Is degradable scaffold a hope for vascular disease under the knee?

Although degradable scaffolds are disappointing in cardiovascular disease, researchers believe that degradable stents may change the treatment of atherosclerotic diseases of the lower extremities. The five-year follow-up results of ABSORB BTK and the one-year follow-up results of DISAPEAR show a high percentage of target blood vessel revascularization-free.

The principal investigators of ABSORB BTK, Ramon L. Varcoe, MBBS, MS, PhD (Prince of Wales Hospital, Randwick, Australia), said at the VIVA press conference, "Under the knee, we have huge unmet clinical demands, which can be said the epidemic of tibial artery now. " In his follow-up report, he stated, "I use this trial as a proof of a new treatment concept. We use coronary scaffold on the tibial artery, and the key clinical data obtained from it proves that this device has great potential. A multi-center randomized controlled trial should be arranged to verify it. "

Is it the new hope for the predicament of inferior knee artery disease?

The prospective, non-random ABSORB BTK clinical trial and DISAPEAR registration study evaluated Absorb BVS, the first generation of Abbott’s degradable coronary scaffold. This product was originally given high expectations, but it finally delisted because clinical data found a higher incidence of major adverse events, especially the thrombosis.

In the ABSORB BTK trial, 71 scaffolds were implanted into the knee arteries of 55 severe limb ischemia (CLI) in 48 patients. The average lesion length is relatively short, which is 20.1mm. The five-year follow-up found that the mortality rate was 38%, which was not related to the device; the initial patency rate was 72.9%, and the rate of target blood vessel revascularization was 90.7%. There are no late and very late thrombi. Varcoe emphasized that this is a huge source of confidence. 90% of patients with tissue loss completely healed without major amputation. Varcoe explained that from the five-year mortality rate of 38%, we can see the difference in the survival of these patients.

And Now…

The DISAPEAR registration study is a purely Asian experiment. Most of the selected patients are Rutherford ’s grade 5-6 patients with tissue loss, and 90% of them have diabetes. The experimental technique has a success rate of 100%, an average lesion length of 22.7%, and 24% of patients belong to the severe calcification grade in the PARC classification. One-year follow-up results showed that the initial patency rate was 86%, the target vessel revascularization rate was 93%, the main amputation rate was 98%, and the amputation-free survival rate was 85%. Nearly 80% of Rutherford grade 5-6 patients healed wounds completely.

Varcoe explained that "the elephant in the room" was the reason why the device failed in the coronary arteries and succeeded in the inferior knee arteries.

"The first generation of degradable scaffolds will defeat the seventh generation of permanent stents because of the slightly higher late thrombosis that occurred in 3-4 years. The high technical success rate of ABSORB BTK stems from PSP (pre-expansion, accurate measurement of blood vessel diameter and high voltage expansion) operation ".

Similarly, Steven Kum, MD (Changi General Hospital, Singapore), researchers of DISAPEAR also admitted that they pay much attention to PSP operation, and no clinical problems occurred in the coronary arteries.

Varcoe believes that "degradable scaffolds may be more suitable for tibial arteries, because compared with the high threshold of continuous improvement of permanent scaffolds in the coronary arteries, the tibial artery intervention equipment is quite broken now, and a little effort can improve a lot. Degradable scaffolds can achieve better results in the inferior knee artery. "

Kum said at the press conference, "I think there is huge space for improvement in CLI treatment. DISAPEAR is just a ‘hypothesis’ trial. We hope the industry will continue to promote the development of a new generation of degradable scaffolds." When asked about the characteristics of an ideal degradable scaffold, he said, "1. Easy to deliver; 2. Longer scaffold; 3. Reliable lumen acquisition. BTK has a high re-intervention rate, and degradable scaffolds should be very suitable for BTK lesions. Currently, the devices containing paclitaxel have no benefit and clinical effectiveness in the area of under the knee, so this is an exciting stage. "

New experiment, new equipment

A few months ago, the US FDA rejected the registration application of the Lutonix-containing paclitaxel balloon under the knee. And the paclitaxel device has undergone severe scrutiny in the past 11 months because a meta-analysis result shows its high long-term mortality.

Kum also mentioned that in his DISAPEAR trial, the improvement in the symptoms of Rutherford ’s grade 5-6 severe patients was “amazing”. The pictures in his report showed that patients with severe tissue loss in the legs or feet have improved dramatically after treated. He also pointed out that intervention is not enough to achieve this improvement. A full range of teamwork to provide good wound care is also needed.

Varcoe announced that he will lead the FDA-approved IDE clinical trial LIFE-BTK. This multi-center, randomized controlled clinical trial is planned to be followed up for 5 years and enrolled 225 patients. It will use Abbott ’s new-generation BVS scaffold Esprit. When asked why the control group was a PTA balloon instead of DES, he said that as an FDA-approved IDE clinical trial, the control group must be an FDA-approved indication including BTK devices.

Compile Author: szhotdog

Auditor: Vinjo

Source of this article: https://www.tctmd.com/news/hope-bioresorbable-vascular-scaffolds-peripheral-disease-below-knee