The main purpose of PTCA balloon dilatation catheter is to dilate patients' narrow coronary artery diseased vessels and improve myocardial blood flow through minimally invasive interventional surgery. It can also be used to deliver the release stent to the coronary artery stenosis of patients.

Here is that the content:

• Circumferential stress

• Tracking force

Circumferential stress

The non-radial force exerted on the circumferential surface of the balloon during balloon expansion is called circumferential stress. Because the pressure is equal to the pressure per unit area, when the pressure is constant, the balloon with large surface is subjected to greater circumferential stress than the balloon with small surface. Circumferential stress t equals pressure p and balloon diameter d: T=PXD For a given balloon material and inflation pressure, the larger the balloon diameter, the greater the circumferential stress on its surface. Therefore, with the same material, the big balloon will rupture under a small pressure. In other words, choose different size balloons made of the same material, and each balloon will rupture when subjected to the same circumferential stress. However, due to the above-mentioned relationship, for a given circumferential stress, the pressure is inversely proportional to the diameter of the balloon. Therefore, the pressure required to achieve the circumferential stress of rupture is relatively small for large spherical bladder. As a result, the largest balloon has the smallest burst pressure. The existing "high-pressure balloon" which can withstand 20 atmospheres (but the manufacturer states that the maximum inflation pressure is 10-16 atmospheres) is used for clinical percutaneous angioplasty (PTA). The most important cause of vascular rupture during angioplasty is excessive vasodilatation. The simplest way to prevent this over-dilation and ensure the maximum dilation force on the lesion is to select a non-compliant balloon with an appropriate diameter. When PTA was performed with a balloon without compliance, the expansion force increased linearly with the expansion pressure. Finally, besides the ideal PTA balloon dilatation catheter without compliance, a catheter with limited compliance can also be selected. Some nylon balloon manufacturers use this method, and their PTA balloon dilatation catheter must be used together with a pressure detection device. Because the compliance curve of the balloon is accurate and repeatable, the diameter of the balloon can be predicted by selecting a balloon expansion pressure value. With this system, the 8.0mm diameter balloon can be expanded to 7.5 mm or 8.5mm (or any diameter between the two required limit values) by selecting the correct pressure value corresponding to the desired balloon diameter.

Tracking force

Tracking force refers to the ability of PTA balloon dilatation catheter  to follow the guide wire through the curved path to reach the lesion without displacing the guide wire. In any case, the special anatomical structure, the skill and experience of the operator and the combination of guide wire and catheter all affect whether the catheter can reach the target site. Tracking force is not a factor that must be considered when performing superficial fat vessels and retrograde iliac angioplasty in the early stage.

Therefore, relatively large and hard PTA balloon dilatation catheter is completely acceptable. Because these hard catheters are easy to advance, they can pass through and expand most lesions. However, in order to perform PTA from iliac artery to contralateral femoral artery, renal artery and visceral artery, such catheters obviously do not meet the requirements, which puts forward new requirements for manufacturers.

In order for the operator to successfully complete the operation, the catheter design needs to have enough flexibility. The flexibility of the catheter is largely achieved by manufacturers reducing the cross-sectional areas of the catheter and balloon. In order to reduce the cross section, it is mainly through the production of thin-walled conduits. However, it has to pay the price that the catheter is easier to bend and the pushability is weakened. Therefore, it is necessary to cooperate with various guide wires to increase the tracking force of PTA balloon dilatation catheter . An ideal guide wire for the operator to pass through the lesion. The tip is soft, flexible, controllable and opaque to X-rays, and its body is hard to increase and guide the catheter forward. At present, the guide wires of 0.014~0.035 inches in the market have good controllability, and it is easy to pass through narrow or even blocked arterial lesions. Once the catheter passes through the lesion, the guide wire is withdrawn, and contrast agent is injected through the catheter. After the position in the lumen of the blood vessel is determined to be correct, the PTA balloon catheter is replaced by the exchange wire, and the PTA balloon dilatation catheter  is guided through the narrow part. Balloon catheter with tracking force difference will pull out the replacement guide wire from the target blood vessel into the aorta or superior artery, so the previous selective intubation efforts are all in vain.

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