– Higher case volumes matter for getting better outcomes in acute ischemic stroke patients treated with endovascular thrombectomy, according to data from more than 13,000 Medicare patients treated during 2016 and 2017.

Dr. Laura K. Stein, stroke neurologist, Mount Sinai Health System, New York Mitchel L. Zoler/MDedge News

Dr. Laura K. Stein

That’s hardly surprising, given that it’s consistent with what’s already been reported for several other types of endovascular and transcatheter procedures: The more cases a center or individual proceduralist performs, the better their patients do. Routine use of endovascular thrombectomy to treat selected acute ischemic stroke patients is a new-enough paradigm that until now few reports have come out that looked at this issue (Stroke. 2019 May;50[5]:1178-83).

The new analysis of Medicare data “is one of the first contemporary studies of the volume-outcome relationship in endovascular thrombectomy,” Laura K. Stein, MD, said at the International Stroke Conference sponsored by the American Heart Association. The analysis showed that, when the researchers adjusted the Medicare data to better reflect overall case volumes (Medicare patients represent just 59% of all endovascular thrombectomies performed on U.S. acute ischemic stroke patients), the minimum case number for a stroke center to have statistically better in-hospital survival than lower volume centers was 24 cases/year, and 29 cases/year to have a statistically significant higher rate of “good” outcomes than lower-volume centers, reported Dr. Stein, a stroke neurologist with the Mount Sinai Health System in New York. For individual proceduralists, the minimum, adjusted case number to have statistically better acute patient survival was 4 cases/year, and 19 cases/year to have a statistically better rate of good outcomes.

For this analysis, good outcomes were defined as cases when patients left the hospital following their acute care and returned home with either self care or a home health care service, and also patients discharged to rehabilitation. “Bad” outcomes for this analysis were discharges to a skilled nursing facility or hospice, as well as patients who died during their acute hospitalization.

The analyses also showed no plateau to the volume effect for any of the four parameters examined: in-hospital mortality by center and by proceduralist, and the rates of good outcomes by center and by proceduralist. For each of these measures, as case volume increased above the minimum number needed to produce statistically better outcomes, the rate of good outcomes continued to steadily rise and acute mortality continued to steadily fall.

The study run by Dr. Stein and associates used data collected by the Center for Medicare & Medicaid Services on 13,311 Medicare patients who underwent endovascular thrombectomy for acute ischemic stroke at any of 641 U.S. hospitals and received treatment from any of 2,754 thrombectomy proceduralists. Outcomes rated as good occurred in 56% of the patients. The statistical adjustments that the researchers applied to calculate the incremental effect of increasing case volume took into account the variables of patient age, sex, and comorbidities measured by the Charlson Comorbidity Index.

The analysis also showed that, during this 2-year period, the average number of endovascular thrombectomy cases among Medicare patients was just under 21 cases per center, with a range of 1-160 cases; for individual proceduralists, the average was just under 5 cases, with a range of 1-82 cases.

The 19 case/year volume minimum that the analysis identified for an individual proceduralist to have a statistically significant higher rate of good outcomes, compared with lower-volume proceduralists, came close to the 15 cases/year minimum set by the Joint Commission in 2019 for individual operators at centers seeking accreditation from the Joint Commission as either a Thrombectomy-Capable Stroke Center or a Comprehensive Stroke Center. The CMS has not yet set thrombectomy case-load requirements for centers or operators to qualify for Medicare reimbursements, although CMS has set such standards for other endovascular procedures, such as transcatheter aortic valve replacement. When setting such standards, CMS has cited its need to balance the better outcomes produced by higher-volume centers against a societal interest in facilitating access to vital medical services, a balance that Dr. Stein also highlighted in her talk.

“We want to optimize access as well as outcomes for every patient,” she said. “These data support certification volume standards,” but they are “in no way an argument for limiting access based on volume.”

Dr. Stein had no disclosures.

SOURCE: Stein LK et al. ISC 2020, Abstract LB11.