Introduction to Cutting Balloons
1: Cutting Balloon Definition
The Cutting Balloon is a clever combination of micro-cutting technology and a conventional balloon that is well suited for the management of specialised, complex lesions. The surface of the balloon has three or four sets of longitudinally parallel micro-blades, with the surface blades having folding points every 5mm to allow the balloon to flex. When the balloon is not dilated, the blades are wrapped in the folded slits of the balloon, and when dilated, the blades protrude from the balloon surface to cut the vascular plaque;
2: Cutting Balloon (Cutting Balloon) Features
According to the description in the consensus of the Chinese Expert Consensus on the Diagnosis and Treatment of Coronary Artery Calcified Lesions (2021 Edition), the cutting balloon is also suitable for mild to moderate calcified lesions or for further lesion pretreatment after coronary plaque rotational milling. However, the use of cutting balloons is not recommended for severely calcified lesions of grade III-IV as suggested by IVUS. The cutting balloon should be dilated at the nominal pressure according to the instruction manual, which should not exceed a maximum of 12 atm in order to avoid excessive pressure that may lead to insertion of the blade and make it difficult to retract;
Contraindications to the use of the cutting balloon are as follows: (1) small diameter of the reference vessel (<2 mm in diameter); (2) diffuse lesions (>20 mm in length); and (3) unprotected left main trunk lesions. Because of the slow withdrawal of pressure from the cutting balloon, use in left main lesions is risky and limited to very skilled operators; (4) lesions with severely angulated and extremely tortuous vessels. It is often difficult to reach the lesion because of the poor compliance and stiffness of the cutting balloon; (5) severely calcified lesions, which are difficult to dilate adequately by the cutting balloon; and (6) chronic completely occluded lesions and lesions with >95% stenosis. Because of the large diameter and shape of the cutting balloon, it is difficult to reach and pass through such lesions, which should be pre-dilated with a small balloon with a diameter of 1.5~2.0 mm before dilating with the cutting balloon.
Structural analysis of coronary artery cutting balloon
Figure 1, Schematic diagram of a coronary artery cutting balloon
As can be seen from the above schematic, it mainly consists of proximal shaft (usually designed for the sea wave tube), distal end of the shaft (polymer tubing), the balloon and cutting blade (fixed in the outer surface of the balloon) of these four parts, the following small will be from the point of view of R & D and design on the proximal shaft, the balloon and the cutting blade for a detailed analysis;
1 – Proximal shaft (seapipe)
Hypotube is a long metal capillary tube that is an important component of minimally invasive catheters used in conjunction with balloons and stents to open arterial blockages; it can also be used in conjunction with balloons and cutting blades to remove diseased plaque; the balloon portion of the catheter is attached to the distal end of the Hypotube. The catheter enters the body and pushes the balloon along long, tortuous blood vessels toward the arterial blockage, where the well-performed catheter resists kinking and bending, and is able to track and rotate smoothly through the body’s architecture;
Figure 2, Schematic diagram of seapipe products
Seawave tube base material commonly used in medical grade stainless steel, grades such as: 304, 304L, 304V, etc., and in the stainless steel surface is coated with a thin layer of PTFE coating (generally 5μm ~ 15μm), in order to reduce the frictional resistance of the seawave tube transported in the blood vessels; seawave tube distal cutting design is often as follows in Figure 2 in several ways.
Figure 3, Schematic diagram of the sea-wave tube cutting structure
2- Balloon bag
The cutting balloon can generally be used as the balloon platform of the cutting piece with a semi-compliant balloon, which has good flexibility. Such a design is conducive to improving the passability of the product, improving the holding back performance of the balloon, as well as controlling the degree of embedding of the blade in the calcified plaque during the dilatation, which provides a strong guarantee of the safety of the procedure.
3-Cutting blades
Cutting balloon surface longitudinally equipped with a microblade, before the cutting balloon does not reach the lesion, the blade is tightly wrapped in the balloon material, will not damage the normal blood vessels; cutting blade is one of the important design of the cutting balloon products, the design points include the choice of blade material, blade structure design, the layout of the blade in the balloon surface and so on the three aspects, the following will be on the blade of the three aspects of the detailed The following will be a detailed introduction to the three aspects of the blade;
1) Blade material
In order to be able to cut through the hard calcified plaque, the cutting blade usually needs to have high hardness, high strength and high wear resistance, so the cutting blade is usually made of high-strength stainless steel or special alloys (e.g., 304/304L stainless steel, etc.), which has very high hardness and corrosion resistance; the harder the blade, the stronger its cutting ability, and the more fine its cutting pressure (in the process of balloon dilatation, the blade of the endothelium). Cutting pressure is 30,000 times the balloon surface pressure), on a variety of narrow can be said to be indestructible, and because of the thickness of the stainless steel blade is extremely thin, just cut the lining of the blood vessel wall, the inner wall of the blood vessel carved out a trace, and will not cut the entire blood vessel wall, it is this trace is the key to cut the balloon special expansion mechanism;
Figure 4, Physical display of cutting blade
2) Blade structure design
The design of the blade includes precise geometry and sharp edges to ensure that plaque and fibrous tissue can be effectively cut during dilatation while avoiding damage to the normal vessel wall, the following figure shows the schematic design of foreign imported cutting blades;
Figure 5, Partial detail of Flextome and Wolverine blades
3) Layout of blades
The blades are usually arranged in a spiral or parallel pattern on the surface of the balloon and are firmly fixed to the balloon by a specific process. When the balloon is inflated and expanded, these blades generate a uniformly distributed pressure acting on the stenosis, enabling precise cutting. Existing products are generally designed with the number of blades as follows: 3 blades for balloons with a diameter of 2.0-3.25 mm and 4 blades for balloons with a diameter of 3.5-4.00 mm.
