Gen Thorac Cardiovasc Surg DOI 10.1007/s11748-014-0426-6
CURRENT TOPICS REVIEW ARTICLE
Redo coronary artery bypass grafting Hitoshi Yaku • Kiyoshi Doi
Received: 27 January 2014 Ó The Japanese Association for Thoracic Surgery 2014
Abstract Redo coronary artery bypass grafting (CABG) is more challenging than primary CABG in many aspects. Patients who undergo redo CABG are older, more comorbid, and with more sclerotic coronary and noncardiac arteries than seen in primary CABG. Operative procedures are more complicated, reentry of the sternum is sometimes problematic, and dissection of the heart is needed. If patent vein grafts are diseased, they can be sources of thromboembolism, and the patent left internal thoracic artery (ITA) anastomosed to the left anterior descending artery (LAD) must not be injured. The number of redo CABG procedures has been decreasing, because of frequent use of ITA to the LAD in primary CABG, aggressive percutaneous coronary intervention (PCI) by interventional cardiologists, and optimal medical therapy after primary CABG. In-hospital mortality in redo CABG is two to five times higher than that of primary CABG, although outcomes have been improving in recent years despite the patients’ more comorbid background. Long-term survival after redo CABG is comparable to that of PCI. The indication for redo CABG should be limited to patients who have jeopardized LAD territory, which is viable. CABG is also preferable to PCI in patients with more diseased vein grafts and low cardiac function. Various technical refinements have also improved the surgical results of redo CABG. Retrograde cardioplegia greatly contributed to proper myocardial protection, especially when the occluded coronary arteries are supplied by patent
This review was submitted at the invitation of the editorial committee. H. Yaku (&) K. Doi Department of Cardiovascular Surgery, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan e-mail: [email protected]
in situ arterial grafts. The off-pump technique has been used in redo CABG and may be beneficial in a selected, more comorbid population. Keywords Repeat coronary artery bypass surgery Diseased vein graft Internal thoracic artery Sternum reentry
Introduction Redo coronary artery bypass grafting (CABG) is more challenging than first CABG in many aspects. Patients who undergo redo CABG are older and have more diseased coronary arteries, poorer left ventricular function, more comorbidities, and more noncardiac atherosclerosis, such as peripheral arterial disease. Reentry of the sternum is sometimes problematic when patent grafts, the ascending aorta, or the right ventricle have adhered to the sternum. Dissection of the heart is needed, which might cause bleeding, and if there are patent diseased saphenous vein grafts (SVGs), thromboembolism can occur during dissection. The availability of conduit is limited, if the internal thoracic artery (ITA) was used in a previous CABG. Although the number of cases of redo CABG has been decreasing because of the frequent use of arterial conduits at primary operation, a more aggressive approach by interventional cardiologists using percutaneous coronary intervention (PCI), optimal medical therapy, and sufficient antiplatelet administration after the primary operation, redo CABG still needs to be performed when surgical revascularization is indicated. In this review article, we describe the changes in the trends surrounding redo CABG and recent surgical outcomes of redo CABG.
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Gen Thorac Cardiovasc Surg Fig. 1 The number and prevalence of redo CABG procedures in Japan
Although repeat revascularization is rarer after CABG compared to PCI, repeat revascularization, by either PCI or CABG, is needed as time elapses after CABG. The incidence of reoperation after CABG was reported to be 2.6, 10.1, and 24.4 %, at 5, 10, and 20 years, respectively, after the primary operation [1]. Another study showed that freedom from reintervention was 89 % at 10 years and 72 % at 15 years [2]. The rate of redo CABG in relation to the total number of CABG procedures has been decreasing, probably for several reasons: (1) The use of the left ITA for anastomosis to the left anterior descending artery (LAD) has become the standard strategy at primary operation; (2) PCI has been performed aggressively even in patients who underwent CABG previously; and (3) optimal medical therapy, with statins and dual antiplatelet medications, is routinely administered after primary CABG. A study based on the database of the Society of Thoracic Surgery (STS) showed that the peak of the rate of redo CABG was 10 % of CABG in 1992/93, decreasing to 8 % in 1995, and to 7 % by the year 2000 [3]. According to a study from the Cleveland Clinic Foundation [4], the ratio of redo CABG to total CABG has been continuously declining. According to data in the annual report from the Japanese Association for Thoracic Surgery (JATS), the number of redo CABG procedures has decreased dramatically during the last 10 years [5]. The ratio of redo CABG to the total number of CABG procedures has decreased from 10 to 2 % over 10 years (Fig. 1).
The patients who are candidates for redo CABG should have at least one good graftable coronary artery whose territory is ischemic and viable. If the patient is symptomatic, redo CABG is strongly indicated. In a study comparing redo CABG and PCI for patients with previous CABG, the survival rates at 1 and 5 years were comparable between the two revascularization strategies [6]. In the AWESOME randomized controlled trial and registry, overall in-hospital mortality was higher for CABG than for PCI [7, 8]. Considering the initial higher mortality of redo CABG and the comparable long-term mortality, PCI is the preferred revascularization strategy, especially in patients with a patent left ITA and amenable anatomy. CABG is preferred for patients with more diseased or occluded grafts, as well as those with no patent arterial graft. Subramanian et al. [9], from the Cleveland Clinic Foundation, reported that patients with patent left ITA-toLAD grafts who develop non-LAD territory jeopardy derived no survival benefit from either reoperation or PCI over medical therapy. This means that the LAD territory must be jeopardized for coronary reintervention to improve survival. Reintervention in patients with a patent ITA-toLAD graft may be warranted to relieve symptoms, but no survival benefit should be expected. The recommendation classes and evidence levels suggested in the European guidelines are shown in Table 1 [10]. If the patient has stenotic vein grafts, some factors influencing the selection of either CABG or PCI are shown in Table 2 [11].
Indications
Surgical results
The indications for redo CABG should be stricter than that for primary CABG, because operative mortality and morbidity are higher than those of primary CABG. In-hospital mortality in redo CABG is more than twice as that of primary CABG.
Early surgical results
Incidence
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Redo CABG always carries more operative risk than primary CABG. The early mortality of redo CABG has been
Gen Thorac Cardiovasc Surg Table 1 Indications for redo CABG from the European Guidelines for revascularization Class
Level
In early graft failure Coronary angiography is indicated for highly symptomatic patients, or in the event of postoperative instability, or with abnormal biomarkers/ECG suggestive of perioperative MI
I
C
Decision of redo CABG or PCI should be made by the Heart Team
I
C
PCI is a superior alternative to reoperation in patients with early ischemia after CABG
I
B
The preferred target for PCI is the native vessel or ITA graft, not the freshly occluded SVG
I
C
For freshly occluded SVG, redo CABG is recommended rather than PCI if the native artery appears unsuitable for PCI or several important grafts are occluded
I
C
PCI or redo CABG is indicated in patients with severe symptoms or extensive ischemia despite OMT
I
B
PCI is recommended as a first choice, rather than redo CABG
I
B
PCI of the bypassed native artery is the preferred approach when stenosed grafts [3 years old
I
B
Table 2 Indications for redo CABG and PCI when saphenous vein grafts are stenotic Redo CABG better
PCI better
Late ([5 years) stenosis
Early (\5 years) stenosis
Multiple stenotic vein grafts
Single stenotic vein graft
Diffusely atherosclerotic vein grafts Stenotic LAD vein graft
Other patent vein grafts
No patent ITA graft
Patent ITA–LAD graft
Abnormal left ventricular function
Normal left ventricular function
Focal graft lesions
In late graft failure following CABG
ITA is the conduit of choice for redo CABG
I
B
Redo CABG should be considered for patients with several diseased grafts, reduced LV function, several CTO, or absence of a patent ITA
IIa
C
PCI should be considered in patients with patent left ITA and amenable anatomy
IIa
C
reported to be two to five times higher than the rates we would expect for primary CABG. However, there has also been progress in early operative results. At the Cleveland Clinic Foundation, from 1967 through 1991, the in-hospital mortality of redo CABG was 3–4 % [12], and it continued to decrease to 2.5 % in 2002 [4], even though patients’ profiles were more comorbid. Ghanta et al. [13] recently reported an improvement in the early surgical results of redo CABG from the STS Database. They showed that the patients’ profiles became more comorbid in 2009 compared to those in 2000. The patients in 2009 had more left main disease (35.1 vs. 25.5 %), more myocardial infarction (60.9 vs. 55.9 %), more heart failure (18.4 vs. 14.2 %), more incidence of previous PCI (51 vs. 35 %), more renal failure (2.2 vs. 0.7 %), and more cerebrovascular disease (12.4 vs. 8.5 %), and were more likely to need frequent urgent or emergent operation (51 vs. 39 %). Despite those circumstances, the risk-adjusted operative mortality of redo CABG declined from 6.0 % in 2000 to 4.6 % in 2009, and risk-adjusted stroke rate decreased from 1.9 % in 2000 to 1.6 % in 2009. Those improvements in early surgical results can be attributed to various factors that improved
Fig. 2 Operative mortality in redo CABG compared to that of primary CABG in Japan
during those 10 years, including pre- and postoperative patient’s management, cardioplegia strategy, especially retrograde cardioplegia technique, handling of the old patent grafts, avoiding injury to grafts, and frequent use of the ITA graft. Indeed, Sabik et al. [13] have recently reported that by using ITA to the LAD in redo CABG, operative mortality can be significantly reduced compared to that of patients who had SVG to the LAD. Figure 2 shows the operative mortality in redo CABG compared to that of primary CABG from the data in the annual report from JATS. The operative mortality of primary CABG has been improving continuously during the last 10 years, whereas operative mortality in redo CABG has only shown a trend to decrease. Operative mortality in redo CABG was more than three times as high as that of primary CABG (Fig. 2). The higher in-hospital mortality of redo CABG has been reported to be associated with an increased risk of perioperative myocardial infarction. Indeed, in the Cleveland Clinic Foundation series, the cause of perioperative death was cardiovascular events in 85 % of cases, which contrasts with the results of primary CABG, where noncardiac causes of death have been increasingly important [14].
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Fig. 3 The number of cases and operative mortality in electeive and emergent redo CABG
The higher incidence of perioperative myocardial infarction may be attributable to multiple factors unique to redo CABG, including incomplete revascularization, distal coronary artery disease, vein graft thrombosis, ITA graft failure, atherosclerotic embolization from diseased SVGs, injury to bypass grafts, hypoperfusion from arterial grafts [15], preoperative myocardial infarction, and complications of PCI. Figure 3 shows operative mortality of elective and emergent redo CABG in the last 10 years. Operative mortality of elective redo CABG procedures has been about 3 % continually in the last 10 years. Operative mortality of emergent redo CABG has slightly improved in the last several years; however, it is almost three times higher than that of elective cases. The numbers of cases have been decreasing during last 10 years in both elective and emergent redo CABG procedures. Predictors for in-hospital mortality of redo CABG identified in previous studies were increased age, female gender, and emergency operation [16, 17]. Redo CABG has specific anatomic conditions, such as the presence of patent ITA grafts and atherosclerotic SVGs, which might affect operative risk. Lytle et al. [12] documented that patent ITA grafts never increased the mortality rate of redo CABG. They noted that the risk of ITA damage has dropped from 8 % in their earlier experience to 3.7 % in more recent years, with increased surgical experience. When the patent left ITA-to-LAD graft or left ITA-toLCx graft is confined to the left side of the mediastinum along the phrenic nerve, injury of the ITA graft may not occur during reentry of the sternum. When the right ITA-
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to-LAD graft crosses the midline of the sternum and the graft has adhered to the back of the sternum, it could cause problems during reentry of the sternum. In such cases, a small thoracotomy on either the left or the right side may be helpful to dissect the right ITA graft free across the midline [11]. In previous studies, patent atherosclerotic stenotic SVGs increased the risk of mortality [18]; however, more recent studies showed that the risk has been neutralized by a combination of improved technology, the use of retrograde cardioplegia delivery, and increased surgeon experience [12], although more diseased grafts are still associated with higher risks. Late surgical results Patients undergoing redo CABG are older, have more complex pathology in the coronary arteries, and show a shortage of available conduits. Therefore, it is not surprising that the long-term results of redo are worse than those of primary CABG. In a recent study, Yap et al. [19] reported that the 5-year survival of redo CABG was worse than that of primary CABG; however, when the background of the patients was adjusted, the survival curve became almost superimposable. If we compare the long-term results of CABG and PCI for patients who underwent primary CABG, Cole et al. [20] reported that 10-year survival rates were not different; however, freedom from CABG was 90 % in the CABG arm, whereas it was 60 % in the PCI arm.
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Long-term results were also affected by the bypass conduits used in redo CABG. If the ITA was used in redo CABG, the intermediate survival rate and the rates of freedom from cardiac events and recurrence angina were higher than those in patients who underwent revascularization with only SVGs [21].
Technical aspects of redo CABG Redo CABG is technically more difficult and challenging than primary CABG. There are many pitfalls that should be avoided from the beginning through to the end of the procedure.
Dissection of the diseased vein grafts should be minimized; they are just removed from the pericardium. On the other hand, the patent ITA should be dissected free for almost its whole length, because the ITA must be clamped while the heart is arrested in conventional redo CABG, while in off-pump, you cannot rotate the heart without ITA dissection. If the right ITA was used to connect to the LAD across the midline, it must be dissected free in order to secure the aortic cannulation and cross-clamp sites. To dissect the patent ITA graft, the use of a harmonic scalpel is strongly recommended [22]. The blade of the harmonic scalpel is never heated to above 80 °C and never causes thermal injury to the ITA, provided it is used properly.
Sternal reentry Cardioprotection Most redo CABGs are performed through the same median sternotomy as the primary operation. The wires are cut anteriorly but not removed. The sternum is cut with an oscillation saw, while the wires are pulled up, and the tissue beneath the sternum is away from the sternum. It is better to use a micro-oscillator, because it conveys the sensation of cutting the inner layer of the sternum. If the patent ITA or the ascending aorta is seen to have adhered to the sternum on the preoperative CT, a small thoracotomy can be performed on either side of the chest cavity, depending on the site of the adhesion, and dissection of the adhesion should be performed before the sternum is opened [11]. If the adhesion is very severe, cardiopulmonary bypass should be prepared from extracardiac access. For redo CABG, the right axillary artery may be preferable to the femoral artery, because patients undergoing redo CABG often have atherosclerotic extracardiac arteries. Dissection of the heart, the ascending aorta, and grafts Once the sternum is open, dissection should be started at the lower part of the heart because this is usually the easiest part to dissect. Then, dissection of the ascending aorta and the right atrium is performed next, in order to secure the arterial and venous access. If redo CABG is performed in a conventional fashion (using cardiopulmonary bypass with the heart arrested by cardioplegia), cardiopulmonary bypass can be started at this point, and further dissection can be performed with the heart decompressed on cardiopulmonary bypass. In the case of an off-pump redo CABG procedure, we have to rotate the heart using a heart positioner to facilitate visualization of the dissecting plane. To dissect the heart through a narrow space while it is beating, a harmonic scalpel is very useful.
Cardioprotection is extremely important, especially in redo CABG, because the coronary arteries of patients undergoing redo CABG are often severely atherosclerotic, and totally occluded. Care should be taken to protect myocardium, especially if it is mainly perfused by the ITA. In such a case, cardioplegic solution should be given, not only from the root of the ascending aorta in an antegrade fashion, but also from the coronary sinus in a retrograde fashion.
Management of patent diseased vein graft Management of patent diseased SVG is very important issue in redo CABG. Previously, it was reported that risk of hypoperfusion of the LAD territory was high when a patent diseased vein graft was replaced with an in situ ITA, because immediate flow of an in situ left ITA was lower than the flow of a stenotic vein graft [23]. Therefore, it may be better leave a patent diseased SVG alone even after grafting the left ITA to the LAD, especially when stenosis of the SVG is not very tight. However, because it was reported that graft flow of the skeletonized ITA was more than that of the pedicled ITA [24], a patent diseased SVG may be able to be replaced with the ITA provided it is skeletonized. Further study is needed regarding this issue.
Grafting pattern and the selection of bypass grafts One of the difficulties in performing redo CABG is the selection of bypass conduits. The basic concept of how to select bypass conduits in redo CABG is the same as that in primary CABG. If only the saphenous vein was used in a primary CABG, the left and right ITAs are available for redo CABG. Many patients who undergo redo CABG may
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have a patent ITA-to-LAD graft, whereas SVGs to the right and left circumflex arteries are occluded. In such a case, both bypass grafts to the right and circumflex arteries can be replaced by new SVGs; other choices of grafts are the right ITA and the radial arteries. When the right ITA is used as an in situ graft, it can be used to the circumflex arteries via the transverse sinus; however, dissection of the sinus may be difficult in a redo situation. Another option is to exchange the left ITA-toLAD graft to the circumflex artery, whereupon the in situ right ITA is used for the LAD. In those ways, the single ITA graft arrangement can be upgraded to a bilateral ITA graft arrangement [25]. Another option to convert single ITA use to bilateral ITA use in redo CABG is to use the right ITA as a free graft. Min et al. [27] reported complete revascularization using a free right ITA as a side branch from the previous patent left ITA-to-LAD graft. Those graft arrangements using bilateral ITAs may have a survival benefit, as in primary CABG [26]. Further studies should be conducted. The right gastroepiploic artery can be a good option for a graft to the inferior wall in redo CABG [28]. When the inferior wall is the only target in redo CABG, grafting using the in situ right gastroepiploic artery through the diaphragm is possible in an off-pump fashion [29].
Off-pump versus on-pump in redo CABG There is a lot of enthusiasm for performing off-pump CABG in Japan and other Asian countries. In fact, in Japan, 65 % of CABG procedures are performed off-pump. There have been many studies comparing the surgical results between conventional CABG and off-pump CABG. In general, there is no decisive difference in in-hospital mortality between conventional CABG and off-pump CABG. However, when we look at the results of the offpump technique in patients with more comorbidities, the in-hospital mortality of off-pump CABG remains low [30]. In addition, the off-pump technique could reduce the incidence of catastrophic complications, such as stroke, after CABG [31, 32]. Therefore, there is a possibility that the off-pump technique could reduce in-hospital mortality and the rate of serious complications in redo CABG, which inherently bears a higher operative risk. There have been several studies comparing the off-pump technique with conventional redo CABG, although most of them were single-centered and retrospective [33–36]. Those studies showed that there was no difference in operative mortality between off-pump and on-pump CABG, whereas the durations of mechanical ventilation and hospital stay were shorter, and units of transfused blood were fewer for the off-pump technique. However, the
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Fig. 4 Operative mortality in redo CABG comparing off-pump and on-pump techniques
completeness of revascularization was less, and the number of grafts was lower for off-pump CABG. Therefore, the investigators concluded that off-pump might be effective only in selected patients. From the data in the annual report from JATS, Fig. 4 shows the operative mortality in redo CABG, comparing off-pump and on-pump. Operative mortality in off-pump redo CABG has always been lower than that of on-pump redo CABG, although the patients’ backgrounds were not matched. A propensity analysis was performed, based on the Japan Cardiovascular Surgical Database (JCVSD), comparing the early surgical results between off- and on-pump CABG in patients who had undergone previous CABG [37]. Operative mortality tended to be lower, and the composite endpoint of mortality or major complications was statistically significantly less frequent for off-pump redo CABG compared to on-pump redo CABG.
Future prospects Redo CABG continues to be challenging, because patients have become more comorbid with more complex coronary anatomy and lower levels of cardiac function. In the near future, a less invasive approach for redo CABG may be the standard approach, avoiding reentry of the sternum, and without the use of cardiopulmonary bypass. Hybrid procedures of off-pump CABG and PCI will become one of the options of coronary revascularization for patients with previous CABG. Conclusions Surgical outcomes have been improving in redo CABG despite the fact that we have more comorbid patients than before. However, in-hospital mortality in redo CABG has
Gen Thorac Cardiovasc Surg
been higher than that in primary CABG. A less invasive approach, avoiding reentry of the sternum and without use of cardiopulmonary bypass, needs to be developed. Conflict of interest interest.
All the authors have declared no conflict of
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CURRENT TOPICS REVIEW ARTICLE
Redo coronary artery bypass grafting Hitoshi Yaku • Kiyoshi Doi
Received: 27 January 2014 Ó The Japanese Association for Thoracic Surgery 2014
Abstract Redo coronary artery bypass grafting (CABG) is more challenging than primary CABG in many aspects. Patients who undergo redo CABG are older, more comorbid, and with more sclerotic coronary and noncardiac arteries than seen in primary CABG. Operative procedures are more complicated, reentry of the sternum is sometimes problematic, and dissection of the heart is needed. If patent vein grafts are diseased, they can be sources of thromboembolism, and the patent left internal thoracic artery (ITA) anastomosed to the left anterior descending artery (LAD) must not be injured. The number of redo CABG procedures has been decreasing, because of frequent use of ITA to the LAD in primary CABG, aggressive percutaneous coronary intervention (PCI) by interventional cardiologists, and optimal medical therapy after primary CABG. In-hospital mortality in redo CABG is two to five times higher than that of primary CABG, although outcomes have been improving in recent years despite the patients’ more comorbid background. Long-term survival after redo CABG is comparable to that of PCI. The indication for redo CABG should be limited to patients who have jeopardized LAD territory, which is viable. CABG is also preferable to PCI in patients with more diseased vein grafts and low cardiac function. Various technical refinements have also improved the surgical results of redo CABG. Retrograde cardioplegia greatly contributed to proper myocardial protection, especially when the occluded coronary arteries are supplied by patent
This review was submitted at the invitation of the editorial committee. H. Yaku (&) K. Doi Department of Cardiovascular Surgery, Kyoto Prefectural University of Medicine, 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan e-mail: [email protected]
in situ arterial grafts. The off-pump technique has been used in redo CABG and may be beneficial in a selected, more comorbid population. Keywords Repeat coronary artery bypass surgery Diseased vein graft Internal thoracic artery Sternum reentry
Introduction Redo coronary artery bypass grafting (CABG) is more challenging than first CABG in many aspects. Patients who undergo redo CABG are older and have more diseased coronary arteries, poorer left ventricular function, more comorbidities, and more noncardiac atherosclerosis, such as peripheral arterial disease. Reentry of the sternum is sometimes problematic when patent grafts, the ascending aorta, or the right ventricle have adhered to the sternum. Dissection of the heart is needed, which might cause bleeding, and if there are patent diseased saphenous vein grafts (SVGs), thromboembolism can occur during dissection. The availability of conduit is limited, if the internal thoracic artery (ITA) was used in a previous CABG. Although the number of cases of redo CABG has been decreasing because of the frequent use of arterial conduits at primary operation, a more aggressive approach by interventional cardiologists using percutaneous coronary intervention (PCI), optimal medical therapy, and sufficient antiplatelet administration after the primary operation, redo CABG still needs to be performed when surgical revascularization is indicated. In this review article, we describe the changes in the trends surrounding redo CABG and recent surgical outcomes of redo CABG.
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Gen Thorac Cardiovasc Surg Fig. 1 The number and prevalence of redo CABG procedures in Japan
Although repeat revascularization is rarer after CABG compared to PCI, repeat revascularization, by either PCI or CABG, is needed as time elapses after CABG. The incidence of reoperation after CABG was reported to be 2.6, 10.1, and 24.4 %, at 5, 10, and 20 years, respectively, after the primary operation [1]. Another study showed that freedom from reintervention was 89 % at 10 years and 72 % at 15 years [2]. The rate of redo CABG in relation to the total number of CABG procedures has been decreasing, probably for several reasons: (1) The use of the left ITA for anastomosis to the left anterior descending artery (LAD) has become the standard strategy at primary operation; (2) PCI has been performed aggressively even in patients who underwent CABG previously; and (3) optimal medical therapy, with statins and dual antiplatelet medications, is routinely administered after primary CABG. A study based on the database of the Society of Thoracic Surgery (STS) showed that the peak of the rate of redo CABG was 10 % of CABG in 1992/93, decreasing to 8 % in 1995, and to 7 % by the year 2000 [3]. According to a study from the Cleveland Clinic Foundation [4], the ratio of redo CABG to total CABG has been continuously declining. According to data in the annual report from the Japanese Association for Thoracic Surgery (JATS), the number of redo CABG procedures has decreased dramatically during the last 10 years [5]. The ratio of redo CABG to the total number of CABG procedures has decreased from 10 to 2 % over 10 years (Fig. 1).
The patients who are candidates for redo CABG should have at least one good graftable coronary artery whose territory is ischemic and viable. If the patient is symptomatic, redo CABG is strongly indicated. In a study comparing redo CABG and PCI for patients with previous CABG, the survival rates at 1 and 5 years were comparable between the two revascularization strategies [6]. In the AWESOME randomized controlled trial and registry, overall in-hospital mortality was higher for CABG than for PCI [7, 8]. Considering the initial higher mortality of redo CABG and the comparable long-term mortality, PCI is the preferred revascularization strategy, especially in patients with a patent left ITA and amenable anatomy. CABG is preferred for patients with more diseased or occluded grafts, as well as those with no patent arterial graft. Subramanian et al. [9], from the Cleveland Clinic Foundation, reported that patients with patent left ITA-toLAD grafts who develop non-LAD territory jeopardy derived no survival benefit from either reoperation or PCI over medical therapy. This means that the LAD territory must be jeopardized for coronary reintervention to improve survival. Reintervention in patients with a patent ITA-toLAD graft may be warranted to relieve symptoms, but no survival benefit should be expected. The recommendation classes and evidence levels suggested in the European guidelines are shown in Table 1 [10]. If the patient has stenotic vein grafts, some factors influencing the selection of either CABG or PCI are shown in Table 2 [11].
Indications
Surgical results
The indications for redo CABG should be stricter than that for primary CABG, because operative mortality and morbidity are higher than those of primary CABG. In-hospital mortality in redo CABG is more than twice as that of primary CABG.
Early surgical results
Incidence
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Redo CABG always carries more operative risk than primary CABG. The early mortality of redo CABG has been
Gen Thorac Cardiovasc Surg Table 1 Indications for redo CABG from the European Guidelines for revascularization Class
Level
In early graft failure Coronary angiography is indicated for highly symptomatic patients, or in the event of postoperative instability, or with abnormal biomarkers/ECG suggestive of perioperative MI
I
C
Decision of redo CABG or PCI should be made by the Heart Team
I
C
PCI is a superior alternative to reoperation in patients with early ischemia after CABG
I
B
The preferred target for PCI is the native vessel or ITA graft, not the freshly occluded SVG
I
C
For freshly occluded SVG, redo CABG is recommended rather than PCI if the native artery appears unsuitable for PCI or several important grafts are occluded
I
C
PCI or redo CABG is indicated in patients with severe symptoms or extensive ischemia despite OMT
I
B
PCI is recommended as a first choice, rather than redo CABG
I
B
PCI of the bypassed native artery is the preferred approach when stenosed grafts [3 years old
I
B
Table 2 Indications for redo CABG and PCI when saphenous vein grafts are stenotic Redo CABG better
PCI better
Late ([5 years) stenosis
Early (\5 years) stenosis
Multiple stenotic vein grafts
Single stenotic vein graft
Diffusely atherosclerotic vein grafts Stenotic LAD vein graft
Other patent vein grafts
No patent ITA graft
Patent ITA–LAD graft
Abnormal left ventricular function
Normal left ventricular function
Focal graft lesions
In late graft failure following CABG
ITA is the conduit of choice for redo CABG
I
B
Redo CABG should be considered for patients with several diseased grafts, reduced LV function, several CTO, or absence of a patent ITA
IIa
C
PCI should be considered in patients with patent left ITA and amenable anatomy
IIa
C
reported to be two to five times higher than the rates we would expect for primary CABG. However, there has also been progress in early operative results. At the Cleveland Clinic Foundation, from 1967 through 1991, the in-hospital mortality of redo CABG was 3–4 % [12], and it continued to decrease to 2.5 % in 2002 [4], even though patients’ profiles were more comorbid. Ghanta et al. [13] recently reported an improvement in the early surgical results of redo CABG from the STS Database. They showed that the patients’ profiles became more comorbid in 2009 compared to those in 2000. The patients in 2009 had more left main disease (35.1 vs. 25.5 %), more myocardial infarction (60.9 vs. 55.9 %), more heart failure (18.4 vs. 14.2 %), more incidence of previous PCI (51 vs. 35 %), more renal failure (2.2 vs. 0.7 %), and more cerebrovascular disease (12.4 vs. 8.5 %), and were more likely to need frequent urgent or emergent operation (51 vs. 39 %). Despite those circumstances, the risk-adjusted operative mortality of redo CABG declined from 6.0 % in 2000 to 4.6 % in 2009, and risk-adjusted stroke rate decreased from 1.9 % in 2000 to 1.6 % in 2009. Those improvements in early surgical results can be attributed to various factors that improved
Fig. 2 Operative mortality in redo CABG compared to that of primary CABG in Japan
during those 10 years, including pre- and postoperative patient’s management, cardioplegia strategy, especially retrograde cardioplegia technique, handling of the old patent grafts, avoiding injury to grafts, and frequent use of the ITA graft. Indeed, Sabik et al. [13] have recently reported that by using ITA to the LAD in redo CABG, operative mortality can be significantly reduced compared to that of patients who had SVG to the LAD. Figure 2 shows the operative mortality in redo CABG compared to that of primary CABG from the data in the annual report from JATS. The operative mortality of primary CABG has been improving continuously during the last 10 years, whereas operative mortality in redo CABG has only shown a trend to decrease. Operative mortality in redo CABG was more than three times as high as that of primary CABG (Fig. 2). The higher in-hospital mortality of redo CABG has been reported to be associated with an increased risk of perioperative myocardial infarction. Indeed, in the Cleveland Clinic Foundation series, the cause of perioperative death was cardiovascular events in 85 % of cases, which contrasts with the results of primary CABG, where noncardiac causes of death have been increasingly important [14].
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Fig. 3 The number of cases and operative mortality in electeive and emergent redo CABG
The higher incidence of perioperative myocardial infarction may be attributable to multiple factors unique to redo CABG, including incomplete revascularization, distal coronary artery disease, vein graft thrombosis, ITA graft failure, atherosclerotic embolization from diseased SVGs, injury to bypass grafts, hypoperfusion from arterial grafts [15], preoperative myocardial infarction, and complications of PCI. Figure 3 shows operative mortality of elective and emergent redo CABG in the last 10 years. Operative mortality of elective redo CABG procedures has been about 3 % continually in the last 10 years. Operative mortality of emergent redo CABG has slightly improved in the last several years; however, it is almost three times higher than that of elective cases. The numbers of cases have been decreasing during last 10 years in both elective and emergent redo CABG procedures. Predictors for in-hospital mortality of redo CABG identified in previous studies were increased age, female gender, and emergency operation [16, 17]. Redo CABG has specific anatomic conditions, such as the presence of patent ITA grafts and atherosclerotic SVGs, which might affect operative risk. Lytle et al. [12] documented that patent ITA grafts never increased the mortality rate of redo CABG. They noted that the risk of ITA damage has dropped from 8 % in their earlier experience to 3.7 % in more recent years, with increased surgical experience. When the patent left ITA-to-LAD graft or left ITA-toLCx graft is confined to the left side of the mediastinum along the phrenic nerve, injury of the ITA graft may not occur during reentry of the sternum. When the right ITA-
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to-LAD graft crosses the midline of the sternum and the graft has adhered to the back of the sternum, it could cause problems during reentry of the sternum. In such cases, a small thoracotomy on either the left or the right side may be helpful to dissect the right ITA graft free across the midline [11]. In previous studies, patent atherosclerotic stenotic SVGs increased the risk of mortality [18]; however, more recent studies showed that the risk has been neutralized by a combination of improved technology, the use of retrograde cardioplegia delivery, and increased surgeon experience [12], although more diseased grafts are still associated with higher risks. Late surgical results Patients undergoing redo CABG are older, have more complex pathology in the coronary arteries, and show a shortage of available conduits. Therefore, it is not surprising that the long-term results of redo are worse than those of primary CABG. In a recent study, Yap et al. [19] reported that the 5-year survival of redo CABG was worse than that of primary CABG; however, when the background of the patients was adjusted, the survival curve became almost superimposable. If we compare the long-term results of CABG and PCI for patients who underwent primary CABG, Cole et al. [20] reported that 10-year survival rates were not different; however, freedom from CABG was 90 % in the CABG arm, whereas it was 60 % in the PCI arm.
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Long-term results were also affected by the bypass conduits used in redo CABG. If the ITA was used in redo CABG, the intermediate survival rate and the rates of freedom from cardiac events and recurrence angina were higher than those in patients who underwent revascularization with only SVGs [21].
Technical aspects of redo CABG Redo CABG is technically more difficult and challenging than primary CABG. There are many pitfalls that should be avoided from the beginning through to the end of the procedure.
Dissection of the diseased vein grafts should be minimized; they are just removed from the pericardium. On the other hand, the patent ITA should be dissected free for almost its whole length, because the ITA must be clamped while the heart is arrested in conventional redo CABG, while in off-pump, you cannot rotate the heart without ITA dissection. If the right ITA was used to connect to the LAD across the midline, it must be dissected free in order to secure the aortic cannulation and cross-clamp sites. To dissect the patent ITA graft, the use of a harmonic scalpel is strongly recommended [22]. The blade of the harmonic scalpel is never heated to above 80 °C and never causes thermal injury to the ITA, provided it is used properly.
Sternal reentry Cardioprotection Most redo CABGs are performed through the same median sternotomy as the primary operation. The wires are cut anteriorly but not removed. The sternum is cut with an oscillation saw, while the wires are pulled up, and the tissue beneath the sternum is away from the sternum. It is better to use a micro-oscillator, because it conveys the sensation of cutting the inner layer of the sternum. If the patent ITA or the ascending aorta is seen to have adhered to the sternum on the preoperative CT, a small thoracotomy can be performed on either side of the chest cavity, depending on the site of the adhesion, and dissection of the adhesion should be performed before the sternum is opened [11]. If the adhesion is very severe, cardiopulmonary bypass should be prepared from extracardiac access. For redo CABG, the right axillary artery may be preferable to the femoral artery, because patients undergoing redo CABG often have atherosclerotic extracardiac arteries. Dissection of the heart, the ascending aorta, and grafts Once the sternum is open, dissection should be started at the lower part of the heart because this is usually the easiest part to dissect. Then, dissection of the ascending aorta and the right atrium is performed next, in order to secure the arterial and venous access. If redo CABG is performed in a conventional fashion (using cardiopulmonary bypass with the heart arrested by cardioplegia), cardiopulmonary bypass can be started at this point, and further dissection can be performed with the heart decompressed on cardiopulmonary bypass. In the case of an off-pump redo CABG procedure, we have to rotate the heart using a heart positioner to facilitate visualization of the dissecting plane. To dissect the heart through a narrow space while it is beating, a harmonic scalpel is very useful.
Cardioprotection is extremely important, especially in redo CABG, because the coronary arteries of patients undergoing redo CABG are often severely atherosclerotic, and totally occluded. Care should be taken to protect myocardium, especially if it is mainly perfused by the ITA. In such a case, cardioplegic solution should be given, not only from the root of the ascending aorta in an antegrade fashion, but also from the coronary sinus in a retrograde fashion.
Management of patent diseased vein graft Management of patent diseased SVG is very important issue in redo CABG. Previously, it was reported that risk of hypoperfusion of the LAD territory was high when a patent diseased vein graft was replaced with an in situ ITA, because immediate flow of an in situ left ITA was lower than the flow of a stenotic vein graft [23]. Therefore, it may be better leave a patent diseased SVG alone even after grafting the left ITA to the LAD, especially when stenosis of the SVG is not very tight. However, because it was reported that graft flow of the skeletonized ITA was more than that of the pedicled ITA [24], a patent diseased SVG may be able to be replaced with the ITA provided it is skeletonized. Further study is needed regarding this issue.
Grafting pattern and the selection of bypass grafts One of the difficulties in performing redo CABG is the selection of bypass conduits. The basic concept of how to select bypass conduits in redo CABG is the same as that in primary CABG. If only the saphenous vein was used in a primary CABG, the left and right ITAs are available for redo CABG. Many patients who undergo redo CABG may
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have a patent ITA-to-LAD graft, whereas SVGs to the right and left circumflex arteries are occluded. In such a case, both bypass grafts to the right and circumflex arteries can be replaced by new SVGs; other choices of grafts are the right ITA and the radial arteries. When the right ITA is used as an in situ graft, it can be used to the circumflex arteries via the transverse sinus; however, dissection of the sinus may be difficult in a redo situation. Another option is to exchange the left ITA-toLAD graft to the circumflex artery, whereupon the in situ right ITA is used for the LAD. In those ways, the single ITA graft arrangement can be upgraded to a bilateral ITA graft arrangement [25]. Another option to convert single ITA use to bilateral ITA use in redo CABG is to use the right ITA as a free graft. Min et al. [27] reported complete revascularization using a free right ITA as a side branch from the previous patent left ITA-to-LAD graft. Those graft arrangements using bilateral ITAs may have a survival benefit, as in primary CABG [26]. Further studies should be conducted. The right gastroepiploic artery can be a good option for a graft to the inferior wall in redo CABG [28]. When the inferior wall is the only target in redo CABG, grafting using the in situ right gastroepiploic artery through the diaphragm is possible in an off-pump fashion [29].
Off-pump versus on-pump in redo CABG There is a lot of enthusiasm for performing off-pump CABG in Japan and other Asian countries. In fact, in Japan, 65 % of CABG procedures are performed off-pump. There have been many studies comparing the surgical results between conventional CABG and off-pump CABG. In general, there is no decisive difference in in-hospital mortality between conventional CABG and off-pump CABG. However, when we look at the results of the offpump technique in patients with more comorbidities, the in-hospital mortality of off-pump CABG remains low [30]. In addition, the off-pump technique could reduce the incidence of catastrophic complications, such as stroke, after CABG [31, 32]. Therefore, there is a possibility that the off-pump technique could reduce in-hospital mortality and the rate of serious complications in redo CABG, which inherently bears a higher operative risk. There have been several studies comparing the off-pump technique with conventional redo CABG, although most of them were single-centered and retrospective [33–36]. Those studies showed that there was no difference in operative mortality between off-pump and on-pump CABG, whereas the durations of mechanical ventilation and hospital stay were shorter, and units of transfused blood were fewer for the off-pump technique. However, the
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Fig. 4 Operative mortality in redo CABG comparing off-pump and on-pump techniques
completeness of revascularization was less, and the number of grafts was lower for off-pump CABG. Therefore, the investigators concluded that off-pump might be effective only in selected patients. From the data in the annual report from JATS, Fig. 4 shows the operative mortality in redo CABG, comparing off-pump and on-pump. Operative mortality in off-pump redo CABG has always been lower than that of on-pump redo CABG, although the patients’ backgrounds were not matched. A propensity analysis was performed, based on the Japan Cardiovascular Surgical Database (JCVSD), comparing the early surgical results between off- and on-pump CABG in patients who had undergone previous CABG [37]. Operative mortality tended to be lower, and the composite endpoint of mortality or major complications was statistically significantly less frequent for off-pump redo CABG compared to on-pump redo CABG.
Future prospects Redo CABG continues to be challenging, because patients have become more comorbid with more complex coronary anatomy and lower levels of cardiac function. In the near future, a less invasive approach for redo CABG may be the standard approach, avoiding reentry of the sternum, and without the use of cardiopulmonary bypass. Hybrid procedures of off-pump CABG and PCI will become one of the options of coronary revascularization for patients with previous CABG. Conclusions Surgical outcomes have been improving in redo CABG despite the fact that we have more comorbid patients than before. However, in-hospital mortality in redo CABG has
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been higher than that in primary CABG. A less invasive approach, avoiding reentry of the sternum and without use of cardiopulmonary bypass, needs to be developed. Conflict of interest interest.
All the authors have declared no conflict of
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