Author + information
- †Stanford University School of Medicine, Stanford, California
- ‡University of California San Diego Medical Center, San Diego, California
- ↵∗Reprint requests and correspondence:
Dr. Mark A. Hlatky, Stanford University School of Medicine, HRP Redwood Building, Room 150, Stanford, California 94305-5405.
The United States is a large and diverse country: its physical features vary from mountains to deserts to plains; its people live in large cities, suburbs, small towns, and on farms and include immigrants from every corner of the world; there are wide geographic variations in political affiliations, religious beliefs, preferences for food, and even exercise and smoking habits. If all Americans were exactly the same from coast to coast, the United States would be a far less interesting place to live, and arguably a less vibrant and innovative country.
Pioneering work by Jack Wennberg and his colleagues at Dartmouth University documented wide variations in the practice of medicine across the United States (1). Rates of invasive cardiac procedures, for instance, vary 6-fold across different health care regions. Color-coded maps of the country reveal vast differences in the use of almost every test and procedure, from knee replacement to breast cancer screening. This variation has drawn a great deal of attention from commentators and policy makers. But if we celebrate diversity in most areas of American life, why does it matter if medical practice varies, too?
When standards of care are clear, there should be no variation in practice across the regions of the country. Pilots of commercial aircraft follow the same standard procedures during takeoff and landing at every airport in the country; uniform practice is important for passenger safety. When standards of care in medicine are clear, practice patterns are similar in every part of the country. When there is no clear evidence on the best practices, however, different physicians will adopt different approaches, on the basis of their beliefs, training, incentives, and the local “practice style.” Substantial practice variation suggests that there is a lack of consensus on the best approach, in part because the evidence is insufficient.
Another major reason for the interest in practice variation is that it also affects the cost of medical care, which consequently varies widely in different parts of the country. Unlike most products and services, the cost of medical care is shared by all Americans through payments for medical insurance, private and public. So the areas of the country that use relatively few medical services and have lower costs end up subsidizing the areas of the country that use a lot of services and have higher costs. With health care costs out of control, we are all looking for ways to get more value for the health care dollar.
The third major reason for interest in practice variation is the possibility that it might be associated with variations in clinical outcomes. Perhaps outcomes are worse in areas that use few tests and procedures, or perhaps outcomes are worse in areas that use more tests and procedures. Variations in practice would be more important if the outcomes and quality of care varied as a result. In contrast, if outcomes were the same across geographic areas despite wide variations in the use of medical care, it would not matter which course of action were taken. In that case, we could identify the practice patterns that are most efficient, yet still effective, which could save a lot of money without affecting the quality of care.
Geographic variation in the use of cardiac catheterization, percutaneous coronary intervention (PCI) and coronary artery bypass grafting have been documented repeatedly (1–3). There is a very close correlation between the rate of coronary angiography and the rate of coronary revascularization across geographic regions (2), a correlation that is stronger for PCI than for coronary artery bypass grafting (3). This “diagnostic-therapeutic cascade” can be interpreted several ways, perhaps indicating a visceral response of cardiologists to the angiographic appearance of a coronary stenosis or perhaps resulting from an a priori strategy to perform coronary revascularization on any lesions found at angiography. The correlation between local rates of stress testing and coronary revascularization is also significant but not as strong as the correlation of angiography and revascularization (2). Geographic variation in the use of stress testing before elective PCI has recently been documented (4), as has geographic variation in the use of stress testing after PCI (5).
In this issue of the Journal, Shah et al. (6) analyze data from the National Cardiovascular Data Registry’s CathPCI Registry and document substantial variation among 656 hospitals in the use of stress testing after PCI with coronary stenting, ranging across hospitals from 9% to 66% of patients. When they divided hospitals into quartiles on the basis of use of stress testing, hospitals in the lowest quartile performed stress tests on fewer than 25% of the patients, whereas hospitals in the highest quartile performed stress tests on more than 39% of the patients. On the basis of the available data, the clinical characteristics of patients treated in high-use and low-use hospitals were generally similar. However, no data were available on the presence of symptoms after PCI or the results of stress testing. Patients treated in hospitals with high levels of stress testing after PCI were significantly more likely to undergo repeat revascularization procedures, especially repeat PCI. This finding suggests that the detection of ischemia during stress testing prompted subsequent invasive evaluation and treatment. Nevertheless, the rate of death or of myocardial infarction was not significantly lower among hospitals with high rates of stress testing (6).
The study of Shah et al. (6) adds to previous studies by documenting the subsequent outcomes of patients treated in hospitals with different rates of stress testing after PCI, a key piece of information in evaluating the importance of practice variation. It is tempting to conclude from these data that more stress testing after PCI leads to more procedures and increases costs but has no clinical benefit. But the dots in this neat picture are not well connected, as the study had limited power to detect meaningful differences in hard cardiac outcomes, and there were trends toward lower rates of death and myocardial infarction in the hospitals that used stress testing most often. Furthermore, the study had no data at all on other important clinical outcomes, such as angina, functional capabilities, or quality of life. These limitations suggest that although routine stress testing after successful coronary revascularization is associated with more invasive procedures (and higher cost), the effect on clinical outcomes remains uncertain.
↵∗ 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.
Both authors have reported that they have no relationships relevant to the contents of this paper to disclose.
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