During angioplasty, an immense amount of force typically must be exerted to guide a catheter through an artery. Occasionally a lesion is dense enough to halt the catheter’s progress entirely; sometimes the resistance is such that it causes the hypotube component of the catheter to kink. In this case, it becomes difficult to position the stent and balloon correctly. Additionally, the kinked hypotube may negatively affect balloon deflation, subsequently increasing the difficulty of balloon removal and elevating patient risk. In severe cases, the hypotube can kink to the point of breaking, requiring surgical intervention or a complex nonsurgical procedure to extract the broken portion of tubing.
“There are several factors affecting the ability to successfully deliver a stent or balloon, including vessel tortuosity, presence of vessel calcification, and severity of stenosis,” explains Dr. Frederic Resnic, director of medical information systems at Brigham and Women’s Hospital in Boston, MA, USA. “If I am worried that the catheter shaft is going to kink given the force required to reach and cross a lesion, I will replace it with a different one.”
A recent study in which Resnic participated concluded that improved hypotube kink resistance would save surgeons’ time and make interventional cardiology procedures safer and less expensive. Completed at the end of 2005 by Cambridge Consultants (Cambridge, UK), the study was the result of in-depth interviews with high-profile cardiologists in Germany, the United Kingdom, and the United States. Cardiologists from the three countries agreed on the need for hypotubes with improved kink resistance, citing the difficulty of navigating catheters through tortuous and severely clogged arteries. “A hypotube with increased kink resistance would have a higher failure point, so cardiologists could use a higher force to deliver the stent with confidence,” Resnic explains.
After the study was released, Creganna Medical Devices (Galway, Ireland) announced its introduction of a hypotube with up to 40% better kink resistance compared with existing products. Having assisted Cambridge Consultants in the study, Creganna developed the PoleVault hypotube in response to the needs of cardiologists and medical device manufacturers.
In addition to kink resistance, the hypotube was designed to support rapid balloon deflation. Because it won’t easily kink, the hypotube gives cardiologists the option of using smaller inner diameters than with other products. Supporting quick balloon deflation time, hypotubes with thin inner diameters can minimize patient trauma. The PoleVault also resists package set, and is less likely to be damaged during in-process handling and assembly.
More than 5 million interventional cardiology procedures were performed in the United States alone in 2004. Patient and doctor demand for continued technological progress has spurred the development of products such as drug-eluting stents. But the PoleVault hypotube shows there is also room for improvement in seemingly simple devices.
“Successful innovation is not just about focusing R&D effort on the high-value end of the market, but also on seemingly simple components that are critical for optimal outcomes,” says Clare Beddoes, a consultant at Cambridge Consultants, who coauthored the study with Maura Leahy from Creganna. “With real insight from clinicians, it is possible to identify hidden issues that have an impact on medical device performance—and to innovate even with well-established products so they deliver time- and cost-saving benefits for both doctor and patient.”