Bioengineered valves for the venous circulation

Intraluminal valves: development, function and disease

The circulatory system consists of the heart, blood vessels and lymphatic vessels, which function in parallel to provide nutrients and remove waste from the body. Vascular function depends on valves, which regulate unidirectional fluid flow against gravitational and pressure gradients. Severe valve disorders can cause mortality and some are associated with severe morbidity. Although cardiac valve defects can be treated by valve replacement surgery, no treatment is currently available for valve disorders of the veins and lymphatics. Thus, a better understanding of valves, their development and the progression of valve disease is warranted. In the past decade, molecules that are important for vascular function in humans have been identified, with mouse studies also providing new insights into valve formation and function. Intriguing similarities have recently emerged between the different types of valves concerning their molecular identity, architecture and development. Shear stress generated by fluid flow has also been shown to regulate endothelial cell identity in valves. Here, we review our current understanding of valve development with an emphasis on its mechanobiology and significance to human health, and highlight unanswered questions and translational opportunities.

Present and future options for treatment of infrainguinal deep vein disease

OBJECTIVE

Management of chronic deep vein disease focuses on the alleviation of reflux and obstruction. For the suprainguinal veins, the main underlying pathologic process is obstruction, which has been recognized as a significant contributor to chronic venous insufficiency. This is currently being addressed with venous stenting and the development of dedicated stents designed for this segment of the venous system. Treatment of the femoropopliteal vein (FPV) is far more challenging because of the idiosyncratic anatomy, the hemodynamic physiology, and the technical aspects of size mismatch and valve flow dynamics in managing deep venous reflux. This review article discusses traditional and emerging technologies to treat infrainguinal disease.

METHODS

Previous and current articles addressing this issue were reviewed. Emphasis was placed on emerging techniques and technologies.

RESULTS

Significant bench work, in vitro and in vivo studies, have been conducted over the last 40 years addressing the issue of infrainguinal reflux and obstruction. Historically, open procedures to address FPV reflux and obstruction have had variable success in a few centers around the world. The significant increase of emerging endovascular therapies may allow more appropriate, reproducible, widespread treatment of infrainguinal deep venous disease.

CONCLUSIONS

Adequate and durable therapies for infrainguinal venous disease represent one of the greatest challenges for a vein specialist. Recently, a cluster of interest and techniques/technologies have been developed. The endovascular management of arterial disease is mature. The endovenous management of infrainguinal disease is on the cusp of meaningful innovation. The purpose of this evidence summary is to describe the options for the management of chronic FPV disease, with emphasis on emerging technologies and techniques.