Biomedical subjects

Nayan Sivamurthy

Publications and source records attributed to Nayan Sivamurthy.

8 recordsLinked to original sources

PubMed2006

Endovascular versus open mesenteric revascularization: immediate benefits do not equate with short-term functional outcomes.

BACKGROUND: Percutaneous therapy for symptomatic visceral occlusive disease is rapidly gaining popularity in many centers. This study evaluates the anatomic and functional outcomes of open and endovascular therapy for chronic mesenteric ischemia at an academic medical center. STUDY DESIGN: We performed a retrospective review of patients who underwent endovascular or open mesenteric arterial revascularization for chronic mesenteric ischemia between January 1989 and September 2003. Indications for revascularization included postprandial abdominal pain (92%) or weight loss (54%). All had atherosclerotic visceral occlusive disease with a median of 2 vessels with more than 50% stenosis or occlusion on angiography. Sixty patients (44 women, mean age 66 years) underwent 67 interventions (43 vessels bypassed, 23 vessel endarterectomies, 22 vessel angioplasty and stents). The median numbers of vessels revascularized were two in the open group and one in the endovascular group. RESULTS: Thirty-day mortality and cumulative survival at 3 years were similar (open, 15% and 62% +/- 9%; endovascular, 21% and 63%+/-14%, respectively; p=NS). Cumulative patencies at 6 months were 83%+/-7% and 68%+/-14% in the open and endovascular groups, respectively (p=NS). Major morbidity, median postoperative length of stay, and cumulative freedom from recurrent symptoms at 6 months were significantly greater in the open group (open, 46%, 23 days, and 71%+/-7%, respectively; endovascular, 19%, 1 day, and 34%+/-10%, respectively; p < 0.01). CONCLUSIONS: Endovascular revascularization is attractive because it carries equivalent patency to open revascularization. Symptomatic benefit of endovascular revascularization is not achieved, probably as a result of incomplete revascularization. Despite incomplete revascularization, endovascular therapy has equivalent survival and lower morbidity compared with open revascularization. Complete endovascular revascularization needs further evaluation to determine if it is superior to open revascularization. In the interim, endovascular therapy should be reserved for the patient unable to undergo open revascularization.

Adult↗

PubMed2006

Adjunctive primary stenting of Zenith endograft limbs during endovascular abdominal aortic aneurysm repair: implications for limb patency.

OBJECTIVE: Endograft limb occlusion is an infrequent but serious complication of endovascular abdominal aortic aneurysm (AAA) repair. The insertion of additional stents within the endograft limb may prevent future occlusion. This study evaluates limb patency with and without adjunctive stenting of endograft limbs at the time of endovascular AAA repair. METHODS: We performed a retrospective review of 248 patients who underwent endovascular abdominal aortic aneurysm repair with the Zenith AAA endovascular graft between 1999 and 2004. Among these patients, two groups were identified: 64 patients with adjunctive stents placed in 85 limbs and 184 patients without additional bare stent placement in endograft limbs at the time of endovascular AAA repair. RESULTS: Women comprised 23% of stented and 11% of unstented patients (P = .02). The mean length of follow-up in the stented and unstented groups was 2.0 years. There were 13 instances of limb thrombosis in 13 patients (5.2% of patients, 2.7% of limbs), all in the unstented group. No limb occlusions occurred in the presence of adjunctive bare metal stents. Seventy-three percent of the occlusions occurred < or = 6 months of endovascular AAA repair. Two patients (15%) had no symptoms of lower-extremity ischemia despite graft limb occlusion and did not undergo intervention. The others underwent thrombectomy (n = 2), thrombectomy with bare stent placement (n = 3), femoral-femoral bypass (n = 4), thrombolysis (n = 1), and thrombolysis with bare stent placement (n = 1). Of the seven who underwent thrombectomy or thrombolysis, three had no additional stents placed at the secondary procedure, and two of these three went on to rethrombose. By life-table analysis, primary patency at 3 years in the stented and nonstented limbs was 100% +/- 0% and 94% +/- 3%, respectively (P = .05). CONCLUSIONS: The intraoperative insertion of additional bare metal stents appeared to eliminate the risk of thrombosis and was without complication. Of the 85 stented limbs in this series, not one occluded. The overall rate of limb thrombosis was low, with most limb occlusions occurring < or = 6 months of stent-graft insertion, and would probably have been even lower had we been able to identify all high-risk cases for prophylactic adjunctive stenting. Limb occlusion denotes an underlying problem with the graft, which if left untreated after thrombectomy or thrombolysis will lead to rethrombosis. Postoperative imaging was of little value in detecting impending limb occlusion. Based on these findings, we believe one should identify and stent any limbs that appear to be at risk for thrombosis, but this study lacks the data to predict which limbs need stenting.

Aged↗

PubMed2004

Divergent outcomes after percutaneous therapy for symptomatic renal artery stenosis.

OBJECTIVE: Percutaneous intervention for symptomatic renal artery atherosclerosis is rapidly replacing surgery in many centers. This study evaluated the anatomic and functional outcomes of endovascular therapy for atherosclerotic renal artery stenosis on a combined vascular surgery and interventional radiology service at an academic medical center. METHODS: This was a retrospective analysis of patients who underwent renal artery angioplasty with or without stenting between January 1990 and June 2002. Indications included hypertension (86%) and rising serum creatinine concentration (55%). One hundred forty-six patients (80 women; average age, 71 years [range, 44-89 years]) underwent 183 attempted interventions (64 to treat bilateral stenosis). Forty-five percent of patients had significant bilateral disease: 27% had greater than 50% bilateral stenosis, and the remainder had nonfunctioning, absent, or occluded vessels. RESULTS: Of 183 planned interventions, technical success (<30% residual stenosis) was achieved in 179 vessels (98%) with placement of 137 stents (75%). Thirty-day mortality was 0.7%. The major morbidity rate was 4%, and the procedure-related complication rate was 18%. Five-year cumulative patient mortality was 25%. Primary patency, assisted primary patency, and recurrent stenosis rates were 82% +/- 9%, 100% +/- 0%, and 30% +/- 7%, respectively, at 5 years. Within 3 months of the procedure, 52% of patients who received treatment of hypertension demonstrated clinical benefit (hypertension improved or cured), which was maintained in 68% of patients at 5 years. Serum creatinine concentration was lowered or stabilized in 87% of patients within 3 months of the procedure, but this benefit, including freedom from dialysis, was maintained in only 45% of patients at 5 years. CONCLUSIONS: Endovascular intervention for symptomatic atherosclerotic renal artery stenosis is technically successful. There were excellent patency and low recurrent stenosis rates. There is immediate clinical benefit for most patients, but divergent long-term functional outcomes. Endovascular interventions modestly enhance the care of the patient with hypertension, but poorly preserve long-term renal function in the patient with chronic renal impairment.

Academic Medical Centers↗

PubMed2003

Percutaneous therapy for renal artery fibromuscular dysplasia.

Fibromuscular dysplasia (FMD) accounts for 10% of cases of renal artery stenosis. This study evaluates the anatomic and functional outcomes of endovascular therapy for symptomatic renal artery FMD at an academic medical center. A retrospective analysis of records from patients who underwent percutaneous transluminal renal artery angioplasty (PTRA) found 14 patients (all female) who underwent 19 interventions on 18 renal artery segments. Significant cardiovascular comorbidities were few in this patient population. The PTRA technical success rate was 95%. There were no periprocedural mortalities. Primary patency rates were 81%, 69%, 69%, and 69% at 2, 4, 6, and 8 years. Assisted primary patency rates were 87%, 87%, 87%, and 87% at 2, 4, 6, and 8 years. The restenosis rate was 25% at 8 years. Clinical benefit (improved or cured hypertension) was seen in 79% of patients overall; 65% of patients maintained this benefit at 8 years by life-table analysis. Percutaneous endovascular intervention for clinically symptomatic FMD of the renal arteries is technically successful, safe, and durable. Most patients demonstrate immediate clinical benefit and retain durable functional outcomes.

Angioplasty, Balloon↗

PubMed2002

A biologically active VEGF construct in vitro: implications for bioengineering-improved prosthetic vascular grafts.

Prosthetic arterial grafts are unable to develop an intact endothelial lining after implantation, predisposing them to fail. Strategies have been sought to enhance endothelialization using growth factors and cytokines. This study assessed the biologic activity of vascular endothelial growth factor (VEGF) covalently linked to bovine serum albumin (BSA). Native and modified VEGF were assayed for endothelial cell migration and proliferation. Migration assays were performed comparing the effects of 2% fetal bovine serum (FBS), 50 ng/mL, 100 ng/mL, and 200 ng/mL of native VEGF and VEGF-BSA. Proliferation assays were performed by using Alamar Blue comparing cellular growth in 1% FBS, 10% FBS, 100 ng/mL unbound VEGF, and 100 ng/mL VEGF-BSA. VEGF is a potent chemotactic agent for endothelial cells in both unbound and bound states. Native VEGF solutions (50 ng/mL, 100 ng/mL, and 200 ng/mL) stimulated 23.9 cells/high power field (HPF), 35.3 cells/HPF, and 49.1 cells/HPF (p < 0.005). VEGF-BSA solutions stimulated 25.9 cells/HPF, 39.1 cells/HPF, and 69.0 cells/HPF (p < 0.001). VEGF-BSA and native VEGF supported similar increased cellular proliferation compared with 1% FBS media (p < 0.002). Modified VEGF retains its chemotactic and proliferative properties in vitro. These findings suggest that bare prosthetic surfaces lined with VEGF bound to a "basecoat" albumin may support endothelial cell proliferation and migration and thereby offer new strategies to improve graft patency.

Blood Vessel Prosthesis↗

PubMed2002

Attenuated retinoblastoma gene product and associated E2F/retinoblastoma imbalance in anastomotic intimal hyperplasia.

OBJECTIVE: The retinoblastoma gene product is a cell cycle control protein that when inhibited allows cell proliferation to progress by releasing E2F. Retinoblastoma manipulation has been attempted to prevent intimal hyperplasia (IH) in injured native vessels by arresting vascular smooth muscle cell proliferation. However, no studies have identified the role, if any, of retinoblastoma in anastomotic IH formation after prosthetic arterial grafting. The goal of this study was to describe the relation of retinoblastoma and E2F to anastomotic IH with analyzing retinoblastoma/E2F levels, retinoblastoma phosphorylation, and transcription of retinoblastoma and E2F in prosthetic arterial grafting. METHODS: Six-mm-diameter expanded polytetrafluoroethylene carotid interposition grafts (n = 12) were implanted in 25-kg mongrel dogs. The intervening arterial segments were harvested as controls. The distal anastomoses were harvested at 14 and 30 days after implantation for immunoblot, messenger RNA (mRNA), and immunohistochemistry analyses. Tissue homogenate was separated with sodium dodecylsulfate-polyacrylamide gel electrophoresis and probed with antibody to total retinoblastoma, phosphorylated retinoblastoma at serine 795, serine 780, and serine 807/811, and E2F-1. Bands at each time point were quantitated and compared with control artery (n = 12). Each lane was standardized with reprobing with antibody to beta-tubulin. Immunohistochemistry was performed with antibody to retinoblastoma. Retinoblastoma and E2F mRNA expression levels in anastomotic IH and control artery were analyzed with an oligonucleotide microarray. RESULTS: Total retinoblastoma, from immunoblot analysis, was decreased at the 14-day and 30-day distal anastomoses by 35.7% and 33.6%, respectively, compared with control (P <.01). Furthermore, retinoblastoma at these time points was unphosphorylated at phosphorylation sites serine 795, serine 780, and serine 807/811. E2F-1 levels at 14 days and 30 days were unchanged compared with control. Positive staining for retinoblastoma was seen in endothelial and vascular smooth muscle cell from control, 14-day, and 30-day tissue. A qualitative decrease appeared to be seen in retinoblastoma in the neointima at 14 and 30 days compared with the native wall. No differential expression of retinoblastoma and E2F mRNA was seen in anastomotic IH compared with control. CONCLUSION: This study showed that total retinoblastoma levels are decreased and E2F-1 levels remain unchanged in anastomotic IH. Attenuated retinoblastoma is a novel concept to anastomotic IH after prosthetic arterial grafting. Retinoblastoma/E2F imbalance may not be the result of transcriptional regulation and may increase unbound E2F to promote cell proliferation. Hypophosphorylation of remaining retinoblastoma may minimize uncontrolled proliferation by preventing further increases in unbound E2F. Therefore, retinoblastoma/E2F imbalance may lead to the early but limited increase in cell proliferation seen after prosthetic arterial grafting and appears to contribute to the development and progression of anastomotic IH.

Anastomosis, Surgical↗

PubMedDate not supplied

Endovascular management of central venous stenoses in the hemodialysis patient: results of percutaneous therapy.

The purpose of this study was to determine the functional results of transvenous angioplasty for the treatment of central venous stenoses in patients with failing upper extremity arteriovenous access. Two hundred consecutive patients presented with threatened arteriovenous access from January 1999 through July 2002. Angiographic evidence of central venous stenosis was present in 35 patients (18%) (superior vena cava 5, brachiocephalic veins 14, and subclavian veins 18). Follow-up averaged 873 days from the date of initial intervention. The initial technical success rate was 89%. Primary patency for each intervention was 85% at 30 days, 55% at 6 months, 43% at 1 year, and 0% at 2 years. Assisted primary patency rates were 88% at 30 days, 80% at 1 year, and 64% at 2 years. Freedom from central venous dialysis catheter placement was 82% at 30 days, 63% at 3 months, 51% at 1 year, 37% at 2 years, and 25% at 3 years. Freedom from a dialysis catheter was superior in those patients with autogenous arteriovenous fistulas. Transvenous angioplasty appears to be beneficial for hemodialysis patients with central venous stenoses, and it helps preserve functional access in the affected extremity, particularly in patients with autogenous fistulas.

Adult↗

PubMedDate not supplied

Endovascular exclusion of subclavian artery pseudoaneurysm.

Subclavian artery pseudoaneurysms are typically a rare occurrence commonly caused by iatrogenic injury and trauma. We describe an endovascular approach employing a brachiofemoral through-wire technique for the treatment of a left subclavian artery pseudoaneurysm in the presence of a hostile aortic arch and great vessel anatomy.

Aged↗