Intravenous (IV) t-PA, a “clot-busting” drug approved by the FDA for the treatment of acute ischemic stroke within three hours of the start of symptoms, has been recognized as the standard of care since the pivotal NINDS clinical trial that demonstrated reduced level of disability 90 days after ischemic stroke in eligible patients who received it. However, the subject of acute treatment with the use of thrombectomy has remained controversial until recently. Thanks to recent clinical trial results, the American Heart Association/American Stroke Association guidelines have now been updated recommending the use of this procedure in eligible patients meeting appropriate criteria.
Depending on the geographical region and practices, approximately one to 25% of acute ischemic stroke patients will receive IV t-PA, with the national average being around six to ten percent. Questions that have continued to plague physicians delivering care to this patient population include:
- What, if anything, can be offered to patients who are not eligible for IV t-PA, but who still present to the hospital within hours of stroke onset?
- What should be done for patients who have received IV t-PA, but who are failing to improve clinically, and there is a known blood clot that remains in a major artery of the brain?
A mechanical thrombectomy is a procedure performed with a catheter (a specialized type of wire) with the intention of physically removing the clot if it is not dissolving on its own or with the assistance of IV t-PA. A mechanical thrombectomy can be performed either with or without the administration of a dose of t-PA directly from the catheter within the artery at the site of the clot.
An early catheter for this procedure was the Merci Clot Retriever. Its tip is shaped like a corkscrew, with the goal being to spear a clot and extract it from the artery, restoring blood flow. This was followed by a suction device, made by Penumbra, which aimed essentially to vacuum the clot from the artery. Despite the excitement around
offering patients these procedures in the acute stroke setting, the outcomes trials were discouraging, largely failing to show improved functional outcomes for patients than they could achieve with IV t-PA.
This has changed in the past year though. Five papers have been published within this timeframe showing improved functional outcomes with mechanical thrombectomy with early therapy intervention. The newer retrieval devices involve the use of wire stents to extract the clot, and the result has been less time required to open the artery to restore flow to the brain. A key difference between these more recent trials and the failure to demonstrate improved outcomes in previous mechanical thrombectomy trials is likely due to the more rapid restoration of flow. The mantra of “time is brain” still holds true. The recent trials have shown what is possible when a team of healthcare professionals collaborate effectively to start the procedure as soon as possible. While thrombectomy may have been available for years, waiting on a key person to become present when the others are ready to start creates delays.
The updated guidelines from the American Heart Association/American Stroke Association emphasize the importance of continuing to treat patients with IV t-PA who are candidates for the drug. After all, IV t-PA can be administered quickly, its benefit has been proven, and it should not be withheld in eligible candidates. However, mechanical thrombectomy with stent retrieval devices provides another tool in the battle against acute ischemic stroke.