Journal of the American College of Cardiology Vol. 62, No. 5, 2013� 2013 by the American College of Cardiology Foundation ISSN 0735-1097/$36.00Published by Elsevier Inc. http://dx.doi.org/10.1016/j.jacc.2013.05.013

EDITORIAL COMMENT

DoesPractice VariationMatter?*

Mark A. Hlatky, MD,y Anthony N. DeMaria, MDzStanford and San Diego, California

The United States is a large and diverse country: its physicalfeatures vary from mountains to deserts to plains; its peoplelive in large cities, suburbs, small towns, and on farms andinclude immigrants from every corner of the world; there arewide geographic variations in political affiliations, religiousbeliefs, preferences for food, and even exercise and smokinghabits. If all Americans were exactly the same from coast tocoast, the United States would be a far less interesting placeto live, and arguably a less vibrant and innovative country.

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Pioneering work by Jack Wennberg and his colleagues atDartmouth University documented wide variations in thepractice of medicine across the United States (1). Rates ofinvasive cardiac procedures, for instance, vary 6-fold acrossdifferent health care regions. Color-coded maps of thecountry reveal vast differences in the use of almost every testand procedure, from knee replacement to breast cancerscreening. This variation has drawn a great deal of attentionfrom commentators and policy makers. But if we celebratediversity in most areas of American life, why does it matter ifmedical practice varies, too?

When standards of care are clear, there should be novariation in practice across the regions of the country. Pilotsof commercial aircraft follow the same standard proceduresduring takeoff and landing at every airport in the country;uniform practice is important for passenger safety. Whenstandards of care in medicine are clear, practice patterns aresimilar in every part of the country. When there is no clearevidence on the best practices, however, different physicianswill adopt different approaches, on the basis of their beliefs,training, incentives, and the local “practice style.” Substantialpractice variation suggests that there is a lack of consensus onthe best approach, in part because the evidence is insufficient.

Another major reason for the interest in practice variationis that it also affects the cost of medical care, which conse-quently varies widely in different parts of the country. Unlike

*Editorials published in the Journal of the American College of Cardiology reflect the

views of the authors and do not necessarily represent the views of JACC or the

American College of Cardiology.

From the yStanford University School of Medicine, Stanford, California; and the

zUniversity of California San Diego Medical Center, San Diego, California. Both

authors have reported that they have no relationships relevant to the contents of this

paper to disclose.

most products and services, the cost ofmedical care is shared byall Americans through payments for medical insurance, privateand public. So the areas of the country that use relatively fewmedical services and have lower costs end up subsidizing theareas of the country that use a lot of services and have highercosts. With health care costs out of control, we are all lookingfor ways to get more value for the health care dollar.

The third major reason for interest in practice variation isthe possibility that it might be associated with variations inclinical outcomes. Perhaps outcomes are worse in areas thatuse few tests and procedures, or perhaps outcomes are worsein areas that use more tests and procedures. Variations inpractice would be more important if the outcomes andquality of care varied as a result. In contrast, if outcomes werethe same across geographic areas despite wide variations inthe use of medical care, it would not matter which course ofaction were taken. In that case, we could identify the practicepatterns that are most efficient, yet still effective, which couldsave a lot of money without affecting the quality of care.

Geographic variation in the use of cardiac catheterization,percutaneous coronary intervention (PCI) and coronary arterybypass grafting have been documented repeatedly (1–3). Thereis a very close correlation between the rate of coronaryangiography and the rate of coronary revascularization acrossgeographic regions (2), a correlation that is stronger forPCI thanfor coronary artery bypass grafting (3). This “diagnostic-thera-peutic cascade” can be interpreted several ways, perhaps indi-cating a visceral response of cardiologists to the angiographicappearance of a coronary stenosis or perhaps resulting from ana priori strategy to perform coronary revascularization on anylesions found at angiography.The correlationbetween local ratesof stress testing and coronary revascularization is also significantbut not as strong as the correlation of angiography and revas-cularization (2). Geographic variation in the use of stress testingbefore elective PCI has recently been documented (4), as hasgeographic variation in the use of stress testing after PCI (5).

In this issue of the Journal, Shah et al. (6) analyze data fromthe National Cardiovascular Data Registry’s CathPCI Registryand document substantial variation among 656 hospitals in theuse of stress testing after PCI with coronary stenting, rangingacross hospitals from 9% to 66% of patients.When they dividedhospitals into quartiles on the basis of use of stress testing,hospitals in the lowest quartile performed stress tests on fewerthan25%of thepatients,whereashospitals in thehighest quartileperformed stress tests on more than 39% of the patients. On thebasis of the available data, the clinical characteristics of patientstreated in high-use and low-use hospitals were generally similar.However, no data were available on the presence of symptomsafter PCI or the results of stress testing. Patients treated inhospitals with high levels of stress testing after PCI weresignificantly more likely to undergo repeat revascularizationprocedures, especially repeat PCI. This finding suggests that thedetection of ischemia during stress testing prompted subsequentinvasive evaluation and treatment.Nevertheless, the rate of deathor of myocardial infarction was not significantly lower amonghospitals with high rates of stress testing (6).

Hlatky and DeMaria JACC Vol. 62, No. 5, 2013Does Practice Variation Matter? July 30, 2013:447–8

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The study of Shah et al. (6) adds to previous studies bydocumenting the subsequent outcomes of patients treated inhospitals with different rates of stress testing after PCI, a keypiece of information in evaluating the importance of practicevariation. It is tempting to conclude from these data thatmore stress testing after PCI leads to more procedures andincreases costs but has no clinical benefit. But the dots inthis neat picture are not well connected, as the study hadlimited power to detect meaningful differences in hardcardiac outcomes, and there were trends toward lower ratesof death and myocardial infarction in the hospitals that usedstress testing most often. Furthermore, the study had nodata at all on other important clinical outcomes, such asangina, functional capabilities, or quality of life. Theselimitations suggest that although routine stress testing aftersuccessful coronary revascularization is associated with moreinvasive procedures (and higher cost), the effect on clinicaloutcomes remains uncertain.

Reprint requests and correspondence: Dr. Mark A. Hlatky,Stanford University School of Medicine, HRP Redwood Building,Room 150, Stanford, California 94305-5405. E-mail: hlatky@stanford.edu.

REFERENCES

1. Wennberg DE, Birkmeyer JD, Birkmeyer NJO, et al. The DartmouthAtlas of Cardiovascular Care. Chicago, IL: American Heart AssociationPress, 1999.

2. Wennberg DE, Kellett MA, Dickens JD, Malenka DJ, Keilson LM,Keller RB. The association between local diagnostic testing intensity andinvasive cardiac procedures. JAMA 1996;275:1161–4.

3. Lucas FL, Siewers AE, Malenka DJ, Wennberg DE. Diagnostic-therapeutic cascade revisited. Coronary angiography, coronary arterybypass graft surgery, and percutaneous coronary intervention in themodern era. Circulation 2008;118:2797–802.

4. Lin GA, Dudley RA, Lucas FL, Malenka DJ, Vittinghoff E,Redberg RF. Frequency of stress testing to document ischemia priorto elective percutaneous coronary intervention. JAMA 2008;300:1765–73.

5. Shah BR, Cowper PA, O’Brien SM, et al. Patterns of cardiac stresstesting after revascularization in community practice. J Am Coll Cardiol2010;56:1328–34.

6. Shah BR, McCoy LA, Federspiel JJ, et al. Use of stress testingand diagnostic catheterization after coronary stenting: associationof site-level patterns with patient characteristics and outcomesin 247,052 Medicare beneficiaries. J Am Coll Cardiol 2013;62:439–46.

Key Words: diagnostic catheterization - patient outcomes - site-levelpatterns - stress testing.