NIH-funded study confirms consistently good acute stroke outcomes with Penumbra System


On 13 February 2013 Joseph Broderick University of Cincinnati, USA, and principle investigator of the Interventional Management of Stroke III (IMS III) trial, announced the overall results and major subgroup analyses at the International Stroke Conference in Honolulu, Hawaii. Thomas Tomsick, principle investigator and primary interventional investigator announced results comparing outcomes by intra-arterial approach.

The IMS III trial was a prospective, randomised trial comparing two different treatment approaches—combined intravenous and intra-arterial therapy, and standard intravenous r-tissue plasminogen activator (r-tPA)—to restore blood flow to the brain. The primary goal was to determine if individuals with ischaemic stroke treated using a combined intravenous and intra-arterial approach to recanalisation started within three hours of onset are more likely to have a better outcome than individuals treated with standard intravenous r-tPA alone. IMS III began enrolling in 2006.

In the device-based intra-arterial intervention subset, The Penumbra Aspiration Thrombectomy System showed 84.6% TICI 2-3 revascularisation of ICA and/or M1 occlusions vs. 72.8% for the Retriever category overall (72.7% for the Merci Retriever and 75% for the Solitaire Stent Retriever). Penumbra Aspiration Thrombectomy also achieved 33.3% of patients living independently with a good clinical outcome vs. 23.5% for the Retriever category overall (23.4% for the Merci Retriever and 25% for the Solitaire Stent Retriever.) The study showed that the proportion of good clinical outcomes increased with greater reperfusion rates.

The safety record of the Penumbra System also fared very well when compared to the Retriever category devices. Mortality among patients with ICA and/or M1 occlusions treated with the Penumbra System was very low at 17.9% vs. 33.3% for Retrievers (33.8% for the Merci Retriever and 25% for the Solitaire Stent Retriever). Embolization to New Territory (ENT) when using the Penumbra System occurred only 3.7% of the time vs. 23.0% of the time when Retrievers were used in any treated vessel (22.1% for the Merci Retriever and 40% for the Solitaire Stent Retriever.) The study demonstrated that a stroke patient’s chance of achieving functional independence was very poor when ENT occurred. Without ENT, 30.2% of patients made a good recovery. When ENT occurred, only 17.9% of patients made a good recovery.

IMS III subgroup comparisons by intra-arterial approach

ICA and/or M1 occlusions


Penumbra System


Retrievers Overall



Efficacy endpoints







Revascularization (TICI 2-3)






Merci: 72.7%
Solitaire: 75%

Functional independence (mRS <= 2 at 90 days)






Merci: 23.4%
Solitaire: 25%

Safety endpoints













Merci: 33.8%
Solitaire: 25%

Embolization to New Territory (ENT) per Core Lab (all treated vessels)


3.7% (n=54)


23.0% (n=100)


Merci: 22.1%
Solitaire: 40%




“I am not surprised that the Penumbra System data is better than the other interventional techniques in the IMS III trial,” said Blaise Baxter, director of Interventional Services at Erlanger Hospital in Chattanooga, Tennessee, USA. “The newest devices in the Penumbra System armamentarium, like the 5MAX Reperfusion Catheter, allow us to stay at the site of occlusion using direct aspiration to make sure we remove all of the clot and prevent any embolization to otherwise unaffected territories.”

J Mocco, associate professor of Neurological Surgery, Vanderbilt University Medical Center in Nashville, Tennessee, USA, and principle investigator for the prospective, randomised THERAPY trial of acute stroke intervention said, “The IMS III trial did not use an imaging-based patient selection criteria to screen patients for enrolment. In fact, over 20% of patients enrolled in the intra-arterial arm of IMS III did not even receive intra-arterial therapy. The vast majority of these were because the patient was deemed to have no significant brain artery blockage.”

“Moving forward it is critically important to identify those patients that have a high potential for benefit from intra-arterial intervention, meaning those with a treatable brain occlusion, as well as those hypothesised to have a low likelihood of improving with intravenous tPA alone. The THERAPY trial uses a very easy to implement clot length criteria which we believe will identify exactly this patient group. The ease of determining clot length, and its ability to define a large treatment effect for endovascular therapy, has now been shown in two large trials, one out of Germany, and another recently presented by Albert Yoo et al from Massachusetts General Hospital, USA, here at the International Stroke Conference,” Mocco continued.

“A growing consensus among top stroke hospitals was achieved during a packed meeting at the International Stroke Conference. This consensus points toward a trial design that includes both appropriate imaging-based screening criteria, and the use of the most modern and advanced technologies including Direct Aspiration, and clot capture devices like the Penumbra 3D. THERAPY’s design, and its inclusion of the latest technologies, is strongly supported by data from large, NIH-funded studies such as IMS III and MR Rescue. We owe a huge debt to the work of those pioneering investigators in helping to point the way forward,” concluded Mocco.