A recent study evaluating interventional cardiologists’ perceptions of the performance of catheters used in angioplasty, also known as percutaneous coronary intervention (PCI), suggests that catheters are in need of improvement. Specific areas of improvement are reviewed here with a number of seapipe shaft solutions that promise to improve catheter delivery.
Since the first percutaneous coronary intervention (PCI) stent was introduced to the market in 1993, the industry has focused its resources on the development of stent technology. Drug-eluting stents continue to evolve and increase their market share. However, it should not be forgotten that a good delivery system is the first step to successful stenting;
Well-designed catheters are best distinguished from poorly designed catheters in the navigation of complex anatomy and in the treatment of highly calcified lesions. In these complex therapeutic procedures, the delivery system becomes a critical part of the PCI catheter. The development of delivery systems has evolved quietly but effectively to assist in the delivery process of new devices. If delivery systems in their current form meet the needs of cardiologists, then it can be assumed that they have evolved to a certain point. However, as technology and devices continue to evolve and place more demands on delivery systems, catheter shafts must continue to evolve to address and fulfill these new needs;
There are three main categories of catheter shafts: metals, polymers and composites. For PCI catheters designed for rapid exchange, metal catheter shafts, also known as seaport tubes, are the standard shaft of choice and a critical component for efficient delivery of balloons and stents. If the development of next-generation PCI catheters is to provide real clinical benefits, there must be synergy between balloon and stent technology and the optimization of seawave tubing performance. Further development of delivery technology with seawave tubing may also facilitate the development of new and innovative therapeutic devices.
In an effort to promote PCI procedures, interventional cardiologists were asked what they really wanted from the seapipe component of the delivery system. There are a few points worth mentioning:
1. they place a high value on the ability of the seawave tube to allow the distal portion of the catheter to be pushed and tracked through tortuous anatomy and efficiently so that the stent can be delivered as effectively as possible;
2. they wanted to be confident that the seaport tube would not kink or impede the balloon pressure relief process;
3. although satisfied with the current delivery system, they wanted to improve the kinking properties without compromising the other performance characteristics of the seaboard tubing (e.g., pushing force, tracking properties, torsional properties, or flexibility).
It is important for industry to recognize the potential procedural issues associated with seaborne catheter fracture resistance. If access to a severely calcified lesion is being considered, there is usually a significant point of resistance that interferes with the forward advancement of the catheter. Some procedures require significant force proximal to the catheter in the hope that the stent or balloon will successfully pass through the lesion. However, if the lesion is too severe or calcified for the catheter to successfully pass through it, some components of the delivery system may experience a failure situation. Either the introducer catheter will protrude backward into the artery or, if the introducer catheter is well seated, the seaborne tube or distal shaft may kink at some point along its length.
Although the seaborne tube may cause it to break in severe kinking, it is very rare that surgical intervention or complex nonsurgical extubation maneuvers may be required. Severe kinking may also compromise the cross-section of the seaboard tube and interfere with the balloon pressure relief process. This makes removal of the balloon very difficult, increases the risk of injury due to inadequate blood supply downstream of the balloon, and may result in a long and difficult balloon deflation process. These serious torsion-related problems are high-risk for patients and could lead to cardiologists losing confidence in the device in question, or even lead to a product recall, which could result in a loss of market share, as well as serious financial or legal repercussions. While these are rare events, catheter manufacturers have a responsibility to reduce the risks associated with kinking events. Moving toward zero risk must be a clear goal when optimizing catheter delivery systems and next-generation PCI catheters.
Optimization of seapipe：
Seawave tubes offer the highest axial strength and push force characteristics compared to polymers and composites. The most commonly used metallic seapipe material is medical grade stainless steel. Its high modulus of elasticity provides good push force, but this can be achieved at the expense of polymer shaft flexibility;
Designing the optimal catheter shaft requires considering all of the individual performance characteristics of the seapipe and improving them as much as possible without compromising any of the other characteristics. The goal of the seawave tube designer is to produce a shaft that: displays maximum fracture resistance with maximum push force while optimizing flexibility, especially in the transition to the distal end of the conduit;
Ordinary shaft-end designs often achieve faster balloon relief times by thinning the tube wall (increasing the inner diameter) and must make trade-offs in terms of fracture resistance. With the current availability of metallic seaport tubing, these tradeoffs will no longer be necessary, as it is possible to increase the inner diameter of the seaport tubing while maintaining the current fracture resistance;
In the case of the entire catheter, the seaboard tube is one of many components that affects balloon relief time. Although there is only one design element, any reduction in balloon relief time gained from the optimization of the seaboard tube is very valuable and should be pursued. The rapid exchange of balloon relief time is critical to restoring blood flow to distal vessels and avoiding any long-term damage caused by inadequate blood supply. In terms of increasing I.D., Hippocampal tube optimization will have a positive impact on improving balloon deflation time. This is particularly important in surgical treatments that require larger or longer balloons. Larger balloons contain more fluid and therefore take longer to depressurize. In these cases, any reduction in balloon inflation time will result in a dramatic improvement;
While aiming for zero risk of kinking would provide some benefits, studies have shown that pushability is the factor that interventional cardiologists most want to improve. Pushability and kink resistance are closely related. Seaport tubes with higher kink resistance will allow the catheter to be pushed with greater force before an adverse event occurs. Future seapipe designs must strive to achieve greater pushability without being so stiff as to reduce tracking performance and fracture resistance;
Potential operational problems associated with performance issues with many aspects of PCI catheters remain. While new stent technologies will continue to enter the marketplace, it is also important to note that the challenge of making progress toward simple, safe, and effective delivery of these stents and improving delivery systems is far from over.
