A session on thrombolysis saw discussion on the characteristics of three different thrombectomy devices in the CX Innovation Showcase at this year’s CX Symposium.
Iris Baumgartner, Bern, Switzerland, spoke on the EkoSonic system (EKOS), Gerry O’Sullivan, Galway, Ireland, told delegates about his experience with the Trellis device (Trellis/Covidien), and Kim Hodgson, Springfield, USA, focused his presentation on the Angiojet system (Medrad Possis).
EkoSonic
“The problem we face is that anticoagulation therapy does not actively dissolve the clot and 40% of patients continue to propagate thrombus despite therapeutic levels of heparin. Anticoagulation therapy does not prevent long-term damage to the vein and valves, leading to high levels of post thrombotic syndrome, particularly iliofemoral, and we still have high mortality rates from pulmonary embolism despite anticoagulation,” Baumgartner said.
In 2008, for the first time a grade 2B recommendation for catheter directed thrombolysis was issued by the American College of Chest Physicians, she added. “In patients with extensive proximal deep vein thrombosis, meaning iliofemoral (symptoms
One possibility for the management of thrombus in patients with extensive iliofemoral thrombosis is the MicroSonic Accelerated Thrombolysis (EkoSonic), Baumgartner told delegates.
“This is a catheter system that is inserted mostly in extensive thrombosis via the popliteal vein all the way up to the cava. Ultrasonic energy causes fibrin strands to thin and loosen, exposing plasminogen receptor sites. With extensive thrombus with need high doses and with this system I can lower the dose. Thrombus permeability and lytic penetration are dramatically increased and the ultrasound pressure waves force the lytic agent deep into the clot. As compared to systemic thrombolysis I only need 10% of the dose and this is relevant for bleeding complications,” she described.
Baumgartner referred to a study from Francis et al which showed that thrombus exposed to ultrasound absorbed 48% more tissue plasminogen activator (tPA) in one hour, and 89% more tPA in four hours than thrombus not exposed to microsonic pressure.
“As compared to non-ultrasound accelerated catheter-directed thrombolysis, the overall lysis proportion with the EKOS system is higher and the time needed to resolve is significantly shorter. Major bleeding rates are also lower, although this is on the borderline of being statistically significant as compared to non-ultrasound accelerated thrombolysis.”
“A second field where we now have a grade 2B recommendation is in patients with pulmonary embolism who are not haemodynamically compromised where we have an indication for intravenous thrombolysis,” she pointed out.
Baumgartner added that the EkoSonic system consists of a three-lumen catheter with a wire support that is exchanged by the ultrasound system cooling the area around, and a third layer where we have the recombinant tPA infused, and it goes out directly into the thrombus.
“You can have these areas where you want to treat between 6 and 50cm in length. You can separate your treatment area by decision on which device you are using, 6, 12, 18, 30, 50cm,” she concluded.
Trellis
“I need something which happens in a single session, so Trellis is what I use. You can look at deep vein thrombosis treatment in many ways, but for me single session vs. multisession is the way to look at it. That is the reason why I consider the use of Trellis and Angiojet devices,” O’Sullivan said.
The Trellis device is designed byThomas Fogarty and promotes targeted delivery of thrombolytic agents. The treatment area is isolated within occluding balloons, and there is mechanical dispersion of infused thrombolytic agents and aspiration following treatment.
It is an over-the-wire device, with an 8F sheath.
“You have balloons inflated at both ends of your treatment zone. The treatment zone is where you deliver the tPA or other thrombolysis drug that you choose to use. At the end of the treatment time, which takes 5–10 minutes, you aspirate the tPA out,” O’Sullivan said.
He presented four different scenarios where and how the Trellis device would be used:
- Type 1: Inferior vena cava clear/no pulmonary embolism, ilio-femoral deep vein thrombosis and patent popliteal vein. “This is the easiest and quickest case, with Trellis Peripheral Infusion System only,” he said
- Type 2: Inferior vena cava thrombus/pulmonary embolism and ilio-femoral (and not popliteal vein) deep vein thrombosis: There is need for an inferior vena cava filter but it is possible to treat the case in a single session with the Trellis Peripheral Infusion System.
- Type 3: Inferior vena cava clear, all calf veins acutely thrombosed, deep vein thrombosis up to iliacs: Catheter-directed thrombolysis 48–72h or Trellis system in the popliteal vein upwards and catheter-directed thrombolysis for 24h afterwards.
- Type 4: Inferior vena cava to ankle venous thrombosis: “This is the most difficult case and will need an inferior vena cava filter, the Trellis Peripheral Infusion System and 24–48h catheter-directed thrombolysis,” noted O’Sullivan.
O’Sullivan said that, in the Galway experience of isolated pharmaco-mechanical thrombolysis with Trellis, performance of the device was technically successful. “Technical success with SIR Class 2/3 clearance of thrombus was achieved in 89 out of 91 patients, and primary and secondary patency rates were high. There were no access site haematoma, no bleed requiring transfusion, no gastro-intestinal or intracranial bleed. There was one minor nasal bleed. Overall pharmaco-mechanical thrombolysis is a safe technique with low risks,” he concluded.
Angiojet
Hodgson said that thrombolysis/ thrombectomy devices work in different ways – mechanical vs. pharmacological or vs. a combination of both. However, he said, “what really counts is clearance of the clot and re-establishment of flow but without damaging the thrombosed blood vessel, without damaging the access vessel or pathway to the thrombus, the downstream vessels, tissues or organs, or the bystander organs (brain or kidneys), and achieving thrombolysis rapidly enough to avoid tissue necrosis.”
He told delegates that in terms of successful outcomes, the devices are ‘good’ in chronic thrombi, ‘better’ in sub-acute thrombi and have their best results in fresh thrombi.
“But with increasing age comes increasing drug doses, devices passages and revascularisation times, as well as local and systemic complications and failure to achieve revascularisation. Any claims of superiority for one device over another in actual clinical practice are unsubstantiated,” he stated.
The Angiojet thrombectomy system, he said, is the only device that can work without the use of a lytic agent, it is the only device that has a purely mechanical mode. You can use this without fearing that your patients will develop cerebral haemorrhage, gastro-intestinal bleeding or other problems. It can be used when lytic agents are contraindicated. The system comes in 4–6F catheter diameters, 50–140cm shaft lengths, for 2–20mm vessel diameters.
Hodgson said that the Angiojet device can also be used as a high pressure drug delivery system with its Power-Pulse mode. It promoted deep penetration of lytic agent into the clot. “To varying degrees it extracts the lytic and prevents systemic lysis. But the degree to which this enhances overall efficacy is unquantified.”
Hodgson summarised the pros and cons of the Angiojet device. “The pros are that it is a purely mechanical lysis, or can be used in combination with a lytic drug, and you can treat a broad range of vessels, veins and arteries, and get a rapid restoration of flow,” he said. The cons are that there are some limited run-times, there are potential systemic effects, and the risk of iatrogenic haemorrhage, Hodgson concluded.
