Nirvana Sadaghianloo

Vein graft adaptation and fistula maturation in the arterial environment

Veins are exposed to the arterial environment during two common surgical procedures, creation of vein grafts and arteriovenous fistulae (AVF). In both cases, veins adapt to the arterial environment that is characterized by different hemodynamic conditions and increased oxygen tension compared with the venous environment. Successful venous adaptation to the arterial environment is critical for long-term success of the vein graft or AVF and, in both cases, is generally characterized by venous dilation and wall thickening. However, AVF are exposed to a high flow, high shear stress, low-pressure arterial environment and adapt mainly via outward dilation with less intimal thickening. Vein grafts are exposed to a moderate flow, moderate shear stress, high-pressure arterial environment and adapt mainly via increased wall thickening with less outward dilation. We review the data that describe these differences, as well as the underlying molecular mechanisms that mediate these processes. Despite extensive research, there are few differences in the molecular pathways that regulate cell proliferation and migration or matrix synthesis, secretion, or degradation currently identified between vein graft adaptation and AVF maturation that account for the different types of venous adaptation to arterial environments.

Pelvic ischemia and quality of life scores after interventional occlusion of the hypogastric artery in patients undergoing endovascular aortic aneurysm repair

OBJECTIVE The aim of this study was to analyze the pelvic ischemic complications and their impact on quality of life after interventional occlusion of the hypogastric artery (IOHA) in patients undergoing endovascular aortic aneurysm repair (EVAR). METHODS Between January 2004 and April 2012, 638 consecutive patients with aortoiliac aneurysm treated by EVAR were prospectively registered in two teaching hospitals. We identified all EVAR patients who underwent IOHA. Demographic, clinical, and radiologic data were extracted from electronic databases and patient records as requested. All patients who survived the postoperative period took part in a quality of life survey, the Walking Impairment Questionnaire (WIQ), which included four items: pain, distance, walking speed, and stair climbing. Outcome measures included the 30-day rate of pelvic ischemic complications, the buttock claudication (BC) rate at 30 days and during follow-up, and the comparative WIQ scores between patients with persistent BC, those with regressive BC, and those who never had BC after the IOHA procedure. RESULTS A total of 71 patients (97% men; mean age, 76 years ± 7.69) required 75 IOHA procedures. These were deemed proximal in 44 cases and distal in 31, with use of coil embolization in 64%, Amplatzer plug in 24%, or a combination of coils and plugs in 12%. The technical success rate was 100%. Two patients (2.8%) experienced fatal acute pelvic ischemic complications in the postoperative period after EVAR. Another patient died of iliac rupture during EVAR, leading to an operative mortality rate of 4.3%. Eighteen patients (25.3%) suffered BC, among whom 11 cases resolved at a median follow-up of 42 months. Young age (odds ratio, 0.92; 95% confidence interval, 0.85-0.99; P = .03) and distal IOHA (odds ratio, 3.5; 95% confidence interval, 1.01-11.51; P = .04) were independent predictors of BC occurrence. The actuarial rate of persistent BC was 85% at 18 months. The WIQ scores were lower for patients with persistent BC (median score, 35.04; interquartile range, 16.36; P = .001) compared with patients with regressive BC (median score, 76.5; interquartile range, 36.66; P = .02) or those who never experienced BC after the IOHA procedure (median score, 65.34; interquartile range, 10.94; P < .0003). CONCLUSIONS Pelvic ischemia associated with IOHA may be severe and lead to fatality after EVAR. Our data show that BC may lead to severe quality of life impairment when it does not regress during follow-up.

Early surgical thrombectomy improves salvage of thrombosed vascular accesses

OBJECTIVE The timing and urgency of salvage attempts for acutely thrombosed hemodialysis vascular accesses remain poorly defined. We examined the outcome of early surgical thrombectomy after acute access thrombosis to assess the influence of expedited timing on access salvage. METHODS Between January 2007 and October 2012, 114 surgical thrombectomy attempts were performed on 82 patients to salvage 89 accesses. The time between the diagnosis of thrombosis and admission to the operative suite (T1), the time between diagnosis and the following dialysis session (T2), and clinical and biologic parameters were collected prospectively. Data were retrospectively compared between the early (T1 <6 hours) and later (T1 >6 hours) treatment groups. The main outcome measure was technical success. Kaplan-Meier survival analysis was used to estimate functional patency rates. RESULTS Mean patient follow-up was 22 ± 18 months. The mean time from referral to procedure (T1) was 5.7 ± 4.5 hours. The mean time T1 was 3.6 ± 1.2 hours in the early group and 10.3 ± 5.4 hours in the later group. The mean time to dialysis (T2) was 14.3 ± 6.5 hours in the early group and 23.9 ± 9.4 hours in the later group. Thrombectomy performed ≤ 6 hours after diagnosis (T1 <6 hours) had significantly higher technical success of 86% compared with 69% for thrombectomy performed later (T1 >6 hours; P = .04). The two groups did not differ significantly in patient comorbidities, type of access, or adjunctive procedures performed (P ≥ .1). At 12 months, the primary patency rate for all index cases, including technical failures, was 55% ± 7.1% in the early group and 33% ± 9.7% in the later group (P = .13). The secondary patency rate was 67% ± 6.8% in the early group and 50% ± 9.9% in the later group (P = .05). CONCLUSIONS After acute access thrombosis, early surgical thrombectomy was associated with higher technical success and potentially improved midterm patency.

The mouse aortocaval fistula recapitulates human arteriovenous fistula maturation

Several models of arteriovenous fistula (AVF) have excellent patency and help in understanding the mechanisms of venous adaptation to the arterial environment. However, these models fail to exhibit either maturation failure or fail to develop stenoses, both of which are critical modes of AVF failure in human patients. We used high-resolution Doppler ultrasound to serially follow mice with AVFs created by direct 25-gauge needle puncture. By day 21, 75% of AVFs dilate, thicken, and increase flow, i.e., mature, and 25% fail due to immediate thrombosis or maturation failure. Mature AVF thicken due to increased amounts of smooth muscle cells. By day 42, 67% of mature AVFs remain patent, but 33% of AVFs fail due to perianastomotic thickening. These results show that the mouse aortocaval model has an easily detectable maturation phase in the first 21 days followed by a potential failure phase in the subsequent 21 days. This model is the first animal model of AVF to show a course that recapitulates aspects of human AVF maturation.

Blunt abdominal aortic trauma in paediatric patients.

BACKGROUND Blunt abdominal aortic trauma (BAAT) is a very rare occurrence in children, with significant morbidity and mortality. Varied clinical presentations and sparse literature evidence make it difficult to define the proper management policy for paediatric patients. METHOD We report our centres data on three consecutive children with BAAT managed between 2006 and 2010. A Medline search was also performed for relevant publications since 1966, together with a review of references in retrieved publications. RESULTS Forty children (range 1-16 years) were included in our final analysis. Motor vehicle crashes (MVC) were the leading cause of injury (65%). The in-hospital mortality rate was 7.5% (3/40). Nine patients (22.5%) ended up with residual sequelae. Main primary aortic lesions were complete wall rupture (12.5%), intimal transection (70%) and pseudoaneurysm (15%). Twenty-eight children underwent aortic surgical repair (70%). Among the 12 non-operatively managed patients, 41.6% had complications, including one death. CONCLUSION Symptomatic lesions and complete ruptures should undergo immediate surgical repair. Circumferential intimal transections are at high risk of complication and should also receive intervention. Partial intimal transections and delayed pseudoaneurysms can be initially observed by clinical examination and imaging. Patients with these latter pathologies should be operated on at any sign of deterioration.

Percutaneous angioplasty of long tibial occlusions in critical limb ischemia.

BACKGROUND The aim of this study was to assess the midterm results of percutaneous angioplasty in patients with critical limb ischemia (CLI) and long tibial occlusions. METHODS Between January and September 2011, 34 consecutive patients with patent femoropopliteal artery and 49 segmental tibial occlusions >8 cm were included in our prospective, single-center cohort study. Clinical success (defined as wound healing and survival without major amputation), patency, and freedom from target vessel revascularization (TVR) were examined. RESULTS The median age of the patients was 75 (53-89) years, 74% were diabetic, and 89% of the limbs studied were Rutherford 5 and 6. Median follow-up was 12.5 (1-15) months. The 1-year clinical success rate was 65%, higher among patients with technical success (76% vs. 25%, P = 0.01) and patients with 2 or 3 patent tibial arteries after the procedure (90% vs. 41% in patients with only 1 patent artery, P = 0.003). At 1 year, primary and secondary patency rates were 13% and 32%, respectively (24% and 58% without technical failures). The 1-year freedom-from-TVR rate was 34%. CONCLUSIONS Despite high technical failure rates and the need for repeat procedures, percutaneous angioplasty of long tibial occlusions enhances wound healing, especially when integrated into a maximal revascularization approach.

Increased reintervention in radial-cephalic arteriovenous fistulas with anastomotic angles of less than 30 degrees

OBJECTIVE Although radial-cephalic (RC) and brachial-cephalic (BC) fistulas are the recommended primary accesses for hemodialysis, access failure is frequently due to juxta-anastomotic stenosis (JAS). Because increased turbulence at the anastomosis may lead to JAS, we hypothesized that an acute angle at the arteriovenous anastomosis is associated with JAS, reduced fistula patency, and increased reinterventions. METHODS Between February 2013 and September 2014, the anastomotic angle and vessel diameters were prospectively collected for all patients who underwent RC or BC fistula creation. The primary end point was reintervention on the juxta-anastomotic segment. Secondary end points were primary and secondary patency of the fistula. RESULTS A total of 149 patients (median age, 72 years) received 73 RC and 76 BC fistulas; the median follow-up was 7 months (range, 1-22 months) for RC and 12 months (range, 2-24 months) for BC fistulas. The median anastomotic angle in RC fistulas, was 30°. Anastomotic angles of <30° were associated with reduced primary patency (38% vs 66%, P = .003) and secondary patency (84% vs 97%, P = .02) and increased numbers of reinterventions (67% vs 34%, P = .001). Cox analysis showed that an anastomotic angle of <30° was an independent factor predicting decreased primary patency (P = .009) and secondary patency (P = .03) as well as increased reinterventions (P = .004). In BC fistulas, the median anastomotic angle was 90°. Patients with anastomotic angles <90° and ≥90° had similar rates of primary patency (67% vs 67%, P = .39) and secondary patency (93% vs 94%, P = .89) at 6 months, with a similar reintervention rate at 12 months (31% vs 32%, P = .56). Vein diameter was the only factor that predicted reintervention (P < .0001). CONCLUSIONS RC fistulas with anastomotic angles of <30° have reduced primary and secondary patency and increased numbers of reinterventions, suggesting that, if possible, surgeons should avoid an anastomotic angle of <30° when creating RC fistulas. Anastomotic angles of <90° or ≥90° may not play a role in outcome of BC fistulas.

Successful treatment of a spontaneous rupture of the left external iliac vein in a man

Spontaneous rupture of the external iliac vein associated with a May–Thurner syndrome is infrequent, particularly in men. We report a case of previously healthy 73-year-old man with a left iliac vein thrombosis, who presented a large lower left abdominal hematoma of sudden-unset. Emergent laparotomy revealed a 3-cm longitudinal tear in the left external iliac vein, which was repaired primarily. Patients recovery was uneventful. Possible etiological factors have been identified as venous hypertension due to iliac vein thrombosis associated with Cockett syndrome, as well as inflammatory venous wall. Some other estrogenic factors could explain female preponderance of the event.

Ephrin type-B receptor 4 activation reduces neointimal hyperplasia in human saphenous vein in vitro

BACKGROUND Vein bypass is an essential therapy for patients with advanced peripheral and coronary artery disease despite development of neointimal hyperplasia. We have shown that stimulation of the receptor tyrosine kinase ephrin type-B receptor 4 (Eph-B4) with its ligand ephrin-B2 prevents neointimal hyperplasia in murine vein grafts. This study determines whether Eph-B4 in adult human veins is capable of phosphorylation and activation of downstream signaling pathways, as well as functional to release nitric oxide (NO) and prevent neointimal hyperplasia in vitro. METHODS Discarded human saphenous veins were taken from the operating room and placed in organ culture without or with ephrin-B2/Fc (2 μg/mL) for 14 days, and the neointima/media ratio was measured in matched veins. Primary human umbilical vein endothelial cells were treated with ephrin-B2/Fc (2 μg/mL) and examined with quantitative polymerase chain reaction, Western blot, immunoassays, and for release of NO. Ephrin-B2/Fc (2 μg/mL) was placed on the adventitia of saphenous veins treated with arterial shear stress for 24 hours in a bioreactor and activated Eph-B4 examined with immunofluorescence. RESULTS The baseline intima/media ratio in saphenous vein rings was 0.456 ± 0.097, which increased to 0.726 ± 0.142 in untreated veins after 14 days in organ culture but only to 0.630 ± 0.132 in veins treated with ephrin-B2/Fc (n = 19, P = .017). Ephrin-B2/Fc stimulated Akt, endothelial NO synthase and caveolin-1 phosphorylation, and NO release (P = .007) from human umbilical vein endothelial cells (n = 6). Ephrin-B2/Fc delivered to the adventitia stimulated endothelial Eph-B4 phosphorylation after 24 hours of arterial stress in a bioreactor (n = 3). CONCLUSIONS Eph-B4 is present and functional in adult human saphenous veins, with intact downstream signaling pathways capable of NO release and prevention of neointimal hyperplasia in vitro. Adventitial delivery of ephrin-B2/Fc activates endothelial Eph-B4 in saphenous veins treated with arterial shear stress in vitro. These results suggest that stimulation of Eph-B4 function may be a candidate strategy for translation to human clinical trials designed to inhibit venous neointimal hyperplasia.

Customized femoral vein grafts for inferior vena cava reconstruction

After extended en-bloc resection of a retroperitoneal neoplasm, prosthetic grafts can efficiently replace the inferior vena cava. However, in cases of concomitant biliary or bowel surgery, there is a risk of infection, and autogenous materials typically used present with size match. We present a method of autogenous graft construction using the femoral vein for replacement of the inferior vena cava, with an alternate configuration for renal vein implantation.