Heart 1997;77:21 1-218

Indications for coronary revascularisation: a

Dutch perspective

Henk Rigter, Annejet P Meijler, Joseph McDonnell, Jan K Scholma, Steven J Bernstein

AbstractObjective-To assess the appropriatenessof indications for coronary artery bypassgraft (CABG) surgery and percutaneoustransluminal coronary angioplasty(PTCA).Methods-A modified Delphi groupjudgement process with input from apanel of six interventional cardiologistsand six cardiopuhmonary surgeons. Therewas one clinician from each of the 12 ter-tiary referral heart centres in TheNetherlands.Main outcome measure-Ratings bypanel members, on a 1 to 9 scale, of indi-cations presented as a choice between twotreatments (CABG v medical treatment,PTCA v medical treatment, and CABG vPTCA) for 1182 model cases. Each caserepresented a unique combination of clin-ical features in terms of symptoms, med-ical history, and results of tests. Ratingswere analysed with respect to degree ofagreement among panelists, degree ofappropriateness of indications, andpanel's preference for invasive or medicaltreatment.Results-The panel agreed on 58-6% anddisagreed on 3-2% of the indications. Thepanel opted for invasive treatment in48-2% and medical treatment in 22-8%,and had no clear preference for eithermethod in 29-0% of the cases. When com-pared with medical treatment, CABG wasmore often rated appropriate than PTCA:35.4% v 21P6% (P < 0.001). Panel scoresdepended on severity of anatomical dis-ease. For instance, for 51-5% of the modelcases with one-vessel disease not includ-ing the proximal left anterior descendingartery, the panel preferred medical treat-ment to invasive treatment, while the lat-ter was preferred in 18% of the cases. Incases with type C lesions, the panel fre-quently rated PTCA as inappropriate.Panel scores were also affected by non-clinical factors. Cardiologists and sur-geons rated the procedure of their ownspecialty higher than the alternative inva-sive intervention.Conclusions-The panel method yieldslogically consistent scores of the appro-priateness of indications for carrying outmedical procedures. It may be an aid informulating clinical practice guidelines.

(Heart 1997;77:211-218)

Keywords: coronary artery bypass grafting; percuta-neous transluminal coronary angioplasty; indications;appropriateness

The provision of "appropriate care" has been apriority on the political agenda in TheNetherlands since 1992, when the governmentpublished a white paper on the subject, butthere is confusion among policy makers aboutwhat it means.' We consider care appropriatewhen the benefits of using a medical proce-dure exceed the risks, exclusive of monetaryCoSt.23 Central to determining appropriatenessof care is identifying appropriate reasons, orindications, for carrying out the procedure.Determining the appropriateness of indica-tions is not seen in The Netherlands as a toolfor health insurance companies to limit thecost of health care, but primarily as an aid forphysicians and other health care workers toverify and enhance the quality of their profes-sional decisions.

Assessments of the appropriateness of indi-cations should ideally be based on the evi-dence in published work on the risksand benefits of applying the procedure. Unfor-tunately, for most procedures there are manypossible indications for which this informationis incomplete, inconsistent, or out of date. Acommonly used method for dealing with thedeficiencies of outcome results in the literatureis the RAND/UCLA appropriateness method,which requires a panel of experts to review thepublished reports thoroughly and then to rate,in two rounds, the appropriateness of indica-tions for carrying out a medical procedure.This method presumes that experiencedphysicians can use clinical insights to supple-ment the published reports.2A Panel scores canbe used to evaluate the appropriateness oftreatment decisions in everyday practice.The RAND/UCLA method has been

applied to a variety of medical procedures.4 6Since 1988 panels in the USA, the UnitedKingdom, The Netherlands, Canada, andSweden have determined the appropriatenessof indications for coronary artery bypass graft(CABG) surgery and percutaneous translumi-nal coronary angioplasty (PTCA) for patientswith coronary artery disease.6'0 We describehere the views of the Dutch panel. In addition,we present findings from analyses aimed atidentifying clinical and non-clinical determi-nants of the panel scores. In a second paper"we report on the appropriateness of treatmentdecisions in coronary artery disease, in 10 ter-tiary referral centres in The Netherlands. This

Institutes for MedicalTechnologyAssessment, and ofPublic Health andSocial Medicine,Erasmus UniversityRotterdam, TheNetherlandsH RigterA P MeijlerJ McDonnellJ K ScholmaSchools ofMedicineand Public Health,University ofMichigan, Ann Arbor,and Ann ArborVeteransAdministration HealthServices Research andDevelopment FieldProgram, Ann Arbor,USAS J BernsteinCorrespondence to:Professor H Rigter, TrimbosInstituut, PO Box 725,3500 AS, Utrecht, TheNetherlands.Accepted for publication16 September 1996

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work is part of the DUCAT (Dutch inventoryof invasive coronary atherosclerosis treat-ments) study. 12 13

MethodsPANELIn The Netherlands invasive cardiovascularinterventions such as CABG and PTCA arecarried out exclusively in specialised heart cen-tres on the basis of a permit issued by the gov-ernment. At the start of the DUCAT study, in1991, there were 12 heart centres, seven form-ing part of university hospitals and five of non-university hospitals. We asked 12 prominentexperienced clinicians, one from each centre,to participate in the panel. They all acceptedthe invitation. Six (including the only woman)were cardiopulmonary surgeons and six wereinterventional cardiologists. Unlike similarpanels in the USA, Canada, and Sweden7-10our panel did not include internists or primarycare practitioners, as these physicians usuallydo not refer patients to heart centres in TheNetherlands. The panelists varied in age(34-53 years), number of years since specialistregistration (3-19), and school of specialisttraining, but not in volume of invasive cardio-vascular procedures personally performed (atleast 100 in 1991). They were instructed togive their best personal clinical judgement andnot to try to represent the position of theircentre or specialty. The panelists took part inall steps of the RAND/UCLA method. Theywere provided with reviews of publicationsfrom 1971 to 1991 on the effectiveness andrisks of CABG and PTCA, and with the reportof the American College of Cardiology/American Heart Association task force onbypass surgery.78 14

SET OF THEORETICAL INDICATIONSA fundamental step in the RAND/UCLAmethod is to develop a comprehensive list ofmodel cases. In drawing up the initial list weused as guides the reviews of published reports,experience from previous panels, and feedbackfrom our panelists. We identified eight mutu-ally exclusive "chapters" of model cases withsignificant coronary artery disease according topresenting symptoms or problems: (1) asymp-tomatic, (2) chronic stable angina, (3) unstableangina, (4) acute myocardial infarction, (5)recent myocardial infarction, (6) near suddendeath, (7) CABG carried out with valvesurgery, and (8) PTCA as palliative treatmentin patients with non-cardiac terminal disease.(For definitions see the appendix.) Within eachclinical chapter, model cases were charac-terised by unique combinations of clinical fea-tures in terms of symptoms, medical history,and the results of diagnostic tests. Althoughthe chapters defined were identical to thoseidentified by panels in other countries,7-'0 thepanels did not end up with exactly the samenumber of model cases and indicationsbecause of generally minor differences in num-ber of clinical features, and number of levelsper feature, selected.An example of a model case is a patient with

chronic stable angina on mild exertion (that is,Canadian Cardiovascular Society class III),who is receiving adequate medication (that is,a ,B blocker, calcium channel antagonist, andnitrate, unless contraindicated), has two-vesseldisease not including the proximal left anteriordescending artery (PLAD) with at least onestenosis being a type C lesion,'5 has evidence ofischaemia on an exercise stress test, has severeleft ventricular dysfunction, and is at high riskfor significant postoperative complicationsaccording to the Parsonnet index.'6 Examplesof type C lesions are stenoses longer than 20mm, or with rugged contours or tortuousshape, or located at spots not readily accessiblefor a catheter, or total vessel occlusions olderthan three months. For other definitions seethe appendix.

For most model cases the DUCAT panelrated three indications, presented as a choicebetween two treatments, namely: (1) CABG vmedical treatment, (2) PTCA v medical treat-ment, and (3) CABG v PTCA. For the chap-ters "CABG with valve surgery" and "palliativePTCA", the panel rated only CABG v medicaltreatment and PTCA v medical treatment,respectively. There were 1658 model cases and4890 indications in the initial round of ratings.

Sheets were prepared on which the panelistscould rate each indication on a scale rangingfrom 1 (extremely inappropriate) to 9(extremely appropriate). The sheets, whichhad the form of a long tabular list with therows presenting model cases and individualcells the indications, were mailed to the pan-elists, who individually completed the ratings(round 1). One and a half months later, inAugust 1991, the panelists convened for a twoday meeting (round 2) to discuss issues ema-nating from round 1 and to rerate the indica-tions confidentially. In both rounds thepanelists were instructed to rate each indica-tion keeping in mind average cases in the aver-age practice in the heart centres in TheNetherlands. That practice implies that refer-ring cardiologists who have diagnosed coro-nary artery disease in a patient present thefindings, including the coronary angiogram, toan interventional cardiologist or cardiopul-monary surgeon or both. This presentationmay be made either in person or by referral let-ter or telephone.The results of round 1 were precirculated

before the DUCAT panel met for round 2.Each panelist received, for each indication, theanonymous ratings of all the other panelists,along with a reminder of his or her own rating.During the panel me'eting the indications werediscussed, concentrating on areas where thepanelists disagreed. The primary purpose ofthe discussion was to ensure that panelists had ashared understanding of the type of casesdescribed. Thus any remaining disagreementswould represent different treatment philoso-phies. The panel refined some of the defini-tions and revised the indications list, leaving atotal of 1182 model cases and 3446 indica-tions. After discussing each clinical chapter,the panelists rated anew the appropriateness ofeach indication.

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Three months after the panel meeting, thepanelists were sent a set of indications (66 intotal) randomly selected from the first six clin-ical chapters. The panelists were asked torerate these indications in the same way as

they had done in round 2. Eleven panelistsreturned the completed rating sheets.

ANALYSISThe ratings were analysed on two partly inter-dependent dimensions: degree of agreementamong panelists and degree of appropriate-ness. The scale was divided into three 3-pointregions, 1-3, 4-6, and 7-9. Agreement was

defined as at least nine of the ratings laying inone of these regions. By definition there was

disagreement if the ratings of the panelistswere split, with four or more falling in each ofthe two outer regions. In all other cases, thepanel was said to be indeterminate. Theappropriateness score for each indication was

taken as the median of the ratings of the pan-elists.589 When comparing CABG or PTCAwith medical treatment, the invasive treatmentwas appropriate if the median score was 7 to 9,inappropriate if the median score was 1 to 3,and uncertain if that score was 4 to 6 or ifthere was disagreement among the panelists.For CABG v PTCA indications the appropri-ateness score 7 to 9 meant that surgery was

preferred to angioplasty, and 1 to 3 that angio-plasty was preferred. Ratings and reratingswere defined as matching each other if they layin the same 3-point region. Test-retest concor-

dance was assessed with the c statistic. 17

Comparison of the scores between the tworounds was only done on indications commonto both rounds. The analysis was restricted toclinical chapters 1 to 6, that is, the chapterswith all three sets of indications. The results ofthe comparison were displayed in 3 x 3 con-

tingency tables and analysed with the test ofmarginal symmetry.'8

Clinical and non-clinical determinants ofappropriateness scores were assessed for eachchapter with the least squares regressionmodel, with the median of the ratings of thepanelists, or subset of panelists, being thedependent variable for each indication.

ResultsAlthough no attempt was made to reach con-

sensus, agreement among the panelistsincreased from 48 1% for the PTCA v medicaltreatment indications in round 1 to 61-7% inround 2, partly as a result of improved under-standing of the rating process.'9 Conversely,disagreement for these indications fell from7 9% to 3-8% and indetermination from48-6% to 34-5%. Similar changes occurred forthe two other sets of indications, CABG v

medical treatment and CABG v PTCA (X2 =

161-7; df 2; P < 0001). For the three setstogether the DUCAT panel agreed in round 2on 58-6% and disagreed on 3-2% of the indi-cations. Appropriateness scores also changedfrom round 1 to round 2, although to a lesserdegree (for the three sets of indicationstogether, x2 = 41-4; df 2; P < 0001). Thenumber of indications where CABG or PTCAwas judged appropriate compared with med-ical therapy rose by approximately 4-5% inboth cases, while the number where CABG or

PTCA was considered inappropriatedecreased by 2-0% and 1-5%, respectively.The number of CABG v PTCA indicationswith clear preference for either surgery or

angioplasty increased by 2-4%.Test-retest concordance for the sample

of 66 indications was significant (K = 072;P < 0001). Ten retest scores differed from theoriginal scores by 2 points, the maximum dif-ference seen.

In the second round of ratings, CABG was

considered appropriate when compared withmedical treatment in 35-4% and inappropriatein 36-5% of the cases. The corresponding fig-ures for PTCA were less favourable: 21 6%appropriate and 55-4% inappropriate.Appropriateness scores varied by clinical chap-ter (table 1). For clinical chapters where bothCABG and PTCA were considered, appropri-ateness scores were highest for predominantlyurgent conditions: unstable angina, acutemyocardial infarction, and near sudden death.Performing these procedures was consideredinappropriate in many of the cases which were

asymptomatic, had chronic stable angina, or

had a recent myocardial infarction.

Table 1 Appropriateness of indications for coronary revascularisation and preferred treatment by clinical chapterICABG v MED indications PTCA v MED indications Preferred treatment#

Chapter$' Appropriate Inappropriate Appropriate Inappropriate Invasive Medical

1 Asymptomatic (96) 30-2% 53-1% 7-3% 77-1% 35-4% 41-7%2 Chronic stable angina (480) 24-8% 48-8% 14 8% 59-8% 34-4% 31-9%3 Unstable angina (144) 57-6% 13-2% 40 3% 36-8% 78-5% 2-8%4 Acute myocardial

infarction (68) 39 7% 16-2% 35-3% 22-1% 64-7% 5-9%5 Recent myocardial

infarction (248) 36-3% 36-7% 14-1% 65-7% 44-4% 25-8%6 Near sudden death (96) 53 1% 8-3% 29-2% 57-3% 72-9% 4-2%.7 CABG and valve surgery (2) 100-0% 0 0% - - 100-0% 0 0%8 Palliative PTCA (48) - - 66-7% 16 7% 66-7% 0 0%Total (1182) 35-4% 36-5% 21-6% 55-4% 48-2% 22-8%

IData are percentages of the total number of indications for either CABG v medical therapy, PTCA v medical treatment, orpreferred treatment. Number of model cases in parentheses.#Invasive treatment was preferred to medical treatment when CABG and/or PTCA were rated appropriate. Medical treatment waspreferred when both CABG and PTCA were rated inappropriate.(OClinical chapters were defined by presenting symptoms or problems. For definitions see Appendix.-Not applicable.CABG, coronary artery bypass grafting; MED, medical treatment; PTCA, percutaneous transluminal coronary angioplasty.

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The fact that CABG and PTCA were fre-quently rated inappropriate when comparedwith medical treatment does not necessarilyimply that the panel preferred medical treat-ment. There were many model cases for whichthe panel judged CABG to be inappropriatebut PTCA appropriate, or the other wayround. In these cases, and when both CABGand PTCA were rated appropriate, the panelobviously preferred invasive treatment to med-ical treatment. On the other hand, medicaltreatment was preferred to invasive treatmentwhen both CABG and PTCA were rated inap-propriate for a model case. Overall the panelopted for invasive treatment in 48-2% of themodel cases, while medical treatment was pre-ferred in 22-8% of the cases. For the remain-ing 29-0% of the model cases the panel did notexpress a preference for either invasive treat-ment or medical treatment (table 1).

As anatomical disease became more severein the model cases, the panel increasingly pre-ferred invasive treatment to medical treatment(table 2). The panel opted for invasive treat-ment in 18-0% of the model cases with one-vessel disease not including the PLAD,compared with 94 0% of the cases with leftmain disease. One-vessel disease involving thePLAD was seen as a stronger reason for inva-sive treatment than two-vessel disease notinvolving the PLAD. At the same time thenumber of cases where medical treatment waspreferred decreased as vessel disease becamemore severe, from 51-5% in one-vessel diseasenot including the PLAD to 0% in left maindisease. Table 3 shows the preference of thepanel for CABG or PTCA in model patientsfor whom invasive treatment was preferred to

Table 2 Panel's preference for invasive or medical treatment by level of anatomicaldisease

Preferred treatment¶

Anatomical disease Invasive Medical None

One-vessel, -PLAD 36 (18-0) 103 (51-5) 61 (30 5)One-vessel, +PIAD 80 (40 0) 59 (29 5) 61 (30 5)Two-vessel, -PLAD 52 (26 0) 71 (35 5) 77 (38-5)Two-vessel, +PLAD 99 (49-5) 30 (15-0) 71 (35 5)Three-vessel 110 (65 5) 2 (1-2) 56 (33 3)Left main 158 (94-0) 0 (0 0) 10 (6 0)

¶Numbers (%) of model cases for which the panel opted for invasive or medical treatmnent.Invasive treatment was preferred to medical treatment when CABG and/or PTCA were ratedappropriate. Medical treatment was preferred when both CABG and PTCA were ratedinappropriate. None of the treatments was preferred if neither invasive nor medical treatmentwas preferred to the other treatment.CABG, coronary artery bypass grafting; PTCA, percutaneous transluminal coronary angio-plasty; +PLAD and -PPLAD, with and without involvement of the proximal left anteriordescending coronary artery, respectively.

Table 3 Panel's preference for CABG or PTCA, or equally for both, by level ofanatomical disease¶

Preference

Anatomical disease n CABG PTCA Both

One-vessel, -PLAD 36 0.0% 97-2% 2 8%One-vessel, +PLAD 80 6-3% 75 0% 18 8%Two-vessel, -PLAD 52 7-7% 78-8% 13 5%Two-vessel, +PLAD 99 29-3% 44-4% 26 3%Three-vessel 110 65-7% 0 0% 34-3%Left main 158 98-7% 0.0% 1-3%

1Limited to model cases (n = number) for which the panel preferred invasive treatment tomedical treatment. "Both": cases where both CABG and PTCA were appropriate compared withmedical treatment and where CABG was not preferred to PTCA or vice versa.CABG, coronary artery bypass grafting; PTCA, percutaneous transluminal coronary angio-plasty; + PLAD and - PLAD, with and without involvement of the proximal left anteriordescending coronary artery, respectively.

medical treatment. There was near absolutepreference for surgery in left main disease,while the panel had few doubts that PTCAwas to be preferred in one-vessel disease. Intwo-vessel disease angioplasty was favoured,particularly in cases without PLAD stenosis.

CLINICAL FACTORS BEARING ON PANEL SCORESThe aggregate figures presented so far provideonly limited insight into the considerationsunderlying the appropriateness scores.Therefore we developed regression models toexplain the median panel ratings. For brevitywe only present the results for the three sets of480 indications for the model cases withchronic stable angina (table 4). Severity ofcoronary artery disease, anginal symptoms,extent of medical treatment, and degree ofperi-interventional risk were significantlyrelated to appropriateness scores for all threesets of indications. For CABG v medical treat-ment indications the lesion characteristic ofthe coronary artery stenosis (type A, B, or C)made no difference, in contrast to both PTCAv medical treatment and CABG v PTCA indi-cations. The outcome of an exercise stress testand the degree of left ventricular dysfunctionwere important for choosing between eithertype of invasive intervention and medicaltreatment, but they were not significant factorsfor choosing between CABG and PTCA.To illustrate the data in table 4 we take as

an example a model patient who suffers fromtwo-vessel disease not including the PI.AD,has class II angina, is on adequate medication,has a positive exercise stress test, who does nothave severe left ventricular dysfunction (thatis, ejection fraction is > 20%), and whose riskof significant peri-interventional complicationsis not high. For this case both CABG andPTCA were rated uncertain when comparedwith medical treatment, that is, the appropri-ateness score lay in the middle range (4 to 6)of the rating scale (see "constant" in table 4).For CABG v medical treatment indicationsthe appropriateness score was 4-8 regardless oflesion type. Lesion type did matter in PTCA vmedical treatment indications, the score being5-8 if the lesion was type A or B and 2-7(5 8 - 3 1) if type C. If an invasive procedurewas to be done, the DUCAT panel preferredPTCA to CABG, as suggested by the constantscore of 2-8. When the model case had leftmain disease preference swayed to CABG (2-8+ 5 0 = 7 8), while in one-vessel disease thescore fell by 0 7 points (2 8 - 0 7 = 2.1).

NON-CLINICAL FACTORSAppropriateness scores were also affected bynon-clinical factors. Age, years since specialistregistration, and school of specialist training ofthe panelists did not influence the scores, butspecialty (surgeon or cardiologist) did.Summed over all of the clinical chapters, sur-geons rated slightly more CABG v medicaltreatment indications appropriate than cardiol-ogists (37 3% v 34-9%; X2 = 5-65; P < 0 01)and slightly fewer of these indications inap-propriate (34-2% v 37-3%; x2 = 6-92;P < 0-001). The two specialties differed most

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Table 4 Clinical determinants of appropriateness scores for treatment indications for chronic stable angina cases

Regression coefficienry (95% CI)

Clinicalfactori CABG v MED PTCA v MED CABG v PTCA

Anatomy#:one-vessel, -PLAD -1-3 (- 19 to -1-6)t 0.0 -0-7 (-09 to -05)4one-vessel, + PLAD 0 4 (0-2 to 0 7) 0-9 (0-6 to 114)i -0-7 (-09 to -04)4two-vessel, - PLAD¶ - - -

two-vessel, -PLAD 1-6 (1-4 to 1 9)t 0 5 (0 3 to 0 8)4 0-5 (0-3 to 0-8)4three-vessel 3-0 (2-7 to 3-3) 0 0 2-7 (2-5 to 3-04)left main 5-5 (5-3 to 58)4 -1-6 (-1-8 to -1-3)t 5 0 (4 7 to 5 2)4

Lesion type:A or B¶ - -

C 00 -31 (-33 to -29) 26 (25 to 27)Anginal symptoms:

absentorI -1-3 (-1-5 to-1 1)t -09 (-I 1 to-0 7)t -0-2 (-0 4to-01)$II* - -

III or IV 1-3 (1 1 to 1-4)4 1 1 (0-9 to 1-3)t 0 3 (0-2 to 05)tMedication:

adequate¶ - - -

not adequate -0-1 (-1 1 to -0 8)4 -09 (-1 0 to -07)4 -0-1 (-0-2 to -00)*Exercise stress test:

positive¶not positive -09 (-I 0 to -0 7)4 -0-9 (-I 0 to -0 7)4 00 (-0 1 to 0 1)

Left ventricular dysfunction:not severe¶severe -0-6 (-07 to -0 4)4 -0 3 (-05 to -0 1)t 00 (-0 1 to 0 1)

Peri-interventional risk:not high¶high -0-8 (-09 to -0-6)4 -03 (-05 to -02)4 -0-2 (-004 to -01l)t

Constantll 4-8 (4-5 to 5-1) 5-8 (5-6 to 6-1) 2-8 (2-6 to 3-0)

¶The reference model case was characterised by the factor levels marked with this symbol, that is, a constant, two-vessel disease notinvolving the PLAD, type A or B lesions, angina class II, adequate medication, with the outcome of an exercise stress test pointingto ischaemia, no severe left ventricular dysfunction, and not at high peri-interventional risk. For the CABG v medical treatment indi-cation (CABG-MED) this patient's appropriateness score would be: 4-8 + 0 + 0 + 0 + 0 + 0 + 0 + 0 = 4-8. Scores for the reference caserepresent values on a 1-9 scale.4Computed with multiple linear regression analysis, not truncated. All values are differences relative to the score of the referencecase. 95% CI = 95% confidence interval. R2 values were 0-81, 0-89, and 0-91 for CABG v medical treatment, PTCA v medical treat-ment, and CABG v PTCA indications, respectively.# + PLAD and - PLAD , with and without involvement of the proximal lett anterior descending coronary artery, respectively.*P <0-05, tP <0-01, tP < 0-001.CABG, coronary artery bypass grafting; MED, medical treatment; PTCA, percutaneous transluminal coronary angioplasty.CABG-MED, PTCA-MED, and CABG-PTCA: the three sets of indications.

regarding the PTCA v medical treatment indi-cations. Surgeons rated fewer of these indica-tions appropriate and more of theminappropriate than cardiologists (18 4% v25-7% X2 = 59-7, and 59-1% v 48-8%, x2 =84-6, respectively; P < 0001). On average,surgeons were more critical of PTCA v med-ical treatment indications than cardiologistswere of CABG v medical treatment indica-tions.

Considering only clinical chapters 1-6, thetendency of the surgeons to rate PTCA v med-ical treatment indications lower than the cardi-ologists was significant for the chronic stableangina, unstable angina, acute myocardialinfarction, and recent myocardial infarctionchapters. The picture for CABG v medicaltreatment indications was more variable. Thesurgeons rated these indications significantlyhigher than the cardiologists did for the clini-cal chapters "asymptomatic", "unstableangina", and "near sudden death", but lowerfor "chronic stable angina" and "acutemyocardial infarction". The pattern of resultsfor acute myocardial infarction was particu-larly noteworthy. Here the surgeons rated bothPTCA v medical treatment and CABG vmedical treatment indications lower than thecardiologists, which suggests that they hadmore doubts about the usefulness of any inva-sive intervention.

Surgeons and cardiologists differed mostconsistently in how they appraised CABG vPTCA indications. We wondered if this differ-ence depended on interactions between spe-

cialty and clinical factors, owing to differencesbetween surgeons and cardiologists in theirappreciation of the importance of these fac-tors. We tested for this possibility by carryingout for each clinical chapter two multipleregression analyses of CABG v PTCA scores,one with and one without interaction terms,using the clinical factors defining the referencemodel cases as input variables. Table 5describes the reference model cases and pre-sents the results of the analyses without inter-action terms. Surgeons rated CABG v PTCAindications higher than cardiologists for all ofthe clinical chapters, suggesting stronger pref-erence for CABG among surgeons or, in otherwords, stronger preference for PTCA amongcardiologists if a procedure was to be done. Inanalyses using interaction terms the CABG vPTCA scores of the surgeons were not signifi-cantly higher than those of the cardiologists forthe chapters "asymptomatic" and "acutemyocardial infarction", except for a subset ofindications. Surgeons' scores were higher formodel cases with one-vessel disease notinvolving the PLAD in the chapter "asympto-matic" and for model cases with cardiogenicshock in the chapter "acute myocardial infarc-tion". For all other chapters the disparity inscores between surgeons and cardiologistsremained significant when interaction termswere added to the regression models.However, this difference was not constantacross subsets of indications in each chapter.In general there was little discrepancy in thescores of surgeons and cardiologists for model

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Table S Choosing between CABG and PTCA: regressionanalyses of difference in appropriateness scores betweensurgeons and cardiologists by clinical chapter

Clinical chapter Difference¶

1 Asymptomatic 054t2 Chronic stable angina 0 57:3 Unstable angina 0 59t4 Acute myocardial infarction 0-92t5 Recent myocardial infarction 0-82t6 Near sudden death 0-29*

¶Differences in appropriateness scores expressed as valuesrelative to the scores for the reference cases (that is, theconstants of multiple regression analyses) on a 1-9 scale. Thehigher the difference, the stronger the preference for CABGamong surgeons or, in other words, the stronger the preferencefor PTCA among cardiologists.Characteristics of reference model cases. Common to all cases:two-vessel disease without involvement of the PLAD, type Aor B lesions, no severe left ventricular dysfunction, not at highrisk for peri-interventional complications. Additional features:Asymptomatic, evidence of ischaemia on an exercise stress test.Chronic stable angina, angina class II, adequate medication,evidence of ischaemia on an exercise stress test. Unstableangina, pain on adequate medication. Acute myocardialinfarction, continuing paint. Recent myocardial infarction, non-Q-wave infarction, asymptomatic, no evidence of ischaemia onan exercise stress test. Near sudden death, pain and/or evidenceof ischaemia on an exercise stress test.*P< 005, tP < 0001.CABG, coronary artery bypass grafting; PTCA, percuta-neous transluminal coronary angioplasty; PLAD, proximalleft anterior descending coronary artery.

cases with left main disease or three-vessel dis-ease and for model cases with type C lesions.The greatest disparities were found for modelcases with one-vessel disease, where the ten-dency of the surgeons to rate CABG v PTCAindications higher than the cardiologistsamounted to a 1 5-2 points difference on the1-9 scale for the chapters "chronic stableangina" and "recent myocardial infarction".

Finally, we averaged for each of the pan-elists their ratings of all CABG v medicaltreatment indications and all PTCA v medicaltreatment indications. We then determinedthe rank order of the panelists for each set ofindications, the one with the highest meanscore being placed in the first and the one withthe lowest score in the 12th position. Theresults are shown in table 6. Numbers 1 and 2in the table, a cardiologist and a surgeon,ranked high on both sets of indications. Thesetwo clinicians can be said to favour, at least onpaper, an aggressive practice style regardless ofthe type of invasive intervention. In contrast,members 1 1 and 12 made up the rear on bothCABG v medical treatment and PTCA v

Table 6 Rank order ofpanelists based on their average ratings of all indications involvinga choice between CABG and medical treatment or between PTCA and medical treatment

Rank number

CABG-MED PTCA-MEDPanelist¶ indications indications Sum@'

1 Cardiologist 3 1 42 Surgeon 2 4 63 Cardiologist 7 2 94 Surgeon 1 9 105 Surgeon 5 6 116 Cardiologist 9 3 117 Surgeon 4 7 118 Cardiologist 8 5 139 Cardiologist 6 10 16

10 Surgeon 10 8 1811 Cardiologist 11 11 2212 Surgeon 12 12 24

INumbers in order of sum total.9Sum of rank number for CABG indications and rank number for PTCA indications.CABG, coronary artery bypass grafting; MED, medical treatment; PTCA, percutaneous trans-luminal coronary angioplasty.

medical treatment indication ratings, whichmay correspond to a conservative style. Otherpanel members, such as panelists 3, 4, and 6,ranked high on the indications involving theinvasive intervention from their own specialtybut lower on the other indications.

DiscussionWe asked a Dutch expert panel to rate theappropriateness of indications for usingCABG and PTCA in hundreds of modelcases. Ideally, deciding whether indicationsare appropriate or not should be based on theoutcomes of randomised clinical trials.However, we cannot expect trials with theirstrict selection of patients to address all clini-cal permutations with sufficient precision toprovide guidance about how to treat all of thecases seen in practice. Inevitably, physiciansmust also rely on clinical judgement and infer-ence. This is not to excuse physicians fromscrutinising and testing the effects of theiractions. Rendering clinical judgement explicitshould be integral to the practice of medicine.The RAND/UCLA method provides a feasibletool for this purpose.The method may have limitations though.

One could wonder whether panelists are ableto rate large numbers of indications reliablyand consistently. The evidence is that panelistsare up to this task. In our study there was satis-factory test-retest concordance for a randomsample of indications and others also havefound panel scores to be reliable.5 A potentialproblem with group judgement methods is therisk that the outcomes are biased by collectiveerror. This leads us to the issue of validity.Construct validity reflects the degree to whichthe features used to describe model cases arerelevant for clinical practice. The list of modelcases for CABG and PTCA appears to havegood construct validity. Not only did panels invarious countries select largely the same set ofclinical features,7-"0 but an analysis of treat-ment decisions in everyday practice alsoshowed that these and a few additional fea-tures indeed influenced if not determined clin-icians' decision making." 19 Moreover, thescores of the DUCAT panel correspondedwell to clinical guidelines developed concur-rently but independently on behalf of theNetherlands Society of Cardiology.20 Contentvalidity is the degree in which the panel scoresaccurately reflect the appropriateness of indi-cations. There were no clear discrepanciesbetween the evidence in published reports atthe time of the panel meeting on the one handand the DUCAT panel scores on the other.The key question is how valid the scores werein the many cases where the evidence wasincomplete. One way to answer this questionis to look at research data that became avail-able after the DUCAT panel met.

Since the panel meeting in 1991, results ofseveral randomised trials comparing PTCAwith medical treatment and PTCA withCABG have been published."'7 In the ACMEtrial coronary angioplasty was better thanmedical treatment in relieving angina at six

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Indications for coronary revascularisation: a Dutch perspective

months' follow up and improving exercise tol-erance in patients with one-vessel disease.2' Itremains to be seen whether these modest ben-efits outweigh the procedure related complica-tions of PTCA. The DUCAT panel favouredmedical treatment in one-vessel disease with-out PLAD stenosis. A meta-analysis of resultsfrom trials comparing PTCA with CABG inpatients with either one-vessel or multivesseldisease failed to show a treatment difference inrates of death and non-fatal myocardial infarc-tion during up to three years' follow up.28However, patients in the PTCA groups moreoften had angina, took more antianginal drugs,and required further revascularisation morefrequently. All investigators neverthelessagreed that PTCA remains a suitable optionand a simple initial alternative to CABG.2>27This conclusion does not run counter to theopinions of the DUCAT panel. The panel pre-dominantly preferred PTCA to CABG in one-and two-vessel disease, and CABG to PTCAin three-vessel disease (table 3). It should benoted, though, that the indications rated bythe panel were not weighted for frequency ofoccurrence in actual practice. Consequently,these findings do not necessarily represent theproportion of cases that would be foundappropriate or inappropriate in everyday prac-tice.

Another issue is PLAD stenosis. The panelconsidered PLAD stenosis to be important fordeciding between treatments. It more oftenopted for invasive treatment in cases with one-vessel disease with PLAD stenosis than in two-vessel disease not including the PLAD (table2). A review of the 10 year results from ran-domised trials comparing CABG with medicaltreatment,29 published after the panel meeting,suggests that the panel was right. The reviewrenders it likely that patients with one-vesseldisease involving the PLAD benefit more fromsurgery than those with two-vessel diseasewithout PLAD stenosis.Taken together the results from recent trials

and meta-analyses support the views of theDUCAT panel. However, the evidence forhow to treat many patients with coronaryartery disease is still incomplete and will prob-ably remain so. It is likely that the majority ofmodel cases considered by the panel will neverbe the subject of externally valid randomisedtrials, and this is precisely why using appropri-ateness methods is potentially so important,for instance for formulating clinical practiceguidelines.The best way to assess the validity of the

RAND/UCLA method is to relate panel scoresto patient outcomes. So far this has mainlybeen done in retrospective studies in which themedical records of patients were searched forrelevant information after the intervention hadtaken place.5303' Further proof of the validityof the method may come from prospectivestudies. One would expect patients with an.appropriate decision to fare better after theintervention than similar patients with aninappropriate decision.32 Some evidence tothis effect has come from a retrospectivecohort study.33 The DUCAT project includes

a prospective study of this sort.The DUCAT panel scores were not free

from bias. Bias is apparent from the impact ofnon-clinical factors such as the distinctionbetween cardiologists and surgeons. Also inother panel studies physicians carrying out aprocedure tended to rate indications for thatprocedure higher than those for alternativeprocedures.34 The importance of these non-clinical factors should not be exaggerated.Although the number of inappropriate indica-tions might even have been higher if non-clini-cal factors had not been in effect, the DUCATpanelists considered many indications to beinappropriate. How one assesses the influenceof non-clinical factors such as panel composi-tion depends in part on the goals one wishes toaccomplish with the RAND/UCLA method.35One aim of DUCAT is to provide clinicians inThe Netherlands with a decision aiding tool fitfor use in the "bipartisan" (interventional car-diology and cardiac surgery) environment ofspecialised tertiary referral centres. As thepractice of medicine continues to evolve, thistool can be used to trace and monitor changesin medical practice and to update professionalpolicies regarding indication setting.

This work was part of the DUCAT (Dutch inventory of inva-sive coronary atherosclerosis treatments) study, funded by theNational Health Insurance Board (Ziekenfondsraad) in TheNetherlands. The study design was approved by the medicalethics committee of the University Hospital Dijkzigt inRotterdam. The panel members were J J R M Bonnier, TEbels, JM P G Ernst, Th R van Geldorp, L A van Herwerden,G J Laarman, B A J M de Mol, N H J Pijls, K B Prenger, G Lvan Rijk-van Zwikker, P W Westerhof, and F Zijlstra.

AppendixDEFINITIONS OF CLINICAL CHAPTERSAsymptomatic, patients with significant coronary arterydisease without a history of angina, or who have noangina on their current medical regimen for more thanthree months, or who have sustained a myocardialinfarction more than 30 days ago with no recurrence ofangina for at least three weeks.Chronic stable angina, patients meeting three of four con-ditions: (1) substemal or left sided chest pain; (2) radia-tion of pain to the left arm, left side of the neck, or leftjaw; (3) the pain is usually precipitated by exercise; (4)the pain is relieved within 10 minutes by rest or sublingualglyceryl trinitrate.Unstable angina, chest pain thought to be due to myocar-dial ischaemia requiring hospital admission because ofdifficulty in control or concern about the possibility ofmyocardial infarction, including (1) recent increase inthe intensity, frequency, or duration of chronic angina;(2) the development of angina at rest; or (3) new onsetof severe chest pain.Acute myocardial infarction, infarction within 24 hours.Recent myocardial infarction, infarction between 1 and 30days.Near sudden death, patients who are presumed to havesustained a cardiac arrest without evidence of a myocar-dial infarction.CABG and valve surgery, bypass grafting done concur-rently with valve surgery.Palliative PTCA, PTCA as palliative treatment inpatients with non-cardiac terminal disease who wouldnot be considered candidates for bypass surgery in theevent of PTCA failure.

CLINICAL CHARACTERISTICS NOT DEFINED IN THE TEXTOR IN CITED REFERENCES

Significant coronary artery disease, at least 50% stenosisin the left main artery; at least 70% stenosis in oneartery in case of one-vessel disease; at least 70% stenosis

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in one artery and 50% in other arteries in case of multi-vessel disease.Adequate medication, chronic stable angina: patientreceives or has received drugs from three classes ofmedication: ,B blockers, calcium channel antagonists,and long acting nitrates, or less as far as justified by thepresence of contraindications; unstable angina: patientreceives or has received drugs from the same threeclasses of medication and receives intravenous heparinand/or intravenous glyceryl trinitrate, unless con-traindicated.Severe left ventricular dysfunction, ejection fraction< 20%.Stress test, any exercise stress test or stress imagingstudy; positive outcome: ST depression equal orgreater than 1 mm (exercise test), or total or partialreversible defect in one arterial territory (imagingstudy). The outcome of the stress test was consideredto be "not positive" if the test was performed and had anegative or indeterminate result or if the test was notperformed.

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