Transcription
Hi, this is Manus Berlakis from the Minneapolis Heart Institute and the Cardiovascular Innovations Foundation, presenting video 8.4 for the Manual of Percutaneous Coronary Interventions. This video presents four techniques that can be used to remove a microcatheter. Wiring is the eighth of the 14 steps of percutaneous coronary intervention and can be performed in 10 steps, that are discussed in detail in video 8.1. What is addressed in the current video is step number nine, about removing a microcatheter, assuming, of course, that the microcatheter was used in the first place for facilitating wiring. We want to remove the microcatheter while maintaining wire position into the coronary artery, and to do that there are four techniques: trapping technique, the hydraulic technique (also called the Nando technique), use of a guide wire extension, and finally, the circumcision technique.
We'll start by discussing the trapping technique, which I believe is the strategy of choice for performing microcatheter removal, leaving the guide wire in place. Again, the reason for all of these techniques is to maintain the guide wire position in the coronary artery while allowing removal of the microcatheter. In some cases, and over-the-wire balloon trapping can be performed in five steps. The first step is to withdraw the microcatheter inside the guide catheter. Typically, we pull it back as far as possible, and this is how it looks on fluoroscopy. The microcatheter is removed back into the guide catheter; here it is. The next step is to advance a balloon next to the guide wire, digital to the tip of the microcatheter. The balloon can be either a standard compliant balloon; typically we use 2.5 millimeter balloons (2.5 by 20 for 6 French guide catheters) and 3.0 by 20 millimeter compliant balloons for 7 or 8 French guide catheters. Balloons are typically inflated at 15 to 20 atmospheres. The balloon is advanced without a guide wire; therefore, it is very important to not make it exit from the tip of the guide catheter, as this could cause vessel injury. This is how it looks; this is the type of microcatheter, and the balloon is advanced, and now the balloon is located distal to the tip of the microcatheter. There are also dedicated trapping balloons, such as the Trapper balloon, that can be used for facilitating trapping. The Trapper balloon does not have a wire lumen, and that is why it's very important to not have it advanced through the tip of the guide catheter. To prevent that, there is actually a stopping mechanism, but because some guides can be short, it is important to monitor the position of the Trapper balloon. The third step is to inflate the balloon, typically at 15 to 20 atmospheres, and what this does is it pins the guide wire against the wall of the guide catheter. After doing that, then we can withdraw the microcatheter. We typically perform fluoroscopy in the initial second or two during the withdrawal, and if the guidewire position is stable, then there is no need for continued fluoroscopy. In this way, the trapping technique also reduces the radiation dose. This is how this looks: the balloon is inflated, and after the balloon is inflated, it immobilizes the guide wire, and now the microcatheter can be removed without moving the tip of the guide wire. Once the balloon is inflated, we should see disappearance of the guide pressure. If the guide pressure does not change, that should be a source of alarm; that means we're not providing effective trapping. Also, when trapping, it is important to notify the control room and the person who monitors the pressure that we are trapping; therefore, it is normal to lose the aortic pressure for the duration of trapping. Once the microcatheter is removed, the next step is to deflate the trapping balloon and remove it. The final step is to back bleed the sheath. This is a critical step because during the trapping, air can come, and usually does come, inside the guide catheter. So, if the guide and the introducer are not very carefully cleaned, air embolization—sometimes massive air embolization—can occur, as it happened in this particular case. So, it is very critical during trapping to back bleed the guide catheter to empty the air. What I typically do: I have a hemostat next to the guide, and that helps me hit the guide catheter and the introducer and ensure that there's back bleeding and all the air is evacuated. So, five steps for performing the trapping technique. Once again, this is the preferred technique for removing equipment, but sometimes the technique is not feasible, for example, when using bulky equipment through 6 French guide catheters. So, it is good to have other approaches as well.
The second technique is the hydraulic technique, and this technique is performed by using an endoflator or a syringe with normal saline. We pull back the microcatheter as much as possible, connect the tip of the microcatheter with the inflation device, and then inflate to 15 to 20 atmospheres. What this does is it reduces the friction between the wire and the wall of the microcatheter and allows for the microcatheter to be removed while the guide wire remains in place. I am personally not a big fan of this technique because it's unpredictable; quite often it works well, but if it does not, you just lost your wire. And if it's an easy wiring, no big deal, but if it has been a challenging wire, that can be obviously a big problem.
The next option is to use a guide wire extension. Each company has its own guide wire extension; that is important to have those specific extensions for different types of wires. This is an example of how the extension is done for the Asahi wires. The extension part is an extra piece of the guide wire that essentially fits on the back end of the guide wire that we still have in place. It is important to advance it as far as possible to ensure the connection is secure, and after doing that, we now have converted our short guide wire for a long guide wire, and now we can remove the microcatheter under continuous fluoroscopy using this now long guide wire.
The last technique is the circumcision technique; that's the least commonly used technique, and this is most commonly used when there are issues such as stickiness between the guide wire and the microcatheter. What is done in this technique is that the microcatheter is pulled back as far as possible over the short guide wire, and then a scalpel is used to cut the microcatheter around the guide wire. And once this is done, then that piece of the microcatheter is removed, then the microcatheter is moved back again, and then it's cut again until the entire microcatheter is removed. There is actually a specific video of this on how to use the microcatheter circumcision technique that is already uploaded on YouTube.
In summary, there are four techniques for removing a microcatheter when using a short guide wire while leaving the guide wire in place. Those techniques are: trapping, hydraulic technique, use of a guidewire extension, and the circumcision technique. The trapping technique is the preferred technique whenever possible. Thank you.