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Accountable Care Organizations: what they mean for the country and for neurointerventionalists
  1. Timothy M Meehan1,
  2. H Benjamin Harvey1,
  3. Richard Duszak Jr2,3,
  4. Philip M Meyers4,
  5. Geraldine McGinty5,
  6. Gregory N Nicola6,
  7. Joshua A Hirsch7
  1. 1Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
  2. 2Harvey L Neiman Health Policy Institute, Reston, Virginia, USA
  3. 3Department of Radiology and Imaging Sciences, Emory University, Atlanta, Georgia, USA
  4. 4Departments of Radiology and Neurological Surgery, Neurological Institute of New York, Columbia University, College of Physicians & Surgeons, New York, New York, USA
  5. 5Department of Radiology, Weill Cornell Medical College, New York, New York, USA
  6. 6Hackensack University Medical Center, Hackensack, New Jersey, USA
  7. 7NeuroEndovascular Program, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
  1. Correspondence to Dr Timothy M Meehan, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, FND 216, Boston, MA 02114, USA; tmmeehan{at}


The Affordable Care Act is celebrating its fifth anniversary and remains one of the most significant attempts to reform healthcare in US history. Prior to the federal legislation, Accountable Care Organizations had largely been part of an academic discussion about how to control rising healthcare costs, but have since become a fixture in our national healthcare landscape. A fundamental shift is underway in the relationship between healthcare delivery and payment models. Some elements of Accountable Care Organizations may remain unfamiliar to most healthcare providers, including neurointerventional specialists. In this paper we review the fundamental concepts behind and the current forms of Accountable Care Organizations, and discuss the challenges and opportunities they present for neurointerventionalists.

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The Affordable Care Act (ACA) of 2010 dramatically increased the profile of Accountable Care Organizations (ACOs), which have now become a critical component in the future of the American healthcare delivery system. The aim of an ACO is to distribute responsibility both through cost control and quality measures,1 with the goal of better aligning incentives across different healthcare providers for a specific patient population. The provider network includes physicians, non-physician caregivers, hospitals, and extended care facilities. The intended purpose of ACOs is to curb spending growth while simultaneously delivering higher quality care through improved coordination and through a reduction in duplicative services, unnecessary tests, and medical errors.

Most ACOs are still incompletely implemented with regard to specialty areas such as neurointerventional (NI) surgery, which have thus been insulated from changes involving this healthcare delivery model even at institutions currently participating in these programs. While there has been minimal impact on reimbursement or care delivery for image-guided procedures related to the initiation of ACOs,2 this will probably not remain the case. Specialty services will become subject to the ACO model in the extremely dynamic healthcare reform environment. Thus far, ACOs have primarily focused their attention on chronic care, primary care, and other non-specialty areas. Nonetheless, ambitious goals are now in place to test new payment models in specialty care, which could soon affect neurointerventionalists. Resultant reductions could be disruptive to current practice patterns. The US Department of Health and Human Services (HHS) recently set an ambitious goal of allocating 30% of Medicare payments to quality or value through alternative payment models such as ACOs, bundled payments, and capitation by 2016.3 Change is quickly approaching.

Brief history

In 2006 Elliott Fisher from The Dartmouth Institute for Health Policy and Clinical Practice established the term ‘ACO’ at a public meeting of the Medicare Payment Advisory.4 In the ensuing years, the concept of accountable care gained traction as a method to align incentives with cost control. Subsequently, ACOs were legally established in March 2010 as a provision of the Patient Protection and ACA (PPACA) legislation.5

The ACA represents an effort to address inconsistencies in the quality of care and unsustainable growth rates in healthcare spending. As one of their many initiatives, ACOs were intended to create a system in which physician and delivery system incentives are better aligned to provide high-quality and cost-effective care, consistent with nationally recognized standards of practice. This drive is, in part, a response to disturbing data on Medicare beneficiaries in the USA, which demonstrated that regions with higher per capita spending tended actually to produce lower quality care and less patient satisfaction.6 While direct comparison with other industrialized nations can be difficult, broader data suggest that the US healthcare system underperforms when compared with other industrialized countries, despite having the highest health expenditures in the world (figures 1 and 2).7

Figure 1

USA ranking among 11 industrialized countries on metrics of healthcare quality and healthcare expenses per capita, 2011. Republished with permission from the Commonwealth Fund.7

Figure 2

Healthcare spending as a percentage of total GDP, 2012. A comparison of the USA with selected OECD member countries. Modified from data from OECD, 2015. Available at: (accessed 13 April 2015).

The ACA also delineates specific requirements for ACO creation including types of provider groups, which include group practice arrangements, networks of individual practices, partnership or joint venture arrangements, and hospital employment models. A tax identification number and application approval is required to participate.

What is an ACO?

An ACO is a legal entity that must apply to the Government to be awarded a contract to provide ‘accountable’ care, measuring quality and cost of care for a specified patient population.8 At present an ACO must accept responsibility for a patient population of at least 5000 Medicare Fee-For-Service (FFS) beneficiaries for a period of at least 3 years. In order to participate, the healthcare entity must invest in infrastructure necessary to effectively coordinate care at the population health level as well as to audit and report relevant quality and cost metrics back to the Center for Medicare and Medicaid Services (CMS). The ACO payment model is directed at the institutional level and intentionally allows for flexibility and discretion for different payment schemes for individual provider groups within the ACO, including FFS. Furthermore, individual providers are permitted to participate in more than one ACO.

Under an ACO model, provider payments can be allocated on a FFS basis even though the ACO's gross revenue is effectively capitated in a risk-sharing agreement with Medicare or other payer entities. If an ACO meets predefined financial and quality benchmarks, then it could receive a financial bonus in return. Certain ACO models also incorporate the risk of a financial penalty if healthcare expenditures exceed a predefined threshold.

At present, several different forms of ACOs exist: the Medicare Shared Savings Program (MSSP), the Advance Payment ACO Model, the ACO Investment Model, the Pioneer ACO Model, and the recently initiated Next Generation ACO Model. These are in addition to Medicaid ACOs adopted by several states, as well as Commercial ACOs where a commercial payer (rather than Medicare) provides the financial incentives for cost performance and quality.

To date, the MSSP has been the bellwether of the ACO model and permits participants to receive a portion of the organization's savings, which is calculated by comparing costs with a benchmark value established by CMS. There is a minimum saving hurdle rate (which currently ranges between 2.0% and 3.9%) that must be met before savings are shared. During the initial period, an organization has the option to select one of two tracks: (1) one which eliminates financial risk in exchange for a lower shared saving rate; or (2) one which allows for greater profit from shared savings with the downside risk of shared cost liability if savings goals are not met.9

Results reported by CMS for the first year of the MSSP showed that almost half of the participating MSSP ACOs reduced costs, but only about a quarter of ACOs were able to achieve cost containment levels necessary to earn shared savings. Although the savings achieved were modest and unevenly distributed, real cost savings and quality improvements were indeed achieved.10

The Advance Payment and ACO Investment models are ancillary programs to the MSSP designed as supplementary incentive programs targeting (1) rural and physician-based organizations and (2) those that need funds to invest in infrastructure and care systems. The Pioneer ACO program—the first Medicare ACO model and one which is no longer accepting applications—was designed for early adopters. Overall, this model achieved only mixed results.11

In March 2015 a new ACO variant was developed termed the Next Generation Model ACO. It aims to expand the capacity of an ACO to bear financial risk while simultaneously decreasing payment variations. Benchmarking issues associated with MSSP ACOs are specifically addressed by this new model.12 Financial targets for Next Generation ACOs will be set at the beginning of each year and take into account healthcare costs from previous years and regional projected healthcare cost trends adjusting for risk, quality, and efficiency. The minimum savings rate for MSSPs will be replaced with ‘hurdle benchmark rates’ based on quality, regional, and national efficiency and will range from 0.5% to 4.5%. Ultimately, the goal is to encourage participating ACOs to invest in care improvement infrastructure by providing a more stable revenue stream that rewards top performers. In order to qualify, ACOs in this model will have to maintain a population of 10 000 Medicare beneficiaries.13

ACOs are only one way to incentivize improved care at a lower cost. Proliferation of other risk share payment models, such as capitation and bundled payments, are also expected to drive the transition from FFS to value-based payments as mandated by lawmakers and regulators. A variety of risk share options are likely to be necessary to meet the very aggressive timeline recently outlined by CMS, which would result in 30% of Medicare payments tied to quality or value through alternative payment models by the end of 2016 and 50% by the end of 2018, as well as 85% of Medicare FFS payments linked to quality or value by 2016.3 ,14

Bundled payments and ACOs

Bundled payments are a specific reimbursement methodology which is currently not part of the ACO model. However, this may change as the impetus to pivot from volume-based FFS payments to value-based payments grows. In essence, bundled payments would be considered a value-based payment that would provide a lump sum for a single care episode. Episodes could be defined in a variety of ways, and much work is yet to be done in this area before such initiatives could be broadly implemented. In most models, distribution of a bundled payment among all healthcare providers participating in the predefined care episode would be handled at the institution level. If the cost to treat the patient is less than the bundled payment, then those cost savings represent profit to the healthcare institution. In contrast, if the costs associated with an episode of care cannot be contained due to care inefficiencies, inappropriate resource utilization, preventable complications, or a variety of other reasons, then the healthcare institution would assume a financial loss. Taken to an extreme, quality itself could become a victim of cost containment, with cost-effectiveness theoretically sacrificed at the altar of cost alone. Although many different approaches have been suggested to execute bundled payments with or without an ACO, the underlying concept remains unchanged. As recently noted in JNIS, the Bundled Payment for Care Initiative includes a specific focus on stroke, a topic of particular and direct interest to NI specialists.15 Finally, it is worth noting that disease-specific ACOs are being developed to address unique patient populations. Oncology and end stage renal disease are examples of this phenomenon.16 ,17


Technological advances in NI procedures have accelerated growth in clinical applications and the diffusion of these services across the country. Increased utilization has resulted in increased healthcare costs associated with NI procedures. With the potential widespread adoption of ACOs, a decision point may arise for neurointerventionalists—that is, whether they should advocate for broader interventional use or possibly transition to the role of gatekeepers who assume responsibility for both access and cost.18 While shifting away from the FFS volume-driven model will represent difficult change, simply performing more procedures will almost certainly be unsustainable under new payment models.

A possible outcome of widespread adoption of value-based payment models could be a reduction in image-guided procedures. This would obviously impact NI surgery. Even if procedural volume is unaffected, historical reimbursements for NI procedures are unlikely to continue as cost containment pressures grow.19 ,20 In addition, if bundled and value-based payments are initiated as intended by a variety of policy makers, NI service lines could quickly change from being hospital profit centers to cost centers. As a result, it may become harder to justify equipment upgrades necessary to effectively deploy new technologies and the replacement cycle for used equipment could lengthen (eg, replacement of a biplane suite). Moreover, the expensive disposable and implantable equipment necessary to provide high-quality modern NI services could come under further scrutiny and pressure.

Taking these threats together, NI specialists could become increasingly marginalized if cost-saving initiatives lead to a continued national de-emphasis of advanced and expensive technology. Since these procedures are often at the cutting edge of medicine, some do not necessarily have a large body of evidence to support their use. As such, they will likely be rendered even more vulnerable targets in an environment of heightened price sensitivity and evidence burdens if the benefits of these procedures to patients and budgets are not proven.

The role and opportunities for the neurointerventionalist

ACOs are still in the early stages of formation and implementation, but all are progressing rapidly. In 2012, Medicare made almost no payments through value-based metrics.21 Now, approximately 20% of Medicare payments are value-based.3 To succeed in this environment, neurointerventionalists—like all other specialists—must prove their worth through their contributions to value-based care beyond the current foundation of high-quality technical and clinical proficiency. Strategically expanding one's traditional duties by thinking of creative ways to add value and validate existing roles will be imperative.

Three new studies validating the efficacy of intra-arterial thrombolysis for the treatment of acute ischemic stroke represent a historic step in demonstrating the value that neurointerventionalists bring to patient care.22–24 Going forward, there must be a sustained effort to produce ongoing high-quality outcomes-based and cost-effectiveness research necessary to support the specialty's work.25 Ultimately, outcomes data will be a neurointerventionalist's most effective shield against unfettered cost containment. Nevertheless, if bundled payments for common diseases such as stroke are implemented, then this could bode poorly for neurointerventionalists. The distribution of payments among providers as well as access to expensive care in a capitated or bundled payment environment will likely be determined by multispecialty panels and a reduction in the traditional availability to NI services seems quite possible. Thus, neurointerventionalists should actively participate in discussions and decisions regarding institutional responses to bundled payment initiatives. When available, leadership-level engagement through hospital or organizational committees will be vital to ensuring a voice during organizational risk-sharing decision-making.

Neurointerventionalists and other specialists represent a large repository of value-based skills. Working together, this group can leverage their clinical and procedural expertise. This wide breadth of medical and organizational knowledge, coupled with experience in making large capital expenditures (such as sophisticated biplane imaging equipment), is a unique skill set that can add value to a healthcare organization beyond NI patient care. These skills are often unrecognized. Engaging in systems management by facilitating more efficient care where possible at a systems-wide level is an example of leveraging such clinical expertise and effectively applying it to organizational resource allocation. While some of these initiatives may be both time-consuming and poorly (or not at all) remunerated in the near term, in the long term they will establish a stronger engaged leadership position for a future bundled payment scenario.26

In these emerging models of care, NI specialists will increasingly be expected to make prudent decisions about surgical devices, drugs, and implant selections. Simultaneously, judicious and thoughtful purchasing can create opportunities for neurointerventionalists to demonstrate their commitment to value-based care paradigms. Thus, NI specialists should become more familiar with resource costs and become more open to considering a more diverse spectrum of equipment as cost pressures take on a greater role in selection.27 This will be increasingly important as consumers and payers alike drive the marketplace towards greater price transparency.

Clinical decision support is yet another area where neurointerventionalists can assume a leadership role by ensuring appropriate utilization in addition to expert care delivery. Providing and supporting formalized decision support tools for diagnostic angiography and therapeutic neurointervention—with the goal of evidence-based decision-making in individual patients—can create institutional and health system capacity by eliminating unnecessary procedures while ensuring indicated neurointerventions are undertaken. Similarly, efforts to drive early and rapid diagnosis and intervention can save time and money for additional specialist care downstream,28 all resulting in better care and cost savings.

Neurointerventionalists are encouraged to participate in comparative effectiveness research and benchmarking studies. The move toward ACOs has renewed the focus of best practices. Such research will have an important role in developing base rates for success and complications while validating clinical outcomes.27 ,29 ,30 Establishing relevant landmarks for goals of care and quality will be critical for the success of value-based payment models. Embracing leadership roles in evidence-based and comparative effectiveness research will ultimately help neurointerventionalists enhance and add credibility to their primary jobs as patient advocates, ensuring that well indicated procedures are performed irrespective of specialty bias.

It should be noted that one only need look at the recent Final Rules from the CMS to realize that this type of evidentiary requirement is moving to the point of being an expectation for reimbursement as well as for Maintenance of Certification.31 One way the NI community can participate in this effort is to work with CMS to create more detailed registries reflecting the nuances of NI work. This could have the beneficial result of receiving credit via the Physician Quality Reporting System. To that end, the Society of NeuroInterventional Surgery has launched the Neurovascular Quality Initiative (NVQI) Series of Registries.32 These registries will facilitate tracking of procedures, outcomes, and complications across a spectrum of neurovascular conditions.


The past 5 years have seen the beginning of an unprecedented sea change within the US healthcare system. Three driving forces behind this conceptual shift, including the formation of ACOs, are (1) improving patient care experiences; (2) creating healthier populations; and (3) reducing the per capita cost of healthcare. While remaining out of the fray during the formative period of ACOs may seem comforting, in the long term it comes at the expense of valuable missed opportunities. ACOs are in their incipient phases of growth and development. Decisions made today could shape an institution's healthcare practices for years to come. Therefore, the time for all physicians to materially participate in transforming our healthcare delivery system is now. Neurointerventionalists must be engaged in the development and implementation of ACOs and other alternative healthcare delivery models. As with all physicians, neurointerventionalists can either be victims or agents of change: patients need us to be the latter.



  • Contributors TMM and JAH drafted the original manuscript. All authors reviewed the draft, provided meaningful edits and contributions in the design and analysis of the work, revised it critically, approved the final version to be published and are in agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.

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