Results of the CHEETAH clinical study highlight the potential role of mechanical aspiration thrombectomy in conjunction with percutaneous coronary intervention (PCI) in native coronary arteries in patients with high thrombus burden according to the study’s principal investigator, Jay Mathews (Manatee Memorial Hospital, Bradenton, USA). Mathews spoke to Cardiovascular News following the presentation of the study’s findings at the Transcatheter Cardiovascular Therapeutics annual meeting (TCT 2021, 4–6 November, Orlando, USA and virtual).
Trials including TASTE and TOTAL have previously investigated the utility of routine thrombus aspiration in patients undergoing PCI. “They found that routine manual aspiration really did not show any benefit, and of more concern did show an increased rate of stroke,” Mathews explains.
In 2018, the TOTAL authors studied a subset of patients with high thrombus burden from the trial. They found an increased rate of stroke in the high thrombus burden patient subset, but with a reduction of distal embolisation.
This was the rationale for the CHEETAH clinical study, Mathews tells Cardiovascular News. “Essentially everybody has shied away from thrombectomy, which we believe is appropriate, but the concept still exists that selective bailout thrombectomy in high thrombus burden patients may potentially be beneficial if the technology was better, so that is what CHEETAH was trying to show,” he says.
The prospective, single-arm study enrolled 400 patients with high thrombus burden who were treated with continuous mechanical aspiration prior to PCI using the Indigo CAT RX catheter system (Penumbra). “CAT RX is a novel technology in comparison to prior aspiration catheters that have largely been held back by the limitations of manual aspiration, which is that the suction force drops off significantly over time,” Mathews explains, adding that CAT RX combines a large bore catheter and allows for continuous powered aspiration. “The reason why this is effective is it is able to maintain a continuous aspiration force throughout the entire duration of the procedure, as it is a powered system,” he adds. “This is a significant advantage over these syringes that have been used in the past.”
When performing PCI in patients with high thrombus burden without aspiration, the key concerns are the emergence of distal embolisation and potential damage to areas of the vessel that do not have a lesion, Mathews explains. “When you have thrombus you cannot really see where the true lesion is and so you may indiscriminately perform angioplasty in areas that do not necessarily need to be intervened upon,” he adds.
Patients were eligible for the trial if they had a Thrombolysis in Myocardial Infarction (TIMI) thrombus grade of 4 or 5, “a very high thrombus burden”, according to Mathews, and post-wire crossing. Patients were treated within 12 hours of symptom onset. Primary endpoints of the trial included a composite of major adverse clinical events (MACE) including cardiovascular death, recurrent myocardial infarction (MI), cardiogenic shock and new or Class IV hear failure. Secondary endpoints included final TIMI flow and thrombus grade, myocardial blush grade (MGB), distal embolisation rate, and device-related adverse events and stroke within 30 days.
Headline findings presented by Mathews at TCT include an overall freedom from MACE of 96.5%, as well as a significant reduction in TIMI thrombus grade, with 99.5% of patients having achieved TIMI thrombus grade 0 after CAT RX and PCI. Investigators also reported that the procedure improved TIMI flow grade with 97.5% of patients having TIMI flow grade 3 after CAT RX and PCI, while TIMI 2‒3 increased significantly from 16.6% at baseline to 85% after CAT RX alone. Additionally, the study found an enhanced MGB, with 99.8% of patients having achieved MBG 3 after CAT RX and PCI—described by Mathews as the most impressive take away from the study. Finally, no device-related serious adverse events occurred.
Asked for his view on the implications of the findings, Mathews expresses cautious optimism—noting that a larger study is needed to inform any future change in practice.
“We used the word tantalising, because finally we have a device that works really effectively within the high thrombus burden space. Of course, changing practice cannot really be done without more data, but the present findings really point towards reopening this door and really looking at utilising this type of device in this population,” Mathews comments.
“Certainly, it is going to invite more study and I think there are a lot of people who are very much interested in this now because, really, there has been no advance in the thrombectomy space for years, partly because everybody thought that the story was closed after the TOTAL trial.”
In particular, Mathews believes the enhanced MGB witnessed among patients undergoing mechanical thrombectomy is a particularly key finding from the study, and says this should be an important area for future research.
“I think CHEETAH now suggests that maybe this story is not over and that there could be a huge potential as MGB, as a surrogate marker, does seem to be associated with better outcomes in these patients in general. So, I think that we certainly will want to continue to study this and hopefully change practice in the future.”
In terms of research into mechanical aspiration after PCI, Mathews said he believes CHEETAH is “just the beginning”.
“Even though these numbers are incredible, there are other questions that still need to be asked too—like ‘can we show improvement from an economic standpoint?’, ‘can we make PCI more efficient?’—there are a lot of other questions that I and our other investigators have that we are going to look at as we mine the data,” Mathews concludes.