Our results indicate that after Medicare’s expansion of coverage for carotid stenting in March of 2005, carotid stents were adopted by a significantly smaller number of U.S. hospitals compared to the number of hospitals providing similar invasive cardiovascular procedures. However, the lower adoption rate did not result in inequitable availability of stents in areas with large black populations, lower average incomes, or in rural areas. Medicare’s coverage policy was followed by a more limited number of hospitals delivering carotid stents to Medicare beneficiaries without unintended reductions in availability of this treatment to historically disadvantaged groups.
Medicare’s carotid stent coverage policy was unique and innovative, in that no prior coverage decision had required hospitals to be certified for the provision of a particular technology in order to seek reimbursement for that technology. This policy was intended to enhance the quality of care received by Medicare beneficiaries undergoing carotid stenting by requiring that hospitals wishing to perform the procedure meet a set of structural quality-of-care requirements.(7
Prior evidence of suboptimal clinical outcomes among hospitals providing carotid endarterectomy to Medicare beneficiaries suggests that carotid revascularization (i.e., stenting or endarterectomy) outcomes may be particularly sensitive to hospital factors such as volume and adequate support services. Thus, policymakers may have viewed carotid revascularization as a particularly appropriate target for coverage policies that were institutionally focused.(15
) While Medicare did not derive its list of carotid stenting quality-of-care requirements from outcomes data,(7
) the certification requirements do represent a relatively uncontroversial list of factors likely to predict better clinical outcomes.
Medicare’s coverage policy also recognized that carotid stenting was not a “proven” technology that is clearly superior to alternative treatments, thus providing ethical justification for limiting availability to a subset of Medicare beneficiaries nationwide.(26
) Indeed, the absence of a nearby hospital offering stents in 2005–2007 was highly predictive of lower use among Medicare beneficiaries with carotid disease;(20
) thus, availability of the technology in 2005–2007 was clearly not equal across the U.S. population of Medicare enrollees.
However, even in retrospect, the welfare effects of lowering the number of hospitals providing carotid stents are difficult to ascertain, as the carotid stent’s effectiveness compared to alternative therapies such as carotid endarterectomy remains uncertain. While the Johnson & Johnson-supported Stenting with Angioplasty and Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) multi-center trial demonstrated therapeutic equivalence between carotid stenting and carotid endarterectomy for patients meeting the clinical characteristics that were incorporated in Medicare’s coverage decision,(5
) other studies have suggested that stenting outcomes may be inferior to endarterectomy.(2
Had Medicare enacted a less restrictive coverage decision with no requirement for hospital certification, this may have resulted in carotid stents being delivered to Medicare beneficiaries with lower quality of care and potentially worse outcomes at some centers. It is also possible, however, that Medicare’s restrictive coverage policy resulted in worse outcomes by preventing patients who otherwise would have benefited from receiving stents. As the current study was not designed to examine how coverage policy affected clinical outcomes, this remains a critical area for future comparative effectiveness research.
Another important policy goal of Medicare’s recent coverage decisions, including its Coverage with Evidence Development (CED) initiatives, was to collect “real world” patient data among Medicare beneficiaries to guide future expansion or modification of coverage (this was among the requirements imposed on hospitals for carotid stent coverage).(8
) A systematic bias in the availability of carotid stents among black, low-income, or rural patients under the limited coverage policy used for carotid stenting would have been antithetical to those goals, as data generated from these groups would have been sparse. The current study provides reassuring evidence that Medicare’s coverage policy did not disproportionately reduce opportunities for receipt of carotid stents among historically disadvantaged groups, and thus the evidence developed from the coverage policy should not be biased by under-representation of these patients.
As technological innovation continues to drive the rising costs of health care,(28
) there is clearly a need for policies to move beyond blanket coverage of treatments by any willing provider toward more selective coverage requiring providers to demonstrate both their a priori
ability to produce optimal treatment outcomes and their willingness to report data on patient outcomes.(8
) Our study provides important evidence consistent with the carotid stent coverage policy’s effectively limiting excess hospital adoption while simultaneously maintaining equitable technology availability.
It is possible that utilization rates of carotid stents in 2005–2007 among the hospitals included in our study would have been low even if Medicare’s coverage policy had been less restrictive. Alternatively, if the hospital utilization rates of comparable cardiovascular technologies represent “full” adoption, the coverage policy for carotid stents may have reduced carotid stent adoption by between 200 and 550 U.S. hospitals (as illustrated in )--a remarkable 19–38 percent reduction in the rate of hospital uptake.
It is noteworthy that use of carotid stenting in areas with larger black populations initially appeared higher than white areas, although addition of hospital academic status, ownership, and volume to the regression models appeared to explain this difference. A possible explanation is that restrictive coverage policies paradoxically favored availability of new treatments among patient groups that were more likely to receive care in high-volume and/or academic hospitals, which were the strongest predictors of carotid stent use.
Our study was limited in its ability to adjust for concurrent policies and economic pressures that may have simultaneously influenced hospitals’ decisions to adopt carotid stents. For example, until Oct 1, 2006 carotid stents were reimbursed under the same diagnosis-related group that covered carotid endarterectomy (i.e., 533–534). In 2006, CMS established a separate group for carotid stenting (577) in recognition of the unanticipated higher costs of that routinely exceeded the level of reimbursement for groups 533–534.(31
It therefore is possible that hospitals not adopting carotid stenting were responding to the lower anticipated revenue from the procedure,(32
) rather than to the CMS coverage policy. However, we did not observe a marked increase in carotid stent adoption rates in 2007, as would have been expected if reimbursement rates had been the operative factor in preventing hospital adoption in 2005–2006.
Another potential explanation of lower carotid stent adoption was the emergence of new clinical evidence during 2005–2007. Publication of the 2006 Endartertomy Versus Angioplasty in Patients with Severe Symptomatic Carotid Stenosis (EVA-3S) trial(2
) may have lowered enthusiasm for hospital adoption of carotid stenting, particularly in relation to more positive evidence emerging during the same time about the effectiveness of similar technologies (e.g. implantable defibrillators).(33
It is possible that equal availability of new technologies at the level of the hospital referral region does not necessarily entail equal use of carotid stents among patients from different racial or socioeconomic backgrounds.(18
) However, it is also increasingly clear that some health care disparities are caused by the absence of availability in localities where historically disadvantaged groups are concentrated.(18
) Our findings encouragingly suggest that lack of local availability would not be a major contributor to any disparities in stent use.
Finally, our method of identifying hospitals with the technological capacity to adopt the procedure used arbitrary cutoffs for volume of use of related cardiovascular procedures. While prior use of comparable technologies has been shown to be highly predictive of a hospital’s likelihood of adopting a new technology,(18
) it is possible that alternative methods of identifying hospitals as “technologically equipped” may have yielded different results. However, our main results were robust to variation in the threshold number of annual cardiovascular procedures used to define the study cohort.
The carotid stent coverage policy and its aftermath provide a useful comparison to other Medicare technology coverage policies enacted at almost the same time. Limiting provision of advanced technological services to selected hospitals based on a technology-specific quality-of-care checklist appears to be a potentially more promising method of ensuring high-quality delivery of new technology than, for example, a device registry requirement alone.
The widespread adoption of implantable cardioverter-defibrillators was not significantly blunted by the registry requirement imposed by Medicare, although it is not clear if all hospitals providing defibrillator implantation would have been able to meet defibrillator-specific quality-of-care criteria had Medicare enacted defibrillator coverage in a manner similar to carotid stent coverage.
It is likely that similar CMS coverage policies would have different effects for different technologies. Hospital uptake of new technologies is influenced by published evidence on efficacy, peer-institution behavior, ease of implementation, the presence of clinical “champions,” manufacturer marketing, and the anticipated income stream.(32
) These factors vary substantially across new medical technologies, so it is uncertain that CMS coverage policies requiring hospital quality-of-care certification would inevitably produce similar hospital adoption patterns to that observed for carotid stents.
Nevertheless, the carotid stent policy experience presents a useful introduction to future possibilities of coverage combined with quality assurance.
Following Medicare’s 2005 coverage policy for carotid stenting, substantially fewer hospitals adopted the technology during 2005–2007 than what would have been expected based on hospitals’ unrestricted utilization patterns of similar cardiovascular technologies. However, the lower rates of adoption did not result in reduced availability of the new treatment among historically disadvantaged groups of Medicare beneficiaries. The carotid stent coverage decision therefore may be a useful model for future CMS coverage decisions.