Another potential way to grow the inclusion criteria is to investigate thrombectomy in patients with larger infarcted cores than were enrolled in DAWN and DEFUSE 3, but assessing this will require a new prospective study, Dr. Albers said.
Running the 6- to 24-hour numbers
Adoption of the 6- to 24-hour time window for endovascular intervention in selected patients means that suddenly the U.S. acute stroke infrastructure needs to accommodate a significantly increased number of patients. Just how many added patients this means is uncertain for the time being, and will vary from region to region and center to center. Dr. Albers roughly guessed that the new late time window might double the number of stroke patients undergoing thrombectomy at his center in Stanford. Dr. Khatri put together a more data-driven but still very speculative estimate that at the University of Cincinnati, it will mean about 40% more stroke patients going to thrombectomy. She shared the numbers behind this estimate in a report she gave at the conference.
To calculate the incremental change produced by the late time window, she used data collected on 2,297 acute ischemic stroke patients from the Greater Cincinnati/Northern Kentucky region who were seen at the University of Cincinnati during 2010. Prior analysis by Dr. Khatri and her associates showed that 159 of these patients presented quickly enough and with an appropriate stroke to qualify for thrombolytic therapy, and that 29 patients would have qualified for thrombectomy performed during the 0- to 6-hour time window.
In the new analysis Dr. Khatri calculated that 791 patients presented at 5-23 hours, and of these 34 had other features that would have made them eligible for enrollment in DAWN. Because no imaging data existed for these 2010 patients, she applied an estimate that 22% of these patients would qualify by the size of their infarcted core and ischemic penumbra, resulting in seven additional thrombectomy-eligible patients. Accounting for patients who would qualify by the more liberal DEFUSE 3 criteria added another 5 patients for a total increment of 12 patients during 2010 who would have been eligible for thrombectomy, about 40% of the number from the 0- to 6-hour window.