We read with great interest the article by Dell et al. titled “How Controlled is the Expansion of VIATORR CX?” [1] In this benchtop investigation, the authors compared the chronic outward radial force (COF) and radial resistive force (RRF) of both the Viatorr® Controlled Expansion (VCX) and legacy Viatorr® (W.L. Gore; Newark, DE) stents. This study confirmed the proposed engineering design of the VCX in vitro, demonstrating that passive expansion of the stent effectively ceases around 8 mm, with “controlled” expansion up to nearly 9.3 mm resulting following 10 mm balloon angioplasty.

Optimal sizing for transjugular intrahepatic portosystemic shunt (TIPS) placement is a heavily debated topic, with a trade-off between symptomatic relief of portal hypertension and the risk of overshunting (i.e., hepatic encephalopathy). Several factors also contribute to this outcome, including the patient's baseline liver function, portosystemic pressure gradient (PSG), and compliance with medications. Li et al. [2] from a technical perspective, 8 or 10 mm Viatorr® stents are commonly chosen for TIPS placement, with the risk of overshunting from greater PSG reduction theoretically increased by larger diameter stents. Wang et al. [3] to provide better titration of the PSG during TIPS, historical methods have included primary constrained techniques, post-TIPS bidirectional parallel stenting, and/or underdilation of a 10 mm Viatorr® to 8 mm at time of stent placement [4,5,6].

The VCX simplifies this step by allowing the operator to nominally dilate the stent to a desired size between 8 and 10 mm, effectively giving stepwise control of the PSG to the operator. This also avoids passive dilation of the stent to its nominal diameter, a phenomenon reported both in this investigation and other prior clinical studies with the original Viatorr®. Dell, Mollaiyan, and Gaba [1, 6, 7] in this age of personalized medicine, we believe the controlled approach using VCX for TIPS to optimally balance the risk of under- and overshunting may represent the most significant technical advancement in TIPS placement since the advent of covered stents to prevent early stent thrombosis/dysfunction [8].

Moving forward, we hope that studies such as this publication by Dell et al. will spur future clinical investigations to validate these reported findings in vivo. Similar studies to query the clinical benefit of this technical advancement are also needed. Existing literature on the topic is conflicting, as an early retrospective study demonstrated high rates of hepatic encephalopathy with the VCX stent. Kloster et al. [9] however, a more recent prospective study reported improved survival using VCX for TIPS when compared with underdilated 10 mm Viatorr® stents [10].

Finally, future investigations can hopefully aim to clarify the value added with VCX for TIPS and identify added areas of need for technical advancement related to stent design. Recent venous literature has explored the importance of other features related to nitinol-based self-expanding stent design, such as crush resistance and flexibility, which may be applicable when trying to optimize long term TIPS patency. Dabir et al. [11] such efforts may permit stent optimization as we now enter the era of controlled expansion for TIPS.