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(Circulation. 2000;101:640.)
© 2000 American Heart Association, Inc.
Clinical Investigation and Reports |
From the Departments of Cardiovascular Surgery and Cardiology (S.O., K.N.), Kumamoto Central Hospital, Japan.
Correspondence to Ryuzo Sakata, MD, Kumamoto Central Hospital, 96 Tainoshima, Tamukae-machi, Kumamoto City, 862-0965 Japan. E-mail masashik{at}orange.ocn.ne.jp
| Abstract |
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Methods and ResultsOf the 1456 patients who underwent isolated coronary artery bypass grafting between January 1989 and December 1998 at Kumamoto Central Hospital, 393 patients (mean age, 62.4±9.0 years) with the RITA anastomosed to the major branches of the circumflex artery were studied. Left ITA grafting was performed in 384 patients, and in 369, the in situ left ITA was anastomosed to the left anterior descending coronary artery using standard methods. Early postoperative angiography was performed in 381 patients. The RITA was occluded in 4 patients, and string-like artery and significant stenosis were present in 11 and 7 patients, respectively; RITA graft patency was thus 94.1%. Of the preoperative variables and angiographic data, simple and multiple logistic regression analyses identified decreased severity of native stenosis, diffuse sclerosis of native vessels, and residual side branches of the ITA as independent predictors of nonfunctional grafts. The method of ITA grafting did not influence the patency of the graft.
ConclusionsThe excellent patency rate demonstrated by this study, the largest angiographic study to date of RITA grafting via the transverse sinus, indicates that this technique can provide reliable revascularization of the left ventricle and that it has the potential to be applied to a wide variety of patients with diseased circumflex arteries.
Key Words: mammary arteries coronary artery bypass vascular patency
| Introduction |
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| Methods |
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During 1998, 109 RITA grafts via the transverse sinus (63.4%) were
performed in the 172 patients undergoing isolated CABG. Of the 393
total patients studied, 310 were men and 83 were women; they had
a mean age of 62.4±9.0 years (range, 13 to 78 years). Patient
characteristics are summarized in Table 1
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The group of patients studied included 10 dialysis patients (2.5%) and 99 patients (25.2%) with diabetes mellitus (13 required insulin treatment, 39 were on oral drug therapy, and 47 were on diet control). In the 14 patients with severe atherosclerosis of the ascending aorta, BITA grafting was performed during hypothermic ventricular fibrillation.
Data Definitions
A perioperative myocardial infarction was
documented if a new Q wave appeared on the ECG or if creatine kinase MB
levels rose beyond 100 IU/L. Mediastinitis was defined as infection
involving the mediastinal area, with sternal instability and positive
organism culture.
Only permanent or reversible focal complications, such as reversible ischemic neurological deficit or transient ischemic attacks, were categorized as strokes. Confusion, agitation, dementia, disorientation, or psychosis were categorized as strokes only if new focal neurological signs were also present.
The residual side branches of the ITA were defined as large if their size was at least half the diameter of the ITA and as small if their size was less than half.
Operative Procedures
The operative technique used was similar to that described in
our previous reports.3 5 After dissection, the ITA pedicle
was wrapped with papaverine-soaked gauze (200 mg/50 mL of saline
solution). No intraluminal papaverine injections were given.
As shown in Table 2
, the technique
of in situ RITA grafting via the transverse sinus was most commonly
used to revascularize the posterolateral wall; LITA grafting was
used to revascularize the anterolateral wall of the left ventricle. The
RITA was directed to the most important branches of the circumflex
artery with good drainage. LITA grafting was performed in 384
patients; in 369 (81%), the in situ LITA was anastomosed to the LAD
using standard methods.
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We used the following types of arterial grafts: BITA (264 patients), BITA and the gastroepiploic artery (113 patients), RITA and the gastroepiploic artery (5 patients), and RITA (11 patients). Multiple arterial grafting was common in this group. Supplementary saphenous vein grafts were used in most patients. The mean number of distal anastomoses was 3.7±1.0 (range, 2 to 6). Concomitant procedures included mitral annuloplasty (4 patients), left ventricular aneurysmectomy (5 patients), mitral annuloplasty and tricuspid annuloplasty (1 patient), tricuspid annuloplasty alone (1 patient), and mitral valve replacement and left ventricular aneurysmectomy (1 patient).
Preoperative and Postoperative Angiography
All patients underwent preoperative angiography. The size of the
perfusion areas of each of the major branches (target vessels) was
qualitatively graded by independent observers from 1 to 4 (tiny, small,
medium, or large, respectively). The dominance of the left
coronary artery system was also qualitatively graded from 1 to
3 (small, balanced, or large, respectively).
To evaluate the early patency rate, postoperative angiography was performed 2 to 3 weeks after surgery. All ITA grafts were evaluated for occlusion, the development of string sign, or the presence of significant stenosis (flow limitation or >50% stenosis of the vessel diameter at any point along the body of the graft or at any anastomoses). For purposes of analysis, occluded grafts and grafts showing string sign without a definite technical failure (anastomotic stenosis) were considered nonfunctional.
All angiographic data were reviewed by independent observers (S.O. and K.N.) who were unaware of the operative outcomes.
Statistical Methods
Data are presented as means with 95% confidence
intervals. Simple (univariate) and multiple
(multivariate) logistic regression analyses
were performed to determine the predictors of nonfunctional ITA among
the preoperative variables (sex, body surface area [BSA],
age, hypertension, diabetes, hyperlipidemia, chronic
renal failure, previous myocardial infarction, and ejection
fraction) and the angiographic data (laterality of ITA, site of ITA
grafting, the perfusion area of ITA, major side branches of the ITA,
the size [dominance of] of the left coronary artery system,
and degree of native coronary artery stenosis).
P<0.05 was considered significant. For comparison purposes,
only cases with the ITA anastomosed singly to the recipient artery were
analyzed. All analyses were performed using
commercial statistical software (SAS version 6.12).
| Results |
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Postoperative intra-aortic balloon pumping was required in 4 patients (1.0%). A perioperative myocardial infarction occurred in 22 patients (5.5%). There were 14 re-explorations for bleeding (3.6%), but none was related to the RITA graft. The other noncardiac operative complications included mediastinitis (6 patients; 1.5%), prolonged (>48 hours) ventilation (19 patients; 4.8%), and cerebrovascular accident (16 patients; 4.1%).
Angiographic Examinations
Early postoperative angiography was performed in 381 patients
(96.9%) 2 to 3 weeks after surgery. This study was not performed in 12
patients due to severe atherosclerosis of the ascending
aorta in 6, chronic renal failure in 3, and postoperative
cerebrovascular accidents in 3. The study failed to evaluate the
RITA grafts in 8 patients and the LITA grafts in 3 patients. In these
patients, complete opacification of the ITA grafts was not performed
because of the difficulty of selective engagement into the grafts.
Although these ITA grafts were determined to be nonoccluded by means of
semiselective angiography and retrograde flow from the native
coronary artery, these data were excluded from the
analysis. Thus, complete data for angiography of the ITA was
obtained for RITA grafts in 373 patients and for LITA grafts in 355
patients. The RITA graft was occluded in 4 patients (1.1%), and
string-like artery and significant stenosis were present in
11 (2.9%) and 7 (1.9%) patients, respectively; thus, the patency of
RITA grafts was 94.1%. Six LITA grafts (1.7%) were occluded, and
string-like artery and significant stenosis were present in
3 patients each (0.85%), which gave a patency rate of 97.2% for LITA
grafts. No significant differences existed in patency rates between the
LITA and RITA grafts.
Among the patients who did not undergo angiography (including 1 patient who died postoperatively) and those in whom adequate data were not obtained, no evidence existed that suggested ischemia of the left ventricle occurred in either the postoperative clinical course or stress tests.
Predictors of Graft Failure
Both simple and multiple logistic regression analysis
identified decreased severity of native stenosis, diffuse
sclerosis of native vessels, and residual side branches of ITA as
independent predictors of nonfunctional grafts (Tables 3 through 5![]()
![]()
).
The method of ITA grafting (laterality of RITA or LITA), BSA, sex, or
location of distal anastomoses did not influence the patency of the
graft.
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| Discussion |
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Although our previous study3 demonstrated the excellent
early patency rate of RITA grafting, only 21 women were among the 116
patients studied. Nishida et al9 reported the effects of
smaller physical size on complex arterial grafting in CABG.
They noted that the 1-month patency rate of arterial grafts
was not significantly different between the groups (98.7% versus
96.7%; P=0.16), but that of venous grafts was significantly
lower in groups with a smaller physical size (88.9% versus 97.7%;
P=0.045). Although their study included 264 RITA grafts and
34 woman among the 445 patients who underwent CABG with
2 distal
anastomoses, the site and method of anastomosis were not described.
Small body size and female sex have been recognized as major
contributors to the increased risk of coronary artery bypass
grafting; however, little is known about the independent influence of
body size and sex on RITA grafting via the transverse sinus to the
circumflex and diagonal arteries.8 9 10 11 12 13 14
Several studies have drawn attention to the technical difficulty of arterial grafting in woman and patients with a small body size. OConnor et al10 reported that a small mid-LAD diameter was associated with a substantially increased risk of in-hospital mortality resulting from CABG. Although body size is correlated with mid-LAD diameter, women have smaller coronary arteries than men, even after compensating for differences in body size. OConnor et al10 also noted that their smaller coronary arteries explained the higher perioperative mortality associated with CABG in women and smaller people. Christakis et al12 noted that after adjusting for preoperative risk variables and body size, sex remained a significant predictor of both operative mortality and low-output syndrome. Grandjean et al15 reported that incremental risk factors for the occlusion of the gastroepiploic artery were pump time (operative complexity) and female sex. However, in our study, neither sex nor body size were predictors of graft failure.
In our experience, by creating the shortest route for the ITA and
harvesting the ITA as proximally as possible, an RITA with an
acceptable diameter can be anastomosed to the target coronary
artery, even in high-risk groups, such as women, smaller people, and
elderly patients. In fact, as shown in the Figure
, there has
been a steady increase, with the accumulation of experience, in the use
of this method in CABG patients.
Kurlansky et al16 reported the largest series to date of 327 bilateral internal mammary artery grafts in women, and they concluded that bilateral internal mammary artery grafting can be achieved with low hospital mortality and morbidity rates. They noted that 11 of 327 patients (3.4%) suffered postoperative in-hospital cardiac arrest, which suggested that the relatively higher incidence of this complication seemed to be related to a technical factor rather than sex. Their study covered a wide variety of ITA grafting methods, including 107 cases of the RITA grafted to the right coronary artery system in the 331 RITA grafts. Dietl et al17 reported an increased rate of RITA graft failure when it was used to bypass the right coronary and posterior descending arteries; they attributed this problem to spasm of the distal end of the RITA graft and tension on the graft.
In our experience, although the number of female patients in this study was relatively small (n=83), none required the postoperative use of intra-aortic balloon pumping and, despite a hospital mortality rate of 1.3%, no sternal infections developed. Although no definite conclusions could be drawn due to a lack of angiographic data in Kurlansky et als study16 and the relatively small number of women in our study, the excellent patency of RITA in the posterolateral wall of the left ventricle may explain the comparatively good results in the woman in our series.
Large ITA side branches have been suspected of causing a diversion of blood away from the myocardium, but no cause-and-effect relationship has ever been established.18 In our series, the residual side branches of the ITA were identified by multivariate analysis as independent predictors of nonfunctional grafts. Although a residual side branch of the ITA may result from a nonfunctional graft, we think that with this method of RITA grafting, harvesting the ITA as proximally as possible is mandatory to gain the maximum length of graft and prevent any tension on the RITA.
Several authors have reported significantly lower patency in RITA grafts compared with LITA grafts when the vessel bypassed was not the left anterior descending artery.17 19 However, in our study, once other variables related to graft patency were compensated for, the laterality of the RITA or LITA and the location of distal anastomoses were not predictors of graft failure. Several studies have reported higher operative mortality and an increased rate of graft failure in patients undergoing RITA grafting. He et al11 reported that operative mortality was significantly higher in patients undergoing RITA grafting (21.62%; 8 of 37) than in patients undergoing only LITA grafting (6.53%; 31 of 475; P<0.004). They speculated that the higher operative mortality in elderly patients with RITA could be due to the fact that an extensive length of artery is usually required to reach the posterior descending artery or that the branches of the left coronary artery increase the risk of spasm. When the RITA is used to bypass the right coronary artery, especially segment 3, the dilatation and motion of the right atrium may apply tension to the graft, promoting graft failure. When anastomosed to the circumflex artery, however, once anastomosis is complete at the site of the RITA graft, the course of the graft seems to be smooth due to a lack of exposure to tension or excessive motion.
Other variables associated with graft failure in this study included decreased severity of native stenosis and diffuse sclerosis of the native vessels. Manninen et al20 noted that the frequency of string sign correlated with a decreased severity of stenosis. The results of our multivariate analysis may be partly due to categorizing grafts showing string sign as nonfunctional. In our institution, RITA grafting was sometimes performed on a mildly stenotic circumflex artery when the LITA was anastomosed to a LAD with severe lesions. Although the patency rate of the RITA was comparable to that of the LITA, a better patency rate would be expected when anastomosing the RITA to a circumflex artery with good drainage despite severe lesions.
Study Limitations
Because of the retrospective nature of this study and a lack
of data, the recipient coronary artery diameters were not
included in our analysis. However, previous studies
demonstrated that coronary artery diameter is related to both
sex and measures of body size.10 Thus, we think that
including variables such as sex, BSA, and age will add to the
existing evidence regarding the universal feasibility of RITA
grafting.
In this study group, angiography was not performed for various reasons in 12 patients, including 1 patient that died in the hospital. Also, the study failed to evaluate the RITA graft in 8 patients and the LITA graft in 3. Because it is impossible to include patients with no or inadequate angiographic data in the analysis and because it is also impossible to extrapolate the results of patients with data to patients with no data, the final analysis was based on the angiographic data of patients in whom complete opacification of ITA grafts was feasible. For RITA grafting, despite the 393 patients entered in the study, data from only 373 patients were obtained. Considering the relatively small number of patients who were not included in the analysis (5.1%) and the lack of clinical data suggesting ischemia of the left ventricle or indirect demonstration of patent grafts in these patients, we think that the results of our final analysis using this method reflect the results of the entire patient body.
Conclusions
Multivariate analysis revealed that
routing the RITA via the transverse sinus (laterality of RITA or LITA
and location of distal anastomosis) was not a predictor of graft
failure once other variables related to graft patency were
compensated for. The excellent patency rate demonstrated by this, the
largest angiographic study to date of RITA grafting via the transverse
sinus, indicates that this technique could provide reliable
revascularization of the left ventricle; it seems
to have the potential for application to a wide variety of patients
with diseased circumflex arteries.
Received May 21, 1999; revision received August 23, 1999; accepted September 9, 1999.
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