American
Heart Journal
May, 1977, Volume 93, Number 5
Editorial Surgical therapy for coronary artery disease" Caveat emptor Stephen G. Pauker, M.D., F.A.C.P., F.A.C.C. Boston, Mass.
The past decade has seen the coronary artery bypass graft evolve into the most common form of cardiac surgery at many institutions. Fueled by the high prevalence of coronary disease in this country, this extraordinary growth of coronary surgery has been little checked by the scarcity of controlled prospective studies designed to examine the efficacy of the coronary bypass graft as a means of relieving pain, prolonging life, preventing myocardial infarction, and improving ventricular function. This JOURNAL, as have others, has been a forum for discussion concerning these issues. At this time, only one conclusion seems clear: sufficient data are not yet available about the long-term effects of bypass surgery. Indeed, it may be a long time before consensus is reached. In the meantime what shall today's physicians and patients do? Coronary surgery is available now and decisions must be made based on the best data now available. The patient or the physician who defers his decision until "the final answer is in" may not survive long enough to learn t h a t answer. He is, in effect, opting for medical therapy. Several "easy" solutions might be tried. The physician, cognizant of the need to insure informed consent, could summarize the present controversy for his patients, tailor that summary From the New England Medical Center Hospital, Boston, Mass. Received for publication Sept. 22, 1976. Reprint requests: Stephen G. Pauker, M.D., New England Medical Center Hospital, 171 Harrison Ave., Boston, Mass. 02111.
May, 1977, Vol. 93, No. 5, pp. 543-546
to reflect the prognosis of each individual patient, and place the burden of the decision on t h a t patient by saying "Only you can make this decision!" Unfortunately, few patients are equipped to comprehend the controversy, sort out the details, and arrive at a logical choice. Most will either choose blindly or will take the second "easy" solution: "Doctor, I just don't know. Please tell me what I should do." The physician may then suggest a therapeutic plan, but all too often that suggestion will reflect the physician's own values and does not adequately reflect what would be best for a particular patient. Of course this scenario is often bypassed when the physician does not consult the patient but summarily suggests: "The x-rays show t h a t you need surgery." In a recent article in the Annals of Internal Medicine, one possible solution to this dilemma was proposed. 1 Decisions which must be made despite uncertainties in the data upon which the decision must be based can be approached by decision analysis. 2-~ Briefly, the technique involves the explicit consideration of every possible outcome of each course of action. For each of these potential outcomes, the decision maker assigns aprobability, reflecting the relative likelihood of t h a t outcome's occurrence, and a utility, reflecting the relative worth of t h a t outcome. The product of t h a t probability and utility is a measure of the worth which t h a t potential outcome would be expected to have. The sum of these products for every potential consequence of a therapeutic choice is the
American Heart Journal
543
Pauker
Table I. C a l c u l a t i o n of expected values
Probability Ou~ome
HosP.A
I HosP.B
Utility Mr. Jones
Mr. Smith
Expected value Mr. Jones at Mr. Smi~ at Hosp. Hosp. HosP.A [ HosP.B A B
Surgical therapy: Peri-operative death Pain relief but fatal MI* Long-term pain relief Short-term pain relief Persistent pain and fatal MI* Spontaneous relief of pain Persistent pain Surgical total
.15
.05
0
0
.25
.30
60
85
.20 .13 .13 .04 .10
.40 .09 .09 .01 .06
100 80 40 80 70
100 85 70 85 80
1.00
1.00
.50 .10 .40 1.00
.50 .10 .40 1.00
Medical therapy: Persistent pain and fatal.MI* Spontaneous relief of pain Persistent pain Medical total
50 90 80
80 95 90
0 15 20 10 5 3 7 60
0 18 40 7 4 1 4 74
0 21 20 11 9 3 8 72
0 26 40 8 6 1 5 86
25 9 32 66"
25 9 32 66
40 10 36 86
40 10 36 86
*Fatal MIrefersto death within fiveyears.
expected value of t h a t t h e r a p y . T h e r a t i o n a l decision m a k e r will select the t h e r a p y which h a s the greatest expected value. W h e n e v e r one a t t e m p t s to use this a p p r o a c h to decision-making, three questions b e c o m e i m m e d i ately a p p a r e n t : (1) which of the a l m o s t infinite a r r a y of possible o u t c o m e s should one consider? (2) where can one obtain the d a t a which reflect the relative likelihood of occurrence of e a c h of these o u t c o m e s ? and (3) whose values should the utilities reflect? E a c h of these p r o b l e m s will be considered in t u r n with reference to the choice of t h e r a p y for c o r o n a r y a r t e r y disease. T h e m o s t difficult p r o b l e m centers a r o u n d t h e proper s t r u c t u r i n g of the decision so t h a t it reflects the clinically significant facts b u t nevertheless r e m a i n s m a n a g e a b l e . One m i g h t imagine an endless s p e c t r u m of possible outcomes: c e r e b r o v a s c u l a r accidents a f t e r surgery, debilitating p o s t o p e r a t i v e m u s c u l o s k e l e t a l pain, congestive h e a r t failure. Ideally, all these possibilities should be considered, b u t those p o t e n t i a l o u t c o m e s which are e x t r e m e l y unlikely h a v e little influence on the decision unless the utility of these o u t c o m e s i s either e x t r e m e l y high or e x t r e m e l y low relative to the utility of the m o r e likely events. T h e model" proposed in the Annals does n o t a t t e m p t to be complete; r a t h e r it tries to reflect the m o s t likely o u t c o m e s in r e a s o n a b l y simple
544
terms. I t considers only those o u t c o m e s which are considered in our current, empirical clinical decision-making processes. T h e m o d e l s t r u c t u r e s the potential o u t c o m e s along two d i m e n s i o n s - l e n g t h of life a n d freedom f r o m disabling angina. T h e five y e a r time horizon of the analysis reflects the limitations of p r e s e n t l y available d a t a a b o u t prognosis. Survival is divided into t h r e e periods: {1) i m m e d i a t e death, (2) d e a t h within five years, and (3) survival b e y o n d t h a t time. Disability is quantized into two states: the presence or absence of disabling angina. W i t h t h e c o n v e n t i o n t h a t d e a t h within five years is labelled " F a t a l M I , " T a b l e I s u m m a r i z e s the possible o u t c o m e s of b o t h surgical a n d medical t h e r a p y . Given a p a t i e n t with disabling angina, this m o d e l yields seven p o t e n t i a l o u t c o m e s of surgical t h e r a p y a n d three possible o u t c o m e s of medical t h e r a p y . T h e next t a s k is to e s t i m a t e the likelihoods of these o u t c o m e s for the p a t i e n t u n d e r consideration. T h e p a t i e n t ' s c o r o n a r y a n a t o m y and ventricular function m u s t be assessed since prognosis is determined, in large part, by these variables. F u r t h e r m o r e , as p o i n t e d out elsewhere, ~ additional clinical variables such as exercise tolerance, segmental function, t h e results of m y o c a r d i a l imaging, and the presence of a r r h y t h m i a s , hypertension, and co-existing disease should all be considered. T h e proposed model suggests only the form t h a t such consideration should take: Given
May, 1977, Vol. 93, No. 5
Surgical therapy for CAD-Caveat emptor the patient's total clinical presentation, what is the likelihood of each relevant outcome if only medical therapy is employed. What is the likelihood if bypass surgery is undertaken? This latter question is particularly difficult since reported series are often not comparable and since there is considerable variation among these series. 6' ~ The truly relevant data would bear on the prognosis of the particular patient at the particular institution where he is to be managed and where it is proposed t h a t surgery be performed. If th at surgery is to be performed at a community hospital averaging just fifty bypass procedures annually, are data t h a t refer to a hospital performing over a thousand procedures each year relevant? Thus, the second major problem has become the lack of availability of relevant data. This is just the point where the physician must employ his greatest skill. After appropriate consultation and laboratory examination, he must arrive at the best available estimate of the prognostic probabilities. This process of estimation is difficult, but it must clearly underlie any reasonable process of clinical decision-making. One advantage of the decision analysis model is t h a t these estimates are explicit and therefore can be reexamined, discussed, and improved. The third problem encountered in this approach centers about the question of utilities-whose values should be used and how can they be obtained? Setting aside limitations imposed by resource constraints and over-all societal cost, the most logical source of these values is the patient himself since only he can express the burden which his angina represents and only he can evaluate the burden which early death would create. Since the proposed model is quite simple, only ten outcomes need be considered. Therefore, one can examine the patient's attitudes toward each of the potential outcomes explicitly. T he m e t h od described in the Annals proposes the lottery technique for debriefing the patient of his values. The essence of t hat technique is to offer the patient a series of simple choices between one hypothetically guaranteed outcome and a gamble between two more extreme alternatives. By altering the odds of t hat gamble, the physician can find a point where the patient is indifferent between the guaranteed outcome and the gamble. The odds of the gamble at t h a t point of indiffer-
American Heart Journal
ence can be used to establish the utility of the guaranteed outcome. In my experience, such debriefing can be comfortably accomplished in less than one hour, and most patients can understand and respond to the hypothetical alternatives. The analysis reported in the Annals demonstrates that the optimal decision for any individual patient cannot be determined solely from his clinical or angiographic presentation. The past surgical results at the particular institution and the patient's own attitudes can easily alter the optimal choice and must therefore be considered. Let us consider an example. Imagine two identical 50-year-old men with disabling angina, not responsive to nitrates or beta-adrenergic blockade. Assume t hat they both underwent cardiac catherization and were shown to have lesions causing 70 to 80 per cent obstruction of both the proximal right coronary artery and the left anterior descending artery in its middle third with good distal run-off in both vessels. In both patients the ejection fraction was 30 per cent with segmental dysfunction along the anterior and posterior walls but without discrete areas of aneurysm. Let us consider two hospitals where these patients might undergo bypass surgery. Hospital A has had little experience in dealing with patients having marginal or depressed myocardial function, while Hospital B has had broad experience with such patients. Table I summarizes the best estimates of the probabilities of the various outcomes for these patients in each hospital. Mr. Jones is a truck driver and is willing to take some risks to obtain pain relief, whereas Mr. Smith is an executive who would tolerate his disability if his life expectancy might be jeopardized by surgery. Table I also summarizes hypothetical utilities t h a t might be obtained from these patients, T he patients' perceptions of the relative benefits and costs of the possible outcomes are reflected in these utilities. As pointed out above, the expected value for surgical and medical therapy can be calculated by forming the product of the probability and the utility of each outcome and summing these products for surgical and medical therapy, respectively. These calculations are summarized in Table I for both Mr. Jones and Mr. Smith receiving treatment at either Hospital A or
545
Pauker
Hospital B. For example, there is a 0.25 p r o b a bility of " P a i n relief b u t f a t a l M I " {death within five years) if surgery is p e r f o r m e d a t Hospital A. Since Mr. J o n e s assigns a utility of 60 to this outcome, the c o n t r i b u t i o n of this o u t c o m e to the expected value of surgery for Mr. J o n e s a t Hospital A is 0.25 x 60, or 15. In c o n t r a s t , Mr. S m i t h assigns a utility of 85 to this o u t c o m e , a n d the c o n t r i b u t i o n of this o u t c o m e to t h e expected value of surgery is 0.25 x 85, or 21, for him. M a k i n g similar calculations for e a c h p o t e n t i a l o u t c o m e of surgery a n d s u m m i n g , one can see t h a t a t Hospital A the expected v a l u e for Mr. Jones is 60, whereas t h e expected value for Mr. S m i t h is 72. One would expect the r a t i o n a l p a t i e n t to elect the t h e r a p y which offers him the higher e x p e c t e d value. Thus, Mr. J o n e s would likely choose medical t h e r a p y at Hospital A b u t surgical t h e r a p y at Hospital B. Similarly, Mr. S m i t h should also opt for medical t h e r a p y at HospitalA but should consider the o p t i m a l choice a t Hospital B to be a "toss up." One can see from this e x a m p l e t h a t given identical a n a t o m y a n d clinical presentation, t h e " c o r r e c t " decision varies from p a t i e n t to p a t i e n t and f r o m h o s p i t a l to hospital. This analysis raises several serious questions a b o u t the medical care t h a t m i g h t be offered to these patients. Is it r e a s o n a b l e - f o r p a t i e n t s who present to HospitalA to decline surgical t h e r a p y ? Should they be i n f o r m e d a b o u t the b e t t e r results at Hospital B a n d be offered surgery there? Indeed, should a n y p a t i e n t be offered b y p a s s surgery at Hospital A if he m i g h t h a v e a b e t t e r result at Hospital B? C e r t a i n l y a d d i t i o n a l f a c t o r s such as geographic constraints, convenience, a n d availability enter into such decisions. These complex questions c a n n o t be decided here a n d p r o b a b l y should not be decided b y individual physicians. T h e s e issues m u s t eventually be addressed b y b o t h organized medicine and society, b u t until t h a t time, the m e t h o d of clinical decision m a k i n g proposed here should allow the choice to be optimized for t h e individual patient facing the resources of a specific hospital. Certainly, the use of this t e c h n i q u e will create
546
problems for b o t h the p a t i e n t and the physician. T h e p a t i e n t will be forced to explicitly e x a m i n e his i n n e r m o s t feelings a b o u t life and death. T h e physician will h a v e to take m o r e t i m e in order to help the p a t i e n t in t h a t e x a m i n a t i o n a n d will be forced to deal with his own u n c e r t a i n t i e s a b o u t prognosis in an explicit m a n n e r . T h e s e p r o b l e m s m u s t be faced b y the physician if he is to provide his p a t i e n t s a basis for t r u l y informed consent. This a p p r o a c h will, of course, n o t be a p p r o priate for all patients facing the possibility of bypass surgery. S o m e p a t i e n t s m a y not wish to bear the b u r d e n of p a r t i c i p a t i o n in the decisionmaking process, while others m a y h a v e difficulty with the concepts involved. A l t h o u g h the physician m u s t rely on his p e r c e p t i o n of the p a t i e n t ' s attitudes in such circumstances, this a p p r o a c h should still assist the clinician as he considers the uncertainties a b o u t prognosis. T h e use of decision analysis is not limited to choices involving surgical t h e r a p y . R a t h e r , it is generally applicable to those t h e r a p e u t i c decisions which m u s t be m a d e despite u n c e r t a i n t i e s m data a b o u t prognosis and to t h o s e decisions which might be strongly influenced b y the p a t i e n t ' s attitudes. In such situations, explicit decisionmaking should lead to b e t t e r d e c i s i o n s - d e c i s i o n s tailored to t h e available resources, decisions consistent w i t h the p a t i e n t ' s desires and attitudes, a n d decisions reflecting the t r u e skill of t h e physician. REFERENCES
1. Pauker. S. G.: Coronary artery surgery: the use of decision analysis. Ann. Intern. Med. 85:8. 1976. 2. Raifla. H.: Decision Analysis, Reading, Mass.. 1968. Addison-Wesley. 3. Schwartz. W. B.. Gorry, G. A.. Kassirer, J. P.. and Essig, A.: Decision analysis and clinical judgment, Am. J. Med. 55:459. 1973. 4. Kassirer. J. P.: The principles of clinical decision making: an introduction to decision analysis, Yale J Biol. Med. 49:149, 1976. 5. Humphries. J. O.: Decision analysis and coronary surgery, Ann. Intern. Med. 85:123. 1976. 6. Dunkman. W. B.. Perloff. J. K. Kastor. J. A_ et al.: Medical perspective in coronary artery surgery-a caveat, Ann. Intern. Med. 81:817, 1974. 7. Mundth. E. D.. and Austen. W. G.: Surgical measures for coronary heart disease. N. Engl. J. Med. 293:13-18.75-80. 124-30. 1975.
May, 1977, Vol. 93, No. 5
Heart Journal
May, 1977, Volume 93, Number 5
Editorial Surgical therapy for coronary artery disease" Caveat emptor Stephen G. Pauker, M.D., F.A.C.P., F.A.C.C. Boston, Mass.
The past decade has seen the coronary artery bypass graft evolve into the most common form of cardiac surgery at many institutions. Fueled by the high prevalence of coronary disease in this country, this extraordinary growth of coronary surgery has been little checked by the scarcity of controlled prospective studies designed to examine the efficacy of the coronary bypass graft as a means of relieving pain, prolonging life, preventing myocardial infarction, and improving ventricular function. This JOURNAL, as have others, has been a forum for discussion concerning these issues. At this time, only one conclusion seems clear: sufficient data are not yet available about the long-term effects of bypass surgery. Indeed, it may be a long time before consensus is reached. In the meantime what shall today's physicians and patients do? Coronary surgery is available now and decisions must be made based on the best data now available. The patient or the physician who defers his decision until "the final answer is in" may not survive long enough to learn t h a t answer. He is, in effect, opting for medical therapy. Several "easy" solutions might be tried. The physician, cognizant of the need to insure informed consent, could summarize the present controversy for his patients, tailor that summary From the New England Medical Center Hospital, Boston, Mass. Received for publication Sept. 22, 1976. Reprint requests: Stephen G. Pauker, M.D., New England Medical Center Hospital, 171 Harrison Ave., Boston, Mass. 02111.
May, 1977, Vol. 93, No. 5, pp. 543-546
to reflect the prognosis of each individual patient, and place the burden of the decision on t h a t patient by saying "Only you can make this decision!" Unfortunately, few patients are equipped to comprehend the controversy, sort out the details, and arrive at a logical choice. Most will either choose blindly or will take the second "easy" solution: "Doctor, I just don't know. Please tell me what I should do." The physician may then suggest a therapeutic plan, but all too often that suggestion will reflect the physician's own values and does not adequately reflect what would be best for a particular patient. Of course this scenario is often bypassed when the physician does not consult the patient but summarily suggests: "The x-rays show t h a t you need surgery." In a recent article in the Annals of Internal Medicine, one possible solution to this dilemma was proposed. 1 Decisions which must be made despite uncertainties in the data upon which the decision must be based can be approached by decision analysis. 2-~ Briefly, the technique involves the explicit consideration of every possible outcome of each course of action. For each of these potential outcomes, the decision maker assigns aprobability, reflecting the relative likelihood of t h a t outcome's occurrence, and a utility, reflecting the relative worth of t h a t outcome. The product of t h a t probability and utility is a measure of the worth which t h a t potential outcome would be expected to have. The sum of these products for every potential consequence of a therapeutic choice is the
American Heart Journal
543
Pauker
Table I. C a l c u l a t i o n of expected values
Probability Ou~ome
HosP.A
I HosP.B
Utility Mr. Jones
Mr. Smith
Expected value Mr. Jones at Mr. Smi~ at Hosp. Hosp. HosP.A [ HosP.B A B
Surgical therapy: Peri-operative death Pain relief but fatal MI* Long-term pain relief Short-term pain relief Persistent pain and fatal MI* Spontaneous relief of pain Persistent pain Surgical total
.15
.05
0
0
.25
.30
60
85
.20 .13 .13 .04 .10
.40 .09 .09 .01 .06
100 80 40 80 70
100 85 70 85 80
1.00
1.00
.50 .10 .40 1.00
.50 .10 .40 1.00
Medical therapy: Persistent pain and fatal.MI* Spontaneous relief of pain Persistent pain Medical total
50 90 80
80 95 90
0 15 20 10 5 3 7 60
0 18 40 7 4 1 4 74
0 21 20 11 9 3 8 72
0 26 40 8 6 1 5 86
25 9 32 66"
25 9 32 66
40 10 36 86
40 10 36 86
*Fatal MIrefersto death within fiveyears.
expected value of t h a t t h e r a p y . T h e r a t i o n a l decision m a k e r will select the t h e r a p y which h a s the greatest expected value. W h e n e v e r one a t t e m p t s to use this a p p r o a c h to decision-making, three questions b e c o m e i m m e d i ately a p p a r e n t : (1) which of the a l m o s t infinite a r r a y of possible o u t c o m e s should one consider? (2) where can one obtain the d a t a which reflect the relative likelihood of occurrence of e a c h of these o u t c o m e s ? and (3) whose values should the utilities reflect? E a c h of these p r o b l e m s will be considered in t u r n with reference to the choice of t h e r a p y for c o r o n a r y a r t e r y disease. T h e m o s t difficult p r o b l e m centers a r o u n d t h e proper s t r u c t u r i n g of the decision so t h a t it reflects the clinically significant facts b u t nevertheless r e m a i n s m a n a g e a b l e . One m i g h t imagine an endless s p e c t r u m of possible outcomes: c e r e b r o v a s c u l a r accidents a f t e r surgery, debilitating p o s t o p e r a t i v e m u s c u l o s k e l e t a l pain, congestive h e a r t failure. Ideally, all these possibilities should be considered, b u t those p o t e n t i a l o u t c o m e s which are e x t r e m e l y unlikely h a v e little influence on the decision unless the utility of these o u t c o m e s i s either e x t r e m e l y high or e x t r e m e l y low relative to the utility of the m o r e likely events. T h e model" proposed in the Annals does n o t a t t e m p t to be complete; r a t h e r it tries to reflect the m o s t likely o u t c o m e s in r e a s o n a b l y simple
544
terms. I t considers only those o u t c o m e s which are considered in our current, empirical clinical decision-making processes. T h e m o d e l s t r u c t u r e s the potential o u t c o m e s along two d i m e n s i o n s - l e n g t h of life a n d freedom f r o m disabling angina. T h e five y e a r time horizon of the analysis reflects the limitations of p r e s e n t l y available d a t a a b o u t prognosis. Survival is divided into t h r e e periods: {1) i m m e d i a t e death, (2) d e a t h within five years, and (3) survival b e y o n d t h a t time. Disability is quantized into two states: the presence or absence of disabling angina. W i t h t h e c o n v e n t i o n t h a t d e a t h within five years is labelled " F a t a l M I , " T a b l e I s u m m a r i z e s the possible o u t c o m e s of b o t h surgical a n d medical t h e r a p y . Given a p a t i e n t with disabling angina, this m o d e l yields seven p o t e n t i a l o u t c o m e s of surgical t h e r a p y a n d three possible o u t c o m e s of medical t h e r a p y . T h e next t a s k is to e s t i m a t e the likelihoods of these o u t c o m e s for the p a t i e n t u n d e r consideration. T h e p a t i e n t ' s c o r o n a r y a n a t o m y and ventricular function m u s t be assessed since prognosis is determined, in large part, by these variables. F u r t h e r m o r e , as p o i n t e d out elsewhere, ~ additional clinical variables such as exercise tolerance, segmental function, t h e results of m y o c a r d i a l imaging, and the presence of a r r h y t h m i a s , hypertension, and co-existing disease should all be considered. T h e proposed model suggests only the form t h a t such consideration should take: Given
May, 1977, Vol. 93, No. 5
Surgical therapy for CAD-Caveat emptor the patient's total clinical presentation, what is the likelihood of each relevant outcome if only medical therapy is employed. What is the likelihood if bypass surgery is undertaken? This latter question is particularly difficult since reported series are often not comparable and since there is considerable variation among these series. 6' ~ The truly relevant data would bear on the prognosis of the particular patient at the particular institution where he is to be managed and where it is proposed t h a t surgery be performed. If th at surgery is to be performed at a community hospital averaging just fifty bypass procedures annually, are data t h a t refer to a hospital performing over a thousand procedures each year relevant? Thus, the second major problem has become the lack of availability of relevant data. This is just the point where the physician must employ his greatest skill. After appropriate consultation and laboratory examination, he must arrive at the best available estimate of the prognostic probabilities. This process of estimation is difficult, but it must clearly underlie any reasonable process of clinical decision-making. One advantage of the decision analysis model is t h a t these estimates are explicit and therefore can be reexamined, discussed, and improved. The third problem encountered in this approach centers about the question of utilities-whose values should be used and how can they be obtained? Setting aside limitations imposed by resource constraints and over-all societal cost, the most logical source of these values is the patient himself since only he can express the burden which his angina represents and only he can evaluate the burden which early death would create. Since the proposed model is quite simple, only ten outcomes need be considered. Therefore, one can examine the patient's attitudes toward each of the potential outcomes explicitly. T he m e t h od described in the Annals proposes the lottery technique for debriefing the patient of his values. The essence of t hat technique is to offer the patient a series of simple choices between one hypothetically guaranteed outcome and a gamble between two more extreme alternatives. By altering the odds of t hat gamble, the physician can find a point where the patient is indifferent between the guaranteed outcome and the gamble. The odds of the gamble at t h a t point of indiffer-
American Heart Journal
ence can be used to establish the utility of the guaranteed outcome. In my experience, such debriefing can be comfortably accomplished in less than one hour, and most patients can understand and respond to the hypothetical alternatives. The analysis reported in the Annals demonstrates that the optimal decision for any individual patient cannot be determined solely from his clinical or angiographic presentation. The past surgical results at the particular institution and the patient's own attitudes can easily alter the optimal choice and must therefore be considered. Let us consider an example. Imagine two identical 50-year-old men with disabling angina, not responsive to nitrates or beta-adrenergic blockade. Assume t hat they both underwent cardiac catherization and were shown to have lesions causing 70 to 80 per cent obstruction of both the proximal right coronary artery and the left anterior descending artery in its middle third with good distal run-off in both vessels. In both patients the ejection fraction was 30 per cent with segmental dysfunction along the anterior and posterior walls but without discrete areas of aneurysm. Let us consider two hospitals where these patients might undergo bypass surgery. Hospital A has had little experience in dealing with patients having marginal or depressed myocardial function, while Hospital B has had broad experience with such patients. Table I summarizes the best estimates of the probabilities of the various outcomes for these patients in each hospital. Mr. Jones is a truck driver and is willing to take some risks to obtain pain relief, whereas Mr. Smith is an executive who would tolerate his disability if his life expectancy might be jeopardized by surgery. Table I also summarizes hypothetical utilities t h a t might be obtained from these patients, T he patients' perceptions of the relative benefits and costs of the possible outcomes are reflected in these utilities. As pointed out above, the expected value for surgical and medical therapy can be calculated by forming the product of the probability and the utility of each outcome and summing these products for surgical and medical therapy, respectively. These calculations are summarized in Table I for both Mr. Jones and Mr. Smith receiving treatment at either Hospital A or
545
Pauker
Hospital B. For example, there is a 0.25 p r o b a bility of " P a i n relief b u t f a t a l M I " {death within five years) if surgery is p e r f o r m e d a t Hospital A. Since Mr. J o n e s assigns a utility of 60 to this outcome, the c o n t r i b u t i o n of this o u t c o m e to the expected value of surgery for Mr. J o n e s a t Hospital A is 0.25 x 60, or 15. In c o n t r a s t , Mr. S m i t h assigns a utility of 85 to this o u t c o m e , a n d the c o n t r i b u t i o n of this o u t c o m e to t h e expected value of surgery is 0.25 x 85, or 21, for him. M a k i n g similar calculations for e a c h p o t e n t i a l o u t c o m e of surgery a n d s u m m i n g , one can see t h a t a t Hospital A the expected v a l u e for Mr. Jones is 60, whereas t h e expected value for Mr. S m i t h is 72. One would expect the r a t i o n a l p a t i e n t to elect the t h e r a p y which offers him the higher e x p e c t e d value. Thus, Mr. J o n e s would likely choose medical t h e r a p y at Hospital A b u t surgical t h e r a p y at Hospital B. Similarly, Mr. S m i t h should also opt for medical t h e r a p y at HospitalA but should consider the o p t i m a l choice a t Hospital B to be a "toss up." One can see from this e x a m p l e t h a t given identical a n a t o m y a n d clinical presentation, t h e " c o r r e c t " decision varies from p a t i e n t to p a t i e n t and f r o m h o s p i t a l to hospital. This analysis raises several serious questions a b o u t the medical care t h a t m i g h t be offered to these patients. Is it r e a s o n a b l e - f o r p a t i e n t s who present to HospitalA to decline surgical t h e r a p y ? Should they be i n f o r m e d a b o u t the b e t t e r results at Hospital B a n d be offered surgery there? Indeed, should a n y p a t i e n t be offered b y p a s s surgery at Hospital A if he m i g h t h a v e a b e t t e r result at Hospital B? C e r t a i n l y a d d i t i o n a l f a c t o r s such as geographic constraints, convenience, a n d availability enter into such decisions. These complex questions c a n n o t be decided here a n d p r o b a b l y should not be decided b y individual physicians. T h e s e issues m u s t eventually be addressed b y b o t h organized medicine and society, b u t until t h a t time, the m e t h o d of clinical decision m a k i n g proposed here should allow the choice to be optimized for t h e individual patient facing the resources of a specific hospital. Certainly, the use of this t e c h n i q u e will create
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problems for b o t h the p a t i e n t and the physician. T h e p a t i e n t will be forced to explicitly e x a m i n e his i n n e r m o s t feelings a b o u t life and death. T h e physician will h a v e to take m o r e t i m e in order to help the p a t i e n t in t h a t e x a m i n a t i o n a n d will be forced to deal with his own u n c e r t a i n t i e s a b o u t prognosis in an explicit m a n n e r . T h e s e p r o b l e m s m u s t be faced b y the physician if he is to provide his p a t i e n t s a basis for t r u l y informed consent. This a p p r o a c h will, of course, n o t be a p p r o priate for all patients facing the possibility of bypass surgery. S o m e p a t i e n t s m a y not wish to bear the b u r d e n of p a r t i c i p a t i o n in the decisionmaking process, while others m a y h a v e difficulty with the concepts involved. A l t h o u g h the physician m u s t rely on his p e r c e p t i o n of the p a t i e n t ' s attitudes in such circumstances, this a p p r o a c h should still assist the clinician as he considers the uncertainties a b o u t prognosis. T h e use of decision analysis is not limited to choices involving surgical t h e r a p y . R a t h e r , it is generally applicable to those t h e r a p e u t i c decisions which m u s t be m a d e despite u n c e r t a i n t i e s m data a b o u t prognosis and to t h o s e decisions which might be strongly influenced b y the p a t i e n t ' s attitudes. In such situations, explicit decisionmaking should lead to b e t t e r d e c i s i o n s - d e c i s i o n s tailored to t h e available resources, decisions consistent w i t h the p a t i e n t ' s desires and attitudes, a n d decisions reflecting the t r u e skill of t h e physician. REFERENCES
1. Pauker. S. G.: Coronary artery surgery: the use of decision analysis. Ann. Intern. Med. 85:8. 1976. 2. Raifla. H.: Decision Analysis, Reading, Mass.. 1968. Addison-Wesley. 3. Schwartz. W. B.. Gorry, G. A.. Kassirer, J. P.. and Essig, A.: Decision analysis and clinical judgment, Am. J. Med. 55:459. 1973. 4. Kassirer. J. P.: The principles of clinical decision making: an introduction to decision analysis, Yale J Biol. Med. 49:149, 1976. 5. Humphries. J. O.: Decision analysis and coronary surgery, Ann. Intern. Med. 85:123. 1976. 6. Dunkman. W. B.. Perloff. J. K. Kastor. J. A_ et al.: Medical perspective in coronary artery surgery-a caveat, Ann. Intern. Med. 81:817, 1974. 7. Mundth. E. D.. and Austen. W. G.: Surgical measures for coronary heart disease. N. Engl. J. Med. 293:13-18.75-80. 124-30. 1975.
May, 1977, Vol. 93, No. 5
