T Ad Hoc Committee of The Society of Thoracic Surgeons

Transcription

1 The Society of Thoracic Surgeons National Database Status Report Richard E. Clark, MD Chairman, Ad Hoc Committee* to Develop a National Database for Thoracic Surgery This report describes the development of the first known national surgical database designed for the practicing community cardiothoracic surgeon. Acceptance by members of The Society of Thoracic Surgeons has been gratifying. The number of patients on the system has grown from 116,109 at the end of 1991 to an anticipated 350,000 to 450,000 by the end of At the time of this report, 842 surgeons were participating, and more than 1,200 will be on the system by the end of A risk stratification system has been incorporated into the software, which predicts each patient's risk based on the individual surgeon's past experience. Trend analyses demonstrate a substantial increase in the number of patients at increased risk fior perioperative death for coronary artery bypass operations over the past 5 years, while observed mortality has remained relatively constant. Programs are available for adult and congenital heart disease, lung cancer, and esophalgea1 cancer, and modules for mediastinal tumors, pleural disorders, and benign pulmonary disease will soon be added. We anticipate that growth will continue as the need for practice profile data increases because of reimlb ursement issues. ( 1994;57:20-6) his status report is a compilation of the activities of the T Ad Hoc Committee of The Society of Thoracic Surgeons (STS), which has worked diligently on The Society's behalf lor the past 3 years to make available to the membership a method for compiling data from their individual and group experiences in cardiac and thoracic surgery. The members have found the STS system useful for quality assurance reports, medical legal affairs, promotion and maintenance of referral patterns, and publication purposes. The system was designed for the community cardiothoracic surgeon, rather than the large tertiary referral centers, for several reasons. First, the majority of the STS membership is composed of those who work outside of For editorial comment, see page 6. large centers. Second, the traditional teaching and large tertiary referral centers have previously established databases, usually of unique design. Hence, the data contained within this report represent only a portion of the total United States activity and come from those in private practice in smaller community institutions. The reader is further cautioned that the most recent data for 1990,1991, Presented in part at the Twenty-ninth Annual Meeting of The Society of Thoracic Surgeons, San Antonio, TX, Jan 2527, Address reprint requests to Dr Clark, Cardiovascular and Pulmonary Research Center, Allegheny-Singer Research Institute, 320 E North Ave, Pittsburgh, PA * The members of the Committee are Anthony J. Acinapura, MD, Richard P. Anderson, MD, Douglas M. Behrandt, MD, Fred H. Edwards, MD, L. Penfield Faber, MD, Frederick L. Grover, MD, William R. E. Jamieson, MD, Forrest L. Junod, MD, Constantine Mavroudis, MD, Richard B. McElvein, MD, Victor Parsonnet, MD, Richard M. Peters, MD, Quentin R. Stiles, MD, and Donald C. Watson, MD. and 1992 represent the first 2% years of operation of the National Database system at the community level. The number of subscribers is growing rapidly; hence, interpretation of these data miist be made in terms of their source and brevity of the database. The purposes of this report are (1) to describe the rapid growth of the database, (2) to describe the accomplishments and goals of the Committee, and (3) to demonstrate important trends in mort'dity and risk factors. Historical Framework The development of the STS Nationall Database for thoracic surgery began with the release by the Healthcare Financing Administration of raw mortality data for coronary artery bypass grafting (CABG) operations in 1986 by institution. In response to widespread public misinterpretation caused by newspaper misrepresentation, the Standards and Ethics Committee of the!jts met in New Orleans in October 1986 to develop a "Statement of Concern," which was published later in that year in The Annals of Thoracic Surgery. The Healthcare Financing Administration continued the fcdlowing year to publish data with little in the way of risk stratification, which prompted a proposal from the Standards and Ethics Committee to the Council that the development of a national database for thoracic. surgery would be useful for its members. This proposal was approved by Council in September of 1987, and the process of determining feasibility and logistics began. The initiation of the National Database was hastened by the conference and report of the Committee for the State of the Art of Coronary Arterial Surgery, sponsored by the American Heart Association and National Heart, Lung, and Blood Institute in In the preface of this report, Drs Edmunds and by The Society of Thoracic Surgeons /94/$7.00

2 1994;572M CLARK 21 Kaiser stated, Proper solution to the risk-benefit equation requires knowledge of the natural history of the disease and of the incremental risk factors that affect operative mortality and long-term results. The surgeon must provide these data for the patient, the family and the cardiologist. Risk stratification is the essence of responsible cardiac surgery [l]. In his keynote address, Dr Paul Ebert noted, We, as a profession, should demand that data only be released on patient classification. If the profession is not willing to develop a classification system that is simple enough to be understood by the public, then we cannot complain if data continue to be released in a somewhat questionable manner [2]. The decision was made by the Ad Hoc Committee, with the approval of Council, to seek an outside contractor as a partner with the STS to accomplish the mission of establishing a national database system. Several software firms were interviewed and one (Summit Medical Systems, Inc) was selected to enter into negotiations with the assistance of legal counsel for the STS. A dual contract system was developed for member participation: one related to the obligations of the memberhendor relationship and the other to the member/sts obligations. In June 1990, the first mailing was made to the members of the STS announcing the establishment of an STS National Database. In September of that year, a special presentation was made at the interim meeting held in Chicago, and a workshop demonstration was provided [3]. Five months later, in February 1991 in San Francisco, a special presentation following the regular program was made to interested prospective members. The first Annual Report of data from 1980 through 1991 was provided to the subscribers in January 1992; the second Annual Report, containing updates and new data, was made available to all subscribers and interested members in January 1993 at the Twenty-ninth Annual Meeting of The Society of Thoracic Surgeons in San Antonio, TX. Growth After the first mailing, 50 members had enrolled by September Summit Medical Systems, Inc, contributed 57;555 patients from a previously owned database covering the years 1980 through September These data came from approximately 40 surgical group practices, primarily based in community hospitals, and were used to formulate the initial approach to data management and analyses. These will be deleted when the STS database grows to sufficient size. By February 1991, 330 STS members working in 81 groups and in 135 hospitals had brought the total number of patients in the National Database to more than 70,000. The first Annual Cardiac Report covered 11 years of experience with 18 months of prospective data; the second Annual Cardiac Report, issued in January 1993, contained an 86% increase in the number of patients (Table 1). Committee Accomplishments The initial efforts of the Committee were to develop data collection formats for adult cardiac surgery and lung Table 1. Change in National Database Status by Number of Patients, Groups, Surgeons, and Hospitals Variable Change (%) No. of patients 116, , No. of groups No. of surgeons No. of hospitals cancer as first modules in the cardiac and thoracic surgery programs. Subcommittees were formed to hasten the process, although the full committee debated each variable with vigor until consensus was reached. Over the past 3 years, the General Thoracic Surgery group (McElvein, Faber, Peters, and Grover) has added esophageal cancer and mediastinal tumor modules. Congenital heart surgery is not easily categorized because of the myriad of diagnoses and possible operations in a wide spectra of disorders. Doctor C. Mavroudis undertook this task with a special subcommittee (Bove, Cameron, Drinkwater, Edwards, Hammon, Kron, Mayer, Schwartz, Szarnick, and Watson). They developed several versions, which were field tested until a workable system evolved. Subsequently, the software has been fully documented and the program has been made available to all STS members. The Committee has worked closely with the Canadian group, headed by Dr W. R. E. Jamieson, and has benefited by access to the Canadian Valve Registry format for tracking outcome of prosthetic heart valve patients. Other liaisons include use of the International Society for Heart Transplant Registry and the Ventricular Assist Device Registry, formerly held at Penn State and now incorporated into the STS system. The Committee has struggled for the past 2 years with revising the original list of definition of terms provided to database members in The new edition is now in the hands of the subscribers and should enhance the uniformity of reporting. A quality assurance program has been developed by the contractor to determine data consistency, error, and omissions. Patient files that do not fit the entry criteria are returned to the surgeon for revision. The major advance in assuring that quality data are submitted for merging into the National Database was the establishment of the Database Training Institute in Minneapolis, MN. New users of the STS/Summit Medical system have benefited by sending their data managers for this 4-day educational course. A major effort was made by a subcommittee to develop a user-friendly risk stratification program. This goal was approved by Council in February 1991 and has culminated in a software program now incorporated into each subscriber s computer, which estimates the local risk for any individual patient if there are more than 500 cases of a specific category, eg, CABG. The risk of any patient based on the national data is available at any time. This subcom-

3 22 CLARK 1994;57204 mittee, headed by F. H. Edwards, examined the known existing systems of Parsonnet [4], New York State [5], Department of Veterans Affairs [6], Medis [7,8], Coronary Artery Surgery Study [9], and, more recently, those of the Northern New England Research Group [lo], University of Alabama [ll], and The Cleveland Clinic [12]. Two general approaches have been used for risk assessment, the additive and logistic regression. In the first, integers are assigned to a particular risk variable and the total score is used as a correlate to perioperative risk. The Apgar and APACHE scares are examples of clinically accepted additive systems. Logistic regression is a more difficult method, which generally requires complete data for all variables for each patient entered. The output is a series of "beta" coefficients, which assign relative weight to each variable. Once the coefficients are determined for a data set, individual patient risk can be assigned. Examples of this method are contained in the Coronary Artery Surgery Study, New York State, and Department of Veterans Affairs reports. In the development process of the STS system, both additive and logistic regression methods were applied to the STS data for the years 1984 through 1990, involving more than 59,000 patients who had CABG operations. After much trial and error, a third statistical method was used, which is well recognized in the field of decision making. The Bayesian theorem approach uses past experience to compute probability matrices for each risk variable [1>16]. The result of this approach was a good fit of predicted to observed mortalities as shown in Table 2. The method was reviewed by two nationally known statisticians, one an expert in Bayes' theorem and the other an expert in multiple regression techniques. Both consultants found the system to be scientifically valid. The Council reviewed the analyses and recommendations of these consultants and approved implementation in October An article describing the technical aspects of the STS method is contained in this issue of The Annals of Thoracic Surgery [17]. Work continues on risk assessment as recent data may require an adjustment of the model. Additionally, work has begun using multiple variable regression methods to analyze the STS experience. Com- ODerative Mortalitv. - % 8 0 % I Age In Years Fig I. Operative mortality by age group for corfma y arte y bypass graftingfrom 1988 through 1992 (n = 62,473). parisons of the two methods will be made in the future. The use of neural networks i!j under study. Summary of the National Cardiac Database Experience to Date At the end of the harvest on November 1, 1992, there were 216,075 patients listed in the National Database. Seventy-three percent (158,3134) have had CABG operations only, whereas an additional 8% have had CABG with valve replacement or another procedure. Thus, the majority of work performed aver 12!(ems involves CABG procedures. The average patient age inow exceeds 64 years and is on a gradual trend upward. If the trend remains linear, it is estimated that by the year 2005 the average age for patients receiving their first CABG will be 69.5 years. Despite increasing risks, as will be described later, the trend for mean ejection fraction over tlne past 4 years has remained constant at approximately In looking at more receni data for the last 5 years, reoperations have been constant at alp proximately lo%, and postoperative length of stay for first-time elective CABG operations is decreasing to appximately 8.5 days. Preoperative length of stay is also decreasing to approximately 3 days at the present time. However, the total length of stay is dependent on whether or not the patient had a catheterization during the sarne hospitalization. I Table 2. Comparison of Predicted and Observed Mortality for All Coronary Arteq Bypass Grafting Patients ( Y' Mortality Observed Predicted Range (%) Patients Deaths Mortality (%) Mortality (%) >o-5 24, >%I0 3, >1o-20 1, > >3CL All patients 29,850 1, a p > IstOpElect IstOp/ErnerS(enlt ReOp/EIt?cit ReOp/Ernergent Fig 2. Operative mortality as u function of urgency of operation and reoperation for coronay artery bypuss grafting from 1988 through 1990 (n = 85,614).

4 ~ ;57:2&6 CLARK 23 8% 1 6%-' 4% - ~2, % -, n-68,629 8 % % % n % 12% 10% 6% With catheterization, the average total length of stay is 14 days, whereas without catheterization, it is approximately 9 days. The percentage of emergent operations has shown a slight decrease from 1988, when it was approximately 23%, to a current level of approximately 18%. Whether or not this trend will continue is unknown. The operative mortality by age is shown in Figure 1 and clearly represents a major risk factor in an aging population. The influence of urgency of operation and reoperation is shown in Figure 2. Reoperation results in a threefold increase in operative mortality for CABG compared with those done on an elective basis. The worst case situation is an emergent reoperation, which carries a mortality rate of approximately 13%. The proportion of female patients has been rising and is currently almost 30%. The influence of gender during the period 1988 through 1992 continues to be important, as it has for the past 20 years, with a significant increase in operative mortality for female (4.2%) versus male patients (2.4%). Figure 3 shows the influence of percutaneous transluminal coronary angioplasty and timing of operation. Coronary artery bypass operations, when performed on an elective first-operation basis more than 6 hours after balloon angioplasty, have a low mortality rate of 1.5%. However, if the operation is performed within 6 hours of the balloon angioplasty, the mortality rate is 3.5 times higher. An analysis of the entire database (1980 through 1991) concerning the mortality rate associated with and without use of the internal mammary artery on both elective and emergent bases was presented in the first Annual Report. The data were reanalyzed for the most recent 5 years and are shown in Figure 4. The complete analysis of the influence of the internal mammary artery is contained in this issue of The Annals of Thoracic Surgery [18]. Aortic valve replacement (AVR) procedures continue to carry a low risk for male patients and a higher risk for female patients, which very closely approximates CABG mortality rates for the past 5 years. In 2,781 AVR operations, male patients had a 2.3% mortality rate whereas female patients (n = 1,836) had a 3.7% mortality rate. The average age for first AVR operation was close to that for CABG, being approximately 64.5 years. Figure 5 shows the urgency of operation and the influence of reoperation for AVR. The operative mortality by age is very similar to that of the CABG group for first operation on an elective basis. Mortality for elective first AVR operations over time has been relatively constant for the last 5 years (Fig 6). Mitral valve replacement, on the other hand, continues to carry a higher mortality rate for age greater than 60 years than either CABG or AVR (Fig 7). The mean age of Operative Mortality % Observed Mortality 'Or ~ ~ ~ ~ 8% n Elect Elect Emergent Emergent wlo IMA wlth IMA wlo IMA Wlth IMA Fin 4. Operative mortalitu associated with use of internal mammaru artery (IMA) and coronay artery bypass grafting 1988 through 1952 (n = 77,150) n Fig 6. Operative mortality for elective first aortic valve replacement from 1980 through 1992 (n = 6,002).

5 24 CLARK 1994;572M Operatlve Mortality % Observed Mortality 4% n-537 2%. 0% J'Y n Age In Years Fig 7. Operative mortality by age group for mitral valve replacement from 1980 through 1992 (n = 1,614). the patients (approximately 61.5 years) was less than the average age of patients having the other two major procedures. The reoperation rate has continued to rise gradually over time, probably as a result of dysfunctioning bioprosthetic heart valves, to approximately 32% of the total experience during Figure 8 shows the operative mortalities by urgency of operation and reoperation as compared with the first procedure. Mortality for elective first operation mitral valve replacement operations over time is shown in Figure 9. Changing Risk Using the risk stratification system, the data from 1984 through 1992 for CABG patients were examined to determine if the clinical impressions of many were reflected by the data accrued. Three predicted operative mortality categories were chosen: 0% to 5% (low), 5% to 20% (moderate), and greater than 20% (high). Each patient for each year had a predicted risk determined, and the summed averaged risk per year was plotted as shown in Figures 10, 11, and 12. These demonstrate that there was a decrease of approximately 19% in good-risk patients (86% to 67%) over the 8-year interval and a concomitant 17% increase in the moderate risk group (13% to 30%). The high-risk group, which represents a low percentage of the total case load, has increased from 0.6% of all patients to 3.6% n Fig 9. Operative mortality for elective first-operation mitral valve replacement from 1980 through 1992 (n = 3,087). All cases of CABG were ihen plotted to contrast observed to predicted mortality. These data are shown in Figure 13. The predicted risk has risen since 1988 and is now at 5.3%. In contrast, tliei-e has been no increase in the observed overall mortality, which has, fluctuated around 3% until 1992, when it was ;!.4%. Clearly, this constant-to-improved mortality rate is not the result of better-risk patients being ireferred for surgical palliation as the predicted mortality data show that risk has gone up. Thus, higher ri!jk patients are being referred and operated on with a low mortality rate. The explanation of the relatively constant mortality rate would suggest that major factors, such,as increased use of the internal mammary artery, improved pharmacology and myocardial protection techniques, and the use of various assist devices, have contributed significantly to maintaining low mortality in the face (If an increasing risk in an increasingly older population. These STS data reflect the aggregate operative experience over a wide geographic distribution (Fig 14). Although such data may represent an average standard of care, it is important to remember that they only reflect results from centers that pa1 ticipate' in the National Database. It is not appropriate at this time to say that the data reflect the national experience because the database is relatively small and still young. Only with time, and ODerative Mortality 20% n-165 n %- % Of Population 90 i l I 15% - IstOp/Elect IstOp/Emergent ReOplElect ReOplEmergent Fig 8. Operative mortality by urgency of operation and reoperation for mitral valve replacement from 1988 through 1992 (n = 2,529). Fig 10. Trend of low-risk (0% to 5%) cor~nc~ry artery bypass grafting patients from 1984 through 1992.

6 1994; CLARK i.l 1 % Mortality 6% Fig 11. Trend of predicted medium-risk (5% to 20%) coronary artery bypass grafting patients from 1984 through perhaps millions of patients, will the STS have a true National Database. Nonetheless, these data can be used to observe trends and to make various comparisons based on a large experience. Clearly, larger numbers of patients in high-risk categories are required before definitive statistical statements can be made. The reliability of any statistical model is strongly influenced by the number of patients in the model population, the completeness of the data, and the accuracy of the data entered into the files. The model must receive a certain minimal amount of clinical information to achieve an acceptable degree of accuracy. Consequently, it is incumbent upon the users of the National Database to supply both accurate and complete data for use in the national system if their local needs for prediction and self-assessment are to be met. Future The goals for this forthcoming year are to increase the total number of patients within the database to 350,000 and to have broader representation, not only by more surgeons, but also by surgeons from larger centers. It is hoped that the number of groups, currently 256, will increase to 355, such that approximately 1,100 surgeons will be participating in more than 700 hospitals. Should this occur, the Committee believes that this would represent participation by more than 50% of the groups, Obs Mort ++ Pred Mort,, i -, - - I 0% L-J n , ,478 Fig 13. Trend of predicted risk (Pred Mort) and observed operative mortality (Obs Mort) for all corona y artery bypass grafting patients from 1984 through (n = 132,203). surgeons, and hospitals currently performing cardiac sur- Fry. Additionally, the Committee plans to add new modules to the general thoracic surgery program. Under development is a data format for benign esophageal disease and a second on benign pulmonary diseases. Work has already begun on organizing the multiple variables associated with risk for congenital heart surgery. It may be possible to model a certain population of patients with congenital heart disease and begin to develop risk stratification schemes for subsets. Sufficient interest has now been generated at many large centers that wish to contribute their voluminous retrospective and prospective data. This would greatly enhance the National Database and carry it toward the goal of representing true national character. Finally, the Committee hopes to attract more surgeons doing general thoracic surgery so that reports representing their important work may be issued on an annual or biannual basis. 05 I Fig 12. Trend of predicted high-risk 020%) coronary artery bypass grafting patients from 1984 through IT-.., Fig 14. Geographic distribution of hospitals participating in the National Database. (Map of the United States 0 Creative Teaching Press, Inc. Reprinted by permission.)

7 26 CLARK 1994;572&6 Conclusion The National Database has been enthusiastically received by members of the STS. Those who have joined have come predominantly from private practices outside of the large metropolitan centers, and the data presented must be interpreted in this light. Analysis of CABG, which constitutes approximately 80% of the experience to date, shows that several major risk factors are increasing in incidence, with a concomitant increase in overall predicted risk. Contrary to that expected, the actual observed mortality rates for the last 5 years have remained relalively constant at approximately 3% for all CABG operalions. The analysis of operative techniques in the population studied for the years 1988 through 1992 for first-operation CABG procedures (n = 77,150) shows that use of the internal mammary artery, in both elective and emergency operations, contributed significantly to decreased mortality. However, the widening gap between predicted and observed mortalities suggests that other factors surely must be considered. New pharmacologic agents and drug treatment strategies in all phases of care may well be inaking a difference. Importantly, the great attention given to myocardial protection in the research laboratory may now be having an impact at the local level in maintaining low mortality for coronary artery bypass operations despite increasing risk. :References 1. Edmunds LH Jr, Kaiser GA. State-of-the-art symposium on coronary arterial surgery. Preface. Circulation 1989;79 (6 Pt 2):I Ebert PA. State-of-the-art symposium on coronary arterial surgery. Keynote address. Circulation 1989;79(6 Pt 2): Clark RE. Report of the first presentation of the National Database. 1991;52: Parsonnet V. A method of uniform stratification of risk for evaluating the results of surgery in acquired adult heart disease. Circulation 1989;79(6 Pt 2): Hannan EL, Kilburn HK, O'Donnell JF, Lukacik G, Shields El'. Adult open heart surgery in New York State. An analysis of risk factors and hospital mortality rates. JAMA 1990;264: 276& Grover FL, Johnson R, Marshall C, Hammermeister KZ. Impact of mammary grafts on coronary bypass operative mortality and morbidity. Ann Thorac 'Surg (in press). 7. The Pennsylvania Health Care Cost Containment Council. Coronary artery bypass graft surgery: a technical report. Harrisburg, PA: The Pennsylvania Health Care Cost Containment Council, Blumberg MS. Biased estimates of expected acute myocardial infarction mortality using MedisGroups admission severity groups. JAMA 1991;265: Killip T, Pasamani E. Davis K, and the CASS principal investigators and their associates. Coronary Artery Surgery Study (CASS): a randomized trial of coronary bypass surgery. Eight years follow-up survival in patients with reduced ejection fraction. Circulation 1985;72(Suppl 5): O'Connor GT, Plume SK, Olmstead EM, et al. Multivariate prediction of in-hospital mortality associated with coronary artery bypass graft surgery. Circulation 1992;85:211M. 11. Kirklin JW, Akins CW, Blackstone EH, et al. Guidelines and indications for coronary artery bypass graft surgery. A report of the American College of Cardiology/American Heart Association Task Force on Assessment of Diagnostic and Therapeutic Cardiovascular Procedures (Subcommittee on Coronary Artery Bypass Graft Surgery). J.Am Coll Cardiol 1991; Higgins TL, Estafanous FG, Loop FD. Stratification of morbidity and mortality outcome by preolperative risk factors in coronary artery bypass patients. JAW4 1992; Edwards FH, Graeber GM. The theorem of Bayes as a clinical research tool. Surg Gynecol Obstet 1987;165: Edwards FH, Albus RA, Zajtchuk R, et al. Use of a Bayesian statistical model for risk assessment in coronary artery surgery. 1988;45: Edwards FH, Albus RA, Zajtchuk R, et al. A quality assurance model of operative mortality in coronary artery surgery. 1989;47: Edwards FH, Cohen AJ, Bellamy RF, Thompson L, Weston L. Risk assessment in urgent/emergent coronary artery surgery. Chest 1990;97: Edwards FH, Clark RE, Schwartz M. Coronary artery bypass grafting: The Society of Thoracic Surgeons National Database experience. 1994; Edwards FH, Clark RE, Schwartz Id. Impact of internal mammary artery conduits on operative mortality in coronary revascularization. 1!994;