Cath Lab Digest

We designed the staple with a surgeon’s mentality, and chose titanium as the metal. Titanium is a very cheap, very inert metal that actually is what surgeons will implant most of the time with heart valves and with hip replacements. The staple is a very small, low-profile 3-mm staple. Figure 2 is really 3 millimeters, and portion A is designed to sit above the artery. The B portion is designed to actually implant into the outer walls of the vessel, avoiding the lumen of the vessel. This VCD is totally extraluminal in its action, which is one of its major advantages.

Closing the Vessel from the Outside

When we do coronary bypass surgery, when the heart is beating, we will put a tube in the aorta the size of a thumb. In order to do that, we put a suture on the outside of the aorta with little pledges, and then as soon as we pull the tubing out, we tie the suture. This is the classic purse string suture, which is used hundreds of times a day in cardiac and vascular surgery, and is the same concept we want to develop in the cath lab to close vessels from the outside. The EVS staple is designed to open, expand, move forward and grasp tissue just the way a surgeon would suture around the vessel outer wall (Figure 3). In the OR, the purse string suture is then tied down over the arteriotomy, closing it from the outside and avoiding narrowing of the vessel lumen. The current staple design will open to accommodate a 15 Fr arteriotomy, but can be designed for closing smaller or even more exciting larger holes, so this device has the potential of closing all of the larger sheath-based technology coming on the scene. You pull the trigger and a little plunger makes the staple open; it expands and it purses (Figure 3). Again, we call this a purse string effect and what it gathers is the femoral sheath, the adventitia and the media of the vessel wall, which are the outside layers, not the inside, meaning no narrowing, no injury, and no thrombosis. The Angiolink closes the arteriotomy in one single pull of the trigger. The staple device is also sterile and loaded in a separate delivery system.

Figures 4-5 are from a bovine model, and are magnified, showing the arteriotomy viewed from inside the vessel. You can see what the device looks like in a bovine artery, and what the outside and inside of the artery look ike with multiple closures. Again, there are no endoluminal components, and no narrowing of the lumen. The device basically closes everything from the outside in. Figures 6-8 show the current device, but there is also a newer design, a second generation, which will be the one that will probably go on the market if FDA approval is given (or it will be available soon thereafter). The second generation device can be deployed via the existing case sheath and not via an introducer sheath.

At this time, the device has a 3-step introducer. When we first got involved with the device four years ago, there were 18 steps; it drove you crazy. It’s not easy to design a staple VCD, so we’ve gone though a lot of technical changes to make it happen. You will localize the artery lumen, similar to what needs to occur with a Perclose® device (Abbott Vascular Devices, Redwood City, CA). A bleed-back port allows you to localize the vessel. You have to stabilize the anterior vessel wall with the introducer step. The whole question here is, if you’re going to bring something down from above, how do you localize the arteriotomy and how do you stabilize it? Through the introducer system, we are able to stabilize the anterior wall and then bring in the completely sterile staple with the trigger-released staple mechanism.

Staple Sterility: No Infection

Since the staple is completely sterile until deployed at the artery level, we’ve removed infection from the whole process. You don’t think of stents getting infected, because they really and truly don’t. That’s because they are inert metal, inserted completely sterile to the level of the artery. Collagen, sutures, etc., if they are flipping around on the wound, may increase the risk of infection. One of the reasons we designed the inert staple-mediated VCD was to address the complex infection issue.

How Does the Device Work?

The staple is loaded into the introducer sheath above the artery; you pull the trigger and the staple opens, expands, grasps the femoral sheath above the artery, the adventitia, and then the media and this closes the arteriotomy, all with a single trigger pull. Figure 9 is the arteriotomy, shown closed as a slit between the pledget-like arms of the staple. You can see little nitinol filaments which we call the feet that stabilize the anterior vessel wall. As you pull the trigger, the introducer system gives you the anterior wall support that you need. Then, with the last release of the trigger, the nitinol filaments straighten out and pull out of the wound immediately, just as the staple is deployed.