA graft can change its luminal diameter in response to flow demand [25–28]. It is more capable of accommodating a blood supply as a graft to the coronary artery than the GEA. In our series, quite a few patients exhibited the increase in the luminal diameter of the sequential LITA on the postoperative angiograms. Therefore, the LITA can almost always be used as a sequential graft when the artery is long enough to conform to the sequential anastomoses. Regions that allow for a smooth graft sequence is another important factor.The sequence most frequently used and which best conforms to the course of the LITA, is a series of side-to-side anastomoses to the diagonal branches of the LAD with termination in an end-to-side anastomosis to the LAD. This combination is most often encountered in cases in which both the diagonal branches and the LAD are involved. In our series, almost all sequential anastomoses of the LITA (115/121) were constructed in such a sequence. However, in the inferior region of the heart, there are much fewer combinations of the affected branches suitable for smooth sequential grafting of the GEA. In addition, the proximal RCA around the acute margin or the crux, which is sometimes selected for the side-to-side anastomosis, is affected by atherosclerosis more often than not. These facts, along with the limitation of the GEA itself as a graft, resulted in a rather smaller number of patients undergoing GEA sequential grafting in our series. Inasmuch as the proximal anastomosis is the most crucial in the sequential grafting technique, several points have to be emphasized from the technical aspect. The side-to-side anastomosis should be constructed in a manner in which the graft is attached to the coronary artery longitudinally, i.e. parallel anastomosis. Diamond anastomosis in which the graft is attached to the coronary artery perpendicularly is more liable to cause ‘gull wing’ deformity CARDIOVASCULAR SURGERY

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Figure 8 A double sequential (a) and a triple sequential (b) graft of the GEA.In order to avoid flow competition between the coronary artery, the diameter of the distal end of the GEA at the anastomosis must be no smaller than 2 mm

leading to anastomotic stenosis [14, 29]. This is especially true for the ITA. When placing an arteriotomy on the graft for the proximal anastomosis, great care should be taken in selecting the point of arteriotomy. Should the length of the graft between the proximal and the distal anastomoses be too short, it could result in increased tension on the distal segment of the graft leading to possible occlusion. The arteriotomy on the graft should be a little longer than that of the coronary artery. If the arteriotomy on the coronary artery is longer, the graft would be stenotic at the anastomosis because of the stretching effect causing ‘gull wing’ deformity [29]. The efficacy and the long-term results of sequential grafting of the ITA has been confirmed by various reports [19–21, 30, 31]. In our current series, along with those reports, there has been no cardiac event related to the sequential arterial grafts. The patency rate of the ITAs and the GEA has been satisfactory. Increased numbers of grafted vessels with these arterial grafts can be expected to provide a better long-term quality of the cardiac status.

Conclusions In an attempt to utilize the in situ arterial grafts more extensively, we have primarily performed sequential CARDIOVASCULAR SURGERY

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grafting of the ITA and the GEA. In light of our experience, multiple revascularization with in situ arterial sequential grafts is feasible. This technique yields revascularization of multiple vessels with ‘live’ arterial conduits. Although the GEA can also be utilized as a sequential graft, preoperative angiography of the artery may be mandatory to evaluate the adequacy of the size of the artery as a graft. Aggressive application of this technique provides patients requiring multiple coronary revascularization with favorable long-term results.

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Paper accepted 28 February 2000

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