Thrombectomy

Trials

Intra-arterial stroke therapies began in the late 1990s into the 2000s following the landmark NINDS tPA trial showing improved 3 month functional outcome if tPA was given in 3 hours, even though patients experienced increased symptomatic intracranial hemorrhage. ECAS I-III (1995-2008) ultimately established IV tPA as the standard of care into the 3-4.5 hour window.

The 2000's trials also followed on the tail end of a number of PCI trials in the preceding two decades, the 90s serving as cardiology renaissance with the PAMI trials, showing interventional endovascular therapies for STEMI improved outcomes compared to medical therapies despite the added risk of procedure.

The 2000s trials were then followed by the landmark 5 trials of 2015 that shifted the landscape in favor of endovascular therapy and swung the pendulum back. This was followed by late window and large core trials further cementing endovascular therapy before the 2025 medium and distal vessel trials pushing the pendulum back.

The early 2000s started with IA Urokinase (PROACT II) showing improved reanalization but increased symptomatic ICH. This concept of "revascularization" vs "bleeding complication" becomes the overarching theme of endovascular therapy.

EKOS (Boston Sci)

CATCH (Balt)

IMS I showed IA urokinase after IV tPA improved recanalization rates. IMS II used an ultrasound-assisted thrombolysis device (EKOS) that was intended to improve lytic penetration into thrombus - this was apparently painfully slow - and ultimately showed no improved clinical outcome even if reperfusion was established. Finally, IMS III showed no benefit of endovascular therapy over IV tPA alone, but had the added risk of procedure (that "reperfusion vs bleed" equation). Although this included the first generation Solitaire stent retriever, this was still largely Merci retriever, peripheral penumbra, and EKOS systems.

MERCI (Concentric Medical)

Spiotta AM et al., ENDOVASCULAR TODAY Feb 2016 VOL. 15, NO. 2

the renaissance

2013-2020s introduced newer dedicated intracranial devices. Distal access catheters (DAC) sized to the vessel (ICA to small MCA) and new techniques (moving from stent retrievers and thrombolysis) including the "A Direct Aspiration first-pass Technique" - ADAPT.

The 5 pivotal trials of 2015 (MR Clean, ESCAPE, EXTEND-IA, SWIFT-PRIME, and REVASCAT) were primarily stent retriever +\- direct aspiration. Besides the new technologies, also variety of new techniques. The "SOLUMBRA" and "TREVUMBRA" were introduced, and are combining a Solitaire or Trevo stent retriever with a Penumbra system aspiration. These are still primary tools dominating the market in 2025.

Things move fast. "Large" aspiration catheters in 2016 were 0.064 inner diameter but by 2020 became 0.088" followed by "super large bore" 0.092. A number of trials then continue to expand indications into 2025.

MR-CLEAN 2010-2014

19 or older, LVO (about 1/3 ICA+M1, 8% were M2), ASPECT >6, baseline mRS 0-1, NIHSS >2,within 6 hours of symptoms onset - Large study! n=500
Most got tPA BEFORE RANDOMIZATION, 260 min onset-to-groin. 80% were stent retriever.

Similar safety, no change in mortality

Improved outcome, 33% mRS 0-2 in thrombectomy vs 19% in medical management

Importantly for me, although thrombectomy did better, everyone gets better in 24

ESCAPE 2013-2014

Ended early after MR-CLEAN results, and supported MR-CLEAN findings
Similar demographics. Excluded ASPECTS <6. Almost a quarter got tPA. Stent retriever and balloon guide were recommended.
90 day mRS 53% functional independence vs 29% in controls, almost 2x as high again!
This study also showed thrombectomy reduced mortality (but still high overall! 10% vs 19% with medical management).

Same with NIHSS improvement, everyone gets better but favors thrombectomy
Notably, MRCLEAN used GA in 38% but ESCAPE <10%)

EXTEND-IA 2012-2014

Smallest sample size (n=70), also terminated due to MR-CLEAN
CTP used instead of ASPECTS, excluded a calculated core of >70 mL, no mismatch. CTP excluded 30% of patients. mRS 0-2 only again. All got tPA. All had to be within 6 hours. Solitaire stent retriever with aspiration only! Mortality and sICH higher but insignificant (keeping in mind small sampel size, 7/35 dead vs 3 in the control)

2x better reperfusion rates and ~2x better functional outcomes (70% vs 39%)

REVASCAT 2012-2014

Same deal. Very strict though, only mRS 0-1 included. Allowed MRI and again excluded ASPECT 6 or less. Nearly 3/4 got tPA, more in control group. Thrombectomy had to be within 8 hours. Solitaire in almost all!

More of the same, ~2x better functional outcome (44% vs 28%) at 90 days, faster neurologic recovery, but similar overall mortality (~15-20% total, like MR-CLEAN)

SWIFT-PRIME 2012-2014

Trial also stopped early. tPA required. mRS 0-2. Excluded large core again, CT perfusion used again. Solitaire stent retriever only, did not allow tandem carotid stenting, and used GA a lot (like MR-CLEAN)

~2x better functional outcome mRS 0-2 at 90 days (60% w/thrombectomy vs 35%)

Better reperfusion, faster neurologic recovery but mortality not different, again 10-15% range. The only trial to show improved mortality was ESCAPE. There are some other small takeaways like how differences in GA use might affect outcomes, or the use of GBC. These are subject to some debate and not proven.

These 5 trials collectively revitalized the field and cemented the role of endovascular therapy as the standard of care in the treatment of acute ischemic stroke. Across 4 continents, hundreds of patients, primarily with a stent retriever first technique, excluding larger cores, excluding patients with baseline disability, over hundreds of patients a net benefit of thrombectomy in overall functional independent using a modified Rankin score of 0-2 at 90 days is convincingly demonstrated. Although mortality is roughly the same, those who get successful reperfusion recover sooner and have better recovery overall at 90 days. The HERMES collaboration

HERMES collaboration

Highly Effective Reperfusion evaluated in Multiple Endovascular Stroke Trials

Meta-analysis of the 5 big trials to put it all together

New devices, faster work flows, more narrow patient selection

Excluding ASPECTS <6 or Core volume >70 mL

Excluding mRS 3 or more, and in 1 trial even excluding mRS 2

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