HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

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): Donald S. Likosky Robert S. Kramer Louis Russo Bruce J. Leavitt Robert E. Helm Gerald L. Sardella Francis V. DiPierro Yvon R. Baribeau Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Likosky, D. S. Search for Related Content PubMed PubMed Citation Articles by Likosky, D. S. Related Collections Coronary disease Related Article

---

Original Articles: Adult Cardiac

Effect of Prior Cardiac Operations on Survival After Coronary Artery Bypass Grafting

^a Department of Medicine, Dartmouth College, Hanover, New Hampshire
^b Department of Community and Family Medicine, Dartmouth College, Hanover, New Hampshire
^c Dartmouth Institute for Health Policy and Clinical Practice, Dartmouth College, Hanover, New Hampshire
^d Department of Surgery, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
^e Department of Anesthesiology, and Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire
^f Division of Cardiothoracic Surgery, Maine Medical Center, Portland, Maine
^g Department of Surgery, Central Maine Medical Center, Lewiston, Maine
^h Department of Surgery, Fletcher Allen Health Care, Burlington, Vermont
ⁱ Department of Surgery, Catholic Medical Center, Manchester, New Hampshire
^j Department of Surgery, Portsmouth Regional Hospital, Portsmouth, New Hampshire
^k Department of Surgery, Concord Hospital, Concord, New Hampshire
^l Department of Surgery, Eastern Maine Medical Center, Bangor, Maine
^m Department of Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire

Accepted for publication May 27, 2011.

^_* Address correspondence to Dr Likosky, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 (Email: donald.likosky{at}dartmouth.edu).

	Abstract

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Background: We examined a recent regional experience to determine the effect of a prior cardiac operation on short-term and midterm outcomes after coronary artery bypass grafting (CABG).

Methods: We identified 20,703 patients who underwent nonemergent CABG at 8 centers in northern New England from 2000 to 2008, of whom 818 (3.8%) had undergone prior cardiac operations. Prior CABG using a minimal or full sternotomy was considered a prior sternotomy. Survival data out to 4 years were obtained from a link with the Social Security Administration Death Index. Hazard ratios were estimated using a Cox proportional hazards regression model, and adjusted survival curves were estimated using inverse probability weighting. In a separate analysis, 1,182 patients were matched 1:1 by a patient's propensity for having undergone prior CABG.

Results: Patients with prior sternotomies had a greater burden of comorbid diseases and increased acuity and had a greater likelihood of returning to the operating room for bleeding and low cardiac output failure. Prior sternotomy was associated with an increased risk of death out to 4 years for patients undergoing CABG, with an unmatched hazard ratio of 1.34 (95% confidence interval, 1.10 to 1.64) and a matched hazard ratio of 1.36 (95% confidence interval, 1.01 to 1.81).

Conclusions: Analyses of our recent regional experience with nonemergent CABG showed that a prior cardiac operation was associated with a nearly twofold increased hazard of death at up to 4 years of follow-up.

	Introduction

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Given the chronic and progressive nature of coronary artery disease and the increasing life expectancy of Americans, there is an increasing need to understand the epidemiology and outcomes of surgical reinterventions for the treatment of coronary artery disease. A limited number of reports have focused on the clinical outcomes for patients undergoing repeat cardiac operations in the setting of coronary artery bypass grafting (CABG):

• Yap and colleagues [1] reported 13,436 patients who underwent isolated CABG in Australia and New Zealand between 2001 and 2008. A prior cardiac operation was an independent predictor of in-hospital death, but did not remain a significant factor out to 6 years [1].

• LaPar and colleagues [2], in a single-center experience, reported the experience of 1,603 patients undergoing isolated CABG between 1996 and 2007. They found a reduction in the risk of death associated with prior cardiac operations across the eras of 1996 to 2003 and 2004 to 2007. In the later era, prior cardiac surgical procedure was no longer associated with an increased risk of in-hospital death [2].

We undertook two analyses to explore the effect of a prior cardiac operation in the setting of CABG on perioperative and midterm outcomes. First, we identified 20,703 patients who underwent nonemergency CABG at 8 medical centers in northern New England. Second, in a subgroup analysis, 1,568 patients were matched 1:1 by a patient's propensity for having had a prior CABG procedure.

	Material and Methods

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Study Population
Consecutive patients were enrolled into the current cohort study if they underwent an isolated CABG procedure at any of the 8 medical centers between 2000 and 2008 in Maine, Vermont, and New Hampshire that provided this operation. Patients were excluded if they were aged younger than 30 years, had undergone a prior valve operation, had a life-threatening malignancy, required an emergency operation, or had an incision other than a full or ministernotomy.

Baseline Characteristics
Prospective cohort
There were 64,196 patient-years of follow-up comprising 61,724 primary and 2,472 prior cardiac operations. Of the 20,703 patients who underwent an isolated nonemergency CABG, 3.8% had undergone prior CABG. Annual procedure volumes diminished in both groups: 3,068 total procedures in 2000 (5.0% prior cardiac operations) and 1,622 total procedures in 2008 (2.3% prior cardiac operation). The proportion of patients who underwent percutaneous coronary intervention (PCI) during this period who had also undergone prior CABG remained stable at 18% (Fig 1 ).

View larger version (31K): [in this window] [in a new window]   Fig 1. Rates of revascularization after a prior sternotomy are shown for coronary artery bypass grafting (first y axis; gray bars) and percutaneous coronary intervention (second y axis, solid line).

Data Collection
Data were obtained from the surgical registries of the Northern New England Cardiovascular Disease Study Group (NNECDSG). The NNECDSG is a voluntary regional consortium of clinicians, allied health professionals, administrators, and clinical scientists who seek to foster continuous improvement in the quality, safety, and effectiveness of cardiovascular care in the region [3–5]. Participating centers collect and submit data on consecutive CABG procedures, including patient demographics, comorbid conditions, cardiac history, cardiac anatomy, cardiac function, procedural indication and priority, procedural process, and outcomes [6].

We calculated each patient's degree of under-revascularization. The degree of revascularization was calculated as the ratio of the number of distal anastomoses to the number of diseased vessels, and patients with a ratio of less than 1 were defined as being under-revascularized.

In-hospital death was obtained from validated registry data. Postprocedural deaths out to 4 years were obtained by linking our registry to the Social Security Administration's Death Master File using a combination of first name, last name, date of birth, date last known alive, and Social Security number.

We ascertained the mode of death among patients who died during their hospital stay. Methods describing the determination of mode of death have been described previously [7]. Mode of death was available among 87.2% of patients who died during their hospitalization.

Institutional Review Board approval was obtained at each participating medical center. Seven of the 8 NNECDSG member center's Institutional Review Boards have designated the NNECDSG as a Quality Improvement Registry, and therefore patient consent was not required. Written patient consent was obtained for the remaining center.

Statistical Analysis
Patient and disease characteristics were summarized by percentages for categoric variables and means for continuous variables and compared using ² tests and t tests, respectively. We used the Wilcoxon rank sum test for nonparametric data.

A multivariable logistic regression model was used to assess the relationship between a prior cardiac surgical procedure and in-hospital death. We included covariates that have been associated with death in this setting, including age, sex, ejection fraction, acuity, vascular disease, diabetes, prior myocardial infarction, renal failure or creatinine at 2 mg/dL or higher, left main disease, chronic obstructive pulmonary disease, body mass index, medical center, and year [6]. We additionally adjusted for preoperative atrial fibrillation and a history of hypertension.

The risk of death associated with prior cardiac surgical operations was compared using the Wald test within a Cox proportional hazards model adjusting for the same covariates as we used in our logistic regression model. Hazard ratios (HR) and 95% confidence intervals (95% CI) were calculated. The time-dependence of the HR was assessed by estimating the HR in separate windows of time after follow-up.

Crude survival curves were estimated using the Kaplan-Meier method. Survival adjusted for differences between patients with and without a history of cardiac surgical operations were estimated using the method of Zhang and colleagues [8] because it does not force proportional hazards upon the difference between patients with and without a history of cardiac surgical operations.

Propensity-matched analyses were conducted to arrive at an estimate of the independent influence of a prior cardiac operation. A patient's propensity score was calculated for having a prior cardiac operation by using a model that included the same covariates as were used in our logistic regression model (c statistic, 0.71). We used a 1:1 ratio to matched 591 patients with prior cardiac surgical operations in a 1:1 ratio to patients without prior cardiac operation who also had the next closest "neighbor" of propensity score. Patients who were not matched were removed from further analyses. We used a Cox proportional hazards regression model to estimate the midterm HR associated with a prior cardiac surgical operation.

Adjusted survival curves were created using the R 2.6.0 public domain statistical program, and all other statistical analyses were performed using Stata 11.0 software (StataCorp, College Station, TX).

	Results

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Intraoperative Care
Intraoperative care was similar in most respects across the prospective and propensity-matched cohorts. Patients who had a prior cardiac surgical operation were more likely to have extended duration of cardiopulmonary bypass and ischemia, to receive antegrade and retrograde cardioplegia, warm induction of cardioplegia, and to have a longer median duration between doses of cardioplegia (Table 2). Patients who had a prior cardiac operation were less likely to have all arterial grafts, were more likely to receive fewer anastomoses, and be under-revascularized. An off-pump operation was more common among patients who had a prior operation, although this difference was only statistically significant among the propensity-matched cohort.

View larger version (18K): [in this window] [in a new window]   Fig 2. (A) Risk-adjusted 4-year survival after isolated coronary artery bypass grafting (CABG) is shown. Survival was adjusted for age, sex, ejection fraction, acuity, vascular disease, diabetes, prior myocardial infarction, renal failure or creatinine 2 mg/dL, left main disease, chronic obstructive pulmonary disease, body mass index, medical center and year. (B) Propensity-matched 4-year survival after isolated CABG is shown. Patients were matched by their propensity to have had a prior sternotomy using the factors of age, sex, ejection fraction, acuity, vascular disease, diabetes, prior myocardial infarction, renal failure or creatinine 2 mg/dL, left main disease, chronic obstructive pulmonary disease, body mass index, medical center, and year.

	Comment

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
The present study describes outcomes from a large, contemporary, regional experience with coronary revascularization in patients who had a prior cardiac surgical operation. During the course of the study period, the rate of a prior cardiac operation decreased from 5.0% in 2000 to 2.3% in 2008 (p < 0.001). In both matched and unmatched cohorts, a prior cardiac operation was associated with an increased risk of death out to 4 years, although the absolute effect diminished beyond 1 year.

We identified a nearly threefold increase in the odds of nonfatal low cardiac output among patients who had a prior cardiac operation. Among patients with mode of death information, those who had a prior cardiac operation were more likely to die of low cardiac output. Additionally, those who died of low output were more likely to be under-revascularized compared with those who died of another cause.

Sabik and colleagues [9] from Cleveland Clinic reported 21,568 patients undergoing isolated CABG between 1990 and 2003. Although patients who had a prior cardiac operation had more risk factors, the absolute risk of death decreased over time in their center's experience. The authors attributed this finding to improved surgical technique. By 1997, a prior cardiac surgical procedure was no longer an independent risk factor for in-hospital death, even after adjusting for year. Although the authors adjusted for patient characteristics, they did not provide details regarding any differences in case-mix over time. The degree to which the findings by Sabik and colleagues are generalizable to northern New England is unclear given apparent differences in the case-mix and rate of prior cardiac operations between their cohort and ours. For instance, 21% of their population of isolated CABG patients had a prior cardiac operation vs 4.0% in our report.

Three multicenter experiences have also focused on the topic of prior cardiac surgical operations and death. O'Connor and colleagues [6], although focused on risk factors for in-hospital death, found prior CABG was an independent predictor of death (odds ratio [OR], 3.6; p < 0.001). From a national perspective, The Society of Thoracic Surgeons has reported an increased risk of in-hospital death associated with prior cardiac operation (OR: 3.1 for 1 previous operation, 4.2 for 2 previous operations) [10]. Yap and colleagues [1] explored the relationship between prior cardiac surgical operations and mortality rates using a database involving 12 hospitals in Australia. Of the 13,436 patients who underwent isolated CABG, 458 (3.4%) had a prior cardiac operation. Patients with prior cardiac operations had more comorbidities, although they were less likely to have had a myocardial infarction within 21 days. Yap and colleagues used the National Death Index in Australia to monitor patients out to 6 years to assess long-term mortality status, and found that a cardiac operation was a predictor of in-hospital death (OR, 2.1; p < 0.001) but not death at 6 years (HR, 1.03; p = 0.85).

One of the postulated reasons for an increased risk of death among patients who have had a prior cardiac operation is injury to prior grafts or cardiac structures upon reentry. Investigators from Mayo Clinic reported 2,555 patients who had undergone a prior cardiac operation between 1996 and 2007 [11]: 60% had a prior CABG, 52% had a mitral or aortic procedure, and 17% had undergone more than one prior sternotomy. The rate of injury was 9.0%. Patients who had injuries were more likely to have had a prior stroke, radiotherapy, infective endocarditis, a patent internal mammary artery, and more than one prior cardiac operation, especially within 1 year of the current procedure. Of all the injuries, 135 (51%) occurred before bypass and 87 (33%) occurred during reentry. Injuries before bypass were predominantly to the saphenous vein graft and the internal mammary artery, whereas injuries during reentry were predominantly to the innominate vein, right ventricle, and aorta. Patients with injuries were more likely to die in-hospital (6.5% vs 18.5%).

Roselli and colleagues [12] investigated 1,847 patients who underwent a variety of cardiac operations between 2002 and 2004. Injuries and adverse events occurred among 7% and included injuries to the grafts, heart, and great vessels, as well as ischemia without graft injury. Of all injuries, 23% occurred during reentry and 39% during prebypass dissection.

Two findings from the present analysis are noteworthy: First, in this large regional experience, we found that a prior cardiac operation was an independent risk factor for decreased survival 4 years after discharge in both risk-adjusted as well as propensity-matching analyses. This finding contrasts with Yap and colleagues from Australia, who reported a nonsignificant 3% increased risk of death 6 years beyond the operation. We found most of the effect of a prior cardiac surgical operation was within the first year after the operation (HR, 1.70; 95% CI, 1.30 to 2.22) and that a prior cardiac operation remained a significant hazard of mortality between 1 and 4 years beyond the operation in unmatched (HR, 1.23; 95% CI, 1.01 to 1.49) and matched (HR, 1.13; 95% CI, 0.83 to 1.52) patients.

Second, we found that low cardiac output was the predominant mode of death among patients who had a prior operation. A number of postulated mechanisms may explain this finding, including injury to the innominate vein, right ventricle, pulmonary artery, aorta, or left internal mammary artery during the reopening of the chest, incomplete revascularization, and iatrogenic injury to patent grafts during the dissection. Patients whose mode of in-hospital death was low cardiac output failure were more likely to be incompletely revascularized compared with those who died of other reasons.

Injury to structures upon reopening or during the subsequent dissection has implications not only with regard to the injury itself but also with risk of significant blood loss and use of derivative blood products. A patient may be at risk of ischemia or infarction before cardiopulmonary bypass is initiated secondary to prolonged hypotension or injury to old functioning grafts. Further, manipulation of prior grafts during dissection may result in ischemia-induced myocardial injury.

Cardiac surgeons commonly take precautions to mitigate the consequences of reentry injuries. For example, a femoral arterial catheter is often placed before sternotomy to facilitate emergency arterial cannulation using the Seldinger technique to assist in establishing expeditious cardiopulmonary bypass necessitated by a reentry injury. In addition, cardiac surgeons are often cautious when handing the heart and dissecting adhesions given the propensity of particulate matter to embolize in this setting.

With this in mind, several investigators have suggested a number of techniques to mitigate injuries. For instance, O'Brien and colleagues [13] suggest that a technique involving direct visualization of the retrosternal area may eliminate moderate to major cardiac injuries for patients undergoing resternotomy. Machiraju [14] reported a 2-center experience with 634 repeat sternotomies during a 4-year period. To prevent intrathoracic structure damage, Machiraju used an oscillating saw. Myocardial preservation becomes increasingly important in this patient population to prevent further morbidity and death. Machiraju found retrograde cardioplegia was a safe approach. Although we were unable to describe the unique methods used by cardiac surgeons in our region to prevent reentry injuries, morbidity, or death, further investigation of the role of mitigating factors is warranted.

We undertook a number of analytic strategies to address issues of confounding inherent in this regional observational study. We used standard methods for dealing with potential confounding, including Cox proportional hazards regression and propensity matching. Although we cannot rule out that there remains some degree of unmeasured confounding, we accounted for differences in rates of prior cardiac surgical operation over time by adjusting for year of the procedure and the medical center in our Cox model and by propensity matching. Nonetheless, prior cardiac surgical operation remained a significant and positive risk factor for death.

We report a regional observational experience of patients undergoing isolated CABG. In this series, we found an increased risk of death 4 years beyond the operation for patients who had a prior operation. Future work should further elucidate the mechanism of injury attributed to prior cardiac operation in this setting.

	Acknowledgments

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
We gratefully acknowledge the following individuals who have assisted with the development of this manuscript: David C. Charlesworth, MD, Donato A. Sisto, MD, Robert A. Clough, MD, Benjamin M. Westbrook, MD, and Gordon R. DeFoe, CCP.

Dr Likosky was supported by a grant from the Agency for Healthcare Research and Quality (1K02HS015663–01A1). This work was partially funded by the Northern New England Cardiovascular Disease Study Group.

	References

Top Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

1. Yap CH, Sposato L, Akowuah E, et al. Contemporary results show repeat coronary artery bypass grafting remains a risk factor for operative mortality Ann Thorac Surg 2009;87:1386-1391.[Abstract/Free Full Text]
2. LaPar DJ, Yang Z, Stukenborg GJ, et al. Outcomes of reoperative aortic valve replacement after previous sternotomy J Thorac Cardiovasc Surg 2010;139:263-272.[Abstract/Free Full Text]
3. Malenka DJ. Indications, practice, and procedural outcomes of percutaneous transluminal coronary angioplasty in northern New England in the early 1990s. The Northern New England Cardiovascular Disease Study Group. Am J Cardiol 1996;78:260-265.[Medline]
4. O'Connor GT, Plume SK, Olmstead EM, et al. A regional prospective study of in-hospital mortality associated with coronary artery bypass grafting. The Northern New England Cardiovascular Disease Study Group. JAMA 1991;266:803-809.[Medline]
5. O'Connor GT, Plume SK, Olmstead EM, et al. A regional intervention to improve the hospital mortality associated with coronary artery bypass graft surgery. The Northern New England Cardiovascular Disease Study Group. JAMA 1996;275:841-846.[Medline]
6. O'Connor GT, Plume SK, Olmstead EM, et al. Multivariate prediction of in-hospital mortality associated with coronary artery bypass graft surgery. Northern New England Cardiovascular Disease Study Group. Circulation 1992;85:2110-2118.[Abstract/Free Full Text]
7. O'Connor GT, Birkmeyer JD, Dacey LJ, et al. Results of a regional study of modes of death associated with coronary artery bypass grafting. Northern New England Cardiovascular Disease Study Group. Ann Thorac Surg 1998;66:1323-1328.[Abstract/Free Full Text]
8. Zhang X, Loberiza FR, Klein JP, Zhang MJ. A SAS macro for estimation of direct adjusted survival curves based on a stratified Cox regression model Comput Methods Programs Biomed 2007;88:95-101.[Medline]
9. Sabik 3rd JF, Blackstone EH, Houghtaling PL, Walts PA, Lytle BW. Is reoperation still a risk factor in coronary artery bypass surgery? Ann Thorac Surg 2005;80:1719-1727.[Abstract/Free Full Text]
10. Shahian DM, O'Brien SM, Filardo G, et al. The Society of Thoracic Surgeons 2008 cardiac surgery risk models: part 1—coronary artery bypass grafting surgery Ann Thorac Surg 2009;88:S2-S22.[Abstract/Free Full Text]
11. Park CB, Suri RM, Burkhart HM, et al. Identifying patients at particular risk of injury during repeat sternotomy: analysis of 2555 cardiac reoperations J Thorac Cardiovasc Surg 2010;140:1028-1035.[Abstract/Free Full Text]
12. Roselli EE, Pettersson GB, Blackstone EH, et al. Adverse events during reoperative cardiac surgery: frequency, characterization, and rescue J Thorac Cardiovasc Surg 2008;135:316-323323 323.e1–6.[Abstract/Free Full Text]
13. O'Brien MF, Harrocks S, Clarke A, Garlick B, Barnett AG. How to do safe sternal reentry and the risk factors of redo cardiac surgery: a 21-year review with zero major cardiac injury J Card Surg 2002;17:4-13.[Medline]
14. Machiraju VR. How to avoid problems in redo coronary artery bypass J Card Surg 2002;17:20-25.[Medline]

This article has been cited by other articles:

				V. R. Machiraju Prior Cardiac Operations Affect Post-Coronary Artery Bypass Graft Survival Ann. Thorac. Surg., July 1, 2012; 94(1): 331 - 331. [Full Text] [PDF]

				D. S. Likosky, R. S. Kramer, and L. J. Dacey Reply Ann. Thorac. Surg., July 1, 2012; 94(1): 331 - 332. [Full Text] [PDF]

				F. G. Bakaeen Invited Commentary Ann. Thorac. Surg., October 1, 2011; 92(4): 1267 - 1268. [Full Text] [PDF]

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): Donald S. Likosky Robert S. Kramer Louis Russo Bruce J. Leavitt Robert E. Helm Gerald L. Sardella Francis V. DiPierro Yvon R. Baribeau Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Likosky, D. S. Search for Related Content PubMed PubMed Citation Articles by Likosky, D. S. Related Collections Coronary disease Related Article