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Ann Thorac Surg 2001;72:2003-2007
© 2001 The Society of Thoracic Surgeons

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Original article: cardiovascular

Influence of internal mammary artery grafting and completeness of revascularization on long-term outcome in octogenarians

^a Division of Cardiothoracic Surgery, Washington University School of Medicine, St. Louis, Missouri, USA

Accepted for publication July 18, 2001.

* Address reprint requests to Dr Moon, Division of Cardiothoracic Surgery, Washington University School of Medicine, 3108 Queeny Tower, #1 Barnes-Jewish Plaza, St. Louis, MO 63110-1013, USA
e-mail: moonm{at}msnotes.wustl.edu

	Abstract

Top Abstract Introduction Material and methods Results Comment References

 
Background. It has been well established that complete revascularization with internal mammary artery (IMA) grafting is important in young patients undergoing coronary artery bypass grafting (CABG). Applying these principles to octogenarians remains controversial.

Methods. From 1986 to 1999, 358 consecutive patients aged 80 to 94 years underwent CABG. Revascularization was complete in 291 (81%) and incomplete in 67 (19%). The IMA was used in 231 (65%) cases.

Results. Operative mortality was 7% ± 1%, but was not statistically different with or without IMA grafting (IMA 5% ± 2% versus no IMA 10% ± 3%, p = 0.11) or complete revascularization (p > 0.41). Midterm survival improved with IMA grafting (70% ± 3% versus 56% ± 5% at 4 years, p < 0.03; 36% ± 4% versus 29% ± 5% at 8 years, p < 0.08), but was not significant beyond 8 years. Among 138 survivors, those with IMA grafts were more likely to be angina free (82% versus 53%, p < 0.001) and in New York Heart Association class I (60% versus 36%, p < 0.03). Survival, recurrent angina, and functional class were independent of completeness of revascularization (p > 0.21).

Conclusions. IMA grafting improved survival, angina, and functional class of octogenarians, but complete revascularization did not have a similar impact.

	Introduction

Top Abstract Introduction Material and methods Results Comment References

 
It has been well established that complete revascularization with internal mammary artery (IMA) grafting is important in young patients undergoing coronary artery bypass grafting (CABG). In elderly patients, these principles remain less absolute. Previous studies, generally performed in patients less than 70 years of age, have demonstrated that IMA grafting to the left anterior descending (LAD) artery is superior to saphenous vein grafting with respect to long-term patency and survival [1–4]. However, use of the IMA in octogenarians has been inconsistent, and similar studies in this ever growing subpopulation of patients have not addressed the long-term results of arterial revascularization [5–10]. In addition, during the last decade, complete revascularization has been shown to improve long-term outcome over incomplete revascularization in young patients [11–13]. However, octogenarians have been excluded from most of these studies. The purpose of the current investigation was to determine how complete revascularization and IMA grafting influenced long-term survival, late recurrent angina, functional class, and quality of life after CABG in octogenarians.

	Material and methods

Top Abstract Introduction Material and methods Results Comment References

 
This retrospective review includes 358 consecutive patients, 80 years of age or older, who underwent isolated, first-time CABG procedures at Washington University Medical Center (Barnes-Jewish Hospital) from January 1986 to June 1999. There were 182 (51%) men and 176 (49%) women, with a mean age (± one standard deviation) of 82 ± 3 years (range, 80 to 94 years). Fourteen (4%) patients had one-vessel disease, 67 (19%) patients had two-vessel disease, and 277 (77%) patients had three-vessel disease. Complete revascularization was accomplished when at least one graft was placed in each of the three major vascular regions distal to a 50% diameter narrowing, if one existed [11–13]. It was not considered necessary to bypass all obstructed diagonal branches of the left anterior descending or marginal branches of the circumflex coronary arteries for revascularization to be considered complete. Revascularization was complete in 291 (81%) patients and incomplete in 67 (19%) patients. Revascularization was incomplete in 13% of patients with two-vessel disease and 21% of patients with three-vessel disease. The IMA was used in 231 (65%) patients, and 127 (35%) patients underwent CABG without IMA grafting. Operative year did not influence completeness of revascularization (p < 0.53), but IMA grafting was more common during the later time periods (p < 0.001; Fig 1). Selected preoperative and intraoperative clinical patient characteristics are listed in Table 1. The number of vessels bypassed, cross-clamp time, and cardiopulmonary bypass (CPB) time were all significantly greater in patients who underwent IMA grafting (p < 0.04) or complete revascularization (p < 0.05). Urgent or emergent versus elective status was more common in the non-IMA group (p < 0.001)

View larger version (20K): [in this window] [in a new window]   Fig 1. Influence of operative year on use of the internal mammary artery (IMA) and completeness of revascularization. The number of patients who underwent bypass grafting each year is indicated.

Data analysis
Operative mortality included any death that occurred during the initial hospitalization or within 30 days of operation for discharged patients. Long-term survival data included death from all causes. Continuous data are reported as mean ± one standard deviation and were compared between groups using Student’s t test or analysis of variance as appropriate. Clinically important ratios are reported with 70% confidence limits. Actuarial survival estimates were calculated using the Kaplan-Meier method and were compared using the log-rank test. Variability of the actuarial estimates is expressed as ± one standard error of the mean. Univariate analysis (² test) and multivariate stepwise regression analysis were used to determine the preoperative and intraoperative risk factors that were significant, independent predictors of operative mortality and long-term survival (SigmaStat 2.03, SPSS Inc, Chicago, IL). Odds ratios are reported with 95% confidence intervals (CI). Twenty-four variables were analyzed: age, year of operation, gender, hypertension, diabetes, pulmonary disease, cerebrovascular disease, peripheral vascular disease, chronic renal insufficiency, cigarette smoking, recent myocardial infarction ([MI] less than 2 weeks), remote MI (more than 2 weeks), angina (absent, stable, unstable), congestive heart failure, ejection fraction, status (urgent, elective), left main disease (greater than 50% stenosis), use of the IMA, total vessels bypassed, CPB time, cross-clamp (myocardial ischemic) time, preoperative intraaortic balloon pump, extent of disease (single-, double-, triple-vessel), and completeness of revascularization.

	Results

Top Abstract Introduction Material and methods Results Comment References

 
Operative morbidity and mortality
The operative mortality rate was 7.0% ± 1.4% overall (25 of 358 patients); 2.9% ± 1.1% (7 of 239) for elective operations, and 15.1% ± 3.4% (18 of 119) for urgent/emergent operations (p < 0.001). There was a tendency for operative mortality to be lower when the IMA was used (5% ± 2% versus 10% ± 3%), but the difference did not reach statistical significance (p = 0.11). Operative mortality was independent of the completeness of revascularization (7% ± 2% complete, 9% ± 4% incomplete, p > 0.66). Multivariate regression analysis identified four factors as independent predictors of operative mortality: earlier operative year (p < 0.02); increased age (p < 0.04); urgent/emergent status (p < 0.001); and increased CPB time (p < 0.005). Postoperative complications included perioperative MI (2% ± 1%), cerebrovascular accident (5% ± 1%), reoperation for bleeding (3% ± 1%), atrial fibrillation (52% ± 3%), and mediastinitis (2% ± 1%), but all were independent of completeness of revascularization and IMA use (p > 0.20).

Postoperative survival
Of the 333 early survivors, there were 188 late deaths, and 7 patients were lost to follow-up. Mean follow-up was 55 ± 38 months. The longest survivor is a 96-year-old woman, alive 15 years after CABG without IMA. Multivariate regression analysis identified three factors as independent predictors of late death: earlier operative year (p < 0.001, odds ratio [OR] = 1.48, 95% CI: 1.33 to 1.64); chronic renal failure (p < 0.001, OR = 4.16, 95% CI: 1.60 to 10.9); and congestive heart failure (p < 0.03, OR = 1.85, 95% CI: 1.01 to 3.41). Actuarial survival rates (including operative deaths) for all patients was 83% ± 2% at 1 year, 54% ± 3% at 5 years, and 18% ± 3% at 10 years.

Survival was significantly superior as long as 8 years postoperatively for patients who underwent IMA grafting (Table 2, Fig 2). At 4 years, survival was 70% ± 3% with IMA use compared with only 56% ± 5% without IMA use (p < 0.005). At 8 years, survival was 36% ± 4% and 29% ± 5%, respectively (p < 0.08). At 6 years, the survival curves began to converge, so that by the ninth postoperative year, the survival difference was no longer present (p > 0.14). There was no significant difference in survival for patients who underwent complete versus incomplete revascularization at any time period (p > 0.21; Table 2, Fig 3).

View larger version (17K): [in this window] [in a new window]   Fig 2. Long-term survival estimates for octogenarians undergoing coronary artery bypass grafting with and without use of the internal mammary artery (IMA). The numbers of patients at risk are indicated.

View larger version (16K): [in this window] [in a new window]   Fig 3. Long-term survival estimates for octogenarians undergoing coronary artery bypass grafting with complete and incomplete revascularization. The numbers of patients at risk are indicated.

	Comment

Top Abstract Introduction Material and methods Results Comment References

 
Coronary artery bypass grafting is associated with increased operative risk for octogenarians compared with younger patients. The Society of Thoracic Surgeons database reports a 2.5% mortality rate for patients 80 years of age or less, compared with 6.8% for those more than 80 years of age; this represents a relative risk of 2.77 [14]. In this study, multivariate analysis similarly identified increased age as an independent predictor of operative mortality (p < 0.04). Arguments against IMA grafting in octogenarians have been based on these types of data, combined with a presumed increase in perioperative morbidity with IMA grafting in the elderly. Although operative mortality is diminished for octogenarians when compared to younger patients, early survival in the current series tended to be lower with IMA grafting, consistent with previous reports [3–5]. Another argument against routine IMA use in octogenarians assumes that elderly patients are unable to realize the long-term benefits of arterial grafting because their life expectancy after CABG is limited. Natural history studies have shown that whereas a 70-year-old person can expect to live 13.2 more years, the average life expectancy for an 80-year-old person is 7.7 years and falls to 5.8 years at 85 years of age [15]. Despite the limited life expectancy for octogenarians, we found that IMA grafting was associated with improved survival as long as 8 years postoperatively, decreased late recurrent angina among long-term survivors, and improved functional class. In the absence of confounding variables, IMA use may have been responsible for these beneficial outcomes. The long-term benefits previously associated with IMA grafting in younger patients were realized by the octogenarians in this series, without an increase in operative morbidity or mortality.

The impact of complete revascularization in this study was not as profound as that seen with IMA grafting. In a previous study, Bell and coauthors [11] noted that complete revascularization improved long-term outcome of patients with three-vessel disease based on data from the coronary artery surgery study (CASS), but this database excluded patients more than 65 years of age. Other studies from Emory University [12] and the Cleveland Clinic [13] reported that complete revascularization was beneficial for patients with two-vessel and three-vessel disease, but again the mean ages were only 57 ± 9 years and 54 ± 9 years, respectively. In the Emory study, complete revascularization correlated with improved survival compared with incomplete revascularization, but the survival curves did not begin to diverge statistically until the second half of the first decade after CABG [12]. Furthermore, in patients with two-vessel disease, the difference was not apparent until the eighth or ninth postoperative year. In the present study, the survival benefit noted with IMA grafting was immediate. At 1 year, survival was 86% ± 2% with IMA grafting compared with 77% ± 4% without IMA grafting (p < 0.02). The difference in survival peaked at 3 years, started to converge by year 6, and was no longer significant beyond 8 years. This difference may explain why octogenarians did not demonstrate the benefits of complete revascularization that have been reported previously for younger patients. Thus, while the limited life expectancy of octogenarians did not eliminate the benefits seen with IMA grafting, it may have minimized the benefits of complete revascularization.

Potential limitations
The current study was subject to all the limitations inherent to a retrospective review; however, it is unlikely, with the current data supporting the benefits of IMA grafting, that a randomized study will ever be performed to address these issues. Another obvious limitation was the possible selection bias with regard to which patients underwent IMA grafting and complete revascularization. For example, IMA grafting may have been withheld from some patients who were considered "high risk." Multivariate analysis was employed in an attempt to account for these and other confounding risk factors, but such biases will always be present in observational studies. When separate analyses were performed for elective status only and urgent/emergent status only patients, the results were similar, and the conclusions were unchanged. Ideally, the reintervention and late myocardial infarction rates would have been included in the results section; however, these data were only available for the 40% of patients that were alive at late follow-up, making their analysis of limited value. Another potential limitation was the relatively small number of patients compared with much larger studies of younger patients. CABG for octogenarians has been uncommon, however, and the number of patients reported in this series is consistent with those from other recent studies of the elderly [5–10]. The number of patients at risk late after CABG was also small, but even in a healthy population of octogenarians, the predicted number alive after 10 years would be low.

In summary, this report demonstrated that octogenarians who underwent IMA grafting during CABG had improved long-term survival for as long as 8 years postoperatively, a lower incidence of late recurrent angina, and an improved functional class when compared with patients who did not receive an IMA graft. Complete revascularization did not have a similar impact, perhaps owing to the limited life expectancy of octogenarians and the delayed time-course necessary to realize the benefits of this more aggressive revascularization strategy. Therefore, IMA grafting is important in octogenarians and should be performed in most elderly patients, even when revascularization is incomplete.

	References

Top Abstract Introduction Material and methods Results Comment References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Marc R. Moon Thoralf M. Sundt, III Michael K. Pasque Hendrick B. Barner William A. Gay, Jr Ralph J. Damiano, Jr Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Moon, M. R. Articles by Damiano, R. J. Search for Related Content PubMed PubMed Citation Articles by Moon, M. R. Articles by Damiano, R. J., Jr Related Collections Coronary disease