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Ann Thorac Surg 1997;64:1287-1295
© 1997 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Third Coronary Artery Bypass Operations: Risks and Costs

Department of Thoracic and Cardiovascular Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio

	Abstract

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Background. Third coronary artery bypass operations are technically difficult and are associated with increased risk.

Methods. We reviewed the cases of 469 patients who had undergone a third isolated coronary artery bypass operation and used univariate and multivariate testing to examine the effect of preoperative and operative variables on outcome and costs.

Results. The in-hospital mortality was 7.0% (33 patients). Advanced age and severe symptoms were found to increase risk (both p < 0.05): the mortality was 14% (n = 74) in patients 70 years old or older who had severe symptoms. However, the overall mortality for 1993 through 1995 was 4.3% (5/117) and only one death (1.3%) occurred among the 79 patients who were less than 70 years old. The late survival rate was 94%, 84%, and 66% at 1, 5, and 10 postoperative years, respectively, and predictors of decreased late survival were advanced age, abnormal left ventricular function, and diabetes (all p < 0.05). Again, age of 70 years or more was a predictor of a poor outcome. Only 52% of patients in that subgroup (including both early and late mortality) were alive 5 years after operation. Analysis of direct hospital costs showed that the mean costs of third coronary artery bypass operations were 21% higher than the mean costs of primary operations but that the elevation in the mean costs for third operations was related to very high costs in 4 patients. Sex was found to influence the cost of both primary and third operations (increased cost for women).

Conclusions. Unfavorable outcomes after third coronary artery bypass operations have been associated with preoperatively definable variables, particularly age of 70 years or more. The in-hospital mortality in patients younger than 70 was low, and long-term survival in this group has been favorable. The increased hospital costs associated with third operations are related to high costs in only a few patients and have been unpredictable.

	Introduction

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Coronary artery bypass reoperations, once unusual, have become more common and more successful. Large series of patients undergoing first reoperations have been examined carefully, and favorable long-term results have been documented in them [1–5]. Atherosclerosis is progressive and patients who have had second coronary artery bypass operations may eventually have recurrent ischemic syndromes that will lead to the consideration of further surgical treatment. Reports of patients undergoing third bypass operations are few and contain relatively small numbers of patients. However, these series are large enough for us to know that the in-hospital risks of third bypass operations are greater than those of first or second procedures [6–11].

The increased difficulty and risks of third bypass operations raise the issue of their effectiveness versus their costs, both human and economic. To examine these issues we reviewed the outcomes in the 469 patients who underwent a third isolated coronary artery bypass operation (CABG x 3) at The Cleveland Clinic Foundation through 1995. For the cost analyses we studied the subgroup of 116 patients who had CABG x 3 during 1993 through 1995 and compared the costs in this group with those in 4,269 patients who underwent a first isolated bypass operation (CABG x 1) during these same years.

	Material and Methods

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
With the aid of a computerized cardiovascular information registry we identified 469 patients who underwent a CABG x 3 at The Cleveland Clinic Foundation through 1995. The previous coronary operations could include Vineberg-type implants, but patients who had undergone previous valve operations were excluded. Patient- and operation-related descriptors are listed in Appendix 1.

Four outcomes were considered for statistical analysis: two in-hospital outcomes and two late outcomes. The in-hospital outcomes were death before discharge regardless of the length of hospitalization and direct hospital cost. Direct hospital costs (DHC) in this study were defined as the specifically traced direct cost of labor and supplies attributed to a defined patient during a specific patient encounter (admission) that is captured by the Transition II Physician Support System cost accounting system used at The Cleveland Clinic Foundation (Transition Systems, Inc, Boston, MA). Direct costs do not include overhead allocations such as heat, light, managerial supervisory, depreciation, or other institutional administrative costs usually allocated on the basis of a formula or a ratio. They also do not involve professional fees. Direct hospital costs were obtained for patients undergoing a CABG x 3 from 1993 through 1995. Cost data were not available for 1 patient, leaving 116 for analysis. For comparison, DHC for patients undergoing CABG x 1 during the same years were studied. Of the 4,318 patients undergoing primary operations, DHC data were unavailable for 22, leaving 4,296 for analysis. The goal of the statistical analyses was to estimate the percentage increase in the cost of CABG x 3 and to determine whether cost differences were related to other identifiable factors. The analyses were complicated by the fact that the distribution of the DHC was positively skewed, with several values much greater than the bulk of the data. Because the mean costs were highly influenced by these few large values, the geometric mean (detransformed mean on the logarithmic scale) better represents the center of the distribution. Both the increase in the mean cost and the increase in the geometric mean of the costs were analyzed. The DHC data were analyzed to identify factors that increased these costs. The increase in mean costs was estimated by a generalized linear model with a log-link function, and increases in geometric mean costs were estimated using a log-transformed linear model. The DHC data are summarized in Appendix 2, along with the in-hospital mortality rates for the subgroups.

Hospital survivors were followed up at a mean interval of 4.5 years. Nine foreign patients were excluded from follow-up, but all domestic patients were contacted during 1996. Late survival figures exclude in-hospital deaths. The two late outcomes examined were survival and survival free of death, cardiac reoperation, or percutaneous transluminal coronary angioplasty (see Appendix 1).

Operative Technique
All patients except for 4 underwent operation through a median sternotomy with the aid of cardiopulmonary bypass. All except 15 received cardioplegia for myocardial protection, with most receiving cold blood cardioplegia. A mean of 2.5 grafts (distal anastomoses) were placed at the third operation. Conduit selection was determined by availability and surgeon preference. In 238 patients at least one internal thoracic artery (ITA) graft had been used at a previous operation. At the third operation, 245 patients (52%) received at least one ITA graft. Four hundred eleven patients (88%) received at least one greater or lesser saphenous vein graft. The numbers of patients who received alternative arterial grafts were as follows: gastroepiploic artery, 19 (4.1%); inferior epigastric artery, 9 (1.9%); and radial artery, 8 (1.7%). Cephalic veins were used in 3 patients and a saphenous vein homograft in 1.

Patient Population
Until 1988, only a small number of third coronary operations were done yearly. Since that time, 35 to 45 have been performed per year. Throughout the period of the study (1968 through 1995), the age of the patients undergoing operation has increased (p < 0.001), as has the interval between the first and third operations (p < 0.001). For the entire study population the mean age at the first operation was 50 years, the mean age at CABG x 3 was 63 years, and the mean interval between operations was 13 years.

	Results

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
In-Hospital Outcome
Thirty-three patients (7%) died before hospital discharge. The causes of hospital death were as follows: new myocardial infarction, 12 (36% of in-hospital deaths); myocardial failure without documented new myocardial infarction, 9 (27%); sepsis, 6 (18%); respiratory failure, 2 (6%); stroke, 2 (6%); ventricular arrhythmia, 1 (3%); and liver failure, 1 (3%). Thus, 22 of 33 deaths (67%) were clearly cardiac related. During 1993 through 1995 the mortality rate decreased to 4.3% (5/116).

The variables listed in Appendix 1 were tested univariately for their association with in-hospital mortality. Based on clinical and statistical considerations, 11 variables were chosen for inclusion in a multivariate logistic regression model. Results of that logistic regression model are given in Table 1. There was a substantial correlation among variables related to symptom status (unstable angina, impending myocardial infarction, and Canadian Function Class, but overall, the Canadian Function Class symptom status appeared to have the most predictive value. Age was the strongest predictor of mortality.

In-Hospital Direct Costs
Direct hospital costs in 116 patients undergoing CABG x 3 during 1993 through 1995 and in 4,296 patients undergoing CABG x 1 during those same years are shown in Appendix 2. These are descriptive statistics and include the DHC associated with coronary angiography. Because not all patients underwent preoperative coronary angiography at The Cleveland Clinic Foundation, the costs associated with coronary angiography were removed for the analysis of the relative costs of CABG x 1 and CABG x 3.

The overall increase in the mean DHC stemming from having a third operation was 21%, and the overall increase in the geometric mean was 1.8% (Table 3). The cost differences, however, were dependent on an interaction among sex, left ventricular function, and CABG x 3. The largest increase in cost occurred in female patients, particularly in those with no or mild left ventricular impairment. There was a decrease in DHC for CABG x 3 in male patients with moderate or severe left ventricular dysfunction. Age and female sex were associated with increased costs in both the CABG x 1 and CABG x 3 groups. The presence of abnormal left ventricular function was associated with increased costs in the CABG x 1 group and with decreased costs in the CABG x 3 group.

View larger version (18K): [in this window] [in a new window]   Fig 1. . Late survival (Kaplan-Meier estimate) and late survival free of reoperation (Reop) or percutaneous transluminal coronary angioplasty (PTCA).

View larger version (17K): [in this window] [in a new window]   Fig 2. . Overall survival (including in-hospital mortality) for patients 70 years of age or more.

Symptom status (Canadian Function Class) at follow-up and the mean postoperative intervals were as follows: 0, 31% and 4.4 years; 1, 26% and 5.7 years; 2, 9% and 6.1 years; 3, 5% and 5.3 years; and 4, 2% and 6.4 years.

	Comment

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Third operations for coronary artery bypass grafting are often technically difficult and have been associated with a higher risk than primary procedures or first reoperations [6–11]. The technical hurdles at third operations are similar to those at second operations but are more common. By a third operation the lack of pericardial planes makes dissection more difficult and access to coronary arteries is often complicated by the presence of multiple previous grafts. Although alternative approaches to a third operation, such as operation through a thoracotomy or a "mini" incision, are sometimes possible, it is not common that the multiple grafts needed at a third operation can be accomplished through a limited incision.

There may be a shortage of available bypass conduits at a second operation, but this is much more common by a third. Fifty-two percent of the patients in this series received at least one ITA graft. This is a low figure for ITA use but reflects the fact that one or both of the ITAs had been used at a previous operation in many of the patients. This series stops in 1995, and only 8 patients in this report received radial artery grafts. However, the revival of the use of the radial artery graft has been of major importance for patients undergoing reoperation. The radial artery is larger and is usually longer than other arterial conduits. At reoperation, epicardial scarring, the presence of old grafts, cardiac enlargement, and the need to graft coronary arteries very far distally often demand the use of relatively long bypass conduits. At a third operation it is common for the ITAs and inferior epigastric arteries to not reach the distal vessels that need to be grafted, except as composite arterial grafts, and radial arteries can be very helpful in this situation. We recognize that the long-term outcome in patients who receive radial artery grafts is uncertain, although early patency data are encouraging [12–14]. Myocardial protection is also challenging during a third operation. This is because most patients have stenotic vein grafts, creating the danger of atherosclerotic embolization. In fact, perioperative myocardial infarction and cardiac failure were the cause of most deaths in this series. A lack of bypass conduits can also influence the way in which stenotic vein grafts are managed at CABG x 3, because to replace these grafts there must be something to replace them with. However, with increased surgical experience and the use of retrograde cardioplegia, myocardial protection has been improved, and this probably accounts for some of the decrease in hospital mortality that has been seen in recent years, particularly that in patients less than 70 years of age. The use of retrograde cardioplegia is particularly helpful in patients with either patent ITA grafts or atherosclerotic but patent vein grafts.

Despite the overall decrease in mortality, patients more than 70 years of age have still been at increased risk. Diffuse cardiac and noncardiac atherosclerosis appears to play a role in creating the risk in these patients. The mean interval between the first and third operation in this series was 13 years and native coronary artery disease is often quite progressive during these intervals, which accounts for the fact that 31% of patients were considered incompletely revascularized. The postoperative complication of respiratory failure occurred in 31% of patients more than 70 years of age, and this complication rate has not decreased in our most recent surgical period. Thus, although technical advances have been responsible for lowering the mortality rate in younger patients, patient-related characteristics common to elderly patients presenting for third operations still create risk.

In today's medical care environment, hospital costs are an important issue. We therefore elected to examine direct costs. We thought that direct costs (labor and supplies) are more patient and operation related, whereas the addition of indirect costs might obscure the issue with institution-related factors. Because our ability to assess costs does not extend throughout the period of this study and changes in cost structure have made only the most recent data applicable, we elected to examine the 1993-through-1995 time frame. We also obtained cost data for patients undergoing primary coronary operations during these years so that we could contrast the relative costs of first and third operations.

Overall, the costs of third operations were greater than the costs of first operations. However, most of the overall increase in DHC was related to the very high costs incurred in 4 patients who had long and complicated hospital stays after CABG x 3. Furthermore, the determinants of DHC and in-hospital mortality risk were not perfectly congruent. That is, patients 70 years of age or older had both increased costs and an increased in-hospital mortality but the increase in cost was small and the increase in mortality was large. Female sex was associated with increased hospital costs but not with an increased mortality. It is important to realize that the 4 patients with high costs did not appear to have characteristics that would have made those increased costs predictable preoperatively.

Abnormal left ventricular function was found to be associated with an increased cost in patients undergoing primary operations but not in those undergoing third operations. Patients with abnormal left ventricular function who sustain a complication during a third operation appear not to survive long enough to increase costs.

The relationship between the costs and the quality of cardiac operations is under study for many types of cardiac operations. In the patients undergoing third operations there is some evidence that increased expenditure was associated with increased quality. The 4 highest-cost patients undergoing CABG x 3 were all in-hospital survivors. The overall mortality of 4.3% during the 1993-through-1995 time frame represents an excellent in-hospital outcome relative to the mortalities noted in previous studies of multiple coronary reoperations. If the 4 high-cost patients had been hospital nonsurvivors, the resulting 7.8% mortality would have been respectable but not remarkable. Thus, low mortality was achieved at a substantial financial cost.

The purpose of bypass operations is to extend survival and relieve symptoms over the long term. Overall, the 84% 5-year survival rate for in-hospital survivors is a favorable outcome. Increased age was associated with decreased late as well as early survival. Abnormal left ventricular function and diabetes were not associated with an increase in in-hospital mortality but were associated with a decrease in the late survival rate.

When analyzing complex operations, attention should be directed toward the identification of subgroups of patients who do not benefit from the procedures. Advanced age (70 years or older) stood out as a factor responsible for decreasing both early and late survival. However, even of those patients 70 years or older, 52% were still alive 5 years after operation.

The late symptom response has been favorable but not perfect. Although only 31% of patients were asymptomatic at late follow-up, 66% of survivors were in Canadian Function Class 0, 1, or 2.

We have concluded the following from this study:

1. The overall risk of CABG x 3 operations is decreasing as technical experience increases, although the patient-related comorbidities that are associated with advanced age still create risk for patients 70 years older. In addition, the overall decrease in mortality has been blunted by the higher numbers of elderly patients undergoing third operations.
   
2. The overall costs of CABG x 3 operations are increased, but this increase is the result of very high costs for only a few patients. Further, we have not defined the characteristics that allow these high-cost patients to be identified before operation.
   
3. Preoperatively definable variables affect in-hospital mortalities and in-hospital costs differently.
   
4. The long-term outcome of patients after third operations is not as favorable as that of patients after primary operations but is good enough such that multiple coronary reoperations do not appear to represent a futile gesture.
   

	Acknowledgments

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

	Footnotes

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 
Presented at the Poster Session of the Thirty-third Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Feb 3–5, 1997.

Address reprint requests to Dr Lytle, The Cleveland Clinic Foundation F25, 9500 Euclid Ave, Cleveland, OH 44195.

	References

Top Footnotes Abstract Introduction Material and Methods Results Comment Acknowledgments References

 

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4. Lytle BW, Loop FD, Taylor PC, et al. The effect of coronary reoperation on the survival of patients with stenoses in saphenous vein bypass grafts to coronary arteries. J Thorac Cardiovasc Surg 1993;105:605–14.[Abstract]
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12. Chen AH, Nakao T, Brodman RF, et al. Early postoperative angiographic assessment of radial grafts used for coronary artery bypass grafting. J Thorac Cardiovasc Surg 1996;111:1208–12.[Abstract/Free Full Text]
13. Acar C, Jebara VA, Portoghese M, et al. Revival of the radial artery for coronary artery bypass grafting. Ann Thorac Surg 1992;54:652–60.[Abstract/Free Full Text]
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This Article Abstract 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): Bruce W. Lytle Jose L. Navia Paul C. Taylor Floyd D. Loop Robert W. Stewart Patrick M. McCarthy Delos M. Cosgrove, III Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lytle, B. W. Articles by Cosgrove, D. M. Search for Related Content PubMed PubMed Citation Articles by Lytle, B. W. Articles by Cosgrove, D. M., III