Most people picture an aortic repair device as a tube that seals off an aneurysm from blood pressure entirely. The multilayer flow modulator works on a different principle. Instead of covering the vessel wall completely, it uses a permeable, braided structure that is engineered to slow and redirect flow into the aneurysm sac while still allowing blood to pass through its porous wall into branch arteries that cross the treated segment. This distinction matters for aneurysms located near or across critical branch vessels, where a fully covered graft would risk cutting off blood supply to organs such as the kidneys or intestines.
What Makes a Flow Modulator Structurally Different from a Covered Graft?
A conventional stent graft is built around an impermeable fabric — typically ePTFE or polyester — bonded to a metal scaffold. Its job is to create a new, sealed conduit for blood so that pressure no longer reaches the weakened aneurysm wall. A multilayer flow modulator takes a different structural approach. It consists of several layers of fine, braided wire mesh, without a covering membrane. Because the wall is porous rather than sealed, blood can still cross it — but the multiple overlapping braided layers are designed to reduce flow velocity and turbulence entering the sac.
This 3D braided stent construction is the defining engineering feature of the device category. Each layer contributes a small amount of flow resistance, and layered together, they are intended to promote a more laminar, slower flow pattern directed down the main aortic channel rather than into the aneurysm itself.
How Does Flow Modulation Encourage Sac Changes Over Time?
The underlying concept is that reducing flow velocity and turbulence within the aneurysm sac encourages stagnation and, over time, thrombus formation inside the sac. As thrombus organizes, the sac may gradually decrease in pressure and, in some cases, in size — a process generally referred to as sac remodeling. Meanwhile, branch vessels that cross the treated aortic segment, such as renal or mesenteric arteries, continue to receive flow through the braided pores, since the device does not rely on precisely cut fenestrations aligned to each branch.
Where This Concept Is Being Applied: STENA MFM
INVAMED's implementation of this concept is the STENA Multi-Layer Flow Modulator for Peripheral, often referred to as STENA MFM. As manufacturer-reported data, INVAMED reports a 98.2% technical success rate in a 55-patient study of the Multilayer Flow Modulator, with no perioperative paraplegia observed and more than 243 patients treated to date. These figures describe one reported clinical experience compiled by the manufacturer and should not be interpreted as a guarantee of individual outcomes; a qualified vascular surgeon determines whether this approach is suitable for a specific patient's anatomy.
What Types of Aneurysms Might Be Considered for This Approach?
Flow modulation as a concept is generally discussed in the context of aneurysms involving segments of the aorta where multiple branch vessels arise close together, making fenestrated or branched graft planning more complex. Because the device does not require patient-specific fenestration alignment, it is sometimes considered as part of the broader toolkit available to treating physicians for anatomically challenging aneurysms. Suitability always depends on detailed imaging review and clinical judgment specific to each patient's aortic and branch vessel anatomy. Additional background on treatment approaches in this space is available on INVAMED's aortic aneurysm and dissection repair category page.
Who decides if this concept is appropriate for a given patient?
A qualified vascular surgeon or interventional specialist evaluates aortic and branch vessel anatomy, aneurysm characteristics, and overall patient health before determining suitability. Availability and indications vary by country, and the Instructions for Use (IFU) should always be consulted.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.