SIroliMus coated angioPlasty versus plain balloon angioplasty in the tREatment of dialySis acceSs dysfunctION (IMPRESSION): study protocol for a randomized controlled trial
Authors: Pang Suh Chien , Tan Ru Yu , Choke Edward , Ho Jackie , Tay Kiang Hiong , Gogna Apoorva , Irani Farah G. , Zhuang Kun Da , Toh Luke , Chan Shaun , Krishnan Pradesh , Lee Kristen A. , Leong Sum , Lo Richard , Patel Ankur , Tan Bien Soo , Too Chow Wei , Chua Jasmine , Tng Ren Kwang Alvin , Tang Tjun Yip , Chng Siew Ping , Chong Tze Tec , Tay Hsien Ts’ung , Yap Hao Yun , Wong Julian , Dharmaraj Rajesh Babu , Ng Jun Jie , Gopinathan Anil , Loh Eu Kuang , Ong Shao Jin , Yoong Gary , Tay Jia Sheng , Chong Kay Yuan , Tan Chieh Suai 
Published: December 2021

Abstract
Background
Percutaneous transluminal angioplasty is the current standard treatment for arteriovenous fistula (AVF) stenosis. The mid- and long-term patency with plain balloon angioplasty (PBA) is however far from satisfactory. While paclitaxel-coated balloon angioplasty has been shown to be superior to PBA, concern over its safety profile has recently arisen after a reported possible increased mortality risk with a meta-analysis of large lower limb studies. An angioplasty balloon with a new type of drug coating, the sirolimus-coated balloon (SCB), has been proven to improve patency in the coronary arteries. However, its effect on AV access has yet to be studied.

Methods/design
This is an investigator-initiated, prospective, multicenter, double-blinded, randomized controlled clinical trial to assess the effectiveness of SCB compared to PBA in improving the patency of AVF after angioplasty. A total of 170 patients with mature AVF that requires PTA due to AVF dysfunction will be randomly assigned to treatment with a SCB or PBA at a 1:1 ratio, stratified by location of AVF and followed up for up to 1 year. The inclusion criteria include [1] adult patient aged 21 to 85 years who requires balloon angioplasty for dysfunctional arteriovenous fistula [2]; matured AVF, defined as being in use for at least 1 month prior to the angioplasty; and [3] successful angioplasty of the underlying stenosis with PBA, defined as less than 30% residual stenosis on digital subtraction angiography (DSA) and restoration of thrill in the AVF on clinical examination. The exclusion criteria include thrombosed or partially thrombosed access circuit at the time of treatment, presence of symptomatic or angiographically significant central vein stenosis that requires treatment with more than 30% residual stenosis post angioplasty, and existing stent placement within the AVF circuit. The primary endpoint of the study is access circuit primary patency at 6 months. The secondary endpoints are target lesion primary patency; access circuit-assisted primary patency; access circuit secondary patency at 3, 6, and 12 months; target lesion restenosis rate at 6 months; total number of interventions; complication rate; and cost-effectiveness. The trial is supported by Concept Medical.

Discussion
This study will evaluate the clinical efficacy and safety of SCB compared to PBA in the treatment of AVF stenosis in hemodialysis patients.

Trial registration
ClinicalTrials.govNCT04409912. Registered on 1 June 2020