Nevertheless , they can progress to the deep veins through the perforator veins .
, they can be responsible for a lung embolism mainly if the head of the clot is poorly attached to the vein wall and is situated near the sapheno - femoral junction .
Nevertheless , they can progress to the deep veins through the perforator veins or , they can be responsible for a lung embolism mainly if the head of the clot is poorly attached to the vein wall and is situated near the sapheno - femoral junction .