So I'm going to first talk about guiding catheters and then we'll talk about the anticoagulation part. So let's do a pre-test first. So we have a 71-year-old female who is in the cath lab for an atherectomy to her left anterior descending artery. We've finished the diagnostic catheter with a tiger catheter, which is in the left main. So question is, what are the next steps? Go ahead and proceed with the diagnostic catheter, go ahead with the wiring and continue with intervention, or do you need to switch to a six-fringe guide catheter and then proceed with the wiring of the vessel? So our objectives for this are, one, why do we need a guide catheter? Can we do it through a diagnostic catheter? How do you decide on the type of guide, the size of guide? How do you decide on the support? And how is a guide catheter then different from a diagnostic catheter? And also, are there differences in guide catheters based on your axis, from femoral axis to transradial axis, which could be left radial or right radial? And what are these new sheathless guides that have now come into the market? So the purpose of a guide catheter in most basic terms is to work as a conduit to get you to the coronary artery with the least amount of friction that it can. Now for you to be using equipment, you need to increase the inner diameter of the catheter. And we'll look at some images to understand what it means. You need a catheter which is going to give you some torque control in case you have to get the catheter into the coronary, give you enough stiffness so that it does not just back out at every, you know, buckling or every slight resistance when you're crossing a lesion. And then inner lumen, which is, let's say, reducing friction and an outer lumen, which resists thrombus formation. And on top of that, the other important part is the tip of the catheter has to be a traumatic because it's going to sit in the coronary artery. Now this is a basic shape. Again, there are different shapes of catheters, but the basic shape of the catheter, you have a hub, then you have a shaft and you have a tip. Now there are some curves, a primary and secondary curve, which again differ based on the type of the guide. And typically there tends to be a radiopic marker at or close to the tip, not exactly at the tip of the catheter, but it's close to the tip of the catheter. So you can identify its presence on fluoroscopy. Now this is one of the important slides I think we should all understand. Now when we talk about a sheath, let's say a femoral axis sheath or a radial axis sheath, the sheath size is actually determined by the inner diameter of the sheath. When we say a six French sheath, it means the inner diameter of the sheath is six French. The outer diameter is bigger. If you use a diagnostic catheter or a guiding catheter, when we say a six French catheter, that means it's the outer dimension of the catheter, because that outer dimension of the catheter has to fit in the inner dimension of the sheath, hence the separation there. Now if you think about it, if you have a thick sheath and you put in, let's say the middle image here, which is the green diagnostic catheter, you're left with very little space in the middle now to use your equipment. You have your balloon, you have intravascular imaging, you have your stents. So it limits the amount of space, increases the amount of friction, and again interferes with your intervention. Hence these guiding catheters, what they do is maintaining the outer dimension, which is let's say six French in this shape, they increase the inner dimension by thinning out the wall. Now by thinning out the wall, you increase the size, but you also make the catheter, let's say thinner, hence more likely to bend or kink, hence needing a type of, let's say material which would increase the strength. So you're not just, you know, kinking and buckling every time you're trying to get through a tortuous vessel, let's say from the groin or a subclavian tortuosity. Now this is that example of what we were talking about. Here on the left with what I've circled with the blue circle. Now if you see a six French diagnostic catheter, the inner dimension of a six French diagnostic catheter is about 1.4 millimeters. Now same thing on a guide catheter, a six French guide catheters inner dimension is about 1.78 millimeters and the increase in this inner dimension is achieved by reducing the thickness of that catheter. Now there are these new sheathless guides which are more relevant to our radial axis. Now one of the limitations of radial axis is that the radial artery has a particularly small size. Now if your radial artery is smaller, you typically can't overdo how much you can distend that radial artery. So you can do a six French, maybe a seven French. The moment you go above it, you increase the spasm risk, you increase thrombosis risk, more damage to the vessel. Hence you're limited by how much you can go up on the French sizing. So here, now if you remember a few slides back, we said when we talk about a sheath, the sheath size is the inner dimension, but the outer dimension of the sheath could be bigger. So these sheathless guides, what they do is you can do these without a sheath in place. And if you see, let's say in the bottom half of this or the bottom part of the screen, a five French sheathless guide catheter essentially has a dimension of a three French diagnostic catheter because of an absence of now a sheath. And these help you by giving you higher French sizing with what you can do on a radial axis. If you see the blue sheath here, you can see that it's an eight and a half French sheathless guide catheter with a diameter of 2.8, which would have been very close to what a six French sheath would have given you. So it gives you more French sizing of your guide catheter without the limitations of the radial arteries. Now how is a radial or femoral guide catheter different? Now one of the important differences in radial that you will often hear about are lack of support and that lack of support from radial guide catheters is because of a few things. One is difficulty in achieving a coaxiality of catheters. So your catheters are not always coaxial looking left or right or up or down, which is then based on how the anatomy is of the brachiocephalic, how much tortuosity do you have in the subclavian and is it a left or a right radial axis. A lot of times from the left radial axis, you can essentially use most of your guide catheters that you would use from the femoral axis. But if you have a right radial, you're often limited by the subclavian tortuosity and the entry of the brachiocephalic trunk into the arch. Hence, sometimes you might end up needing some specialized catheters with different shapes like Aikari guides, which will give you more support for your interventions. Now, there are different shapes of guide catheters, again, depending on which coronary you're engaging. Are you engaging a native coronary? Are you engaging a graft? Are you engaging internal mammary artery? Again, depending on the size of the aortic root, the takeoff of the coronary. So there are many things that play a role in what guide catheter you choose. Hence, you need a diagnostic angiogram to kind of identify which catheter would be ideal for intervention.

guide catheters

angioplasty procedures

coronary artery

sheathless guide catheters

French sizing