The role of established and emerging risk factors in peripheral vascular graft occlusion

One of the most urgent vascular circumstances: Acute limb ischemia

Acute limb ischemia is a sudden decrease in limb perfusion that threatens limb viability and requires urgent evaluation and management. Most of the causes of acute limb ischemia are thrombosis of a limb artery or bypass graft, embolism from the heart or a disease artery, dissection, and trauma. Assessment determines whether the limb is viable or irreversibly damaged. Prompt diagnosis and revascularization by means of catheter-based thrombolysis or thrombectomy and by surgery reduce the risk of limb loss and mortality. Amputation is performed in patients with irreversible damage. Despite urgent revascularization, amputation rate is 10%–15% in patients during hospitalization, mostly above the knee, and mortality within 1 year is 10%–15% due to the coexisting conditions.

Endovascular treatment of critical ischemia in the diabetic foot: new thresholds, new anatomies

This review discusses the role of endovascular treatment in diabetic patients with critical limb ischemia (CLI). Angioplasty of the femoropopliteal region achieves similar technical success and limb salvage rates in diabetic and nondiabetic patients. Angioplasty in as many as possible tibial vessels is accompanied by more complete and faster ulcer healing as well as better limb salvage rates compared to isolated tibial angioplasty. Targeted revascularization of a specific vessel responsible for the perfusion of a specific ulcerated area is a promising new approach: it replaces revascularization of the angiographically easiest-to-access tibial vessel, even if this is not directly responsible for the perfusion of the ulcerated area, by revascularization of area-specific vascular territories. In conclusion, the endovascular approach shows very high efficacy in ulcer healing for diabetic patients with CLI. Larger prospective studies are now needed to estimate the long-term results of this approach.

Pulsed high-intensity-focused US and tissue plasminogen activator (TPA) versus TPA alone for thrombolysis of occluded bypass graft in swine

PURPOSE

Prosthetic arteriovenous or arterial-arterial bypass grafts can thrombose and be resistant to revascularization. A thrombosed bypass graft model was created to evaluate the potential therapeutic enhancement and safety profile of pulsed high-intensity-focused ultrasound (pHIFU) on pharmaceutical thrombolysis.

MATERIALS AND METHODS

In swine, a right carotid-carotid expanded polytetrafluoroethylene bypass graft was surgically constructed, containing a 40% stenosis at its distal end to induce graft thrombosis. The revascularization procedure was performed 7 days after surgery. After model development and dose response experiments (n = 11), two cohorts were studied: pHIFU with tissue plasminogen activator (TPA; n = 4) and sham pHIFU with TPA (n = 3). The experiments were identical in both groups except no energy was delivered in the sham pHIFU group. Serial angiograms were obtained in all cases. The area of graft opacified by contrast medium on angiograms was quantified with digital image processing software. A blinded reviewer calculated the change in the graft area opacified by contrast medium and expressed it as a percentage, representing percentage of thrombolysis.

RESULTS

Combining pHIFU with 0.5 mg of TPA resulted in a 52% ± 4% increase in thrombolysis on angiograms obtained at 30 minutes, compared with a 9% ± 14% increase with sham pHIFU and 0.5 mg TPA (P = .003). Histopathologic examination demonstrated no differences between the groups.

CONCLUSIONS

Thrombolysis of occluded bypass grafts was significantly increased when combining pHIFU and TPA versus sham pHIFU and TPA. These results suggest that application of pHIFU may augment thrombolysis with a reduced time and dose.

Management of transplant renal artery stenosis

End-stage renal disease (ESRD) was universally fatal until dialysis (peritoneal and hemodialysis) and renal transplantation were introduced. However, there are multiple complications associated with transplantation including transplant renal artery stenosis (TRAS). Transplant renal artery stenosis is an important cause of premature renal failure, uncontrolled hypertension, and allograft loss. There are 3 treatment modalities available for TRAS: optimal medical therapy alone, percutaneous intervention, and surgical revascularization both with optimal medical therapy. Percutaneous transluminal angioplasty (PTA) has now become the initial treatment of choice for TRAS. However, there are conflicting data regarding the efficacy of PTA, with growing evidence showing lack of significant benefit in blood pressure (BP) or renal function in patients undergoing PTA versus medical management. However, there have been no randomized control studies that have established the superiority of either method. We review the existing data and analyze management of TRAS as reported in multiple case series including findings from our center.

Intensive statin therapy: a favorable adjunct to the improvement of small-diameter vascular grafts

To assess the effect of intensive statins therapy on the outcome of small-diameter vascular prosthesis, we investigated whether atorvastatin treatment (30 mg/d) could accelerate the re-endothelialization process and improve the patency rate in a canine infrarenal abdominal aorta-expanded polytetrafluoroethylene (ePTFE) bypass model. Furthermore, we also evaluated the effect of atorvastatin on the migratory and adherent capacity of circulating endothelial progenitor cells (EPCs) in vitro. Improved patency was confirmed by Doppler sonography and arteriography. Histological and scanning electron microscopy illustrated enhanced re-endothelialization process. Treatment with atorvastatin enhanced the circulating pool of EPCs with fortified migratory and adherent capacity. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that atorvastatin treatment increased endothelial nitric oxide synthase (eNOS) and kinase insert domain receptor (KDR) messenger RNA (mRNA) expression in cultured EPCs and neointima. In conclusion, intensive statin therapy could be considered a favorable option to improve small-diameter vascular graft patency.

Does Gender Influence the Patency of Infrainguinal Bypass Grafts?

Infrainguinal revascularization is an effective method of treatment for femoropopliteal/tibial occlusive diseases. However, these bypass grafts are prone to stenosis. In this retrospective study, the authors investigate the association of gender with patency of infrainguinal bypass grafts. The outcomes for consecutive 375 male and 200 female patients who underwent infrainguinal bypass surgery for arterial occlusive disease are compared, and associations with characteristics of the patients, surgical procedure, and graft stenosis are determined. It is found that several demographic, biochemical, and etiological factors could influence the patency of bypass procedures in different genders. However, infrainguinal arterial reconstruction procedures performed in women have a worse outcome when compared with that in men.

Do Different Vascular Risk Factors Affect All Arteries Equally?

Established vascular risk factors (ie, smoking, hypertension, diabetes mellitus, and dyslipidemia) play an important role in the development of vascular disease. Emerging evidence suggests that some of these risk factors may have a more intense effect on specific arterial beds, a finding that holds implications for a prognostic role for certain types of vascular disease.

C-reactive protein (CRP): more than just an innocent bystander?

This editorial discusses whether measuring C-reactive protein (CRP) levels can be used as a predictor of vascular risk. The agents that reduce CRP levels and the evidence for a possible causative role of CRP in the pathogenesis of coronary events and atherosclerosis are also considered. There is a need to further elucidate the role of CRP, as well as the clinical relevance, if any, of CRP-lowering agents.

The role of fibrinogen and fibrinolysis in peripheral arterial disease

Peripheral arterial disease (PAD) is associated with high rates of cerebrovascular and cardiovascular events; PAD is a marker of systemic atherosclerosis. As a result, standard therapy for all PAD patients should be directed at both peripheral and systemic atherosclerosis. Modification of established risk factors in the form of smoking cessation, correcting hypertension, optimizing diabetic control and normalizing lipids is essential. Furthermore, novel risk factors have emerged including fibrinogen and other hemostatic factors. Fibrinogen is a coagulation factor and a marker of the acute phase response (inflammation), a platelet activator, a major determinant of plasma viscosity and a component of the atherosclerotic plaque. Fibrinogen appears not only to predict the severity of PAD, but also serves as a marker for future development of PAD. Whether reducing the levels of fibrinogen and other coagulation factors will decrease the incidence and progression of PAD remains to be resolved. This review summarizes the role of fibrinogen in the pathogenesis of PAD and its association with other hemostatic factors. The role of fibrinolysis in patients with PAD is also considered.