Achieving clot retrieval with the fewest possible number of passes is critical in mechanical thrombectomy, and may even hold greater importance than how quickly the procedure is completed—despite the age-old mantra that ‘time is brain’. That is according to a recent presentation from the European Society of Minimally Invasive Neurological Therapy (ESMINT) congress (7–9 September, Nice, France), delivered by outgoing ESMINT president Jens Fiehler (University Medical Center Hamburg-Eppendorf, Hamburg, Germany), who also claimed that, “at any given time, reperfusion is still better than no reperfusion”.
Fiehler began with a nod to the undoubted relevance that time to recanalisation has, referencing previous studies that have demonstrated the direct influence reperfusion times have on computed tomography (CT) perfusion imaging outcomes. “We definitely have a time dependency and we all know that complete reperfusion is the desired outcome for thrombectomy,” he said. “And, Osama Zaidat’s group [Mercy Health, Toledo, USA] made it clear, really for the first time, that it is also about having complete reperfusion as early as possible.”
Moving on to discuss the lauded ‘first-pass effect’ in thrombectomy, defined as complete reperfusion (thrombolysis in cerebral infarction [TICI] 2c–3) with a single device pass, the speaker noted a “huge difference” between achieving recanalisation at the first pass versus with two or more passes. “Any TICI 3 is already 6% worse [on average] than first-pass TICI 3, and any TICI 2b is worse still,” Fiehler asserted.
Here, he also touched on the fact that several publications have shown higher reperfusion rates are achieved with each successive retrieval attempt—“obviously”, because they are essentially “adding up”—but that the rate of good clinical outcomes does not actually improve beyond the third attempt. And, despite the fact that successful reperfusion will naturally always lead to improved outcomes when compared directly to no reperfusion, Fiehler stated that average outcomes associated with four-plus attempts are “no better than if we did not try at all”.
“But the problem is that we cannot go back in time,” he continued. “We cannot say ‘what if we did not try it’—we did try it, because, at any given time, reperfusion is likely better than no reperfusion.” According to Fiehler, prior research has found that failed reperfusion attempts may be harmful as well, with one study involving TICI 0 patients demonstrating a 40% rate of good outcome in 0–1 attempts versus just 4% with two or more attempts. “So, we can actually harm patients [if we are not] successful,” he noted.
Outlining another illustration of this problem, Fiehler claimed that, while TICI 3 reperfusion at both the first and second pass results in better outcomes than first-pass TICI 2b reperfusion, outcomes following TICI 3 in three or more passes are “no better” than those seen with first-pass TICI 2b. “The conclusion is that you need to be pretty sure that, with the second retrieval attempt, you [will] achieve TICI 3,” he explained. “And, if you do not, then you made the wrong decision and you should have stopped right away.”
Referencing a study published by him and his colleagues, Fiehler noted a trend towards elapsing time being linked to poorer outcomes—even within a group of patients who underwent successful recanalisation at the first attempt. He also informed the ESMINT audience that the issue becomes “really complex” when attempting to analyse which of these two factors, time elapsed or number of passes, independently affects patient outcomes more profoundly. “But, the conclusion was that it is not so much the time that makes the difference—it is the number of passes,” he added.
Fiehler conceded that interpreting many of the ‘per-pass’ data these arguments are based on is “very difficult” as well, owing to the variability that can be found across multicentre, self-assessed studies. He cited the fact that different operators will likely define success differently and make contrasting decisions about, for example, whether or not to continue following the first two or three unsuccessful retrieval attempts, and their decision-making process will also be influenced by the individual patient in front of them.
“Theoretically, the only way to solve this is to have a randomised controlled trial […] and I think the most sensible approach would be to have a randomised trial after the third failed attempt,” Fiehler opined. “Similar things are already happening with ICAD [intracranial atherosclerotic disease] patients—for instance, the ANGEL-REBOOT study in China is randomising stenting versus doing nothing after two failed attempts—and I think this could help us better understand the problem.”
Fiehler concluded that first-pass TICI 3 should always be the operator’s goal and, responding to a query from the audience regarding aspiration versus other thrombectomy techniques, stated: “If you are successful at the first pass with aspiration, that is wonderful, but the problem is more to do with how often we get there. My own thinking regarding these data is that [we should] put everything into the first attempt—rather than simply doing a quick aspiration first and then making a more technical effort later.”