Endovascular Venous Stenosis and Thrombosis Large Animal Model: Angiographic, Histological, and Biomechanical Characterizations.

PURPOSE: To characterize an ovine endovascular radiofrequency (RF) ablation-based venous stenosis and thrombosis model for studying venous biomechanics and response to intervention. MATERIALS AND METHODS: Unilateral short-segment (n = 2) or long-segment (n = 6) iliac vein stenoses were created in 8 adult sheep using an endovenous RF ablation technique. Angiographic assessment was performed at baseline, immediately after venous stenosis creation, and after 2-week (n = 6) or 3-month (n = 2) survival. Stenosed iliac veins and the contralateral healthy controls were harvested for histological and biomechanical assessment. RESULTS: At follow-up, the short-segment RF ablation group showed stable stenosis without occlusion. The long-segment group showed complete venous occlusion/thrombosis with the formation of collateral veins. Stenosed veins showed significant wall thickening (0.28 vs 0.16 mm, P = .0175) and confluent collagen deposition compared with the healthy controls. Subacute nonadherent thrombi were apparent at 2 weeks, which were replaced by fibrous luminal obliteration with channels of recanalization at 3 months. Stenosed veins demonstrated increased longitudinal stiffness (448.5 ± 5.4 vs 314.6 ± 1.5 kPa, P < .0001) and decreased circumferential stiffness (140.8 ± 2.6 vs 246.0 ± 1.6 kPa, P < .0001) compared with the healthy controls. CONCLUSION: Endovenous RF ablation is a reliable technique for creating venous stenosis and thrombosis in a large animal model with histological and biomechanical attributes similar to those seen in humans. This platform can facilitate understanding of venous biomechanics and testing of venous-specific devices and interventions.

Management of Phlegmasia Cerulea Dolens with Percutaneous Mechanical Thrombectomy.

Advanced cases of phlegmasia cerulea dolens (PCD) with absent pedal pulses, sensory/motor deficits, and/or venous gangrene likely require more rapid restoration of flow compared to cases without these factors to prevent progression and associated morbidity/mortality. We present a case of PCD with absent pedal pulses and sensory deficit managed successfully with emergent percutaneous mechanical thrombectomy using Inari ClotTriever (Inari Medical, Irvine, CA) with immediate clinical resolution, including restoration of pedal pulses ~ 45 min after thrombectomy. Percutaneous mechanical thrombectomy with the ClotTriever device has the ability to immediately restore venous flow reversing the pathophysiology of PCD in a short time period similar to surgical embolectomy and may be an alternative treatment strategy in patients with phlegmasia cerulea dolens of high severity.

Iliac Vein Stent Placement: Acute Venographic Changes and Relevance to Venous Biomechanics.

PURPOSE: To describe acute venographic changes of external iliac vein (EIV) after ipsilateral common iliac vein (CIV) stent placement. MATERIALS AND METHODS: Retrospective review was performed of 17 cases with placement of a single CIV stent. Central CIV stent diameter and minimal ipsilateral EIV diameter were measured on venogram; vein diameter was measured at the same 2 anatomic locations on venogram obtained before intervention. Relative CIV diameter increase was defined as the ratio of change in central CIV diameter after stent placement to CIV diameter before intervention. Relative EIV diameter reduction was defined as the ratio of change in diameter of EIV after stent deployment in CIV to EIV diameter before intervention. Diameters before and after intervention were compared using a 2-tailed, paired sample t test. Pearson coefficient was calculated for correlations. RESULTS: There was a significant reduction of EIV diameter after ipsilateral CIV stent placement compared with before stent placement (mean 9.3 mm ± 3.1 vs 11.9 mm ± 3.8; P < .01); mean decrease in EIV diameter was 21.7% ± 15.8. There was a correlation between relative CIV diameter increase and relative EIV diameter reduction (r = .8917). CONCLUSIONS: Significant venographic narrowing of the EIV occurs after placement of an adjacent CIV stent, and the degree of narrowing is associated with the relative increase in CIV diameter. These findings may be explained by the inherent anisotropic elasticity of veins. Further study is warranted to guide future venous interventions.

Defining New Metrics in Microwave Ablation of Pulmonary Tumors: Ablation Work and Ablation Resistance Score.

PURPOSE: To investigate pulmonary microwave ablation metrics including ablation work, ablation resistance score, and involution. MATERIALS AND METHODS: Retrospective review was performed of 98 pulmonary tumor ablations using the NeuWave Certus Microwave Ablation System (NeuWave Medical, Madison, Wisconsin) in 71 patients (32 men and 39 women; mean age, 64.7 y ± 11.5). Ablation work was defined as sum of (power) * (time) * (number of antennas) for all phases during an ablation procedure. Ablation zone was measured on CT at 3 time points: after procedure, 1-3 months (mean 47 d), and 3-12 months (mean 292 d). Ablation zones were scored based on location for pulmonary lobe (upper = 1, middle/lingula = 2, lower = 3) and region (peripheral = 1, parenchymal = 2, central = 3), and the 2 were summed for ablation resistance score. RESULTS: Ablation zone on CT at 1-3 months was significantly smaller in regions with higher ablation resistance score (P < .05). There was a significant correlation between ablation work and ablation zone measured on CT performed after procedure (P < .001), at 1-3 months (P < .001), and at 3-12 months (P < .05). Ablation zone significantly decreased from after procedure to 1-3 months (P < .001) and from 1-3 months to 3-12 months (P < .001), with change from after procedure to 1-3 months significantly greater (P < .01). CONCLUSIONS: Pulmonary microwave ablation zone is significantly smaller in regions with higher ablation resistance score. Ablation work correlates to ablation zone with a nonlinear involution pattern in the first year and may be useful for planning before the procedure.

Radiation-Induced Cataractogenesis: A Critical Literature Review for the Interventional Radiologist.

Extensive research supports an association between radiation exposure and cataractogenesis. New data suggests that radiation-induced cataracts may form stochastically, without a threshold and at low radiation doses. We first review data linking cataractogenesis with interventional work. We then analyze the lens dose typical of various procedures, factors modulating dose, and predicted annual dosages. We conclude by critically evaluating the literature describing techniques for lens protection, finding that leaded eyeglasses may offer inadequate protection and exploring the available data on alternative strategies for cataract prevention.