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Eur J Cardiothorac Surg 2001;20:299-304
© 2001 Elsevier Science NL
Department of Cardiac and Thoracic Surgery, The Tel Aviv Sourasky Medical Center, Tel Aviv 64239, Israel
Received 14 November 2000; received in revised form 26 April 2001; accepted 30 May 2001.
Corresponding author. Tel.: +972-3-6923322; fax: +972-3-6274439
e-mail: pevni{at}tasmc.health.gov.il
| Abstract |
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Key Words: Internal thoracic artery Composite graft Technical aspects
| 1. Introduction |
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Until recently, the routine use of bilateral ITA was infrequent, despite excellent results and low mortality and morbidity [47]. The pedicled right ITA is less useful than the left ITA, as it will not always reach the right coronary artery (RCA) branches without tension, leading to its use predominantly as a free graft, with a lower patency rate when attached to the ascending aorta [8]. Another reason for cautious use of bilateral ITA was related to the increased risk of sternal wound infection [6,7].
A surgical technique was recently developed, where the ITA is dissected as a skeletonized vessel [9,10]. The skeletonized artery is isolated gently with scissors and silver clips, without the use of cauterization. The advantage is that the dissected artery is particularly long, and its spontaneous blood flow is greater than in a pedicled ITA [11,12], allowing the use of both ITAs as grafts to practically all coronary vessels requiring surgical revascularization.
Another advantage of using the skeletonized ITA is the preservation of collateral blood supply to the sternum, enabling more rapid healing, and decreasing the risk of infection [1315].
The bilateral skeletonized ITA technique was adopted in our service as the preferred method for myocardial revascularization. The routine use of saphenous vein graft (SVG) was stopped in 1996, and vein grafts are currently used as a third optional graft (the second is the right gastroepiploic artery (RGEA)), or in emergencies, coronary artery bypass grafting (CABG).
The composite arterial grafting technique is a surgical technique whereby a free artery (usually the right ITA) is connected end-to-side to an in-situ ITA. The patency rate of the free graft in this arterial arrangement is similar to that of the in-situ ITA [16].
Between April 1996 and February 1999, 600 consecutive patients underwent CABG by means of bilateral skeletonized ITA, using the composite arterial grafting technique. In this report, we describe our results and technical experience in this subgroup of patients who received composite grafts.
| 2. Materials and methods |
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2.1. Indications for the composite graft arrangement
We prefer the use of bilateral ITA as in-situ grafts for myocardial revascularization. The two ITAs in combination with the RGEA give us three sources of blood supply. We believe that more blood sources are associated with improved long-term outcome. The cross arrangement (right ITA to left anterior descending artery (LAD) across the midline and left ITA to circumflex marginals (Fig. 1)
) is based on the assumption that the patency rate of the right ITA on the LAD is similar to that of the left ITA on the LAD [16].
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When the distal right ITA bifurcation cannot loosely reach the LAD, we favor the composite arterial grafting technique; we use the right ITA as a free graft, and a T-shaped [17], or if more suitable, a Y-shaped anastomosis, at the level of the main pulmonary artery is prepared, before connection to cardiopulmonary bypass (CPB; Fig. 2) .
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Operations were performed with CPB. The myocardial preservation technique involved intermittent mild hypothermic cardioplegia (3032°C).
The proximal composite anastomosis of free right ITA on the left ITA might, at times, be performed on bypass, after constructing all distal and sequential right ITA anastomoses. This is the safest way to precisely determine the location of the composite anastomosis without compromise to left ITA flow to the LAD.
2.3. Sequential grafting with skeletonized ITA
Sequential grafting is essential for complete arterial revascularization with composite grafts. Diamond-shaped side-to-side anastomosis and terminal T-shaped anastomosis for branches of the circumflex and RCA would be our preferred approach. This approach carries the advantage of sparing ITA length using the shortest possible ITA segments between anastomoses (Fig. 2).
The parallel side-to-side anastomosis is preferred for the intramyocardial coronary artery or for vessels buried inside a deep layer of epicardial fat. Constructing a diamond-shaped anastomosis in these cases exposes the ITA to the risk of seagull-wing kinking [18]. The parallel sequential technique in these situations may also be used for LADdiagonal sequential grafting with the left ITA.
2.4. Other types of composite arrangements
To date, injury to the ITA requiring a revision of the original operative plan occurs in less than 5% of our patients, and in most, except for very few cases, the operation can still be based on both ITAs.
If injury is caused to the proximal right ITA, the operation can still be based on constructing a composite graft, where the free graft of the right ITA is anastomosed end-to-side to the in-situ left ITA. The operative plan is changed here only when our original plan was to use the cross technique. However, if the proximal left ITA is injured, and can no longer be used as an in-situ graft, a reverse composite graft can then be constructed, where the free left ITA is connected end-to-side to the in-situ right ITA. This arrangement of free left ITA on in-situ right ITA can also be used when the spontaneous free flow of the left ITA is inadequate.
Despite the extra length obtained with skeletonized ITA harvesting, the left ITA may sometimes not reach the distally located anastomotic site on the LAD. In this case, a composite graft may be constructed where the in-situ left ITA is connected to a marginal branch of the circumflex, a free right ITA is anastomosed end-to-side to the left ITA, and its distal end is connected to the LAD (Fig. 3) .
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2.5. Our approach to diagonal grafting
In cases which require revascularization of both the diagonal and circumflex system, the left ITA is anastomosed to the LAD, and the diagonal is one of the vessels supplied by the free right ITA (sequential grafting). When the diagonal is intramyocardial or buried deep in fat tissue, it is sometimes necessary to use the reverse Y-composite anastomosis to prevent seagull kinking [18]. In these cases, the diagonal sequential anastomosis is constructed as a parallel and not as a diamond-shaped anastomosis.
When grafts to marginal branches of the circumflex are not needed, it is possible to use the left ITA for sequential LADdiagonal, or preferably, to use the left ITA as a small Y-graft for LADdiagonal anastomoses.
2.6. The RCA
The ITA grafted to the RCA has a low patency rate [2,5]. Arterial anastomosis on this calcified or fibrotic vessel tends to close, and we therefore prefer the more distally located posterior descending artery (PDA) for ITA anastomosis.
It is possible to reach the PDA with a right ITA on a left ITA composite graft (Fig. 2). When no graft to the posterior wall of the heart is necessary (the circumflex region), the right ITA may also encircle the apex of the right ventricle on its course to the PDA anastomotic site.
The right ITA may not be long enough to reach the PDA. In this case, we favor the use of the RGEA as our graft of choice for the PDA. When the PDA is unsuitable for RGEA grafting, such as in cases with a potential for high competitive flow in the RCA, we prefer the SVG for revascularization of the RCA system.
To decrease the risk of spasm of the arterial grafts, all patients were treated with high-dose intravenous infusion of isosorbide dinitrate (Isoket 420 mg/h) during the first 2448 h postoperatively [15]. The systolic blood pressure was maintained above 100120 mmHg. From the second postoperative day, the patients whose gastroepiploic artery was used were treated with calcium channel blockers (Diltiazem 90180 mg/day orally) for at least 3 months.
2.7. Statistical analysis
The data are expressed as means±standard deviation or proportions. The
2 test and two-sample t-tests were used to compare discrete and continuous variables, respectively. Multivariate logistic regression analysis was used to predict unfavorable outcome events by various risk factors. Odds ratios (OR) and 95% confidence intervals (CI) are given. Postoperative survival is expressed by the KaplanMeier method. All analyses were performed by SPSS 7.5 software.
| 3. Results |
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In 574 patients, the right ITA was used as a free graft connected to the in-situ left ITA; in 26, the free left ITA was attached to the in-situ right ITA; the small Y-graft was constructed in 38 patients. The RGEA was used in 116 patients (19.3%), and vein grafts were used in 48 (8%).
The operative mortality (hospital plus 30-day postoperative mortality) was 2.8% (n=17). The mortality of urgent and elective cases was 2.4% (14 of 574) and that of emergency operations was 11.5% (three of 26). Our definition of emergency operation is based on STS guidelines and this included patients with ongoing angina, failed percutaneous transluminal coronary angioplasty (PTCA), acute evolving myocardial infarction, pulmonary edema and cardiogenic shock. In patients with cardiogenic shock who were not stabilized after aortic balloon counterpulsation (intra-aortic balloon pump; IABP), we usually use one ITA and vein grafts. In emergency patients who had been stabilized with IABP and were operated upon within 12 h, we harvested bilateral ITAs. Preoperative use of IABP (OR, 21.0; 95% CI, 3.82315.42) and failed PTCA (OR, 3.65; 95% CI, 0.9613.87) emerged as independent predictors of operative mortality. Neither gender nor age were independent predictors of operative mortality. Age was used as a continuous variable and we also arbitrarily established 70 years as our cut-off point. There were seven (1.2%) perioperative myocardial infarctions (CPK MB elevation of more than 50 mU/ml associated with new Q wave or STT changes), and 12 (2%) patients sustained strokes. Deep (sternal) wound infection occurred in ten (1.7%) patients. Neither diabetes (1.9%; P=0.17) nor advanced age (>70; 1.7%; P=0.264) were independent predictors of untoward events. COPD (OR, 8.7; 95% CI, 2.332.8) and failed PTCA (OR, 4.48; 95% CI, 1.0718.63) were independent predictors of sternal infection. Postoperative follow-up (1436 months) was available in 571 (98%) patients by telephone survey. The 1- and 3-year survival rates (KaplanMeier) were 94.8 and 92.5%, respectively, only 14 of the surviving patients (2.4%) reported the return of angina. Forty-one patients underwent postoperative cardiac catheterization during the follow-up period (between 1 week and 28 months; mean, 14 months after operation), 30 because of chest pain, six had positive thallium SPECT scan, and the remainder consented to elective catheterization within the framework of learning to use the composite technique. Of the anastomoses, 103 (95.4%) were patent and five occluded (4.6%). In two of these five, technical problems were noted in the site of composite (free right ITA on in-situ left ITA) anastomosis.
| 4. Discussion |
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The ITA is currently the conduit of choice in CABG because of superior graft patency [19,20]. The right and left ITA are comparable with regard to size, flow capacity and patency [21]. However, the pedicled right ITA is less useful, as it will not routinely reach the target anastomotic sites on the right or left coronary vessels, leading to its use primarily as a free graft attached to the aorta, with a lower patency rate [8,16]. The so-called T-graft was first utilized by Mills [22] and Sauvage et al. [23]. Complete arterial revascularization was achieved in these series with two conduits, in which the right ITA is usually grafted to the in-situ left ITA and directed to the lateral and posterior aspects of the left ventricle, while the left ITA is directed to the anterior surface of the heart. Tector et al. [17] expanded the use of this technique. Dion et al. [24] demonstrated a better patency rate for free right ITAs arising as composite grafts from the in-situ left ITAs when compared with those attached to the aorta.
Our results showed that the skeletonized ITA is an ideal conduit for the composite arterial technique. The extended length obtained with skeletonization [12], and the extra length gained by constructing the proximal right ITA on the left ITA, improved the versatility of the procedure. However, despite this improved versatility, in many patients (particularly those with cardiomegaly), it seemed safer to use a third conduit (RGEA or vein graft) for revascularization of the RCA system.
During the 3-year period of our study, we never encountered hypoperfusion syndrome (low cardiac output syndrome with temporary EKG abnormalities). This may be related to the improved spontaneous flow of the skeletonized arteries [11,25], and the excellent blood flow reserve of the proximal ITA, which is 23-fold larger than the flow required for complete arterial revascularization [26].
A third advantage of the skeletonized dissection is the preservation of sternal collateral blood supply. This advantage may explain the relatively low occurrence of sternal infections in the subgroups of old and diabetic patients, who are usually at increased risk of sternal wound infection when the bilateral ITAs are harvested as pedicles [6]. Our results are even more conclusive, taking into account the fact that 206 of our patients were diabetics, and 246 of them were aged 70 years or older.
In conclusion, we routinely perform complete arterial revascularization with bilateral skeletonized ITA in most of the patients referred for CABG. In our opinion, bilateral skeletonized ITAs are the most appropriate arterial conduits for the composite technique.
| References |
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