Conference Coverage
Late Thrombectomy Improves Ischemic Stroke Outcomes
LOS ANGELES—When performed between six and 16 hours after stroke onset, thrombectomy plus standard medical management yields better functional...
HILTON HEAD, SC—Although two recent studies demonstrated that endovascular thrombectomy is effective up to 24 hours after acute stroke onset in patients with large vessel occlusions, the findings do not diminish the urgency of rapid intervention. According to one expert who spoke at the 41st Annual Contemporary Clinical Neurology Symposium, findings from studies of late thrombectomy are important to the management of only a small group of acute stroke patients and do nothing to alter the premise that time is brain. For better outcomes, “we need to get more patients into therapy more quickly. If we optimize our systems of care, we can achieve that,” said Michael Froehler, MD, PhD, Director of the Cerebrovascular Program at Vanderbilt University Medical Center in Nashville.
Michael Froehler, MD, PhD
Two Trials of Late Thrombectomy
In an analysis of the significance of these two studies as well as of other advances in stroke management, Dr. Froehler explained that rapid intervention is always the goal. The data from these multicenter trials, DAWN and DEFUSE3, were published earlier this year. Both randomized studies compared endovascular thrombectomy with standard care in patients with large vessel occlusion. The window of enrollment was six to 24 hours after stroke onset in DAWN and six to 16 hours in DEFUSE3.
The primary end points of the two trials differed, but the advantage of endovascular thrombectomy was comparable at 90 days when examining a modified Rankin score (mRS). A good outcome, defined as an mRS of 2 or less, was achieved with late endovascular thrombectomy in 49% and 45% of patients in DAWN and DEFUSE3, respectively, versus 13% and 17% of those treated with standard care. According to Dr. Froehler, these results were a surprise, because the effect size was greater in these two late treatment trials when compared with that of early endovascular thrombectomy (46% vs 27%) in a five-trial meta-analysis by Goyal et al published in 2016.
Entry criteria of these late endovascular thrombectomy trials are critical for understanding the results and their clinical significance, according to Dr. Froehler. He explained that both DAWN and DEFUSE3 were designed to enroll patients with salvageable tissue. Selection criteria such as a small infarct volume on imaging assessed with RAPID software ensured a “good collateral” patient population, Dr. Froehler said. Unlike the majority of patients with rapidly advancing infarcts, “good collateral patients hang on to salvageable brain for much longer,” Dr. Froehler explained.
The results of DAWN and DEFUSE3 thus are relevant to a small subpopulation of stroke patients. According to Dr. Froehler, only about 3% of acute stroke patients would meet entry criteria for DAWN or DEFUSE3, and only about 1.1% would meet the criteria for both.
“Unfortunately, the vast majority of patients we are seeing in real life are not going to be eligible for thrombectomy in the six- to 24-hour window,” Dr. Froehler emphasized. As a result, the data from DAWN and DEFUSE3, “do not change the importance of time” as the key factor in achieving good outcomes in patients with acute stroke.