To examine associations between the number of neuro-interventionalists at a hospital and acute ischemic stroke (AIS) outcomes.

Endovascular thrombectomy has become the standard of care for large vessel occlusion AIS involving the anterior circulation. Hence, the need for neuro-interventionalists is growing. There is limited data describing the number of interventionalists per hospital in the US, and correlations with outcomes.

We used complete Medicare datasets and included all AIS admissions from 2018-2019, using validated International Classification of Diseases, 10th Revision, Clinical Modification codes to identify AIS and co-morbidities. We used National Provider Identifier codes to identify distinct interventionalists at the hospital.  We examined outcomes at the hospital level, including percent of AIS 1) with inpatient mortality, 2) with discharge home, and 3) with 30-day mortality.

Among 471427 AIS admissions, 16253 received ET. Only 683 of 4576 AIS-treating hospitals provided ET (14.9%). These hospitals most frequently only had one interventionalist available and were clustered in large metropolitan areas with high AIS volumes.  As AIS volumes, ET volumes, and mean NIHSS scores increased, so did the number of interventionalists. With each additional interventionalist, there was an increased likelihood of poor outcomes at the hospital level including percent of AIS with 1) inpatient mortality (difference in percent with each additional interventionalist 0.13 SE 0.03, p<0.0001), 2) discharge home (-0.17, SE 0.07, p=0.022), and 3) 30-day mortality (0.23, SE 0.04, p<0.0001).

We confirmed a relative lack of neuro-interventionalists among US hospitals, with a concentration of interventionalists in urban, high-volume centers.  Although we found an increasing likelihood of poor outcomes associated with increasing number of interventionalists, this is likely due to increasing complexity and severity of cases at high-volume ET centers, but further study is needed.