Patterns of treatment for peripheral arterial disease in the United States: 1996-2005

Mineralocorticoid receptor expression in human venous smooth muscle cells: a potential role for aldosterone signaling in vein graft arterialization

Experimental studies have suggested a role for the local renin-angiotensin-aldosterone system in the response to vascular injury. Clinical data support that aldosterone, via activation of the mineralocorticoid receptor (MR), is an important mediator of vascular damage in humans with cardiovascular disease. In mineralocorticoid-sensitive target tissue, aldosterone specificity for MR is conferred enzymatically by the cortisol-inactivating enzyme 11β-hydroxysteroid-dehydrogenase-2 (11βHSD2). However, the role of MR/aldosterone signaling in the venous system has not been explored. We hypothesized that MR expression and signaling in venous smooth muscle cells contributes to the arterialization of venous conduits and the injury response in vein bypass grafts. MR immunostaining was observed in all samples of excised human peripheral vein graft lesions and in explanted experimental rabbit carotid interposition vein grafts, with minimal staining in control greater saphenous vein. We also found upregulated transcriptional expression of both MR and 11βHSD2 in human vein graft and rabbit vein graft, whereas control greater saphenous vein expressed minimal MR and no detectable 11βHSD2. The expression of MR and 11βHSD2 was confirmed in cultured human saphenous venous smooth muscle cells (hSVSMCs). Using an adenovirus containing a MR response element-driven reporter gene, we demonstrate that MR in hSVSMCs is capable of mediating aldosterone-induced gene activation. The functional significance for MR signaling in hSVSMCs is supported by the aldosterone-induced increase of angiotensin II type-1 receptor gene expression that was inhibited by the MR antagonist spironolactone. The upregulation of MR and 11βHSD2 suggests that aldosterone-mediated tissue injury plays a role in vein graft arterialization.

Connective tissue reflex massage for type 2 diabetic patients with peripheral arterial disease: randomized controlled trial

The objective of this study was to evaluate the efficacy of connective tissue massage to improve blood circulation and intermittent claudication symptoms in type 2 diabetic patients. A randomized, placebo-controlled trial was undertaken. Ninety-eight type 2 diabetes patients with stage I or II-a peripheral arterial disease (PAD) (Leriche-Fontaine classification) were randomly assigned to a massage group or to a placebo group treated using disconnected magnetotherapy equipment. Peripheral arterial circulation was determined by measuring differential segmental arterial pressure, heart rate, skin temperature, oxygen saturation and skin blood flow. Measurements were taken before and at 30 min, 6 months and 1 year after the 15-week treatment. After the 15-week program, the groups differed (P < .05) in differential segmental arterial pressure in right lower limb (lower one-third of thigh, upper and lower one-third of leg) and left lower limb (lower one-third of thigh and upper and lower one-third of leg). A significant difference (P < .05) was also observed in skin blood flow in digits 1 and 4 of right foot and digits 2, 4 and 5 of left foot. ANOVA results were significant (P < .05) for right and left foot oxygen saturation but not for heart rate and temperature. At 6 months and 1 year, the groups differed in differential segmental arterial pressure in upper third of left and right legs. Connective tissue massage improves blood circulation in the lower limbs of type 2 diabetic patients at stage I or II-a and may be useful to slow the progression of PAD.

Critical evaluation of endovascular surgery for limb salvage

Rest pain, tissue loss, and gangrene are manifestations of critical limb ischemia caused by peripheral arterial disease and define a patient subgroup at highest risk for major limb amputation. Patients with nonhealing lower extremity wounds should be screened for the risk factors for peripheral arterial disease and offered noninvasive vascular testing. The diagnosis of critical limb ischemia mandates prompt institution of medical and surgical management to achieve the best chance of limb salvage. Surgical intervention has evolved from primary amputation to open bypass to the present era of endovascular therapy. The goals of surgical bypass and endovascular therapy are to improve perfusion sufficiently to permit healing. Despite poorer patency rates and the more frequent need for reintervention, endovascular therapy has been shown in multiple retrospective studies to achieve limb salvage similar to open bypass. Only one large, prospective, randomized controlled trial exists comparing open bypass with endovascular therapy: The Bypass versus Angioplasty in Severe Limb Ischemia of the Leg (BASIL) trial. Close clinical surveillance and serial monitoring of limb perfusion by means of noninvasive arterial studies are needed to determine the need for further vascular intervention. Limb salvage patients suffer from multiple comorbidities and benefit from a multidisciplinary, team approach to care.

Long-term Results of Reconstructive Surgery for the Unilateral Aortoiliac Occlusive Disease and Future Risks of Contralateral Iliac Events

OBJECTIVE

Our experience with unilateral iliac reconstructive surgery was retrospectively reviewed, and the long-term patency and the morphological information was disclosed. In addition, the prognosis of contralateral iliac artery was examined, because future contralateral iliac events seem to be important for durability of unilateral iliac revascularizations.

MATERIALS AND METHODS

148 patients (mean age, 66.9 years; 88% male) who had undergone unilateral aortoiliac reconstruction without contralateral iliac lesions were evaluated. The unilateral aortoiliac reconstructive procedures included 112 (76%) aorto or iliofemoral bypasses, 27 (18%) femorofemoral bypasses, and 9 (6%) axillofemoral bypasses. The indications for arterial reconstruction were disabling claudication and limb salvage in 125 (84%) and 23 (16%) patients, respectively. Preoperative arteriograms were reviewed to determine the Inter-Society Consensus (TASC II) classification categorizing iliac artery lesions. Contralateral iliac events were defined as any arterial reconstructive procedure, intervention, amputation for progression of contralateral iliac disease, or repair of abdominal aortic aneurysm (AAA). The Kaplan-Meier survival analysis was used to predict long-term results in patients grouped based on various factors which were compared using univariate and multivariate analyses.

RESULTS

In the 148 patients, unilateral iliac reconstructive procedures were undertaken in 83 (56%) patients with TASC II type D lesions, 34 (23%) patients with TASC II type C lesions, and 31 (21%) patients with TASC II type B lesions. Overall primary and secondary patency rates were 93.8% and 96.5% at 3 years and 90.0% and 93.9% at 5 years. A multivariate analysis disclosed critical limb ischemia influencing primary patency rates, and type of aortoiliac reconstruction or gender influencing secondary patency rates. TASC II classification did not affect primary or secondary patency rates. During the follow-up period, 15 contralateral iliac events occurred, including 11 aortoiliac reconstructive or interventional procedures, 3 repairs of AAA, and one case of bilateral thigh amputation due to acute aortic occlusion. The overall probability of contralateral iliac events was 2.2% at 3 years and 5.9% at 5 years.

CONCLUSION

The long-term patency following unilateral iliac reconstructive surgery was satisfactory, and not affected by morphology of the iliac artery. Also, the future risk of contralateral iliac events appeared to be low.

Bacterial translocation across ePTFE vascular graft surfaces

OBJECTIVES

Vascular graft infections arise from bacterial colonization of either the external or internal graft surfaces. We assessed whether methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli could translocate through pores of ePTFE grafts.

METHODS

To assess translocation from the internal to the external surface, we placed 10(5) cfu of bacterial suspension inside ePTFE graft segments and suspended them in sterile broth for 72 h. To assess translocation from the external to the internal surface, we placed sterile broth inside ePTFE segments, and incubated them for 72 h in a bacterial suspension (10(5) cfu/mL). At 72 h, in addition to culturing the sterile broth and bacterial suspensions, the external and internal surfaces were first qualitatively cultured separately and then quantitatively cultured by sonication.

RESULTS

At 72 h, the sterile broth remained sterile. The bacterial suspensions yielded 10(7)-10(9) cfu/mL. Graft cultures indicated that colonization of one surface with either organism did not result in bacterial translocation to the other surface. Quantitative bacterial counts of the external vs. internal surfaces were significantly different (p < 0.01).

CONCLUSIONS

MRSA and E. coli do not translocate across ePTFE graft surfaces. These in-vitro findings help elucidate the pathogenesis of graft infections and prompt conduction of validation studies in-vivo.

Critical limb ischemia

Critical limb ischemia (CLI) continues to be a significantly morbid disease process for the aging population. Rigid guidelines for the management of patients with CLI are inappropriate due to the complexities that are involved in optimally treating these patients. A thin line exists in the decision process between medical management vs surgical management by revascularization or amputation, and the perception of "success" in this patient population is evolving. This review explores these issues and examines the challenges the treating physician will face when managing the care of patients with CLI. The epidemiology and natural history of CLI is discussed, along with the pathophysiology of the disease process. A review of the literature in regards to the different treatment modalities is presented to help the physician optimize therapy for patients with CLI. New scoring systems to help predict outcomes in patients with CLI undergoing revascularization or amputation are discussed, and an overview of the current status of patient-oriented outcomes is provided. Finally, we briefly examine emerging therapies for the treatment of CLI and provide an algorithm to help guide the practicing physician on how to approach the critically ischemic limb with regard to the complicated issues surrounding these patients.

Regulation of vascularization by hypoxia-inducible factor 1

Vascularization and vascular remodeling represent critical adaptive responses to tissue hypoxia that are mediated by hypoxia-inducible factor 1 (HIF-1). In patients with peripheral arterial disease, these responses are impaired by aging and diabetes, leading to critical limb ischemia and amputation. Intramuscular injection of an adenovirus encoding a constitutively active form of the HIF-1alpha subunit (CA5) increases the recovery of blood flow following femoral artery ligation in a mouse model of age-dependent critical limb ischemia. Intradermal injection of a plasmid encoding CA5 promotes healing of cutaneous wounds in a mouse model of diabetes. In cancer, vascularization is required for tumors to grow beyond microscopic size, a process that involves HIF-1-dependent production of angiogenic growth factors. Daily treatment of prostate cancer xenograft-bearing mice with low-dose anthracycline (doxorubicin or daunorubicin) chemotherapy inhibits HIF-1 DNA-binding activity, HIF-1-dependent expression of angiogenic growth factors, mobilization of circulating angiogenic cells, and tumor vascularization, thereby arresting tumor growth.

Perioperative outcomes and amputation-free survival after lower extremity bypass surgery in California hospitals, 1996-1999, with follow-up through 2004

OBJECTIVE

There are very few population-based studies of long-term outcomes after lower extremity (LE) bypass graft surgery. This study analyzes perioperative and long-term limb salvage and amputation-free survival outcomes for patients undergoing initial aortoiliac or femoropopliteal bypass graft surgery in California hospitals from 1996 to 1999.

METHODS

Administrative data with encrypted identifiers were used to identify a chronologically first, index admission of all patients undergoing LE bypass procedures for occlusive disease from 1996 to 1999. A 1993 to 1995 look-back period was used to exclude patients who had undergone prior bypass surgery or amputation procedures. Patients with incident procedures were then followed forward to determine subsequent hospitalizations and vital status through 2004. The study comprised 28,128 patients discharged from 345 California hospitals with a median 61.5-month follow-up. Risk factors included demographic characteristics, comorbid conditions, admission type, gangrene or ulceration, operation level, hospital LE bypass surgery volume, and year of discharge. Logistic regression was used to analyze 30-day outcomes, and Kaplan-Meier analysis and Cox proportional hazard models were used to analyze amputation-free survival.

RESULTS

Overall 30-day mortality was 4.3, and the 30-day major amputation rate was 2.6%. Limb salvage was 81.9% at 5 years and 76.4% at 9 years. Amputation-free survival was 51.5% at 5 years and 34.1% at 9 years. Risk factors were generally similar for both perioperative and late outcomes. Advanced age, higher comorbidity level, gangrene, and emergency or nursing home admission conferred significantly greater risk. Hospital volume was associated with both perioperative and late outcomes. African American and Hispanic patients had much higher amputation rates but did not have higher mortality risk after controlling for baseline severity of illness.

CONCLUSIONS

Long-term outcomes of LE bypass surgery were superior for high-volume hospital patients. Graft surveillance and risk factor follow-up care provide a major opportunity for quality improvement efforts. The contrast between traditional limb salvage and amputation-free survival outcomes raises questions about the value of surgical treatment, particularly for patients with limited life expectancy and without coding of tissue loss or critical limb ischemia.