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Ann Thorac Surg 2001;72:959-965
© 2001 The Society of Thoracic Surgeons
a Bristol Heart Institute, University of Bristol, Bristol Royal Infirmary, Bristol, United Kingdom
Address reprint requests to Dr Angelini, Bristol Heart Institute, Bristol Royal Infirmary, Bristol BS2 8HW, United Kingdom
e-mail: n.holloway-dee{at}bristol.ac.uk
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Abstract |
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 Top Abstract IntroductionSurgical strategies and long...Complex graftsCommentReferences |
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Introduction |
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TopAbstractIntroductionSurgical strategies and long...Complex graftsCommentReferences |
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Surgical strategies and long-term follow-up outcome |
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TopAbstractIntroductionSurgical strategies and long...Complex graftsCommentReferences |
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Although commonly used, the pedicled RIMA-RCA graft has a patency rate inferior to that of the pedicled LIMA to LAD [9, 11–12]. Potential reasons for this may be that the main RCA is often very diseased, with thick wall or large lumen size, which also results in gross mismatch with that of the RIMA. Moreover, angiographic studies have shown progression of disease in the RCA system beyond a patent graft, particularly in the area between the acute margin and the crux [9]. However, this mismatch is less likely when the pedicled RIMA is directed to the PDA. In this case, however, it is necessary to use the end part of the pedicled RIMA. He [13] argued that the vasoreactivity of the distal section of both IMAs is inversely related to the vessel diameter. This may also explain the superior results of LIMA to LAD grafts or the use of a free RIMA graft, where the shorter length needed allows the use of a segment with less reactivity.
The use of the pedicled RIMA to the posterolateral wall through the transverse sinus was first described by Puig and colleagues [14] who reported the results in 56 patients. The angiographic control was performed in 17 of 56 patients and showed all the RIMA grafts patent and functional. However, 1 year later, Rankin and associates [15] reported only 75% of RIMA grafts patent, using the same technique, whereas the patency rate of RIMA to LAD or LIMA to Cx system was 100%. More recently, larger studies [16–19] have confirmed that pedicled RIMA to posterolateral wall through transverse sinus has excellent angiographic patency comparable with that of the LIMA to the LAD. Gerola and coworkers [16] reported LIMA patency rate of 97.6% at 1 year and 93.8% at 5 and 10 years of follow-up in a group of 201 patients. The RIMA patency was 92.1% at 1 year and 84.1% at 5 and 10 years (no statistical significance). In a recent study, Ura and coworkers [18] reported a patency rate of the LIMA to LAD of 92.3%, and of RIMA grafts via the transverse sinus of 89.9% at 56 months. Cumulative patency rates (actuarial curves) at 6 years were 94.5% and 89.3% for LIMA and RIMA, respectively, with differences not reaching statistical significance.
The main limitation of the RIMA through the transverse sinus is the difficulty of reaching the most distally located branches of the Cx. Furthermore, particular attention must be paid to hemostasis of the RIMA pedicle during harvesting and before placement through the transverse sinus, since this may be problematic once the anastomosis has been performed [7, 20].
The use of a pedicled RIMA to LAD graft is another possible surgical strategy, which is relatively simple and ensures excellent patency rates. Chow and colleagues [12] reviewed the medical history of 413 patients undergoing BIMA grafts using this approach. Angiography was performed in 67 patients (mean interval of 27 months). Overall patency rate of IMA grafts to the LAD was 90% (93% versus 88%, respectively, for RIMA and LIMA). Overall patency rate of IMAs to other coronaries than LAD was 76% (with no difference between LIMA and RIMA). Thus, this study suggests that there is no difference between RIMA and LIMA in terms of patency rates when they are grafted to the same coronary artery, and that patency decreases when they are grafted to other coronaries than the LAD. However, the limitation of the pedicled RIMA to LAD is, again, access to only the proximal and middle thirds of the LAD with the distal third accessible only occasionally, and its rare use for sequential grafts to the LAD and diagonal vessels [6]. Furthermore, several surgeons are reluctant to cross the anterior midline with the RIMA due to the potential risk of injury during reoperation through a median sternotomy [7, 9].
In recent years, the use of skeletonized IMA grafts has received attention as a means of enhancing the versatility of this conduit, while reducing postoperative sternal wound complications [21–23]. Skeletonized IMA dissection leaves the vein, muscle, and surrounding tissue in place. The advantage is that the dissected artery is longer, allowing the use of both IMAs as grafts potentially to all target coronary vessels [21]. Furthermore, since this technique of IMA harvesting usually avoids cauterization, it should reduce the risk of early sternum dehiscence and infection, particularly in elderly and diabetic patients [22]. Early patency for skeletonized IMA grafts is similar when compared with the pedicled technique [21–23].
Clinical midterm and long-term results
In a retrospective analysis of 1,087 patients receiving BIMA grafts and supplemental vein grafts, Galbut and colleagues [11] reported the follow-up for 17 years as an actuarial survival of 80.0 ± 3.2% at 10 years, and 60 ± 5.0% at 15 years. Postoperative angiography in 53 patients showed that 92.1% of the LIMA and 84.9% of the RIMA were patent at a mean of 53 months. Fiore and associates [24] reported an operative mortality of 9% and 2%, respectively, in a retrospective analysis of 2 groups of 100 consecutive patients undergoing either pedicled BIMA or a single IMA with SVG grafts. The mean follow-up of all but 7 hospital survivors was 14.4 ± 2.7 years. At 13 years, the actuarial patency was 85% for RIMA grafts and 82% for LIMA grafts. Patients who had undergone BIMA grafting had better freedom from subsequent events than those who did not undergo this procedure.
Berreklouw and associates [25] reported a retrospective analysis of 286 patients undergoing either pedicled BIMA or single IMA with supplemental vein grafts. No significant differences were observed at 5 to 8 years follow-up in terms of overall survival, cardiac survival, recurrent angina, infarct-free cardiac survival, and coronary reintervention between groups. Sergeant and associates [26], in a multivariable time-related analysis on 9,600 patients undergoing CABG, using a variety of revascularization methods, concluded that the late survival is modestly improved with the use of an arterial graft to a major vessel. However, no late beneficial or detrimental effect was identified with more extensive use of arterial reconstructive surgery on multisystem disease. In a recent, retrospective, matched study, Lytle and coworkers [8] reviewed the surgical strategies and outcomes of 2,015 consecutive patients receiving BIMA grafting with or without additional vein grafts and, for comparison, 8,059 patients receiving single IMA grafts and at least one vein graft. The in-hospital mortality rate was 0.7% for both groups. Overall late follow-up was of 10.3 years in the BIMA group, while 304 BIMA patients reached a mean follow-up greater than 12 years. Survival for the BIMA group was 94%, 84%, and 67%, whereas for the single IMA group it was 91%, 79%, and 64% at 5, 10, and 15 postoperative years, respectively (p < 0.001). They concluded that BIMA grafting improves the survival rate in all age groups, except for those less than 50 years old, and strongly decreases the risk of reoperation for all age groups.
The difference in clinical outcome observed in the reports of Sergeant and associates [26] and Lytle and colleagues [8] is more likely to be due to baseline differences in patient population rather than the use of single or bilateral IMA grafting. Indeed, while the consecutive series of Sergeant and coworkers [26] included patients undergoing CABG in the acute phase of a myocardial infarct or after failed coronary angioplasty, the surgical population reported in the Lytle and associates’ study [8] did not. Furthermore, in the Lytle and coworkers’ study [8], the observation that death, reoperation, and percutaneous transluminal coronary angioplasty were more frequent for patients undergoing single rather than bilateral IMA grafting, remained true despite multiple adjustments for patient selection, sampling, and length of follow-up.
Pick and colleagues [1] reported their results of a retrospective 10-year outcome analysis of 320 patients, undergoing either BIMA (77% pedicled) or single IMA and SV grafts. Grafts were distributed equally to the coronary territories in both groups. One IMA was directed to the LAD in 94% of patients. In the BIMA group, the RIMA was grafted to the left coronary system in 93% of patients. Early outcomes were similar in both groups with only one death occurring in the IMA group. Late follow-up was obtained in all patients with a mean interval of 9.8 ± 2.8 years. The BIMA group experienced significantly fewer late cardiac-related deaths (12 versus 29). Five-to-10 year overall survival was 90% ± 2.4% and 74% ± 3.5% for the IMA group and 96% ± 1.6% and 84% ± 3.0% for the BIMA group. Multivariate analysis demonstrated that the use of only a single IMA graft was the strongest predictor of return of chest pain (p > 0.001), followed by female gender, preoperative obesity, and preexisting hypertension. Single IMA usage also correlated with an increased risk of late myocardial infarction independent of diabetes, constituting the second significant finding in favor of BIMA grafts. At 10 years, the IMA group reported almost twice the incidence of recurrent angina when compared with the BIMA group (63% versus 33%). Repeat angiography showed an overall IMA patency rate of 84%: LIMA (88%), RIMA (75%); by contrast, vein graft patency was 54%.
Excellent mid- and long-term clinical outcome are reported also when the pedicled RIMA is grafted to the left coronary system through the transverse sinus [16, 19]. Gerola and colleagues [16] in a group of 201 patients reported an actuarial survival of 91.2% and 88.3% at 5 and 10 years, respectively.
Clinical outcome of skeletonized BIMA grafting have been recently reported in retrospective series at early postoperative follow-up (ranging from 1 to 29 months) [21–23]. Gurevitch and coworkers [21] reported a 2-year actuarial survival of 96.8%, with 92% of patients angina-free. Similar results were reported by Bical and associates [22] at a similar follow-up time, with a 9% incidence of recurrent angina. However, despite the encouraging immediate results in terms of patency rates, the small number of articles published and the absence of long-term results does not allow conclusions to be drawn yet on skeletonized IMA grafting in terms of comparison with pedicled techniques.
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Complex grafts |
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Verhelst and colleagues [27] reported an early patency of 86.4% for the free RIMA and 100% for the pedicled LIMA. Their surgical strategy was to frequently use a venous hood for the proximal anastomosis with patency rates not significantly different from direct aortic anastomosis (89.7% versus 82.8%). Recently, Tatoulis and associates [9] reported the angiographic evaluation of the free RIMA on symptomatic patients at a mean of 41.5 months. This showed 67 of 71 free RIMA (94.5%) patent. Patency for the free RIMA was 89% ± 8.5% at 5 years and 96% ± 1.5% (not significant) for the pedicled LIMA. Their strategy consisted of grafting the free RIMA to the next most important artery in terms of myocardium supplied (left coronary system in 70% of the cases and PDA in 20%). When this was the case of the RCA system, they preferred to graft the PDA to avoid atheroma at the site of anastomosis or more distally.
Clinical midterm and long-term results
Loop and coworkers [5], in their series, reported a 10-year actuarial survival rate (including all causes of death) of 73.3% at 98 months mean follow-up.
The Tatoulis and associates’ series [9] reporting routine use of the RIMA as a free graft in 1,454 patients having bilateral IMAs, is the largest reported to date and shows lower morbidity and mortality than previous reports [5, 28], with actuarial survival of 96% and 94% at 5 and 7 years, respectively. One possible explanation for their excellent results is the fact that the surgical strategy of using the free RIMA excluded obese patients and those with insulin-dependent diabetes or severe pulmonary disease. They also used the free RIMA for the next most important artery in terms of myocardium supplied. The free RIMA was anastomosed to the left coronary system in 70% of cases and to the PDA in 20%, thus avoiding the mid-portion of the RCA.
The role of patient selection in determining improved long-term outcome seems indirectly confirmed by Verhelst and associates [27] who reported a patency of 86.4% for the free RIMA and 100% for the pedicled LIMA at a mean interval of 15 months. These results led the authors to the conclusions that free IMA mid-term patency rates compared unfavorably with those of pedicled IMA grafts, therefore free grafts should be restricted to cases where pedicled IMA or other arterial grafts are unavailable or unsuitable. However, we relate the different results between Verhelst and colleagues’ [27] and Tatoulis and associates’ [9] to the different exclusion criteria used in the two studies. Tatoulis and coworkers routinely used the free RIMA in elective preoperatively selected patients, whereas Verhelst and associates used the free IMA in conditions such as too short IMA pedicle, IMA injury at harvesting, post-bypass ischemia in areas grafted with pedicled IMA, redo operation, and poor left ventricular function.
Sequential grafting
Surgical strategies and patency rates
Sequential mammary grafting was first described by Kabbani and coworkers in 1983 [29] as a way to extend the use of arterial conduits. Following this, sequential mammary grafting became well established [6, 30–32]. Dion and associates [6] reported sequential mammary grafting with both LIMA and RIMA in 231 consecutive patients. Of the 531 sequential mammary anastomoses, 482 were constructed with the LIMA and 113 (21%) were diamond-shaped anastomoses. The RIMA was brought through the transverse sinus in 44 cases, 10 times for sequential grafting of the Cx branches. One hundred fifty-seven patients (71%) were recatheterized with 95% of the sequential grafts still patent at 6 months. The patency rate of the diamond-shaped mammary anastomoses was 94.5%, and that of the anastomoses corresponding to the RIMA through the transverse sinus was 94.3%.
In a recent follow-up report, Dion and coworkers [32] show that these excellent results were maintained at 10 years with no significant difference between the patency of the single and the sequential anastomoses. The patency of the sequential anastomoses directed to the LAD, the Cx, and the RCA areas was 96%, 92%, and 82%, respectively.
Clinical midterm and long-term results
The study of Dion and colleagues [32] at a mean follow-up of 9.3 years (7.6 to 12.8), reported 4.8% cardiac-related deaths and only 4.4% need for repeat revascularization (10 percutaneous transluminal coronary angioplasty and six CABG). The overall survival was 75.2%, and 79% patients were asymptomatic. This study conclusively establishes the excellent long-term clinical and angiographic results of sequential mammary grafting, although this strategy may be too technically demanding for some surgeons.
Composite grafts
Surgical strategies and patency rates
Several authors [28, 33–35] have championed the use of IMAs in terms of composite grafts, based on the initial experiences of Sauvage and associates [36], as a means to completely revascularize the heart with only two arterial conduits. Revascularization is achieved by performing a T [28, 33] or a Y graft [34–35] anastomosing the free RIMA to the pedicled LIMA.
In the experience of Tector and coworkers [28, 33], postoperative patency was 91.2% (31 of 34) for T anastomoses, 86.5% (77 of 89) for RIMA anastomoses, and 98.3% (59 of 60) for LIMA anastomoses. Chocron and associates [35] reported results of a retrospective study with the Y graft in 80 patients. Angiographic reexamination was performed in 62 patients at 6 to 25 months. Sixty LIMA grafts (97%) were patent versus 39 RIMA (63%). The authors divided the patients into 2 groups regarding the surgical strategy of performing the Y graft. In the first group, the Y anastomoses was performed after the distal anastomoses and attachment of the RIMA on the nonpleural side of the LIMA. In the second group, the Y anastomoses was performed soon after heparinization and as the first step with the RIMA attached on the pleural side of the LIMA. The angiographic analysis of these 2 subgroups showed only 12 of 25 (48%) RIMA patent in the first group, and 27 of 37 (73%) in the second group. Barra and coworkers [34], in a prospective study on 80 patients undergoing the Y procedure, evaluated the patency rates at 16 months of follow-up. The rate of the effective patency of the LIMA was 93.4% (57 of 61) and 85.2% (49 of 61) for the RIMA.
From these data, it is obvious that despite the fact that patency of the LIMA in the T or Y procedures is similar to previously published data on the pedicled LIMA [29], the outcomes regarding the RIMA patency rate remain controversial. However, the important differences observed in terms of results of the composite grafts outcome might be a reflection of the technically demanding procedure and the different amount of experience achieved by each surgeon.
Clinical midterm and long-term results
The absence in the literature of studies, reporting midterm and long-term clinical and angiographic data, does not allow a proper comparison with those surgical strategies such as pedicled, free, or via transverse sinus RIMA grafts. Many surgeons may not feel comfortable with this technique because these grafts are technically complex. Other concerns focus on the adequacy of a single source to provide sufficient flow for this configuration, preferring three or more conduits with one, or, at most, two distal anastomoses per conduit [7, 27]. Furthermore, the Y anastomosis might jeopardize the distal flow in the pedicled LIMA by development of an anastomotic stenosis or a steal phenomenon [27].
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Comment |
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TopAbstractIntroductionSurgical strategies and long...Complex graftsCommentReferences |
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This review has attempted to trace the clinical studies underlying the evolution of bilateral internal mammary grafting. Our analysis of the literature does confirm the superior role of BIMA grafting in terms of mid- and long-term graft patency, reduced cardiac events, and improved survival when compared with single IMA grafting. We agree with Lytle and associates [8] and Tatoulis and colleagues [9] that preoperative patient selection is of paramount importance to optimize the clinical outcome of this procedure by avoiding patients with left ventricular dysfunction, insulin-dependent diabetes, severe obesity, chronic obstructive pulmonary disease, and aged more than 65. Furthermore, analysis of the current literature does suggest a superior intermediate and long-term clinical and angiographic outcome when pedicled, sequential, or free aorto-coronary IMA grafts are used, possibly due to their relative surgical simplicity. The absence, to date, of studies reporting mid- and long-term clinical outcomes, associated with the technical complexity of composite IMA grafts mean that further investigation will be required to establish the place of such strategies in routine BIMA grafting. Finally, large, well-designed prospective randomized controlled trials between different treatment groups are required to define the best surgical strategy and to enhance the quality of publications in this area [41].
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