tempted by purveyors of a burgeoning medical tech- no1ogy.l But since this boom also coincides with a na- tional call for economic restraint, we are more alert.
EDITORIALS
MonkeyBusiness GEORGE A. DIAMOND,
W
hen an African tribesman wants to catch a monkey, he seeks out an old hollow tree, carves a hole in its side, sits down and waits. Sooner or later, a monkey happens by. The tribesman then drops a few seeds into the hole-making very sure that the monkey is watching-and departs. As soon as he’s gone, the monkey runs to the tree, thrusts his hand through the hole, grabs the seeds, and . . . he’s trapped! The hole is too small to let him remove his clenched fist. To escape, he need only drop his prize, but the thought never seems to enter his mind. He values those seeds too highly -more than his own freedom. It works every time. Over the last decade, we have been similarly tempted by purveyors of a burgeoning medical techno1ogy.l But since this boom also coincides with a national call for economic restraint, we are more alert than ever to the danger of placing too high a value on that technology. We read the medical literature with a mature appreciation of the fine balance between risk and benefit-between cost and effectiveness. We’re not about to let high technology make monkeys of us. Or are we?2 Writing in the January 1983 issue of The American Iournal of Cardiology, investigators from the Massachusetts General Hospital reported a sensitivity of only 53% and a specificity of 62% for exercise radionuclide ventriculography in the diagnosis of coronary artery disease.3They concluded that left ventricular ejection fraction was “. . . an insensitive and nonspecific marker of coronary artery disease.” Anyone disheartened by such news, however, literally need only turn the page for relief; for in the very next article,4 investigators from the University Hospital in London, Ontario, Canada, report a sensitivity of 80% and a specificity of 91%. In stark contrast to the comments in the report that precedes it, these authors remark upon “. . . the
From the Division of Cardiology, Cedars-Sinai Medical Center, and the School of Medicine, University of California, Los Angeles, California. Manuscript received July 9, 1985, accepted July 16, 1985.
Address for reprints: George A. Diamond, MD, Division of Cardiology, Cedars-Sinai Medical Center, 8700 Beverly Boulevard, Los Angeles, California 90048. 471
MD
usefulness of rest-exercise radionuclide studies in detecting subjects with CAD . . .” I freely admit that I searched out these particular reports just to make a point, but I didn’t have to look very hard. The medical literature is replete with examples of such discord-so much so that some have come away with the feeling that our technology is insufficiently validated, irresponsibly disseminated and uncritically accepted.5 As a result, the Office of Technology Assessment, in a recent report commissioned by Representative Henry A. Waxman (D-Calif.), chairman of the House Energy and Commerce Subcommittee on Health and the Environment, concluded that Congress should adopt legislation designed “, . . to limit coverage of complex technologies.” Are such stern measures really justified? The assessmentand subsequent utilization of medical technology is surely influenced by a variety of economic,6 psychologic sociologic6 and statistical9 factors. I propose to examine several of these factors that I think commonly contribute to the discordant published record on technology assessment and to outline a program of preventive maintenance. In the course of this discussion, I shall illustrate my points by reference to a number of specific studies in the cardiologic literature, but little should be made of this emphasis. I selected my examples solely for their pedagogic value and am biased toward the field of cardiology only by dint of background experience.
ContributingFactors Small populations: Clinical investigators often perform initial evaluations of a new technology in small pilot populations. Unfortunately, such feasibility studies are sometimes inappropriately viewed as validations, with the result that some investigators make sweeping claims for the technology based on a limited experience. A recent report on the use of positron emission tomography (PET] for detection of non-Qwave myocardial infarction, for example, comprised only 34 subjects .l” Sensitivity was 96% (23 of 241and specificity was 80% (8 of 10). The confidence associated with estimates derived from such small samples is often very low. In this case, a 95% confidence interval
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EDITORIALS
TABLE I Radionuclide Ejection Fraction of Coronary Artery Disease
Response for Diagnosis
Sensitivity
TABLE II Accuracy Scintigraphy
of Stress Electrocardiography
Specificity
Reference
Patients
Mean
Cl
Patients
Mean
12 13 14 15 16 17 18 19 Totals
14114 47147 15/15 48160 60163 65170 Ill11 35140 2921317
100
77-100 92-100 78-100 68-89 87-99 84-98 72-100 73-96 79-98
Ii/l1 25125 15115 13113 21121 19119 717 20120 1341134
100
Cl ST Depression
Cl = 95% confidence
100 100 80 95 93 100 88 92
100 100 100 100 100 100 100 100
72-100 86-100 78-100 75-100 84-100 82-100 59-100 83-100 77-100
interval.
for sensitivity ranges from 79% to lOO%, while that for specificity ranges from only 44% to 97%. Although these confidence intervals are readily obtained from conventional published tables,ll they were not reported by the authors of this study (to our knowledge, in fact, confidence intervals for estimates of sensitivity, specificity and predictive accuracy have never been reported by clinical investigators). Instead, the “discussion” section of this paper opens with the unqualified conclusion that “. . . PET is a sensitive and specific technique for detecting nontransmural myocardial infarction.“lO Right or wrong, such claims stimulate the rapid and widespread diffusion of new technology. Biased populations: Sometimes, investigators unwittingly evaluate their technology in highly biased subjects. In the PET study, for example, only 3 of the 10 normal subjects were patients admitted with a suspected diagnosis of myocardial infarction; the remaining 7 normal subjects were healthy volunteers.1° Such persons are not representative of those for whom the test is actually intended, and they are therefore inappropriate subjects for inclusion in validation studies. Had these volunteers been excluded from the PET study, the observed specificity would have been only 67% (2 of 3). The confidence interval for these data ranges from 9 to 99%. The use of such “populations of convenience” to evaluate the efficacy of new technology is widespread. Table I is a summary of the initial validations of the radionuclide ejection fraction exercise response for diagnosis of coronary artery disease.12-lg Sensitivity averaged 92% (confidence interval 79 to 98%) in 317 “abnormal” patients (an undisclosed number of whom had had a previous myocardial infarction) and specificity was 100% [confidence interval 77 to lOO%] in 134 “normal” patients (71 of whom were healthy volunteers who had not undergone catheterization). These studies, then, compared 2 highly selected populations -what we have termed the sickest of the sick and the wellest of the we11.20 It is well known that limiting the spectrum of the study population in this way results in a substantial overestimation of both sensitivity and specificity.g,20-23 Nevertheless, on the basis of such studies, investiga-
’
Hypoperfusion
Reference
Sn
SP
Sn
27 28 29 30 31 32 33 34 35 Totals Percent Cl
21139 73199
15116 43161 50158 12115 517 25125 14122 17124 15/16 1961244 80 59-93
34139 86199
48165 42181 19133 34176 27134 17141 34142 315/510 61 48-71
52165 6618 1 29133 50176 31134 35141 24142 407/510 80 67-89
SP 16/16 54161 56158 15/15 717 24125 20/22 22124 15116 229t244 94 75-99
and Perfusion
ST Depression or Hypoperfusion Sn
SP
38139 92199
15116 36161 50158 12115 517 23125 12122 10124 14116 1777244 73 51-88
60165 71181 31133 69/76 33134 38741 36142 468/510 92 81-97
Cl = 95% confidence interval; Sn = sensitivity; Sp = specificity; ST Depression = depression of the exercise electrocardiographic ST segment.
tors and clinicians came to the opinion that exercise radionuclide ventriculography was both highly sensitive and specific for the diagnosis of coronary artery disease. Since then, both values have fallen dramatically,23-26but this decrease is less an indictment of the test than of the process of test evaluation.20p21The reason for the fall in specificity is particularly convoluted. Although an abnormal test response doesn’t necessarily mean an abnormal patient, it more often than not prompts referral to angiography. As a result, abnormal test responses tend to cluster in the angiographic population. This biased pattern of referral causes the observed sensitivity of the test to rise and the specificity to fa1120The better a test appears, therefore, the more we will rely on it; and the more we rely on it, the worse it will appear. Catch%!! Inappropriate comparisons: Even when studies are performed in unbiased populations, the data are often subjected to inappropriate comparisons. For example, almost all of the studies published between 1976 and 1983 that sought to evaluate the efficacy of myocardial perfusion scintigraphy compared its sensitivity and specificity directly with that of exercise electrocardiography. However, since scintigraphy was always intended to supplement-rather than supplant -electrocardiography, such comparisons are not really clinically relevant. The more appropriate comparison would be between electrocardiography alone and electrocardiography plus scintigraphy. I performed this “more appropriate” analysis for those published studies which contained the requisite tabular data.27-35All but one of these used a biased study population. For example, at least 20% of the patients (150 of 754) were known to have had a previous myocardial infarction, and since diagnosis was not in question in these patients they probably should have been excluded from analysis.20 That aside, the reported sensitivity and specificity for scintigraphy were each higher than for exercise electrocardiography (80070vs 61% and 94070vs 8070, respectively], al-
February 15, 1986
though confidence intervals tended to overlap [Table II]. From this comparison, one would conclude that scintigraphy is both sensitive and specific-more so, in fact, than electrocardiography. However, when the 2 tests are analyzed in concert (considering either ST depression or hypoperfusion as an abnormal test response], sensitivity improves even further [from 80% to 82%), while specificity falls (from 94% to 73%). In contrast to the earlier conclusion, the latter comparison suggests that scintigraphy improves sensitivity only at the expense of specificity. One can only wonder about the impact of such tradeoffs on the process of technology diffusion. Isolated information: Clinical information is never interpreted in isolation. Physicians always have knowledge of at least some aspects of the history and physical examination before they have knowledge of a diagnostic test response. Nevertheless, technology assessment is often performed using analytic models that ignore the amount of information already known prior to testing, or the ease with which the next unit of information can be obtained. For example, 1 group of investigators used stepwise discriminant function analysis to assess the value of exercise radionuclide ventriculography in predicting subsequent coronary “events” (sudden death, cardiac death, recurrent infarction, worsening angina pectoris, persistent heart failure) in 61 patients soon after acute myocardial infarction. 36 Fifteen variables were analyzed, 5 from the history (age, sex, history of infarction, anatomic location of infarction, Killip classification), 5 from exercise electrocardiography (achieved workload, precipitation of angina, development of ST depression, duration of developed ST depression, ventricular ectopy) and 5 from the radionuclide study (left ventricular ejection fraction, wall motion, end-diastolic volume, end-systolic volume, and the ratio of systolic blood pressure to end-systolic volume). Discriminant analysis identified only the radionuclide variables (ejection fraction, wall motion and end-systolic volume) as providing significant prognostic information. The authors concluded that exercise radionuelide ventriculography I‘. . . is a highly sensitive means for classifying patients . . . according to the likelihood of having cardiac events . . .” in the early months after myocardial infarction.36 Inherent in this conclusion, however, is a very unrealistic assumption: that there are times when the clinician needs to interpret an exercise ejection fraction response in isolation of all other information. In effect, the clinician is asked to disregard all the clinical and electrocardiographic findings, although they could all be known to him even before the decision to obtain a radionuclide ventriculogram. This all-too-common practice37-40can be very misleading. Because academicians tend to consider originality a virtue, confirmatory clinical studies are rarely performed, and less often published. Instead, investigators are inclined to choose from a continually changing menu of variables and to analyze their choices in novel and attention-getting ways. Consequently, each new study is more likely to arrive at a somewhat differ-
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ent conclusion than its predecessors, and such studies are more likely to be selected for publication. As a result of this publication bias, even a randomly selected worthless variable can be elevated to the status of a “significant” predictor. 41 It’s not surprising that the medical literature looks something like a Variable-ofthe-Month Club. When we performed discriminant analysis on a database similar to that in the postinfarction radionuelide study discussed above,36 we too found exercise ejection fraction to be the only variable with statistically significant prognostic value.42 We also analyzed the data according to a clinically realistic hierarchy, however, whereby the individual variables were considered for inclusion in the discriminant model in the very same order in which they actually become available to the physician [first, the historical variables: second, the stress electrocardiography variables; third, the rest/exercise radionuclide variables]. According to this hierarchical analysis, the exercise radionuclide variables no longer provided a significant increment of prognostic information .42 The more we already know, the less there is for us to learn. The excluded middle: Although clinical test responses almost invariably fall along a continuum, they are often arbitrarily pigeon-holed into 2 extreme categories: normal and abnormal. As a result, the natural uncertainty engendered by the intermediate test response-and readily made explicit by the equivocal interpretation-is concealed from view. Common sense suggests that many responses should be considered equivocal (especially during the early experience with a new technology when optimal interpretive criteria are still evolving], but a careful reading of the medical literature uncovers few examples of this practice.43 As a result, the practicing physician is left to discover the clinical significance of these intermediate responses (if any] through personal experience-an inefficient process, at best. Would we as quickly embrace a new technology if we knew that its technical interpretation or its clinical significance were uncertain for as many as 1 in every 3 patients?44
Principlesof PreventiveMaintenance More than 75% of physicians who participated in a recent Harris survey think that unnecessary utilization of medical technology has contributed to the rising cost of health care,45while similar views are voiced both by the general public and by their elected officials2 For some time to come, then, the debate over how to control the quality and cost of health care is likely to focus on assessment and regulation of the technology,46-49 and since the central issues in this debate are economic and ethical as well as scientific, the medical profession is not alone in claiming a partisan interest.* In a political climate such as this, conflicts are sure to arise and compromises just as surely will be struck. For this reason, I think that certain preventive principles should be identified as non-negotiable from the onset: A service is a service. The physician who provides a technology-related service is currently rewarded for its indiscriminant use. We need to restructure these
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incentives in a way that encourages more appropriate utilization. One way to eliminate the inherent conflict associated with self-referral, for example, would be to revise third-party reimbursement schedules so that physicians are paid as much for cognitive services (e.g., consultation] as for technical services (e.g., procedures).50r51One’s intellectual activities should be valued just as highly as one’s physical activities. A prescription is a prescription. New drugs must comply with an explicit set of standards before public release. The regulations concerning non-pharmaceutical technology are much less comprehensive. We need to develop universal standards by which granting agencies, investigators, journal editors, clinicians, third-party payers and government bureaucrats can judge the efficacy and safety of any technology-drug or device-and the adequacy of its clinical validation. In this respect, there should be no difference between a treatment and a test. A test is a test. Clinical pathology laboratories are periodically required to demonstrate their compliance with minimum standards of performance to maintain their operating license. In contrast, there is currently no way to assure that laboratories performing technologic procedures such as cardiac stress testing meet similar standards of quality. These laboratories are free to use their own performance protocols, their own analytic algorithms and their own interpretive criteria. As a result, the public is better assured of the quality of a blood sugar than of a coronary angiogram. I think that all clinical laboratories should be required to adhere to explicit standards of adequate performance. There should be no difference between a heart test and a blood test. Currently, the diffusion of medical technology from the investigational laboratory to clinical practice is fueled more the promise of performance (efficacy), than by performance itself (effectiveness]. If we are to remain in control of the technology we must learn as much about the way it performs in the real world-populated by real doctors, real patients and real problems-as we know about the way it performs in the artificial world reflected in the journal article. There’s a big difference between the seed of efficacy and the fruit of effectiveness. We can’t hope to harvest that fruit from an ill-gotten handful of seed. Just ask that monkey.
References 1. Anderson G, Steinberg E. To buy or not to buy. Technology acquisition under prospective payment. N EngJ / Med 1~84;311:182-185. 2. Blendon RJ,Altman DE. Public attitudes about health-care costs.A lesson in national schizophrenia. N Engl [ Med 1984;311:613-616. 3. Osbakken MD, Boucher CA, Okada RD, Bingham JB, Strauss W, Pohost GM. Spectrum of global left ventricular responses to supine exercise: Jimitation in the use of ejection fraction in identifying patients with coronary artery disease. Am r Cardiol lY83;51:28-35. 4. Manyari DE, Kostuk WJ. Left and right ventricular function at rest and during bicycle exercise in the supine and sitting positions in normal subjects and patients with coronary artery disease: assessment by radionuclide ventriculogrophy. Am / Cardiol 1983;51:36-42. 5. Reuben DB. Learning diagnostic restraint (editorial). N EngJ 1 Med lY83;310:5Yl-593,
6. Bunker JP, Fowles J, Schaffarzick R. Evaluation of medical-technology strategies. Effects of coverage and reimbursement (First of 2 parts). N EngJ 1 Med 1982;306:620-624.Proposal for an Institute for Health-Care Evaluation
[Second of 2 parts). N EngJ r Med 1982;306:687-692. 7. Kahneman D, Slavic P, Tversky A (eds). {udgment Under Uncertainty: Heuristics and Biases. Cambridge: Cambridge University Press, 1982. 8. Freidson E. Profession of medicine. A study of the sociology of applied knowledge. New York: Harper b Row, lY70:158-184, 335-382. 9. Ransohoff DF, Feinstein AR. Problems of spectrum and bias in evaluating the efficacy of diagnostic tests. N Engl f Med 1978;299:926-930. 10. Geltman EM, Biello D, Welch MJ, Ter-Pogossian MM, Roberts R, Sobel BE. Characterization of nontransmurai myocardial infarction by positronemission tomography. Circulation 1982;65:747-755. 11. Deim K, Lentner C (eds). Scientific Tables. 7th ed. Basel: CIBA-Geigy Ltd., 1970:85-106. 12. Borer JS, Bacharach SL, Green MV, Kent KM, Epstein SE, Johnston GS. Real-time radionuclide cineangiography in the noninvasive evaluation of global and regional left ventricular function at rest and during exercise in patients with coronary artery disease. N EngJ \ Med 1977;296:839-844, 13. Barer JS. Bacharach SL. Green MV, Kent KM, johnston GS, Epstein SE. Effect of nitroglycerin on exercise-induced abnormalities of left ventricular regional function and ejection fraction in coronary artery disease. Assessment by radionuclide cineangiography in symptomatic and asymptomatic patients. Circulation 1978;57:314-320. 14. Steele PP, Rainwater J, Jensen D, Vogel RA, Battock D. Isosorbide dinitrate-induced improvement in left ventricular ejection fraction during exercise in coronary artery disease. Chest 1978;74:526-530. 15. Berger HJ, Reduto LA, Johnstone DE, Borkowski H, Sands MJ, Cohen LS. Langou RA, Gottschalk A, Zaret BL. Global and regional left ventricular response to bicycle exercise in coronary artery disease.Assessment by quontitative radionuclide angiography. Am ) Med 1979;66:13-21. 16. Borer JS, Kent KM, Bacharach SL, Green MV, Rosing DR, Seides SF, Epstein SE, Johnston GS. Sensitivity, specificity and predictive accuracy of radionuclide cineangiography during exercise in patients with coronary artery disease. Comparison with exercise electrocardiography. Circulation 1979;60:572-580. 17. Brady TJ, Thrall JH, Clare JM, Rogers WL, Lo K, Pitt B. Exercise radionuelide ventriculography: practical considerations and sensitivity of coronary artery disease detection. Radiology 1979;132:697-702. 18. Jengo JA, Oren V, Conant R, Brizendine M, Nelson T, Uszler JM, Mena I. Effects of maximal exercise stress on left ventricular function in patients with coronary artery disease using first pass radionuclide angiography: a rapid, noninvasive technique for determining ejection fraction and segmental wall motion. CircuJation 1979;59:60-65. 19. Pfisterer ME, Slut&y RA, Schuler G, Ricci DR, Swanson SS, Gordon DG, Battler A, Froelicher VF, Peterson KE, Ashburn WL. Profiles of radionuclide left ventricular ejection fraction changes induced by supine bicycle exercise in normals and patients with coronary artery disease. Cathet Cardiovasc Diagn 1979;5:305-317. 20. Rozanski A, Diamond GA, Berman DS, Forrester JS,Morris D, Swan HTC. The declining specificity of exercise radionuclide ventriculography. N Eni1 r Med 1983;309:518-522. 21. Diamond GA. An improbable criterion of normality. Circulation 1982; 66:618.
22. Beck JR. Quantitative logic and new diagnostic tests. Arch Intern Med 1982;142:681. 23. Rozanski A, Diamond GA, Forrester JS,Berman DS, Morris D, Swan HJC. Alternative referent standards for cardiac normality: implications for diagnostic testing. Ann Intern Med 1984;101:164-171. 24. Jones RH, McEwan P, Newman GE, Port S, Rerych SK, Scholz PM, Upton MT, Peter CA, Austin EH, Leong K, Gibbons RJ, Cobb FR, Coleman RE, Sabiston DC. Accuracy of diagnosis of coronary artery disease by radionuelide measurement of left ventricular function during rest and exercise. Circulation 1981;64:586-601. 25. Austin EH, Cobb FR, Coleman E, Jones RH. Prospective evaluation of radionuclide ongiography for the diagnosis of coronary artery disease. Am 1 Cardiol 1982;50:1212-1216. 26. Bodenheimer MM, Banka VS, Agarwal JB, Weintraub WS, Helfant RH. Relative value of isotonic and isometric exercise radionuclide ventriculography to detect coronary artery disease. [ACC 1983;1:790-796. 27. Carillo AP, Marks DS, Pickard SD, Khaja F, Goldstein S. Correlation of exercise thallium myocardiol scan with coronary arteriograms and the maximal exercise
test. Chest 1978;73:321-326,
28. Melin JA, Piret LJ, Vanbutsele RJM, Rousseau MF, Cosyns J,Brasseur LA, Beckers C, Detry JMR. Diagnostic value of exercise electrocardiography and thallium scintigraphy in patients without myocardial infarction: a Bayesian approach. Circulation 1981;63:1019-1024. 29. Iskandrian AS, Segal BL, Haaz W, Kane S. Effects of coronary artery narrowing, collaterals and left ventricular function on the pattern of myocardial perfusion. Cothet Cardiovasc Diagn 1980;6:159-172. 30. Dash H. Massie BM, Botvinick EH, Brundage BH. The noninvasive identification of left main and three-vessel coronary artery disease by myocardial stress perfusion scintigraphy and treadmill exercise electrocardiography. Circulation 1979;60:276-284. 31. Berman DS, Sale1AF, Denardo GL, Mason DT. Noninvasive detection of regional myocardial ischemia using rubidium-81 and the scintillation camera: comparison with stress electrocardiography in patients with arteriographitally documented coronary stenosis. Circulation 1975;52:61Y-626.
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32. Ritchie JL, Trobaugh GB, Hamilton GW, Gould KL, Narahara KA. Murray JA, Williams DL. Myocardial imaging with thallium-201 at rest and during exercise: comparison with coronary arteriagraphy and resting and stress electrocardiography. Circulation 1977;56:66-71. 33. Botvinick EH, Shames DM, Gershengorn KM, Carlsson E, Ratshin RA, Parmley WW. Myocardiai stress perfusion scintigraphy with rubidium-81 versus stress electrocardiography. Am J Cordial 1977;39:364-370. 34. Bolvinick EH, Taradash MR, Shames DM, Parmley WW. Thallium-201 myocardial perfusion scintigraphy for the clinical clarification of normal, abnormal and equivocal electrocardiographic stress tests. Am J Cardioi 1978;41:43-51. 35. Jengo JA, Freeman R, Brizendine M, Mena I. Detection of coronary artery disease: comparison of exercise stress radionuclide angiocardiography and thallium stress perfusion scanning. Am J Cardiol 1980;45:535-541. 36. Corbett JR, Dehmer GJ, Lewis SE, Woodward W, Henderson E, Parkey RW, Blomqvist GC, WilIerson JT. The prognostic value of submaximal exercise testing with radionuclide ventricuiography before hospital discharge in patients with recent myocardial infarction. Circulation 1981;64:535544. 37. Brown KA, Boucher CA, Okada RD, Guiney TE, Newell JB, Strauss HW, Pohost GH. Prognostic value of exercise thallium-201 imaging in patients presenting for evaluation of chest pain. [ACC 1983;1:994-1001. 38. Multicenter Postinfarction Research Group. Riskstratification and survival after myocardial infarction. N Engl J Med 1983;309:331-336. 39. Harris PJ,Lee KL, Harrell FE, Behar VX, Rosati RA. Outcome in medically treated coronary artery disease. Ischemic events: nonfatal infarction and death. Circulation 1980;62:718-726. 40. Hung J, Chaitman BR, Lam J, Lesperance J, Dupras G, Fines P, Bourassa MG. Noninvasive diagnostic test choices for evaluation of coronary artery disease in women: a multivariate comparison of cardiac fluoroscopy, exercise
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electrocardiography and exercise thallium myocardial perfusion scintigraphy. JACC 1984;4:8-16. 41. Lee KL, McNeer JF, Starmer CF, Harris PJ,Rosati RA. Clinicof judgment and statistics: lessons from a simulated randomized trial in coronary artery disease. Circulation 1980;61:508-515. 42. Staniloff HM, Diamond GA, Forrester JS, Pollock BH, Berman DS, Swan HJC. The incremental information boondoggle: when a test seems powerful but isn’t (abstr). Circulation 1982;66:184. 43. Rozanski A, Diamond GA, Jones R, Forrester JS, Berman D, Morris D, Pollock BH, Freeman M, Swan HJC. A format for integrating the interpretation of exercise ejection fraction and wall motion and its application in identifying equivocal responses. JACC 1985;5:238-248. 44. Atwood JE, Jensen D, Froelicher V, Witztum K, Gerber K, Gilpin E, Ashburn W Agreement in human interpretation of analog thallium myocardial perfusion images. Circulation 1983;64:601-609. 45. Iglehart JK. Opinion polls on health care. N Engl J Med 1984; 310:1616-1620. 46. Iglehart JK. Another chance for technology assessment. N Engf 1 Med 1983:3O9:509-512. 47. Chalmers TC, Van Den Noort 5’. Lockshin MD, Waksman BH. Summary of a workshop on the role of third-party payers in clinical trials of new agents. N Engl J Med 1983;309:1334-1336. 48. Schwartz WB, Aaron HJ. Rationing hospital care: Iessonsfrom Britain. N Engl [ Med 1984;310:52-56. 49. Fuchs VR. The “rationing” of medical care. N Engl [ Med 1984; 311:1572-1573. 50. Lown B. In: Cousins N, ed. The Healing Heart: Antidotes of Panic and Helplessness. New York: W.W. Norton, 1983:26. 51. Omenn GS, Conrad DA. Implications of DRGs for clinicians. N Engf r Med 1984;311:1314-1317.
ValveExcisionOnlyVersus YalveExcisionPlus Rep/acemenf for Active Infective Endocarditis Involving the Tricuspid Valve DEBORAH J. BARBOUR,
MD, and WILLIAM C. ROBERTS, MD
M.B., a 28-year-old intravenous (i.v.) drug user, had Group D alpha Streptococcus endocarditis and underwent tricuspid valve excision without replacement. Late postoperatively, he was asymptomatic, but died from a heroin overdose 11 months after operation [Fig. 2). Y.W., a X&year-old iv. drug user, had Staphylococcus aureus endocarditis with severe right-sided congestive heart failure (CHF) and underwent tricuspid valve excision and replacement with a porcine bioprosthesis. Nearly 5 months later the bioprosthesis became infected and it was excised without being replaced [Fig. 2). Shortly thereafter, however, severe right-sided CHF reappeared and, as a consequence, a porcine bioprosthesis was reinserted into the tricuspid From the Pathology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20205. Manuscript received May 31, 1985, accepted August 13, 1985.
valve position. Six weeks after this third operation she was asymptomatic. Infective endocarditis involving the tricuspid valve is fairly common in i.v. drug users. The infection on this valve, when bacterial in nature, can usually be eradicated by antibiotic therapy. In an occasional patient, however, persistence of positive blood cultures, repeated pulmonary emboli or development of intractable CHF despite appropriate antibiotic therapy without associated left-sided cardiac valve involvement necessitates operative intervention. But what type of operative intervention should be performed? Excision of the tricuspid valve only or excision plus concurrent replacement (Fig. 3]? This article will examine the arguments for each of these z therapeutic options. Review of previous published reports yielded at least 15 patients who had isolated excision of their infected native tricuspid valves with concurrent placement of either a mechanical prosthesis or a bioprosthesis in the tricuspid valve position.1-5 Of the 5 patients
