In-depth analysis of balloon catheter design

01 Proximal design

The proximal push rod of the balloon catheter plays the role of supporting and pushing the balloon to the target blood vessel. Such a demand requires the push rod to have good force transmission and strong support and anti-bending properties;

The proximal push rod generally adopts the design of metal hypotube, because metal has good force transmission effect and tensile strength. Its materials are mainly 304SS, 304VSS, 304LSS and nickel titanium. The toughness relationship is: nickel titanium>304LSS>304VSS>304SS;

A core wire is usually welded near the bonding section between the hypotube and the polymer tube. The groove structure is used as a transition section. Its purpose is to form a hardness intermediate area between the metal hypotube and the polymer outer tube, thereby forming a transition section of the balloon catheter. The existence of the transition section is conducive to the transmission of the proximal push force to the distal end.

02 Inner tube design

During the process of the balloon catheter moving along the guidewire to the target blood vessel, its inner surface is in direct contact with the guidewire; therefore, it is hoped that the inner surface of the inner tube has a lower friction coefficient, which can reduce the friction resistance of the balloon catheter during the process of moving along the guidewire;

In addition, the inner tube of the balloon catheter penetrates the balloon body. When the balloon is in the filled state, the inner tube needs to have a certain pressure resistance, which requires the selection of a material with slightly higher strength as one of the materials of the inner tube;

Methods to reduce the friction between the inner surface of the inner tube and the guidewire: select the inner layer material of the inner tube with a low friction coefficient;

Coat a hydrophobic coating on the inner surface of the inner tube to reduce the friction with the guidewire.

03 Outer tube design

The outer tube of the balloon catheter plays a connecting role. One end is connected to the hypotube and the other end is connected to the proximal pin of the balloon. The points that need to be considered in its design are: hypotube size, balloon size, balloon pressure relief time and distal flexibility. These three points will affect the size design and material selection of the balloon outer tube.

04Tip head design

The tip of the balloon catheter is always at the forefront of danger, in close contact with the narrow plaque, and plays the role of a pathfinder; the editor believes that the tip needs to be designed according to clinical needs. Different types of balloons should have different tip designs; for example, for a semi-compliant pre-expansion balloon, the tip should be made of a soft material, moderate length, and low Tip Entry Profile size to reduce the "fish mouth" effect when the balloon passes through the bend of the blood vessel. For another example, for a balloon for treating CTO lesions, the tip should be made of a harder material, short in length, and tapered. This design is conducive to passing through the small narrow plaque gap of CTO lesions.

05Balloon body design

The most important component of a balloon catheter product is the balloon body, which is the component that plays a therapeutic role; its performance determines the quality of the treatment effect, and the balloon molding process involved in this component is also the most cumbersome and difficult process in the entire product.

The type of balloon you want to design needs to be developed specifically according to clinical needs. For example, if you want to use it to treat mild stenosis, then design a semi-compliant balloon, and the materials are generally Pebax or nylon. If it is used to treat severe calcification or CTO lesions, then you deserve a high-pressure non-compliant balloon, and the materials are generally nylon, mixed materials, co-extruded materials, or adding modified components to the surface of the high-pressure non-compliant balloon, such as adding: mastoid, spinous process, metal cutting components to the balloon surface, to make the recently popular notched balloon or cutting balloon.