Hit NOT miss

How do you avoid placing a stent too far into the vessel? With the help of the Ostial Pro Stent Positioning System, says Dr. Tim Fischell, Director of Cardiovascular Research at the Borgess Heart Institute, Borgess Medical Center.

EHM. What was the rationale for the development of a stent positioning system?

TF. There has historically been a very big problem with the accurate positioning of stents at blockages that occur in the aorto-ostial position. It’s kind of hard with a catheter that injects contrast to see exactly where the blockage starts. Sometimes, the catheter slips into the vessel, in which case you miss the blockage. In about 80 percent of all misses, the stent is placed too far into the vessel such that the stent does not open the vessel where the blockage is.

If you miss the blockage, you only have two choices. You have to put another stent in overlapping the first one and hope not to miss it again. The other miss is that you pull the guiding catheter back and with it the stent. The contrast that you inject is in the aorta, and you can’t see anything. Besides, you may very well leave three to five millimeters of stent sticking out of the vessel into the aorta. This makes it virtually impossible to ever get a catheter back into that blood vessel again.

Both types of misses are expensive, time consuming and potentially increase risks for the patient. And if you don’t treat it, or just treat it with a balloon, you have an 80 or 90 percent re-blockage risk. So there is no such thing as a good miss here. The intended use of the Ostial Pro Stent Positioning System is to assist in a very user-friendly manner the precise positioning of a stent at an aorto-ostial blockage location including the right coronary, the left main saphenous vein graphs, renal arteries and occasionally other arteries that arise from the aorta like the superior mesenteric artery. We’re hoping to get exact placements in about 90 percent of all cases instead of about 40 or 50 percent, which, according to our marketing polls, is the average rate at which an interventional cardiologist misses the blockage.

EHM. Could you describe the device in more detail?

TF. The stent positioning system is made out of nitinol, a memory metal used for standard guiding catheters for either the coronary or the renal. At the distal end of the nitinol wire is a tiny cylinder. On the end of the cylinder are four little nitinol legs that have gold plating on the tips.

The way this works is that you load this device into the guiding catheter. You then proceed as usual. That is, you put the guide wire through the blockage, down the vessel. You then advance the stent delivery system through the cylinder of the Ostial Pro into the vessel. Then you just put the guiding catheter back a tiny bit and advance the Ostial Pro until the four feet pop out. They pop out at about a 30-degree angle.

As you advance the Ostial Pro legs and feet they engage the aortic wall. By doing so they prevent the guiding catheter from going into the vessel. You won’t think you’re in the aorta when you’re really inside the artery. The device will prevent the catheter from entering the artery because the feet are planted on the wall of the aorta.

By preventing you from getting too far in you prevent a miss. You also have a tactile feel. That is, you actually feel the device pushing on the aortic wall. You can feel it, see it, inject contrast and very accurately see the plane of the aortic wall and the aortic blockage.

At that point, when you have it aligned properly, you pull the stent back, lining it up perfectly using all of these markers: feet, the contrast, the guiding catheter tip. Then you expand the stent. We think this will allow you to get it in the right place within 0.5 to 1.0 millimeter of where you want it.

EHM. Who are the product’s end users?

TF. The end users of this product will be interventional cardiologists, predominantly the ones who will use the device for right coronaries, vein graphs, left main arteries. In addition, we expect interventional radiologists and some interventional vascular surgeons will use this device to assist in the placement of stents in peripheral vessel problems, in particular for the renal artery.

EHM. What about product compatibility?

TF. This device is specially designed so that it is compatible in coronary artery applications with virtually anyone’s stent platform. In other words, this is not restricted to being used with, for example, a Boston Scientific, a Medtronic or Abbott stent. This is compatible with all coronary stents.

In the renals, we believe it should be used with either seven or eight French guiding catheters because the stents are much bigger. It will depend on how big a stent is being used for the renal, but it may require a guide as big as eight French in some very large renals. In more normal-sized renals, it will be used with a seven French guiding catheter. It is compatible in coronary artery applications with either a six, a seven or an eight French guiding catheter.

EHM. How many coronary aorto-ostial blockages are being stented each year?

TF. We believe that somewhere in the range of six to seven percent of all coronary interventions involve the treatment of an aorto-ostial blockage, that is either a right coronary, left main or vein graph. So by the end of 2007, about 100,000 procedures of stenting of aorto-ostial coronary artery blockages will have been undertaken in the US. Worldwide 150,000 to 175,000 coronary aorto-ostial blockages are being stented each year. In the renal market, about 60,000 renal artery ostial stenting procedures occur in the US and 90,000-100,000 worldwide.

The worldwide market for this device potentially is in the range of 250,000 to 270,000 uses per year. It’s important to point out there are no other devices cleared, approved, or available in the world today to assist physicians with this difficult problem. This is a unique device, which has no competition at this moment and should create the market for accurate positioning for aorto-ostial stenting.

EHM. When will we see the device on the market?

TF. The device has recently received FDA clearance for commercialization under a 510K. We’ll be rolling out the product in a limited release to some highly trained investigators to get more feedback about its proper use, and its ease of use. We have tested it, so far, in six clinical cases thus far with excellent results. In each of these cases the stent was paced in an ideal location, as confirmed by angiography and intravascular ultrasound.

We plan to gather 50 to 100 cases in experienced hands and make sure this device works as reliably as we believe it will. It’s a very simple device. Based upon our initial clinical cases we believe that this tool will be rapidly adopted as a standard of practice.

Dr. Tim Fischell is the Director of Cardiovascular Research at the Borgess Heart Institute, Borgess Medical Center, Kalamazoo. He is also Training Director and Professor of Medicine at Michigan State University for the interventional cardiology fellowship training program. A clinical interventional cardiologist, he is the primary inventor of the Ostial Pro Stent Positioning System.