When {HEAD ~ the rivet} is released within {TAIL ~ an artificial fistula} formed through the aorta and vena cava walls, it expands to trap the walls between the two expanded heads 
When { HEAD ~ the rivet } is released within { TAIL ~ an artificial fistula } formed through the aorta and vena cava walls , it expands to trap the walls between the two expanded heads
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH