Fig. 22.1
Distribution of radial artery diameters of 250 Japanese patients, along with the percentage of males and females eligible for surgery with 6 Fr, 7 Fr, and 8 Fr catheters respectively
The evolution of interventional equipment and materials has been led by the Slender Club Japan (SCJ) which was initiated by Dr Fuminobu Yoshimachi. They have revolutionized TRI and created a plethora of innovative manoeuvers, which has sprouted the new field of TRI called “Slender TRI” [6].
22.2 Slender Techniques
Slender PCI encompasses a range of techniques and miniaturization of devices and materials. Slender PCI can be categorized into miniaturization of materials (such as sheaths, catheters and wire and balloon catheters), sheathless coronary intervention, guideless coronary intervention and back-up improving techniques.
22.2.1 Miniaturization of Sheaths
In traditional TRI, the sheath is first inserted into the radial artery to house the guiding catheter. The thickness of the sheath is essential in determining how large the outer diameter of the GC can be. The Terumo Corporation recently made a sheath that can accommodate a 6 Fr catheter, but has an O.D. similar to that of a traditional sheath that can house a 5 Fr catheter. This was accomplished by reducing the thickness of the sheath from 0.20 to 0.12 mm, making the Terumo Glidesheath Slender® one of thinnest sheaths on the market (Fig. 22.2). Professor Kamiar Aminian conducted a report in which 114 patients under TRI using the Terumo Glidesheath Slender®. The report showed a 99.1 % procedural success rate and a 4.4 % occurrence of radial artery spasm (RAS) [7].
Fig. 22.2
Comparison of Terumo Glidesheath Slender® O.D. to other industry available sheaths
22.2.2 Miniaturization of Guiding Catheter
Recently, a coronary accessor has been developed by KIWAMI, Heartrail II, TERUMO, Tokyo, Japan. It can access the coronary artery and advance the coronary stents. The outer diameter of the catheter is 1.43 mm, allowing the catheter to be inserted into a 4 Fr introducer sheath and the inner diameter is1.27 mm (0.050 in.), which can accommodate most currently available coronary stents.
Manipulation of 4 Fr guiding catheter is different from 6 Fr or 5 Fr guiding catheter.
The advantage of this system is minimally invasive angioplasty and early ambulation, even when used with the transfemoral approach, without using any haemostatic devices. Also it leads to less consumption of contrast dye. With this technique a conventional 0.014″ guide wire can also be used.
However some disadvantages include the limited size of the devices used and there is less support for the guiding catheter as this is a coronary accessor. For some patients manipulation of the GC is more difficult and also sometimes the device gets damaged due to friction in the small inner lumen [8]. For female operator we need power injectors and also any IVUS cannot be used in this system. The coronary accessor can be used for complex lesions like CTO in RCA using 3 mm size of stent.
The clinical NAUSICA trial, explains the feasibility of this system comparing 4 Fr and 6 Fr systems with 80 patients in each group. Eligible patients were randomly assigned in a 1:1 ratio to undergo either 4-Fr or 6-Fr TRI.
Comparison between 6 Fr and 4 Fr showed, significantly lower incidence of access-site complication (0 % vs 5 %). And also numerically low but statistically no significant incidence of radial artery occlusion (0 % vs 4 %). Compare to 6 Fr system, 4 Fr system had significantly shorter Haemostasis time (3.9 h vs. 5.3 h) but procedural time and fluoroscopy time were similar between these groups. This data shows that the 4 Fr coronary accessory system is feasible [9].
22.2.3 Sheath Less Technique
The Sheathless Eaucath (Asahi Intecc Co., Japan) is a coronary guiding catheter that has been recently developed and makes it possible to perform PCI without using an introducer sheath.
In the Normal System, in order to introduce a 6 French guiding catheter, first we have to insert a 6 French introducer into the radial artery. The outer diameter of a 6 French introducer is as similar as an 8 French guiding catheter. In the Sheathless System: The outer diameter of a 5 French sheathless guiding catheter is equivalent to a 3 French introducer. By putting “3 French” system, we can achieve 0.059-in. diameter in inner lumen. This is the concept of “Virtual” 3 French System.
The Advantages of this sheathless system include less traumatic to the radial arteries, achievement of the bigger lumen for the guiding catheter in a limited size of the radial artery and possible improvement in the preservation of the radial pulse. How the insertion of catheter through skin and arterial wall may be difficult, plus catheter stabilization is poor and catheter exchange is not easy, which needs to be further improved.
22.2.3.1 Procedures of Inserting a Sheathless Guiding Catheter
First give a local anesthesia to make an incision,then insert the angiograph wire for the sheath introducer. While advancing the angiography guide wire to the brachial artery, check the tip of the wire under fluoroscopy to make sure that it is not entering to the side branches. When the angiography wire reaches the brachial artery, insert a sheath introducer and exchange a guide wire for 220 cm angiography guide wire. We need 4 F sheath introducer for 6.5 sheath less catheter because the catheter is thinner than a 5 F sheath introducer. For a 7.5 F sheath less catheter, a 5 F sheath introducer should be used. Advance the 220 cm angiography guide wire to the ascending aorta by carefully observing it under fluoroscopy (Refer to video 1).
Incise the puncture side approximately by 1 mm to reduce resistance of the sheath less catheter and remove the sheath introducer to insert the sheath less catheter. Before you insert the sheath less catheter over the 220 cm angiographic guide wire, you need to dock the dilator with sheath less catheter. In order to avoid deformation of the distal shape of the sheath less catheter, please insert the dilator with the sheath less catheter just before the insertion into the body. After inserting the dilator into the sheath less catheter it should be locked by the docking device at the end of the dilator. By turning it clockwise, you can see the tip of the dilator coming out of sheath less catheter. Insert the system over the angiographic guide wire under this condition. Have an assistant holding angiographic guide wire while you insert the system into the body. If the insertion resistance is considerable you can make another incision. If the catheter is not sufficiently wet there could be considerable resistance, so wet the surface of the catheter with saline solution by using a syringe to allow smooth insertion. Because the sheath less catheter has a hydrophilic coating except the last 15 cm from the connector it would be very slippery when its surface is wetted with saline solution. Another way to enhance lubricity is to hold the piece of gauze of saline solution in your left hand while inserting the catheter. Keep inserting until it reaches the ascending aorta. When the sheath less catheter reaches the ascending aorta release the dilator lock and angiography guide wire. Connect the catheter to a Y connector and release air. As for the rest continue the procedure as usual. Cases of haemorrhage have not occurred according to our knowledge (Refer to the video 2).
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