Delay in Dissolving Clots May Worsen Ischemic Stroke Outcomes

HONOLULU—For patients with ischemic stroke, every 30-minute delay in breaking up a blood clot may decrease the likelihood of a good outcome by 10%, researchers reported at the 2013 International Stroke Conference. Other factors such as stroke severity do not appear to alter this correlation.

The results come from a substudy of the Interventional Stroke Management III (IMS 3) trial, which compared the efficacy of IV t-PA alone and t-PA plus endovascular therapy.

In the substudy, Pooja Khatri, MD, Director of Acute Stroke and Associate Professor of Neurology at the University of Cincinnati, and colleagues examined data for 240 IMS 3 patients with major clots in brain arteries who had received IV t-PA and endovascular therapy. Blood flow was restored in 182 patients within seven hours of stroke onset. Patients’ level of disability was evaluated 90 days after they received treatment.

The researchers defined good clinical outcome as a 90-day modified Rankin score of between 0 and 2. Dr. Khatri’s group analyzed angiographic M1, M2, and ICAT occlusions reperfused during the intra-arterial procedure to isolate the effect of time from stroke onset to successful reperfusion.

Time from stroke onset to successful reperfusion ranged from 180 to 418 minutes. Among patients who received successful reperfusion, faster time to reperfusion, NIHSS score of 19 or lower, and lack of prestroke disability were associated with good outcomes in the multivariable model. NIHSS score was similar between patients who were successfully reperfused (ie, 18) and those who were not (ie, 17).

In the larger IMS 3 study, 900 patients with ischemic stroke were to be randomized to IV t-PA alone or t-PA and endovascular therapy. All patients received t-PA within three hours of stroke onset. The trial was stopped in April 2012 after an interim analysis determined that additional therapy was unlikely to benefit patients. Neither t-PA nor t-PA with endovascular therapy proved superior in the trial. Functional outcomes were similar in the two groups, but patients who had an NIHSS of 20 or higher showed a statistically insignificant benefit from endovascular therapy.

“Endovascular therapy is not going away,” said Joseph Broderick, MD, Chair of the Department of Neurology at the University of Cincinnati, and lead investigator of IMS 3. The treatment could be beneficial for patients who are ineligible to receive IV t-PA. Furthermore, time to treatment is crucial for ensuring outcomes, he concluded.