In the Furthering Access to Stroke Telemedicine (FAST) Act, passed as part of a budget omnibus in 2018, Congress permanently expanded Medicare payment for telemedicine consultations for acute stroke ("telestroke") from delivery only in rural areas to delivery in both urban and rural areas, effective January 1, 2019. Using a controlled time-series analysis, we found that one year after FAST Act implementation, billing for Medicare telestroke increased substantially in emergency departments at both directly affected urban hospitals and indirectly affected rural hospitals. However, at that time only a minority of hospitals with known telestroke capacity had ever billed Medicare for that service, and there was substantial billing inconsistent with Medicare requirements. As Congress considers options for Medicare telemedicine payment after the COVID-19 pandemic, our findings, which are consistent with confusion among providers regarding telemedicine billing requirements, suggest that simplified payment rules would help ensure that expanded reimbursement achieves its intended impact.