Innovation continues in thrombolytic-free thrombectomy

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Stephen A Black

In this article for Venous News, Stephen A Black discusses innovation in the field of thrombolytic-free thrombectomy. He considers “exciting” new developments in mechanical-only approaches and concludes that, “We are making progress on our important objectives as vascular specialists using innovative technologies and approaches to continue to push the boundaries of how we can deliver better outcomes in the treatment of DVT [deep vein thrombosis]”.

As vascular specialists, our main goal in treating deep vein thrombosis (DVT) is to remove the thrombus in order to eliminate post-thrombotic syndrome (PTS). PTS can cause painful, debilitating symptoms and impact a patient’s quality of life. The holy grail for DVT treatment has been the concept of removing the thrombus in a single session without the use of thrombolytic agents. We know the Achilles’ heel of the procedure is dangerous bleeding complications for some patients which are directly related to thrombolytics, hence, the desire to develop non-lytic based therapies. We also need to do so in a cost-effective way. By doing this, we are striving to positively impact the up to 50% incidence of PTS in patients with DVT, as reported in ATTRACT, and the significant associated risk of bleeding in the treatment arm reported in this study.

There have been exciting new developments in mechanical-only thrombectomy approaches that are designed to reduce the need for thrombolytics and engineered specifically for venous use. We have struggled with thrombus removal using devices that were not engineered specifically for the venous system, as there are fundamental differences between arteries and veins that require different technological approaches.

It is exciting that some new wall-contacting technologies have recently reached the market and offer some promise. However, this solution is not the end; it is only the first step to getting to single session thrombectomy reliably, and without the requirement for thrombolytics. Further innovation is underway to improve upon the initial venous-dedicated technologies.

The evolution to the dynamic cage

Innovations that are currently in clinical study include a device with a mechanism of action that goes beyond “coring,” or piecewise removal of thrombus—a coring approach requires many passes to get the thrombus out. New technology utilises a dual-action approach of a “dynamic cage” consisting of a screw and basket combination to predictably remove wall adherent thrombus through wall-to-wall contact. This dual-action technology gives us the best of both worlds, where we can really target the wall-adherent clot while simultaneously transporting it out of the body. The cage dynamically self-adapts to the vessels’ various diameters, and this conformability of the cage to the vessel is an important efficacy and safety feature of the device.

We have had an opportunity to be part of a first-in-human study of this new innovation in 19 patients and are very encouraged by the device and patient outcomes.

Smaller may be better

The use of a smaller catheter—down to 10 French—that is designed for venous use is being studied in this trial. We saw that the smaller diameter catheter tracked well in a retrograde fashion and was easily delivered to the cranial iliac vein. This 10F catheter is significantly smaller than some recent devices and also has the obvious advantages in terms of the size of the access site puncture that is required, thereby mitigating the potential impact on bleeding complications that can arise from larger access site punctures.

Efficient thrombus removal with no safety issues

The procedure is relatively intuitive, and we are seeing an average of just over two passes with this investigational technology to remove wall-adherent thrombus safely and in a relatively efficient manner. This was achieved without the use of thrombolytics in the vast majority of patients we have treated, with a procedure time of approximately 25 minutes, which includes imaging assessments.

The self-adjusting cage technology that conforms to the vessel diameter being treated reduces the risk of damaging either the vein wall or valve mechanisms as clot thrombus is removed. This is corroborated by our patient follow-up observations, where patient symptoms and quality of life scores showed significant improvements in follow-up visits completed out to 12 months.

Figure 1: Baseline (L) and post procedure (R) venograms showing restoration of rapid in-line flow

Improving upon ATTRACT

This promising approach is showing a trend of improving upon the ilio-femoral sub-set analysis results from ATTRACT, which itself showed an improvement in the severity of post-thrombotic syndrome. From the ATTRACT data, we would expect 52% of patients to experience post-thrombotic syndrome, but with this technology we have seen significant improvements in PTS rates, with mean data scoring out to one year showing no PTS within the clinical study, albeit in a small and highly selected population.

Potential for improved costs and efficiencies

This technology also offers the potential to increase procedural efficiency while also improving the cost dynamics of thrombus removal in the clinic. Reviewing the device’s ease of insertion, fewer passes to remove thrombus, minimised need for thrombolytics and overnight stay, and a mean thrombectomy procedure time of 25 minutes in difficult-to-treat patients—all of these attributes contribute to the exciting possibility that we can not only make thrombectomy a better procedure for the patient themselves, but also for the healthcare system. This data obviously needs further validation in the context of a larger study.

These promising early results reinforce that this type of approach is the future of thrombus removal, as no thrombolytics were used in the vast majority of patients and a successful thrombectomy was achieved in all cases with very positive patient outcomes observed during follow-ups.

The clinical outcomes and very low venous disease severity scores we are seeing in our investigation of this new technology is really encouraging and demonstrates that we are making progress on our important objectives as vascular specialists using innovative technologies and approaches to continue to push the boundaries of how we can deliver better outcomes in the treatment of DVT.

Stephen A Black is a consultant vascular surgeon at Guy’s and St Thomas’ Hospital NHS Foundation Trust and professor of Venous Surgery, Kings College Hospital, London. He is also a programme director for the Charing Cross Vascular Symposium.

Disclosures

The author receives consulting and speaking fees from Gore, Cook, Boston Scientific, Medtronic, Optimed, Veryan, Vesper, Phillips-Volcano, BD, Bard, and Vetex Medical. They are on advisory boards for Gore, Phillips-Volcano, Boston Scientific, and Vesper.


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