8.2 Bioresorbable Scaffolds for BTK Interventions: Are They the Answer or Just Another “Hail Mary”?

These proceedings summarize the educational activity of the 17th Biennial Meeting of the International Andreas Gruentzig Society held January 30 to February 2, 2024 in Chiang Rai, Thailand.

Faculty Disclosures     Vendor Acknowledgments

2024 IAGS Summary Document

Statement of the problem or issue

The reason we perform interventions below the knee (BTK) is not only to decrease morbidity, but also to save lives. If you examine the mortality rates of patients with critical limb ischemia (CLI), they are worse than patients with prostate cancer, breast cancer, heart disease, and stroke. Overall, the 1-year mortality rate for patients with CLI is approximately 40-to-50%. This is partly due to the fact that 70% of patients with CLI also have significant coronary disease, and 30% have significant cerebrovascular disease.

Below the knee, the arteries are small vessels, and if you look at treatment modalities, the gold standard is balloon angioplasty (POBA); it is what we compare everything against. The greatest limitation with POBA here is recurrence due to neointimal hyperplasia, or, perhaps, elastic recoil and neointimal hyperplasia. So, the treatment goals are to inhibit or overcome both elastic recoil and neointimal hyperplasia. Both bare metal stents (BMS) and drug eluting stents (DES) have failed in this comparison to POBA. The reason seems to be the remaining mass of metal (the stent) in these small arteries induces such a strong proliferative response that it is difficult or impossible to overcome. These findings have given rise to the strategy of “leave nothing behind.” Presently, this strategy is accomplished by using drug-coated balloons (DCBs), which apply both an expansive dilating force to the lesion as well as deposit an anti-proliferative drug into both the lesion and the adjacent arterial wall. The antiproliferative agent paclitaxel has been used for DCB trials to date. Unfortunately, both DES and DCB trials using paclitaxel BTK have failed.

Gaps in current knowledge

We lack some of the fundamental biologic science that might help devise better treatment strategies. While the “leave nothing behind” strategy appears to be the correct approach, we are still lacking essential basic information regarding DCBs as a method to achieve this. What are the appropriate drug concentrations to place onto DCBs? How long should the balloons be inflated to best deliver drug therapy? Are multiple brief inflations equivalent to one long inflation? What tissue concentrations of drug are needed in the arterial media and adventitia to inhibit hyperplasia? How can we overcome calcification? Can lithoplasty be employed along with DCBs in calcified lesions? These and many other questions require answers.

Possible solutions and future directions

One important group of devices under development are the drug-eluting resorbable scaffolds (DRS). These devices deliver antiproliferative drug to the lesion and arterial wall as they slowly degrade and disappear, leaving “nothing behind.” In addition to these new devices, there is a great deal being learned about optimizing the procedure itself in BTK interventions. This includes vessel and lesion preparation, as well as imaging before, during, and after the procedure. In combination with appropriate biologics and the right strategy, these steps should help improve clinical outcomes in these unfortunate patients.