At the recent Endo Vascular Access (EVA) meeting (14–15 June, Patras, Greece), Ziv Haskal (University of Virginia School of Medicine, Charlottesville, USA) spoke to Timothy Clark (Perelman School of Medicine at the University of Pennsylvania, Philadelphia, USA) about what they referred to as the “gold rush” of thrombectomy devices for large-calibre blood vessels.
Haskal: Is this truly the “gold rush” in thrombectomy devices? Or does this landscape hold no promise?
Clark: There is no question that the portion of patients who are treated with thrombectomy is a small fraction of the number of patients presenting with deep vein thrombosis (DVT). There are differing estimates—we are currently treating somewhere between 4–12% of DVT patients with thrombectomy—you can look at the data and think that that is appropriate, or you can think that that is vastly underutilising endovascular therapy. In the USA, there is only the Acute venous thrombosis: Thrombus removal with adjunctive catheter-directed thrombolysis (ATTRACT) trial that has level one data, and the ATTRACT trial used a semi-quantitative primary endpoint that the US Food and Drug Administration (FDA) required the investigators to use. So, the Villalta score—like all these symptom severity scores—is semi-quantitative at best, and is still a relatively crude metric to assess and compare outcomes, but it is among the best we have.
Haskal: Clinicians like yourself have been pushing to treat patients with lysis well before ATTRACT. Has the expanded recognition of thrombectomy driven individuals to design devices that make money?
Clark: There is no question that there has been a huge surge in the number of dedicated thrombectomy systems and devices in the last several years, and that’s just the tip of the iceberg. There are many more technologies that are in various phases of development and stages of regulatory approval. Now we are going to have a plethora of devices which will make it difficult to choose. The ATTRACT trial had two devices—AngioJet (Boston Scientific) and Trellis (Covidien; now Medtronic)— one of which is no longer in the market and the other is rumoured to being “sun-setted” by the manufacturer at some point in the future. When this happens, we will have no devices that have withstood the rigours of an investigator-initiated randomised trial, and so this leaves us trying to understand where these currently available and emerging systems fit into providing a treatment solution that doesn’t require an intensive care unit (ICU) bed, transfusion for blood loss, or lytics and the resultant need to escalate the level of care and deal with lytic-related complications. So, we all can agree on the attributes of what a perfect device should do.
Haskal: Cost is a fundamental question here, given the extraordinarily high price of these class of devices. Out of cheaper, faster, and safer, we may be able to do safer and faster. What are your thoughts?
Clark: There have been some medical economic estimates that show that the expensive thrombectomy systems are still cost-effective by reducing length of hospital stay and mitigating, or avoiding altogether, the need for expensive ICU stays. Twenty years ago, it wasn’t uncommon for us to perform venous thrombolysis for DVT and require 72–96 hours of urokinase infusions in the intensive care unit, then also have to transfuse the patient if they had blood loss and manage the puncture site haematomas that would occur.
Haskal: For a long time, clinicians still could not get massive pulmonary embolism (PE) patients treated routinely. Now it is more widespread, there is some cost sensitivity to that, but some still struggle with the idea of 18Fr or larger for leg DVT. Is that a concern, or do you see peripheral devices “amping up” to work with smaller catheters?
Clark: I can remember back when certain vena cava filters were being selected by interventionalists because “it goes through a 7Fr or 6Fr delivery system and I don’t want to put that big 8Fr device in”. Now, endovascular clinicians think nothing of putting in a 13Fr, 16Fr, and even larger devices through the popliteal, femoral and jugular veins. Some people are using a pre-close suture technique to get haemostasis. Others are putting in purse string sutures, holding pressure and hoping that that is going to work—and it typically does. I agree there has been an arms race of sorts in PE treatment with progressive escalation of catheter size. You have one vendor that now is up to 16Fr, another goes up to 24Fr, and newer systems are also very large. There seems to be almost no limit. You can also look to the structural heart field where there are trans-venous structural heart systems that go through a 30-French sheath. So perhaps the PE thrombectomy systems have the capacity to get even bigger providing they can safely traverse the right heart into the pulmonary arteries.
Haskal: Do you think it is beneficial to move towards devices that have mechanical actuators and energy-based systems that might be able to increase efficacy and perhaps reduce blood loss, rather than plain old suction?
Clark: With suction, you are limited because you cannot change physics. If your system is an aspiration system, and the tip of the device becomes occluded by impacted clot, there’s just no longer going to be any movement of the clot. You can’t overcome the force.
Haskal: There is only so much, as you say, that you can do due to physics. We need to see devices that move beyond that. Do you see that lying in the long grass out there for us?
Clark: Yes, I see that. I think the other thing that’s not talked about in this post-pandemic world, is that many practices struggle from staffing shortages. There’s a nursing shortage, and a technologist shortage. In the USA, many large health systems and hospitals are, at the present time, financially underwater. Among the most precious commodities we have is time. For example, PE cases aren’t something we schedule. They are add-on cases done urgently and/or emergently as additions to our already busy schedules. So, if you’re incorporating DVT thrombectomy into your already busy interventional practice, when you bring a patient into the interventional suite for a DVT thrombectomy and you don’t know if that procedure is going to take an hour, two hours, or three hours, that becomes a problem. It becomes a huge problem for workflow and staffing demands. As these technologies evolve, if there are systems that can improve procedural efficiency and enable you to basically predict—with a high degree of certainty—whether you’re going to be able to get that patient’s clot out and flow restored in under an hour with little to no blood loss, then these will be incredibly beneficial.
Haskal: Coming full circle, do you feel that this gold rush is because of data that’s arisen from the PE intervention world? There is certainly a lot of interest in mechanical or mechanical-assisted thrombectomy. What are your projections here?
Clark: What informs what clinicians are using frequently is what they are most familiar with. They get comfortable with a system, they learn its little nuances, they figure out workarounds for limitations of that system and they tolerate those limitations. We all have our go-to systems that we use for certain disease states. I think that is true with DVT and PE, and I think on the educational front—the awareness front—or you could also say the sales and marketing front, certain stakeholders are looking well beyond the interventional suite to other points-of-contact in the care cycle for a patient with DVT and say “how can we make other people aware of these catheter-directed therapeutic options?” They are looking to get in front of the decision-makers, whether they are in the emergency room (ER), in the ICU, or on other parts of the front line of people who are seeing DVT and PE, where they can be very influential in determining whether or not a patient is going to end up seeing an interventionist.
