Inari FlowTriever for a Successful Mechanical Thrombectomy

[Michael Barraza]
As I said, I'm not currently using the Inari FlowTriever, but we recently got it approved. Could you walk me through the equipment and a case?

[Thomas Tu]
The pre-procedure assessment of a patient getting a percutaneous thrombectomy is critical. It's important to understand their anticoagulation or thrombolysis status as well as what their respiratory and cardiovascular status is so you know the risks that this patient might need additional support. The physiology of the patient undergoing a pulmonary embolism is that they have acute RV strain and the RV is something that is not used to doing a lot of extra work. It can fail unexpectedly… We try to avoid general anesthesia and intubation if at all possible.

[Venkat Tummala]
I'm 100% in support of what Tom said earlier about sedation. For the Inari procedure, I typically start off with a 6-French sheath in the right common femoral vein.

[Thomas Tu]
I would also mention that about 10% of our users use the internal jugular approach.

[Venkat Tummala]
I get into the pulmonary artery using a pigtail catheter and a good old technique of the back end of a Benson bent in a C-shaped curve. The Benson wire never leaves the catheter but I use the Benson to manipulate the pigtail through the right ventricle into the pulmonary artery. Once I’m there, I don't really do a power injection. Since I have a CTA most of the time, I just get a pulmonary arterial pressure as baseline. Then I do a hand injection to see where I am in the scheme of things. On a side note, very rarely, you could find yourself in the left atrium through a patent foramen ovale or an ASD, so I like to make sure there's no air bubbles and just confirm intraluminal location within the main pulmonary artery. Then I switch out to either a Cobra or a Kumpe 100 cm long catheter, try to get segmental with the catheter, preferentially the lower lobe segmental arteries. Then we use a 1-cm short floppy super stiff Amplatz so that it's just a centimeter-long floppy tip to avoid perforation in the lungs and subsequent hemoptysis and whatnot. Once we have the Amplatz in place, then we use a 22-French Gore DrySeal Sheath in the groin, if you are going with a T20 device. Once we have the sheath, which is about 33 cm long, it's in the intrahepatic IVC. Then, we track the Inari FlowTriever device by itself. If it's a sharp angulation in the pulmonary arteries, you could use a T16 inside a T20 to track the T20 into the necessary location in the main pulmonary artery. Then we aspirate. Sometimes all it takes is two or three good aspirations and then I cross over to the left lung, where I do the same thing. Occasionally you may have to take the device out if it's a long piece of clot, as it can get trapped in the T20 device. Then you maintain your wire access and deflate the valve in the Gold DrySeal. Take the T20 device out, retrieve the clot, and then reassess the situation. We do a repeat pulmonary artery pressure post-thrombectomy and then a power injection for completion's sake to evaluate all the lobar arteries for their patency and whatnot.

[Thomas Tu]
Venkat, that's an excellent summary of the Inari procedure. I just want to underline a few more points. In terms of the phases of the procedure, access is one. We really urge you to use ultrasound-guided access so that you don't inadvertently puncture the artery into vein and therefore create an AV fistula. Passing through the right heart, I think you did an excellent description of how to do so using a pigtail technique. We urge you not to straighten the pigtail, especially with a Glidewire because you could get under a cord and many people do so putting smaller catheters in the lung without realizing it and you can get away with it with a 6 or 8 French system but with a 20-French system, you will not get away with it. And so it's really important to pass through the right heart safely. An alternative technique would be to use a balloon-tipped catheter. Many cardiologists are familiar with pulmonary capillary wedge catheters and balloon-tipped Swan is very effective as well. Lastly is the hemostasis. There are several techniques—figure-of-eight or purse string stitch using a Perclose or pre-close system or just manual compression. Any of those seem to be very effective in hemostasis and we don't see a lot of vascular complications.

[Michael Barraza]
One of the questions I had is about the aspiration because I haven't used this device yet. How are you doing the aspiration?

[Thomas Tu]
The suction itself is applied through a 60 cc locking syringe. This is something specially made by Inari Medical. We attach it using a quick connect to the back of the catheter and then lock the vacuum into place. When we want to activate it, we simply turn a stopcock 90 degrees and all the vacuum is applied in an instant. If you have free flow of blood, you'll see the catheter fill within half a second. That's how quickly this suction occurs. We see aspirational flow rates of our T24 system as high as about 175 cc per second, so you can imagine there's a quick blast of suction that's applied when we turn the stopcock on.

I would mention that aspiration alone to remove the clot is often effective in about 70% of cases. In the 30% of cases where the clot is wall-adherent, then we have the family of Triever disks. These are nitinol disks that are constrained within a catheter. The idea is you pass this catheter through the clot, expose a nitinol disk beyond the clot, and then withdraw this system back into the Triever catheter so you disrupt the bond between the clot and the wall, making that clot susceptible for aspiration. In about 30% of cases, we find that the Triever disks are used and are effective in that regard.