Multi-layer device with gap for treating a target site and associated method

A medical device for treating a vascular abnormality in a lumen, the medical device comprising:

• a multi-layered structure comprising an inner layer disposed within an outer layer and having proximal and distal ends, wherein the inner layer is a first fabric comprising a plurality of braided strands comprising an elastic metallic alloy and the outer layer is a second fabric comprising a plurality of braided strands, the first fabric being discrete from the second fabric, each of the inner and outer layers having a respective longitudinal opening extending between the proximal and distal ends so as to define respective inner and outer surfaces, wherein the multi-layered structure further comprises at least one offset comprising a surface distortion formed helically or annularly in only one of the inner or outer layers, the at least one offset extending between the outer surface of the inner layer and the inner surface of the outer layer to define a gap between the inner and outer layers, wherein a majority of the outer surface of the inner layer is spaced apart from the inner surface of the outer layer by the at least one offset, and wherein the multi-layered structure is configured to be deployed within the lumen such that at least a portion of the outer surface of the outer layer is configured to engage an inner surface of the lumen and the at least one gap is configured to allow blood flow therethrough so as to promote thrombosis between the inner and outer layers.