“Early on, we have a mix of fast and slow progressors. Slow progressors are about a third to half the patients, so there is a lot of potential for [late] treatment, but the majority of patients during the first 6 hours after onset are fast progressors,” patients who won’t benefit from thrombectomy delivery beyond 6 hours, said Dr. Jovin, an interventional neurologist and director of the Stroke Institute of the University of Pittsburgh Medical Center.
“Time is very precious in the 0- to 6-hour window. When we’re dealing with a lot of fast progressors, we pay a price [in added time to treatment] for any imaging we do. We need to understand that this is a real price we pay, even when CT takes perhaps 24 minutes, and MRI adds about 12 minutes. It’s not the case in all patients that doing CT angiography just adds 5 minutes. It can take 15, 20 minutes,” especially at centers that don’t treat these types of stroke patients day in and day out. “There is no question that imaging slows us down,” Dr. Jovin said.
He highlighted that “the main role of imaging is to exclude patients from treatment, a treatment that has unbelievable effects.” Imaging can rule out patients who have a hemorrhage, lack an occlusion, have a large infarcted core, or have none of the brain at risk or just a small amount, he noted. “Excluding hemorrhage is reasonable, but we can do that in the angiography suite, when the patient is on the table. The main benefit from advanced imaging is to more precisely define the core,” but for most patients the size of their core is not important because the vast majority of acute ischemic stroke patients seen within 6 hours of onset have cores smaller than 70 mL.
“Is this much ado about nothing – especially because we punish all the other patients [with smaller cores] who need to be treated [quickly] when we do additional imaging?” asked Dr. Jovin, who was one of the two lead investigators for the Clinical Mismatch in the Triage of Wake Up and Late Presenting Strokes Undergoing Neurointervention With Trevo (DAWN) trial (N Engl J Med. 2018 Jan 4;378[1]:11-21). Another factor undercutting the value of imaging and determining core size is registry results that show patients who undergo thrombectomy with a large infarcted core are not harmed by treatment.