Conference Coverage

Recent Thrombectomy Trials Do Not Reduce Pressure to Treat Acute Stroke Urgently


 

Time Is Still Brain

The standard of care for management of acute stroke is IV t-PA within 4.5 hours, whether or not endovascular thrombectomy is offered, according to Dr. Froehler, but he cited data from the SWIFT PRIME trial, which employed endovascular thrombectomy after t-PA, to emphasize that the earlier the treatment, the better the outcome. In SWIFT PRIME, which was stopped early because of efficacy, the greater overall rate of good outcome (mRS 2) in the endovascular thrombectomy/t-PA versus t-PA alone groups were impressive (60% vs 35%), but time mattered. “Of those treated within 2.5 hours, 91% went home essentially normal,” according to Dr. Froehler.

Returning to his message that early reperfusion is the critical predictor of a good outcome, Dr. Froehler noted that an estimated 1.9 million neurons die for every minute of ischemia. In one analysis he cited, good outcomes dropped by 10% between 2.5 and 3.5 hours and then 20% for every hour thereafter.

One approach to accelerating time to appropriate therapy is optimizing triage strategies, particularly when patients who will benefit from endovascular thrombectomy will require transfer to a center that offers this intervention. Of triage strategies, Dr. Froehler singled out the 10-point ASPECTS scoring system, which is based on a CT scan. If the score is low, endovascular thrombectomy is not an option. Higher scores, particularly 6 or greater, can be a reason to consider and accelerate the time to transfer, which may mean the difference for a full recovery.

Reevaluating t-PA

“When you look at what t-PA has done for patients with large vessel occlusion, it is noteworthy, but it is not that great,” cautioned Dr. Froehler in making a case for endovascular thrombectomy in eligible patients. He called recanalization rates with IV t-PA in those with the largest clots “pretty low,” showing that the majority of patients achieve either partial or no recanalization with this treatment alone.

In fact, the therapeutic margin is “rather narrow” for t-PA overall, according to Dr. Froehler, citing data from 12 trials with alteplase. He noted that a review of the original publications reveals that only two of the investigating teams characterized their results as positive. Although almost all the others discussed risk-to-benefit ratios without labeling the findings positive or negative, he believes clinician should be aware of the limitations of these data.

For the newer thrombolytic ten­ecteplase, which was included as an alternative to alteplase in the most recent American Heart Association/American Stroke Association guidelines, Dr. Froehler said the evidence is even more limited, particularly regarding the optimal dose. In the recently published guidelines, the recommended dose was 0.4 mg/kg , even though this dose has been associated with intracranial hemorrhage in at least one clinical study. Lower doses such as 0.25 mg/kg may be a safer alternative, but Dr. Froehler recommended caution. “I do not think there is evidence that we should be transitioning to tenecteplase now,” he said, concluding that more data regarding the most appropriate dose are needed.

Patients with acute stroke can anticipate a favorable outcome with current therapies, but the urgency of reperfusion remains unchanged despite advances. Dr. Froehler concluded, “We must now work toward optimizing stroke systems of care for endovascular thrombectomy” to increase the proportion of patients who benefit.

Dr. Froehler disclosed financial relationships with Balt USA, Control Medical, EndoPhys, Genentech, Medtronic, Microvention, NeurVana, Penumbra, Stryker, and Viz.ai.

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