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Background Transplant renal artery stenosis (TRAS) may lead to graft dysfunction and failure. Progressive deterioration of renal allograft function may be exacerbated by contrast-induced nephrotoxicity during iodine contrast administration for renovascular imaging of allografts. We present our institutional experience of endovascular management for TRAS using CO2 digital subtraction angiography (CO2-DSA) and balloon angioplasty to manage failing renal transplants. Methods Four patients with renal allografts from March 2017–May 2018 were referred for graft dysfunction and pending renal transplant failure. Indications for referral included refractory hypertension, decreasing renal functioning, and elevated renovascular systolic velocities. Results Median age of the four patients was 41.5 years (22–60 years). There were two male and female patients. Chronic hypertension and type 2 diabetes mellitus were the most common comorbidities. An average total of 75 mL of CO2 was used, supplemented with 17.4 mL of iodinated contrast. All patients had improvements in renal function following intervention with a mean decrease in systolic and diastolic blood pressure of 25.8% and 21.4%, respectively. We also observed a mean decrease of BUN by 13.6% and creatinine by 37.4%. Additionally, eGFR increased by 37.7%. All allografts survived after surgery, and only one patient required repeat angioplasty for recurrence. Conclusions CO2-DSA with balloon angioplasty can be successfully utilized to salvage deteriorating kidney allograft function in patients with TRAS.

Concern over perioperative and long-term durability of lower extremity revascularizations among active smokers is a frequent deterrent for vascular surgeons to perform elective lower extremity revascularization. In this study, we examined perioperative outcomes of lower extremity endovascular (LEE) revascularization and open lower extremity bypass (LEB) in active smokers with intermittent claudication (IC) and critical limb ischemia (CLI).Active smokers undergoing LEE or LEB from 2011 to 2014 were identified in the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) targeted vascular data set. Patient demographics, comorbidities, anatomic features, and perioperative outcomes were compared between LEE and LEB procedures. Subgroup analysis was performed for patients undergoing revascularization for IC and CLI independently.From 2011 to 2014, 4706 lower extremity revascularizations were performed in active smokers (37% of all revascularizations). In this group, 1497 were LEE (55.6% for CLI, 13.4% for below-knee pathology) and 3209 were LEB (68.9% CLI, 34.7% below-knee). Patients undergoing LEE had higher rates of female gender, hypertension, end-stage renal disease, and diabetes (all P ≤ .02). LEE patients also had a higher frequency of prior percutaneous interventions (22.7% vs 17.2%; P .01) and preoperative antiplatelet therapy (82.3% vs 78.7%; P = .02). On risk-adjusted multivariate analysis, LEE patients had higher need for reintervention on the treated arterial segment than LEB (5.1% vs 5.2%; odds ratio [OR], 1.52; 95% confidence interval [CI], 1.08-2.13; P = .02) but had lower wound complications (3.1% vs 13.2%; OR, 0.32; 95% CI, 0.23-0.45; P .01) and no statistically significant difference in 30-day mortality (0.6% vs 0.9%), myocardial infarction or stroke (1.1% vs 2.6%), or major amputation (3.2% vs 2.1%) in the overall cohort of active smokers. In the IC subgroup, myocardial infarction or stroke was significantly higher in the LEB group (1.9% vs 0.6%; OR, 1.83; 95% CI, 1.17-1.97; P = .03), although no difference was found in the CLI subgroup (2.8% vs 1.4%; OR, 0.75; 95% CI, 0.37-1.52; P = .42,). Also in IC group, there was a trend for lower major amputation rates ≤30 days in the LEE group, whereas in the CLI group, LEE had a trend toward higher risk of early amputation compared with LEB.In active smokers, LEB for IC and CLI requires fewer reinterventions but is associated with a higher rate of postoperative wound complications compared with LEE revascularization. However, the risk for limb amputation is higher in actively smoking patients when treated by LEE compared with LEB for CLI. Importantly, cardiovascular complications are significantly higher in actively smoking patients with IC undergoing LEB compared with LEE. This additional cardiovascular risk should be carefully weighed when proposing LEB for actively smoking patients with nonlimb-threatening IC.

ObjectivesCeliac artery, superior mesenteric artery, and inferior mesenteric artery injuries are often grouped together as major visceral artery injuries with an incidence of MethodsThe Trauma Quality Improvement Program (2010–2016) was queried for patients with injury to the celiac artery, superior mesenteric artery, or inferior mesenteric artery. A multivariable logistic regression model was used for analysis. Separate subset analyses using blunt trauma patients and penetrating trauma patients were performed.ResultsFrom 1,403,466 patients, 1730 had single visceral artery injuries with 699 (40.4%) involving the celiac artery, 889 (51.4%) involving the superior mesenteric artery, and 142 (8.2%) involving the inferior mesenteric artery. The majority of patients were male (79.2%) with a median age of 39 years old, and median injury severity score of 22. Compared to celiac artery and inferior mesenteric artery injuries, superior mesenteric artery injuries had a higher rate of severe (grade >3) abbreviated injury scale for the abdomen (57.5% vs. 42.5%, p ConclusionsCompared to injuries of the celiac artery and inferior mesenteric artery, traumatic superior mesenteric artery injury is associated with a higher mortality. Moreover, while superior mesenteric artery injury does not act as an independent risk factor for mortality in adult patients with blunt force trauma, it nearly quadruples the risk of mortality in adult trauma patients with penetrating mechanism of injury. Future prospective research is needed to confirm these findings and evaluate factors to improve survival following major visceral artery injury.

Carotid endarterectomy (CEA) is the most commonly performed surgical procedure to reduce the risk of stroke. The operation may be performed under general anesthesia (GA) or regional anesthesia (RA). We used a national database to determine how postoperative outcomes were influenced by gender and type of anesthesia used.All patients who underwent CEA between 2005 and 2011 were identified from the American College of Surgeons National Surgical Quality Improvement Program database (N = 41,442). Incidence of stroke and myocardial infarction (MI) within 30 days as well as other postoperative complications, operative time, and hospital length of stay were examined in groups separated by gender and anesthesia type. Multivariable logistic regression with effect modification was used to determine significant risk-adjusted differences between genders and type of anesthesia to assess outcomes after CEA.The male-to-female ratio among CEA cases performed was approximately 3:2. Most cases were performed under GA (85% male patients, 86% female patients). Adjusted multivariable analysis showed no statistical difference in rates of MI and stroke based on gender or type of anesthesia used. There were, however, higher 30-day postoperative local complications and MI (both P .05) in those who had GA vs RA regardless of gender before adjustment. Total operative time was decreased (mean difference, -8.15 minutes; 95% confidence interval, -10.09 to -6.21; P .001) and length of stay was increased (mean difference, 0.34 day; 95% confidence interval, 0.14-0.54; P .02) in women, with statistical significance, whether RA or GA was used.On adjusted multivariate analysis, there is no statistically significant difference in postoperative incidence of MI or stroke between men and women undergoing CEA. Use of RA vs GA did not affect this finding. Furthermore, there was no correlation between gender and the type of anesthesia chosen. Women, however, experienced decreased operative times and increased length of stay regardless of anesthesia type.

General anesthesia (GA) and locoregional anesthesia (LA) are two anesthetic options for endovascular repair of ruptured abdominal aortic aneurysms (REVAR). Studies on elective endovascular repair of nonruptured aneurysms have indicated that in select patients, LA may provide improved outcomes compared with GA. We aimed to examine the 30-day outcomes in patients undergoing REVAR using GA and LA in a contemporary nationwide cohort of patients presenting with ruptured abdominal aortic aneurysms.Patients who underwent REVAR using GA and LA from January 2011 through December 2015, inclusively, were studied in the American College of Surgeons' National Surgical Quality Improvement Program (ACS NSQIP)-targeted EVAR database. Univariate and multivariate analyses were used to compare preoperative demographics, operation-specific variables, and 30-day postoperative outcomes between the two groups.Six-hundred ninety patients were identified to have undergone REVAR from 2011 to 2015, of which 12.5% (86) were performed under LA. For the entire cohort, the mean age was 74.3 years, and 80% were male. Mean aneurysm size was 7.6 cm and did not differ between the two anesthetic groups. Major comorbidities were similar between both groups, except a slightly higher rate of congestive heart failure in the LA group (7.0% vs. 2.5%, P = 0.02). Proximal or distal aneurysm extent also did not differ between the two groups. There was a significantly higher rate of bilateral percutaneous access in the LA group (59.3% vs. 25.2%, P 0.01). REVAR under LA had shorter mean operative time (132 vs. 166 min, P 0.01) and lower rate of concomitant lower extremity revascularization (2.3% vs. 10.6%, P 0.01). There were no differences in need for perioperative transfusion or any other adjunctive procedures. Ultimately, 30-day mortality was significantly lower in the LA group (16.3% vs. 25.2%, P 0.01). This difference was more pronounced in the subgroup of patients with hemodynamic instability (15.4% vs. 39.4%, P 0.01). The LA group also demonstrated significantly shorter intensive care unit (ICU) length of stay (3.0 vs. 5.0 days, P = 0.01) and low rates of postoperative pneumonia (3.5% vs. 10.9%, P = 0.03). After adjustment for demographics, comorbid conditions, hypotensive status, and aneurysm characteristics, there was a two-fold higher mortality in patients undergoing REVAR using GA versus LA, with a four-fold increase in the hemodynamically unstable cohort.The ACS NSQIP-targeted EVAR database shows that LA is used in only 12.5% of patients undergoing REVAR in this nationwide cohort. This rate does not change when examining the subset of patients who are hemodynamically unstable. Other benefits include shorter ICU lengths of stay and lower rates of pneumonia. These data suggest that LA should be considered in patients undergoing REVAR, regardless of hemodynamic instability.

Objective Dynamic changes in anatomic geometry of the inferior vena cava from changes in intravascular volume may cause passive stresses on inferior vena cava filters. In this study, we aim to quantify variability in inferior vena cava dimensions and anatomic orientation to determine how intravascular volume changes may impact complications of inferior vena cava filter placement, such as migration, tilting, perforation, and thrombosis. Methods Retrospective computed tomography measurements of major axis, minor axis, and horizontal diameters of the inferior vena cava at 1 and 5 cm below the lowest renal vein in 58 adult trauma patients in pre-resuscitative (hypovolemic) and post-resuscitative (euvolemic) states were assessed in a blinded fashion by two independent readers. Inferior vena cava perimeter, area, and volume were calculated and correlated with caval orientation. Results Mean volumes of the inferior vena cava segment on pre- and post-resuscitation scans were 9.0 cm3 and 11.0 cm3, respectively, with mean percentage increase of 48.6% ( P Conclusions There is significant anisotropic variability of infrarenal inferior vena cava geometry with significantly greater expansive and compressive forces in the minor axis. There can be significant volumetric changes in the inferior vena cava with associated perimeter changes but the major axis left-anterior oblique caval configuration is always maintained. These significant dynamic forces may impact inferior vena cava filter stability after implantation. The consistent major axis left-anterior oblique obliquity may lead to underestimation of the inferior vena cava diameter used in standard anteroposterior venography, which may influence initial filter selection.

Ruptured endovascular aortic aneurysm repair (REVAR) is being increasingly used to treat ruptured abdominal aortic aneurysms (rAAAs). However, the comparison between totally percutaneous (pREVAR) vs femoral cutdown (cREVAR) access for REVAR has not been studied. We used a national surgical database to evaluate the 30-day outcomes in patients undergoing pREVAR vs cREVAR.Patients who underwent EVAR for rAAA between 2011 and 2014, inclusively, were studied in the American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) targeted vascular database. Univariate and multivariate analyses were used to compare preoperative demographics, operation-specific variables, and postoperative outcomes between those who had pREVAR and cREVAR.We identified 502 patients who underwent REVAR, of which 129 had pREVAR (25.7%) and 373 cREVAR (74.3%). Between 2011 and 2014, the use of totally percutaneous access for repair increased from 14% to 32%. Of all patients undergoing REVAR, 24% had bilateral percutaneous access, 2% had attempted percutaneous access converted to cutdown, 64% had bilateral femoral cutdowns, and 10% had single femoral cutdown. Univariate analysis showed there were no significant differences in age, gender, body mass index, AAA size, or other high-risk physiologic comorbidities between the two groups. There was also no difference in rates of preoperative hemodynamic instability (48.1% vs 45.0%; P = .55) or need for perioperative transfusion (67.4% vs 67.8%; P = .94). There was a higher incidence of use of regional anesthesia for pREVAR compared with cREVAR (20.9% vs 7.8%; P .01). The incidence of postoperative wound complications was similar between both groups (4.8% vs 5.4%; P = .79), whereas hospital length of stay was shorter in the pREVAR group (mean difference, 1.3 days). Overall 30-day mortality was higher in the pREVAR group (28.7% vs 20.1%; P = .04), and operative time was longer (mean difference, 6.3 minutes). However, when pREVARs done in 2011 to 2012 were compared with those done in 2013 to 2014, 30-day mortality decreased from 38.2% to 25.3% and operative time decreased by 25 minutes (188 to 163 minutes). Multivariate analysis showed there were no significant differences in mortality, wound complications, hospital length of stay, or operative time between pREVAR and cREVAR.The ACS NSQIP targeted vascular database shows that there has been increased adoption of pREVAR in recent years, with improved mortality and operative time over the 4-year study period. At this point, pREVAR has not yet been shown to be superior to cREVAR for rAAA, but these outcome improvements are encouraging and likely attributable to increased operator experience.

Background Certain critically ill patients with advanced acute limb ischemia with a nonviable extremity may be unsuitable for transport to the operating room to undergo definitive amputation. In these unstable patients, rapid regional cryotherapy allows for prompt infectious source control and correction of hemodynamic and metabolic abnormalities, thereby lessening the risk associated with definitive surgical amputation. We describe our refined technique for lower extremity physiologic cryoamputation and review our institutional experience. Methods After adequate analgesia is administered to the patient, a heating pad is secured circumferentially at the proximal amputation margin and the affected extremity is placed in a customized Styrofoam cooler. A circumferential seal is secured at the proximal chill zone without use of a tourniquet and dry ice is placed into the cooler to surround the entire affected leg. Delayed definitive lower extremity amputation is later performed when hemodynamic and metabolic derangements are corrected. Results We reviewed 5 patients who underwent lower extremity cryoamputation with this technique identified at our institution between 2005 and 2015. Age ranged from 31 to 79 years old. All presented with severe foot infection and septic shock requiring vasopressor support. All 5 patients stabilized hemodynamically following the initial cryoamputation and later underwent definitive lower extremity amputation, with a median time of 3 days following initial cryoamputation. Conclusions Lower extremity physiologic cryoamputation is an effective, immediate bedside procedure that can provide local source control and the opportunity for correction of metabolic derangements in initially unstable patients to lessen the risk for definitive major lower extremity amputation. Refinement of the cryoamputation technique, as described in this report, allows for a predictable and reproducible physiologic amputation.

Background Acute aortic symptomatology is an unusual manifestation of Brucella melitensis infection. We present a rare case of acute multifocal thoracic and abdominal aortic ruptures arising from Brucellosis aortitis managed exclusively with endovascular surgery. Methods A 71-year-old Hispanic male with a history of atrial fibrillation and prior stroke on chronic anticoagulation presented with shortness of breath and malaise. In addition, he had been treated approximately 1 year previously in Mexico for B. melitensis bacteremia after eating fresh unpasteurized cheese. Computed tomography (CT) angiography demonstrated an acute rupture of the descending thoracic aorta just proximal to the celiac trunk and synchronous rupture at the abdominal aortic bifurctation. Results The patient was taken emergently to the hybrid operating room, where synchronous supraceliac thoracic aorta and abdominal aortoiliac stent grafts were deployed under local anesthesia. Completion angiography demonstrated total exclusion of the thoracic and abdominal extravasation with no evidence of endoleak. Twenty hours postoperatively, the patient became acutely obtunded and hypotensive. Repeat CT angiography demonstrated contrast extravasation at the level of the excluded aortic bifurcation. Emergent angiography confirmed a type II endoleak with free extraluminal rupture. Multiple coils were placed at the level of the aortic bifurcation between the left limb of the stent graft and the aortic wall to tamponade the endoleak. No further extravasation was noted on final aortography. Postoperatively, blood cultures confirmed the diagnosis of B. melitensis . The patient was treated with systemic doxycycline, gentamicin, and rifampin. Resolution of the acute event occurred without additional sequelae and he was discharged from the hospital to a rehabilitation facility. Conclusions Concomitant multifocal aortic ruptures arising from Brucellosis aortic infection is a very rare event. In this case, the patient was successfully treated with thoracic and abdominal endovascular stent-graft exclusion, coiling, and long-term targeted antibiotics.

Introduction Peripherally inserted central catheters (PICCs) are a popular alternative to central venous lines. PICCs can provide reliable long-term access for intravenous fluids, antibiotics and total parenteral nutrition. Multiple factors can contribute to difficult PICC removal including adherent fibrin and thrombus formation around the catheter. We discuss a novel endovascular retrieval technique to remove tightly adherent PICCs. Case presentation A 42-year-old male with history of chronic pancreatitis requiring intravenous pain medications, presented with right upper extremity single lumen PICC that could not be removed by standard techniques. The PICC line had been in place for approximately three years and was no longer functioning appropriately. Ultrasonography demonstrated thrombus alongside the length of the PICC. Results In order to remove the PICC we utilized a novel endovascular technique. A 0.018” mandril wire was passed through the lumen of the PICC. Next, a puncture alongside the PICC was performed to place a 6 French (Fr) sheath. A snare was then maneuvered through the sheath and used to capture the tip of the mandril wire. The snare, mandril wire and PICC where withdrawn in unison, looping the PICC tip within the basilic vein. The tip of the PICC was positioned near the antecubital fossa. A small incision was performed to capture the tip of the PICC to remove the catheter. Discussion Tightly adherent PICCs can result after prolonged intraluminal dwell times. We describe a novel endovascular technique that can be utilized for safe and successful removal of difficult embedded PICCs.

Elective endovascular aneurysm repair (EVAR) is generally well tolerated. However, the incidence of hospital readmission after EVAR and the risk factors and reasons for it are not well studied. This study sought to determine the incidence, to characterize the indications, and to identify perioperative patient-centered risk factors for hospital readmission within 30 days after elective EVAR.All patients who underwent EVAR electively in 2012 to 2013 were identified from the American College of Surgeons National Surgical Quality Improvement Program Targeted Vascular database (n = 3886). Preoperative demographics, operation-specific variables, and postoperative outcomes were compared between those who were readmitted within 30 days of the index operation and those who were not. Multivariate logistic regression was then used to determine independent predictors of hospital readmission.The unadjusted 30-day readmission rate after EVAR was 8.2%. Of all readmissions, 55% were for reasons related to the procedure. Median time to readmission was 12 days. Significant preoperative risk factors associated with readmission were female sex, preoperative steroid use, congestive heart failure, and dialysis dependence (P .05). Multiple postoperative medical complications were independently predictive of readmission, including myocardial infarction and deep venous thrombosis (P .05). Surgical complications that were independently predictive of readmission were surgical site infection (odds ratio, 10.24; 95% confidence interval, 5.31-19.75; P .01) and need for unplanned reoperation (odds ratio, 17.50; 95% confidence interval, 10.43-29.37; P .01). Readmitted patients ultimately had significantly higher rates of 30-day mortality (3.5% vs 0.3%; P .01).Hospital readmissions remain a costly problem after vascular surgery and are associated with 30-day mortality after elective EVAR. Whereas female sex and certain irreversible medical comorbidities are nonmodifiable, focusing on medical optimization and identifying those perioperative variables that can affect the need for post-EVAR interventions will be an important step in decreasing hospital readmission.

Popliteal arterial injury (PAI) is the second most common infrainguinal arterial injury after femoral artery injury with an incidence 0.2%. A 2003 analysis of the National Trauma Data Bank (NTDB) reported a below the knee amputation (BKA) rate of 7.1% in patients with PAI as well as higher risk in those with an associated fracture or nerve injury. Given advances in vascular surgical techniques, improved multidisciplinary care, and expeditious diagnosis with computed tomography angiography, we hypothesized that the national rate of BKA in patients with PAI has decreased and sought to identify risk factors for BKA in patients with PAI.A retrospective analysis of the NTDB was performed from 2007 to 2015. Patients ≥15 years of age with PAI were included and grouped by mechanism of injury (blunt versus penetrating). Interfacility transfers were excluded. The primary outcome of interest was BKA. Univariable and multivariable analyses were performed to identify predictors of BKA in patients with PAI.From 4,385,698 patients, 5,143 were identified with PAI (0.2%) with most involved in a blunt mechanism (56.8%). The overall limb loss rate was 5.1% (decreased from 7.1% in 2003, P = 0.0037). After adjusting for covariates, a blunt mechanism (odds ratio [OR] = 3.53, confidence intervals [CI] = 2.49-5.01, P 0.001) and open proximal tibia/fibula fracture or dislocation (OR = 2.71, CI = 2.08-3.54, P 0.001) were independent risk factors for BKA in patients with PAI. A combined popliteal vein injury (PVI) did not increase the risk for BKA (P = 0.64).The national rate of limb loss in trauma patients with PAI has decreased from 7.1 to 5.1%. A blunt mechanism of injury as well as proximal open tibia/fibula fracture or dislocation continue to be the independent risk factors for BKA. Confirming a previous report, we found a combined PVI not to be associated with higher risk for BKA. Future prospective research to determine other possible contributing factors such as intraoperative hemodynamics and utilization of vascular shunt and fasciotomy appears warranted.

Postoperative ischemic colitis (IC) can be a serious complication following infrarenal abdominal aortic aneurysm (AAA) repair. We sought to identify risk factors and outcomes in patients developing IC after open AAA repair and endovascular aneurysm repair (EVAR).The American College of Surgeons National Surgical Quality Improvement Program database was used to examine clinical data of patients undergoing AAA repair from 2011 to 2012 who developed postoperative IC. Multivariate regression analysis was performed to identify risk factors and outcomes.We evaluated a cohort of 3486 patients who underwent AAA repair (11.6% open repair and 88.4% EVAR). The incidence of postoperative IC was 2.2% (5.2% for open repair and 1.8% for EVAR). Surgical treatment was needed in 49.3% of patients who developed IC. The mortality of patients with IC was higher than that of patients without IC (adjusted odds ratio [AOR], 4.23; 95% confidence interval [CI], 2.26-7.92; P .01). The need for surgical treatment (AOR, 7.77; 95% CI, 2.08-28.98; P .01) and age (AOR, 1.11; 95% CI, 1.01-1.22; P = .01) were mortality predictors of IC patients. Predictive factors of IC included need for intraoperative or postoperative transfusion (AOR, 6; 95% CI, 3.08-11.72; P .01), rupture of the aneurysm before surgery (AOR, 4.07; 95% CI, 1.78-9.31; P .01), renal failure requiring dialysis (AOR, 3.86; 95% CI, 1.18-12.62; P = .02), proximal extension of the aneurysm (AOR, 2.19; 95% CI, 1.04-4.59; P = .03), diabetes (AOR, 1.87; 95% CI, 1.01-3.46; P = .04), and female gender (AOR, 1.75; 95% CI, 1.01-3.02; P = .04). Although open AAA repair had three times higher rate of postoperative IC compared with endovascular repair, in multivariate analysis we did not find any statistically significant difference between open repair and EVAR in the development of IC (5.2% vs 1.8%; AOR, 1.25; 95% CI, 0.70-2.25; P = .43).Postoperative IC has a rate of 2.2% after AAA repair. However, it is associated with 38.7% mortality rate. Rupture of the aneurysm before surgery, need for transfusion, proximal extension of the aneurysm, renal failure requiring dialysis, diabetes, and female gender were significant predictors of postoperative IC. AAA patients who develop IC have four times higher mortality compared with those without IC. Surgical treatment is needed in nearly 50% of IC patients and is a predictor of higher mortality.

Abstract 332 Tissue factor (TF) is required for the initiation of thrombin formation and fibrin generation in vivo. However, the functional role of intravascular tissue factor in thrombus formation is the subject of ongoing controversy. To address this question, we compared fibrin generation and platelet thrombus formation between mice lacking tissue factor in either the intravascular or the extravascular compartment using the laser injury model of thrombosis in the mouse cremaster muscle. Laser injury initiation was chosen for three reasons: (i) thrombus initiation in this model has been shown to follow endothelial activation as measured by an increase in intracellular calcium in the endothelium following laser injury; (ii) thrombus formation in this model is dominated by activation of platelets by thrombin rather than collagen; (iii) endothelial disruption by laser injury histologically appears minimal compared with thrombus initiation by ferric chloride, Rose Bengal or mechanical disruption. In this study, TF was selectively deleted in tissues of intravascular versus extravascular origin using the Cre-lox method of targeted gene deletion. TFflox/flox mice were crossed with Tie2Cre+/o mice for combined endothelial and hematopoietic TF deletion, and sm22αCre+/o mice for smooth muscle cell TF deletion. In the Tie2Cre+ TFflox/flox mice, TF DNA was reduced by 93% in the whole blood compared with Cre- controls. In the aortic media of sm22αCre+ TFflox/flox mice, TF mRNA was 96% decreased and TF activity was reduced by 95% compared with control, while there was no difference in circulating TF activity (Wang et al, Blood. 2009;113). Using the laser injury model of thrombosis in the cremaster arteriole of a live mouse, thrombus and fibrin generation were evaluated using intravital multichannel fluorescence and brightfield widefield microscopy. Platelet accumulation was measured using either an Alexa-649 labeled anti-mouse GP1bβ antibody, or Fab fragments of an Alexa-647 labeled anti-mouse GPIIbIIIa antibody directed against CD41. Fibrin formation was measured using an Alexa-488 labeled fibrin-specific antibody. TF deletion in endothelial and hematopoietic tissue resulted in a marked decrease in maximal fibrin generation (82%, p=0.004) compared with Cre- control mice. Maximal thrombus size was decreased by 55% (p=0.04). In contrast, TF deletion in the smooth muscle cell compartment resulted in no change in fibrin formation compared with Cre- control. We conclude that when endothelial disruption is minimized, such as in the laser injury model of thrombosis, intravascular TF plays a significant role in fibrin formation, while smooth muscle cell derived TF does not. Although these models of thrombus formation have no direct parallel in human disease, it is likely that the pathogenesis of thrombosis in humans include some mechanisms in which extravascular tissue factor plays a dominant role and others in which intravascular tissue factor plays a dominant role. Disclosures: No relevant conflicts of interest to declare.