A comparison between intravascular ultrasound and venography in identifying key parameters essential for iliac vein stenting.

OBJECTIVE: Deep venous stenting has become the primary treatment option for obstructive venous disease. Precise identification and quantification of the disease as well as localization of optimal landing zones are key elements to success. Compared with venography (anteroposterior projection), intravascular ultrasound (IVUS) seems to be more sensitive in determining those parameters. This study was a blinded comparison of the relative accuracy of venography compared with IVUS in determining key parameters essential for iliac vein stenting. METHODS: Between October 2013 and November 2015, there were 155 limbs (152 patients) that underwent an endovascular intervention for chronic iliofemoral vein stenosis. Venography and IVUS data were reviewed by vascular surgeons and radiologists, respectively, each blinded to the other to identify location and severity of maximal stenosis, location of iliac-caval confluence, and optimal distal landing zone. Data from venography were compared with data from IVUS. Maximal stenosis was defined as the most severe stenosis found among the four segments-common iliac vein, external iliac vein, common femoral vein, and infrarenal vena cava. IVUS was the "gold standard" for comparisons. RESULTS: Venography failed to identify lesion existence in 19% of limbs. The median maximal area stenosis was significantly higher with IVUS than with venography (69% vs 52%; P < .0001). Furthermore, venographic correlation with IVUS for the anatomic location of maximal stenosis was present in only 32% of the limbs; venography missed the location of maximal stenosis in more than two-thirds of limbs. The iliac-caval confluence location on venography correlated with IVUS findings in only 15% of patients. In 74%, it was located higher with IVUS than with venography. The mean difference was one vertebral body. Agreement between venography and IVUS on location of the distal landing zone was only 26%. The distal landing zone defined with IVUS was lower than with venography in 64% of limbs. CONCLUSIONS: Compared with IVUS, venography substantially and significantly misses stenotic lesions-their location and severity; venography also misidentifies the location of the iliac-caval confluence and the distal landing zone in the majority of limbs. Those differences between IVUS and venography suggest that IVUS is the better diagnostic and procedural tool in iliac-caval stenting.

Characteristics and outcomes of stent occlusion after iliocaval stenting.

OBJECTIVE: With increasing use of iliocaval stenting, complications have become more noticeable. Stent occlusion is one such outcome that has not been studied in detail. Characteristics of stent occlusion in addition to outcomes after recanalization are presented. METHODS: An analysis of 3468 initial iliocaval stents placed during an 18-year period from 1997 to 2015 was performed. A total of 102 stent occlusions were identified, amounting to a 3% stent occlusion rate. Characteristics evaluated included onset after stent placement, techniques used for restoring patency, and their outcome. Kaplan-Meier analysis was used to assess stent patency. Regression analysis was used to evaluate risk factors for stent occlusion. RESULTS: Stent occlusions occurred at a median of 5.8 months after placement. The occluded stent could be reopened after a wide range of intervals, the longest being 14 years. The majority (69%) of occlusions were chronic (>30 days) and the remainder (31%) were acute; 77% of the occlusions occurred in post-thrombotic limbs. The most common technique used to recanalize the acutely occluded stent was pharmacomechanical thrombectomy, whereas wire recanalization with balloon angioplasty was the technique most used for chronic occlusions. Of the 102 occluded stents, patency was achieved in 75 of 88 (84%) attempts. After successful recanalization, the median primary patency was 7 ± 1.9 months, median primary assisted patency was 7.5 ± 3.5 months, and median secondary patency was 25 ± 8.3 months. Clinically, there was improvement in the visual analog scale pain scores from a median of 3.5 to 1 (P < .01), in the median grade of swelling from 2 to 1 (P < .01), and in the mean Venous Clinical Severity Score from 6.4 to 3.8 (P < .01) after recanalization. A 40% ulcer healing rate was noted after recanalization during a median follow-up period of 17 months. There were no significant adverse events or mortality. Regression analysis revealed stent placement for native vein occlusion as the only statistically significant predictor of stent occlusion. CONCLUSIONS: Stent occlusion after iliocaval stenting is a rare occurrence. Recanalization of occluded stents can be performed with minimal morbidity even months to years after occlusion with good outcomes. Long-term patency of occluded stents that were recanalized is poor compared with patency of the initially placed stent.

Optimal sizing of iliac vein stents.

Background Iliac vein stenting has emerged as a therapeutic option in chronic venous disease. The optimal stent size is unknown but should match normal caliber at a minimum. Methods Teleology: The iliac-femoral outflow caliber was measured by Duplex in healthy volunteers to determine normal caliber. Patient IVUS data: The distribution curve of IVUS planimetry data in 345 chronic venous disease limbs was analyzed: values at the right tail end of the curve should approach normal values according to distribution theory. The optimal stent size was also projected using Poiseuille equation and Young's scaling rule. Results The optimal stent sizes in the common iliac, external iliac, and common femoral vein segments are: 16, 14, and 12 mm diameters, respectively. Conclusion Stent correction of iliac vein stenosis should aim to restore the lumen to the minimum recommended caliber during the initial procedure and later re-interventions.

Factors influencing peripheral venous pressure in an experimental model.

BACKGROUND: Peripheral venous hypertension and microvascular injury have merged as central features of chronic venous disease. Peripheral venous pressure in the lower limb is controlled by central and peripheral mechanisms. In the current manuscript, we examine the role of peripheral factors, particularly conduit capacitance compliance, focal stenosis, and arterial inflow into the calf. METHODS: An experimental venous model using Penrose tubing as a venous analogue was used where the aforementioned parameters could be manipulated. Volume-pressure curves were derived in the static mode. The dynamic model attempted to simulate key pressure parameters of lower limb venous flow. RESULTS: Decreasing compliance resulted in progressive reduction of conduit capacitance affecting both bending and stretching regimens and the relative distribution between the two, rotating the volume-pressure curve toward the x-axis. Increased postcapillary (arterial) inflow increased conduit pressure. For a given inflow, pressures varied inversely to conduit caliber. Decreased compliance led to a smaller functional caliber at working pressures. Sideline capacitance with stagnant flow connected to the flow channel (simulating calf vein network) did not influence conduit pressure. Focal stenosis increased "venous pressure" if it was narrower than "optimum outflow caliber," defined as the minimum outflow conduit caliber required to balance inflow. Percentage stenosis as traditionally calculated using adjacent lumen as denominator was uncorrelated to pressure increase. CONCLUSIONS: Conduit pressure is increased with smaller native or functional (poor compliance) caliber, focal stenosis, and increased postcapillary inflow. Many of these features appear to be present in limbs clinically suspected of chronic venous disease. The importance of the geometric factor of Poiseuille equation in pressure effects of caliber reduction and collateralization is discussed.

Pygmy rattlesnake envenomation treated with Crotalidae Polyvalent Immune Fab Antivenom.

UNLABELLED: Documented envenomations by the pygmy rattlesnake (Sistrurus miliarius barbouri) are rare. While there have been no documented fatalities, several older case reports describe significant morbidity. We describe the first known case of pygmy rattlesnake envenomation that was treated with Crotalidae Polyvalent Immune Fab Antivenom (CroFab®). CASE: A 28-year-old man with no significant past medical history presented after being envenomated on the right hand by his friend's pet pygmy rattlesnake. He developed swelling and pain in his hand and forearm. He responded well to a ten vial loading dose and a 18 h maintenance protocol of CroFab and was discharged the following day without developing any hematological or electrolyte derangements. CONCLUSION: This is the first documented use of CroFab for S. m. barbouri envenomation. The outcome of this case suggests that CroFab is a safe treatment modality in this setting.

AGI-1067, a novel antioxidant and anti-inflammatory agent, enhances insulin release and protects mouse islets.

The antioxidant and anti-inflammatory compound AGI-1067 (succinobucol) has potential as an oral anti-diabetic agent. AGI-1067 reduces H(b)A1c, improves fasting plasma glucose, and reduces new-onset diabetes. We investigated AGI-1067 for possible effects on mouse pancreatic islets in vitro. Pretreatment with 10 microM AGI-1067 increased glucose-stimulated insulin secretion (11 mM) without affecting secretion in basal (3 mM) glucose. AGI-1067 enhanced the intracellular calcium response to glucose stimulation in 7 mM and 11 mM glucose, but had no effect in 28 mM or basal glucose. AGI-1067-pretreated islets also showed enhanced calcium responses to methyl pyruvate and alpha-ketoisocaproate at low doses, but not high doses. The AGI-1067-mediated effects on glucose-stimulated calcium were maintained during continuous diazoxide exposure, suggesting effects on the K(ATP)-channel-independent pathway. AGI-1067 also reduced cytokine-induced islet cell death and expression of iNOS, a key component in cytokine signaling. This is the first report of direct stimulatory and protective effects of a first-in-class potential anti-diabetic agent on pancreatic islets.