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Ann Thorac Surg 1999;68:1562-1566
© 1999 The Society of Thoracic Surgeons
a Minneapolis Heart Institute, Minneapolis, Minnesota, USA
Address reprint requests to Dr Arom, Cardiac Surgical Associates PA, Minneapolis Heart Institute, St. Paul Heart and Lung Center, 920 East 28th St, Suite 420, Minneapolis, MN 55407
e-mail: karom{at}csa-heart.com
Presented at Evolving Techniques and Technologies in Minimally Invasive Cardiac Surgery, San Antonio, TX, Jan 22–23, 1999.
Abstract
Background. Coronary artery bypass grafting without cardiopulmonary bypass is gaining popularity as an alternative to conventional on-pump technique for myocardial revascularization. This includes minimally invasive direct coronary artery bypass (MIDCAB) and full sternotomy off-pump (OPCAB) methods. These two approaches should be evaluated for financial and clinical appropriateness.
Methods. Records of patients who had single or double bypass (internal mammary artery and/or saphenous vein) grafts between January 1997 and June 1998 were reviewed. These included 44 MIDCAB, 62 OPCAB, and 243 conventional coronary artery bypass (CCAB) patients. Univariate analysis was applied to pre, intra, and postoperative variables, comparing MIDCAB and OPCAB to the CCAB group. Procedural cost information was obtained from participating institutions.
Results. MIDCAB patients compared to CCAB patients had a higher predicted risk (5.4 ± 11 versus 2.3 ± 2.8, p = 0.012) and OPCAB patients had a predicted risk of 5.3 ± 7.8. MIDCAB and OPCAB procedures required less operating room time and blood utilization. Observed operative mortality rates were MIDCAB 4.5%, OPCAB 1.6%, and CCAB 2.8% (not significant). Mean hospital costs were CCAB at $19,000, OPCAB at $15,000, and $17,000 for MIDCAB.
Conclusions. Off pump procedures currently reflect acute episode-of-care cost savings over CCAB.
New surgical approaches for the treatment of coronary artery disease must be evaluated for financial and clinical appropriateness. Conventional coronary artery bypass (CCAB) surgery utilizing a full sternotomy and cardiopulmonary bypass is considered to be the gold standard for myocardial revascularization. Minimally invasive direct coronary bypass grafting surgery (MIDCAB), through a limited incisional and without cardiopulmonary bypass (CPB), evolved as a method that offers the advantages of surgical revascularization in combination with reduced morbidity. The MIDCAB procedure involves arterial grafting of the left internal mammary artery to the left anterior descending coronary artery and its branches through an anterior thoracotomy incision without arresting the heart, thereby avoiding both a sternotomy and cardiopulmonary bypass. The OPCAB through a full sternotomy technique is particularly useful in high-risk patients such as those with renal failure, respiratory problems, advanced age, cerebral vascular accidents, and those that are most susceptible to the effects of CPB. Although the method was described many years ago, it was abandoned with the advent of cardiopulmonary bypass and cardioplegic arrest. Recently, there has been a resurgence in use of the OPCAB procedure, utilizing the full sternotomy and commercially available stabilizers [1]. This communication is to review our own experience with these three techniques (CCAB, MIDCAB, OPCAB) with particular attention to the safety, efficacy, and cost of each procedure.
Material and methods
A retrospective consecutive review of patients who had one or two coronary bypass grafts at our institution between January 1997 through June 1998 was carried out, and divided into three groups: MIDCAB, coronary artery bypass grafting performed without CPB with a limited incision; OPCAB, coronary artery bypass grafting performed without CPB with a full sternotomy incision; and CCAB, coronary artery bypass grafting performed with CPB and a full sternotomy incision.
All demographics and pre, intra, and postoperative variables were collected according to the Society of Thoracic Surgeons National Cardiac Surgery Database (STS.NCSD). With univariate analysis, the MIDCAB and OPCAB patients were compared to the CCAB group. Total hospital costs (direct, indirect, fixed, and variable costs) were obtained for comparison. Costs per patient were reported by day and by hospital department. This provided the opportunity to identify pre, intra, and postoperative costs associated with each group.
Minimally invasive direct coronary artery bypass grafting surgery
The MIDCAB surgery was performed through an anterior thoracotomy at the fourth or fifth intercostal space. The internal mammary artery harvest was difficult at times due to limited exposure and access. Location of targeted vessels dictated access through a left or right thoracotomy approach. Bradycardia was achieved with pharmacological assistance of intravenous beta-blocking agents and anastomosis was completed on a slowed beating heart.
Off-pump coronary artery bypass surgery
Off-pump coronary artery bypass surgery was carried out through a full sternotomy with takedown of the left internal mammary artery performed in the standard fashion. Deep pericardial traction stitches were placed near the left upper and lower pulmonary veins and to the left inferior cava, thereby achieving elevation of the apex of the heart. To further assist in providing good presentation of targeted vessels on the lateral or inferior aspect of the heart, patients were placed in a gentle right decubitus Trendelenburg position [1, 2]. Stabilization of the heart was accomplished using one of several commercially available stabilizing systems.
Conventional coronary artery bypass surgery
Conventional coronary artery bypass surgery was performed through a full sternotomy incision with internal mammary artery takedown in the usual fashion. Institution of CPB was achieved by cannulating the ascending aorta and right atrium. Retrograde cardioplegia of either blood or crystalloid solution was delivered for myocardial protection of the arrested heart. All cardiopulmonary bypasses were accomplished with a membrane oxygenator and centrifugal pump.
Treatment of all patients followed standard care and processes from surgery until discharge. This includes admission to the intensive care unit from the surgery suite with subsequent transfer to an intermediate care ward within 24 hours, or as dictated by patient clinical status according to standard practice guidelines. A hospital-designed extubation protocol that targets extubation within 4 hours after surgery was followed.
The pre, intra, and postoperative variables used for univariate analysis between groups are listed in Tables 1–3 with the CCAB patient population serving as a control group. The logistic regression risk model, developed by the STS.NCSD, was used to calculate the preoperative predicted risk of each group.
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Preoperative, operative, and postoperative variables were analyzed using Student’s t-test, 
2 test, and univariate analysis to compare MIDCAB and OPCAB to CCAB. A p-value of less than 0.05 was considered to be statistically significant. The Logistic Regression Risk Model, developed by the STS.NCSD, was used to obtain the preoperative predicted risk in each group.
Results
There were 44 MIDCAB, 62 OPCAB, and 243 CCAB patients. The analysis confirmed statistical differences between the MIDCAB and OPCAB populations when compared to the CCAB population. The MIDCAB and OPCAB patients had a higher predicted risk than the CCAB group (5.4 ± 11, 5.3 ± 7.8 versus 2.3 ± 2.8, p = 0.012) respectively. Mean age of these three groups showed MIDCAB 63 ± 15, OPCAB 69 ± 13 and CCAB 64 ± 11 (p = 0.01 for OPCAB versus CCAB) years. Additionally, preoperative factors that are associated with increased operative risk and morbidity were reported more frequently in the MIDCAB and OPCAB; there was a higher occurrence of reoperative status in MIDCAB (30% versus CCAB 13%, p = 0.001), more renal insufficiency in OPCAB (18% versus CCAB 4.5%, p = 0.001), more congestive heart failure in MIDCAB (14%) and OPCAB (23%) and only 3% in CCAB for p = 0.007/<0.001, and more chronic obstructive pulmonary disease in MIDCAB (14%) and OPCAB (14%) when compared to only 5% in CCAB (p = 0.04/0.019) (Table 1).
The preoperative length of stay for the OPCAB versus CCAB was 3.6 ± 4.8 versus 2.3 ± 2.9, p = 0.006, which reflects a negative significance when viewed as a resource consumption variable. For our practice, initial application of the OPCAB approach targeted those patients that presented an increased risk of morbid events secondary to CPB. Possibly, this 1–2 day difference may reflect time required for stabilization and system assessment of a more critically ill population prior to surgical intervention.
Postoperative length of stay of the MIDCAB versus CCAB was 5.7 ± 3.5 days and 7 ± 6 days, with p = 0.06. When comparing the OPCAB of 7 ± 3 days to the CCAB 7 ± 6 days, there was no significance. Suggested efficiencies and effectiveness of off-pump surgery either with a limited or full incisional approach could be attributed to elimination or minimization of side effects of CPB. Effects of CPB are reflected in intra and postoperative blood loss, blood product utilization, and total surgical time data analyses. MIDCAB and OPCAB versus CCAB operative blood loss was 291 ± 241 cc, 401 ± 270 cc versus 517 ± 295 cc, p = <0.001/0.003 respectively. Blood product utilization was significant with respect to platelet administration (Table 2).
Success of aggressive extubation protocols for all surgical patients is reflected in the nonsignificant variation among groups, as indicated by the low mode times of 0 hours for MIDCAB, 3 hours for OPCAB, and 5 hours for CCAB. Despite patient presentation and variation in predicted risk, targeted extubation within 4 hours of procedure demonstrates that multidisciplinary collaborative approaches benefit the patient and are essential in the provision of quality care and results. Incidence of reoperation for postoperative bleeding was 6.8% MIDCAB versus 1.6% in OPCAB and 1.2% in CCAB (p = 0.01). Other postoperative complications are listed in Table 3. Of interest, the occurrence of new atrial fibrillation was nonsignificant across groups.
Patient cost information was provided by the two institutions where the populations were derived. These two institutions operate under the same health system and utilize identical cost accounting software. Individual patient costs were reported by day and by department. Within each department direct and indirect costs were combined. The variable figures include the labor and supplies necessary to care for the patient. Fixed direct costs account for administration and equipment costs associated with care and do not vary significantly over a large volume of patients. Indirect costs are associated with care and other services not directly related to patient care, which act as an ancillary or support the services provided. It is this set of indirect costs that can vary significantly from institution to institution.
Costs obtained from the two institutions are shown in Tables 4 and 5 . A request was made for a breakdown of each individual patient’s total hospitalization account by department or service and by day. Univariate analysis of the cost data indicates that savings are primarily achieved in the operating-room phase of the acute-care episode. Comparing even total costs from one region to another or one software to another can lead to confusion because of the categorization or definitions assigned to each of the cost centers.
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Advantages and disadvantages of the three approaches have been concisely summarized and are presented in Table 6. Comparisons of the clinical outcomes of the two off-pump procedures to the long accepted on-pump procedure are gradually becoming available. In the hands of skilled surgeons, it has been demonstrated that both off-pump procedures can be performed without increased intra or postoperative complications. Evaluation of the presented data can lead one to support the benefits of MIDCAB or OPCAB particularly in the high-risk patient population. Minimally invasive surgery, however defined, must withstand the rigors of clinical and financial evaluation. Technological advancement has laid the foundation for performing, evaluating, and improving the technical aspects of minimally invasive surgery.
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Evaluation of the safety of such techniques can be assessed through retrospective data review. Obviously, longitudinal follow-up to document procedural efficacy and equivalent patency rates, compared to the conventional on-pump full sternotomy population, is mandatory.
Few publications are available that have reported true procedural cost of minimally invasive coronary artery bypass procedures. In 1998, Magovern and associates [3] reported the costs and 6-month outcomes of MIDCAB surgery compared to the conventional CABG. This study was carried out between January 1995 and December 1996, it did not include the indirect costs. The results of that study were, for CCAB, total costs of $15,600 ± $4,200 and for MIDCAB, costs of $11,200 ± $3,100. When high-risk patients were analyzed, total costs revealed CCAB to be $26,800 ± $10,100 versus MIDCAB costs of $16,120 ± $7,200. Earlier, Zenati and associates [4], reported the comparison between MIDCAB and CCAB performed at the University of Pittsburgh Medical Center. There were 17 patients in the MIDCAB group and 33 in the CCAB group. The cost again for the MIDCAB group was less ($12,885 ± $1,511 versus $21,260 ± $5,479). In a more recent study by Del Rizzo and associates [5], safety and cost-effectiveness of high risk MIDCAB surgery was done. Using their Canadian cost model and risk stratification to predict cost for coronary artery bypass surgery in this particular subset, they estimated the cost for MIDCAB was about 6,000 (Canadian Dollars) to 12,000 (Canadian Dollars) for CCAB.
In our study, mean intraoperative costs were $6,273 ± $3,527 for MIDCAB, $5,597 ± $2,154 for OPCAB, and $9,509 ± $2,299 for CCAB. Intraoperative cost savings can obviously be related to decreased expenditure for resources, such as perfusion circuit equipment and skin-to-skin times (MIDCAB = 141 ± 49 minutes, OPCAB 145 ± 37 minutes, CCAB 215 ± 68 minutes; p = value = < 0.001). Admission to surgery LOS costs are presented but not incorporated into the total hospital costs. Costs associated with this time period are influenced primarily by cardiology. Therefore, a comparison of hospital costs is made from procedure through discharge to control for variation. As indicated in Table 4, these costs are significantly lower for both off-pump surgical groups. Even though the predicted risk for operative mortality is significantly higher, with more of the off-pump having a predicted risk of more than 5%, costs are less.
Certain preoperative risk factors have been documented to increase hospital costs such as congestive heart failure, renal failure, and reoperative status. These risk factors were shown to be significant. Postoperative complications affiliated with these particular co-morbidities did not occur in the postoperative recovery of the MIDCAB and OPCAB populations. Therefore, one may conclude that the elimination of CPB risks were avoided or significantly reduced in this high-risk population.
A critique of this study might be that it is a nonrandomized, retrospective review and thus is biased in its selected population. Effort was made to develop a homogeneous patient population for comparison. Patients who received single- or double-vessel bypass were reviewed because initial application of the MIDCAB and OPCAB techniques were focused on these patients. Cost analysis components of this study may also be misleading due to the unsophisticated information systems used and nonstandardized definition of category components. Patient cost information was not accessible on the total population, which again may create biases of the presented data. Long-term follow-up is necessary to interpret off-pump results in terms of graft patency and the occurrence of reintervention. Gundry and associates [6], reported a 7-year follow-up comparison between off-pump with limited revascularization and on-pump with full revascularization. Their results show that the off-pump group had a threefold increase in reinterventions. Initial cost and clinical results are certainly promising especially with a high-risk patient.
Caution must be made in evaluating and recommending new technology or techniques purely on this basis of consumer and payer demands for cost-effective treatments. Our study showed that myocardial revascularization without cardiopulmonary bypass is safe and did not increase the occurrence in mortality or morbid events. Early clinical outcomes would imply that the high-risk patient clinically benefits from either of the two off-pump approaches. Total hospital costs also reflect effectiveness of these two approaches. However, continued evaluation of the techniques with longitudinal outcome analysis is mandatory. Strategies must be focused on the efficacy of this application in the broad-based lower risk population.
References
This article has been cited by other articles:
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  T. Kofidis, M. Y. Emmert, H. G. Paeschke, L. S. Emmert, R. Zhang, and A. Haverich Long-term follow-up after minimal invasive direct coronary artery bypass grafting procedure: a multi-factorial retrospective analysis at 1000 patient-years Interactive CardioVascular and Thoracic Surgery, December 1, 2009; 9(6): 990 - 994. [Abstract] [Full Text] [PDF]
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 E. Kuralay Massive systemic air embolism during off-pump coronary artery surgery Eur. J. Cardiothorac. Surg., January 1, 2009; 35(1): 183 - 184. [Abstract] [Full Text] [PDF]
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 Z. N. Kon, E. N. Brown, R. Tran, A. Joshi, B. Reicher, M. C. Grant, S. Kallam, N. Burris, I. Connerney, D. Zimrin, et al. Simultaneous hybrid coronary revascularization reduces postoperative morbidity compared with results from conventional off-pump coronary artery bypass. J. Thorac. Cardiovasc. Surg., February 1, 2008; 135(2): 367 - 375. [Abstract] [Full Text] [PDF]
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 R A Archbold and N P Curzen Off-pump coronary artery bypass graft surgery: the incidence of postoperative atrial fibrillation Heart, October 1, 2003; 89(10): 1134 - 1137. [Abstract] [Full Text] [PDF]
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 H. M. Nathoe, D. van Dijk, E. W.L. Jansen, W. J.L. Suyker, J. C. Diephuis, W.-J. van Boven, A. B. de la Riviere, C. Borst, C. J. Kalkman, D. E. Grobbee, et al. A Comparison of On-Pump and Off-Pump Coronary Bypass Surgery in Low-Risk Patients N. Engl. J. Med., January 30, 2003; 348(5): 394 - 402. [Abstract] [Full Text] [PDF]
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M. Capdeville and J. H. Lee Off-Pump Coronary Artery Bypass Surgery: Revival of an Old Technique Seminars in Cardiothoracic and Vascular Anesthesia, November 1, 2001; 5(4): 345 - 361. [Abstract] [PDF]
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M. Yeatman, M. Caputo, R. Ascione, F. Ciulli, and G. D. Angelini Off-pump coronary artery bypass surgery for critical left main stem disease: safety, efficacy and outcome Eur. J. Cardiothorac. Surg., March 1, 2001; 19(3): 239 - 244. [Abstract] [Full Text] [PDF]
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K. V. Arom, T. F. Flavin, R. W. Emery, V. R. Kshettry, P. A. Janey, and R. J. Petersen Safety and efficacy of off-pump coronary artery bypass grafting Ann. Thorac. Surg., March 1, 2000; 69(3): 704 - 710. [Abstract] [Full Text] [PDF]
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