Vascular calcification, a cause of cardiovascular morbidity and mortality, is an actively regulated process involving vitamin K dependent proteins (VKDPs) among others. Vitamin K is an essential micronutrient, present in plants and animal fermented products that plays an important role as a cofactor for the post-translational γ-carboxylation of glutamic acid residues in a number of proteins. These VKDPs require carboxylation to become biologically active, and they have been identified as having an active role in vascular cell migration, angiogenesis and vascular calcification. This paper will review the process of vascular calcification and delineate the role that vitamin K2 plays in the modulation of that process, through the activation of VKDPs. One such VKDP is Matrix Gla Protein (MGP), which when activated inhibits osteogenic factors, thereby inhibiting vascular and soft tissue calcification.

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Polytetrafluoroethylene (PTFE) grafts have proven to be an adequate alternative conduit for peripheral bypass operations. Whether or not one uses PTFE depends on several factors: surgeon preference, individual patient circumstances, or when autologous greater saphenous vein is not available or adequate. These conventional grafts have evolved and undergone modification. The intraluminal surface has been coated with carbon or bonded with heparin. The structure of grafts has been modified with the creation of a hood or cuff, with the incorporation of a stent-graft segment for a sutureless anastomosis, or the fusion of PTFE with an outer polyester layer to minimize suture hole bleeding. This evolution intends to limit graft thrombogenicity, ameliorate the formation of intimal hyperplasia, decrease complications, and improve overall graft patency.

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Critical limb ischemia (CLI) results from inadequate blood flow to supply and sustain the metabolic needs of resting muscle and tissue. Infragenicular atherosclerosis is the most common cause of CLI, and it is more likely to develop when multilevel or diffuse arterial disease coincides with compromised runoff to the foot. Reports of good technical and clinical outcomes have advanced the endovascular treatment options, which have gained a growing acceptance as the primary therapeutic strategy for CLI, especially in patients with significant risk factors for open surgical bypass. In fact, endovascular recanalization of below-the-knee arteries has proven to be feasible and safe, reduce the need for amputation, and improve wound healing. The distribution of various vascular territories or angiosomes in the foot has been recognized, and it appears advantageous to revascularize the artery supplying the territory directly associated with tissue loss. In addition, the targeted application and local delivery of drugs using drug-coated balloons (DCB) during angioplasty has the potential to improve patency rates compared to balloon angioplasty alone.

The treatment of chronic limb ischemia involves the restoration of pulsatile blood flow to the distal extremity. Some patients cannot be treated with endovascular means or with open surgery; some may have medical comorbidities that render them unfit for surgery, while others may have persistent ischemia or pain even in the face of previous attempts at reperfusion. In spinal cord stimulation (SCS), a device with electrodes is implanted in the epidural space to stimulate sensory fibers. This activates cell-signaling molecules that in turn cause the release of vasodilatory molecules, a decrease in vascular resistance, and relaxation of smooth muscle cells. SCS also suppresses sympathetic vasoconstriction and pain transmission. When patient selection is based on microcirculatory parameters, SCS therapy can significantly improve pain relief, halt the progression of ulcers, and potentially achieve limb salvage.

In this animal model, infrarenal aortic clamping causes a significant decrease in renal cortical flow and urine output with no significant changes in filling pressures, cardiac output, or medullary blood flow. These adverse effects are prevented by pretreatment with prostaglandin E1, which prevents cortical ischemia and maintains brisk diuresis.

Advances in the treatment of atherosclerotic disease by transluminal angioplasty and intra-arterial stenting have led to the development of a transfemoral endovascular approach to the treatment of aortic aneurysmal disease. The authors investigated this technique using an endovascular graft employing self-expanding anchors for the exclusion of infrarenal aortic aneurysms. They investigated the technique of transfemoral endovascular aortic grafting in 13 male mongrel dogs weighing an average of 30 kg. Eleven animals had fusiform infrarenal aortic aneurysm models created. One week to three months after surgery all animals underwent midstream aortography under general anesthesia to examine aneurysm morphology. A 14 French catheter was introduced through the right common femoral artery, and under fluoroscopic guidance the endovascular graft was delivered in an infrarenal aortic position. Completion aortography was then performed to confirm placement. They tested two endovascular graft prototypes. The first employed a proximal anchor attached to the graft and a separately delivered distal anchor. Successful graft delivery was achieved in five of six attempts. Unsuccessful graft delivery occurred in 1 case because of an inability to negotiate aneurysm tortuosity. After delivery graft twisting occurred in 1 case and graft invagination occurred in 2 others upon the attempt to deliver the distal anchor. Successful exclusion was achieved in 3 of 4 remaining cases with an aneurysm model using this prototype. The second prototype employing proximal and distal anchors attached to the graft was successfully deployed in seven of seven attempts. Successful aneurysm exclusion was achieved in 5 of these 7 cases. Failure to exclude the aneurysm neck occurred in 2 cases. In this preliminary study the authors found the concept of endovascular delivery of a self-anchoring tube graft to be feasible. The optimal delivery system is flexible and possesses a small outer diameter to allow a transfemoral approach through moder ately tortuous iliac arteries. Accurate delivery is aided by intermittent fluoroscopic examination. Doubly anchored grafts are necessary to ensure aneurysm exclusion and prevent graft twisting. Self expanding anchors allow simple endovascular graft deploy ment in a single pass. Continued animal investigation into the fate of aortic side branches, distal embolization, and graft migration is necessary to ensure the eventual success of this technique.