Dimensional disparity between duplex and intravascular ultrasound in the assessment of iliac vein stenosis.

Minimum iliac vein caliber necessary to maintain normal peripheral venous pressure can be derived by the Poiseuille equation. Duplex was compared to intravascular ultrasound (IVUS) in the assessment of iliac vein stenosis in this single center retrospective study. Parallel IVUS and duplex caliber data for common iliac vein (CIV) and external iliac vein (EIV) in 382 limbs were separately compared. One or both segments were stenotic by IVUS criteria in 213 limbs. Neither segment was stenotic by IVUS in 22 limbs. Bland-Altman analyses and Passing-Bablok linear regressions were used. Duplex calibers were dimensionally smaller than corresponding IVUS images of CIV and EIV segments in Bland-Altman comparison by a mean of 54 mm2 and 34 mm2, respectively. Passing-Bablok regression suggested the difference was due to a systematic bias and not proportional. Duplex yields a smaller cross-sectional image of CIV and EIV compared to IVUS. Duplex is not a reliable diagnostic test for iliac vein stenosis.

Elevated plasma factor VIII levels in a mixed patient population on anticoagulation and past venous thrombosis.

BACKGROUND: Thrombophilia conditions are associated with an increased risk of venous thromboembolism. Elevated plasma levels of factor VIII (>150 IU/dL) increase the risk of venous thrombosis. The aim of this report is to analyze a subset of patients in whom plasma factor VIII levels were investigated as part of a thrombophilia panel at a specialty venous clinic at a tertiary care hospital. METHODS: From January 2019 to December 2019, records of all patients (n = 306) who had a plasma factor VIII level assay performed as part of a thrombophilia panel were retrospectively analyzed. Group 1 (n = 92) had normal factor VIII levels (≤150 IU/dL), whereas group 2 (n = 214) had elevated factor VIII levels (>150 IU/dL). Venous thromboembolic events were classified as provoked if there was an association with surgery, trauma, immobilization, orthopedic fracture, peripartum period, or use of hormones. If there was no associated factor identifiable in the patient's history, the event was considered unprovoked. RESULTS: The median age for patients in groups 1 and 2 was 55 and 65 years, respectively. Family history of deep venous thrombosis (DVT) was noted in 6 patients in group 1 (6.5%) vs 77 patients in group 2 (36%), P value: .0001. Unprovoked DVT was more commonly noted in group 2 patients (66%) compared with group 1 patients (5%), P value: .0001. In addition, venous ulceration was more commonly encountered in group 2 (23%) than group 1 (11%), P value: .008. Factor VIII level >150 IU/dL was a significant predictor of DVT occurrence itself (odds ratio: 3.3, P value <.005). Factor VIII level >200 IU/dL was a significant predictor of occurrence of two or more episodes of DVT (odds ratio: 12.3, P value < .005). CONCLUSIONS: Factor VIII levels were found to be elevated in a significant proportion of patients in whom thrombophilia testing was performed at a specialty venous clinic. This elevation was more common in patients with venous ulceration, a positive family history of DVT, and a personal history of an unprovoked DVT. Levels above 200 IU/dL were associated with DVT recurrence. This has important implications for secondary prophylactic strategies for DVT.

Long-term outcomes following use of a composite Wallstent-Z stent approach to iliofemoral venous stenting.

OBJECTIVE: An endovascular approach has essentially replaced open surgery in the management of symptomatic chronic obstructive iliofemoral venous disease. In the last several years, such a minimally invasive approach has shifted from use of Wallstents alone to a combination of Wallstent-Z stent (composite stenting) to better deal with the iliocaval confluence. This study evaluates the clinical and stent related outcomes following use of composite stenting. METHODS: A retrospective review of contemporaneously entered EMR data on 535 patients (545 limbs) with initial iliofemoral stents placed over a 4-year period from 2014 to 2017 for symptomatic chronic iliofemoral venous obstruction was performed. Patients who underwent stenting after intervention for acute deep venous thrombosis were excluded. The impact of stenting on clinical outcomes before and after the intervention were evaluated through use of the visual analog scale pain score (0-10), grade of swelling (0-4), and Venous Clinical Severity Score (0-27). Quality of life was appraised using the Chronic Venous Disease quality of life Questionnaire 20 instrument. Kaplan-Meier analysis was used to assess primary, primary assisted and secondary stent patencies, and paired and unpaired t-tests were used to examine clinical outcomes. RESULTS: Of the 545 limbs that underwent stenting, 183 were in men and 362 were in women. The median age was 60 years. Laterality was right in 205 limbs and left in 340 limbs. Post-thrombotic syndrome was seen in 441 limbs and nonthrombotic iliac vein lesions/May-Thurner syndrome in 104 limbs. At 24 months, visual analog scale pain score went from 5 to 2 (P < .0001), grade of swelling went from 3 to 1 (P < .0001), and Venous Clinical Severity Score went from 6 to 4 (P < .0001). Ulcers were present in 67 limbs and had healed in 49 limbs (73%) over a median follow-up of 26 months. Global Chronic Venous Disease quality of life Questionnaire scores improved from 60 to 36 (P < .0001) after stenting. Cumulative primary, primary-assisted, and secondary patencies at 60 months were 70%, 99% and 91%, respectively. Thirty limbs (5.5%) required contralateral stenting. There was only one instance (0.2%) of contralateral iliofemoral deep venous thrombosis. One hundred eleven limbs (20%) underwent reintervention, including for in-stent restenosis in 44 limbs, stent compression in 2 limbs, in-stent restenosis and stent compression in 48 limbs, and stent occlusion in 17 limbs. CONCLUSIONS: In patients undergoing iliofemoral venous stenting for obstructive disease, clinical improvement, quality of life improvement, and stent patencies after use of a composite stent configuration are comparable with those seen after exclusive use of Wallstents. However, the use of a composite stent configuration not only decreases the need for contralateral stenting to relieve chronic obstruction, but also decreases the incidence of contralateral iliofemoral deep venous thrombosis.

An alternative explanation for the phasic variations in venous flow.

BACKGROUND: Phasic venous flow variation with respiration is surrounded by controversy and not well understood. The current concept assigns a major role to the "abdominal pump." According to this model, inspiratory increases in abdominal pressure compress the vena cava, increasing its internal venous pressure and propelling blood upstream. Some have assigned a secondary role to the "thoracic pump," with the negative intrapleural pressure aiding blood flow toward the heart. The aim of the present study was to examine the phasic changes in flow, pressure, and volume in the central veins and named tributaries. METHODS: Caliber area changes were measured using intravascular ultrasonography in 37 patients undergoing iliac vein stenting. The pressure was measured in 48 patients using transducer tip catheters with electronic zero calibration. Duplex ultrasound flow in the head and neck and truncal and limb veins during inspiration and expiration was measured in 15 normal volunteers. RESULTS: The caliber of the abdominal inferior vena cava had increased by 32% and its lateral pressure had decreased significantly during inspiration. Intravenous pressure in the central veins of the chest and right atrium was positive at 6 to 14 mm Hg. Negative pressures were rarely seen and then only transiently. The internal jugular vein displayed little phasic variation. The upper limb veins displayed weak inspiratory phasicity. Phase polarity was reversed in the lower limbs, with near flow stoppage during inspiration. CONCLUSIONS: These observations conflict with the current notions of venous flow phasicity, which are based on push-pull pressure changes in the abdominal and thoracic veins. The paradoxical inspiratory inferior vena cava caliber increase probably explains the concurrent pressure decrease. Sustained negative pressures in the thoracic central veins and right atrium did not occur. We have proposed an alternate hypothesis for venous flow phasicity based on alternate stretching and relaxation of the mobile section of the great veins with respiratory movement.

The two-segment caliber method of diagnosing iliac vein stenosis on routine computed tomography with contrast enhancement.

BACKGROUND: Iliac vein stenosis is a frequent pathologic process in advanced chronic venous disease. Intravascular ultrasound (IVUS) has emerged as the "gold standard" to diagnose iliac vein stenosis and to guide stent treatment. A pre-IVUS test is often obtained. Routine venography is deficient in several respects to fill this role; absence of an internal scale is a critical deficiency. Computed tomography venography (CTV) may be superior; its measurement capabilities can be used to precisely identify stenotic iliac vein caliber. Furthermore, the calibers of common iliac vein (CIV) and external iliac vein (EIV) can be individually assessed, yielding two data points instead of single-point assessment used in venography and current CTV protocols. We compared the diagnostic accuracy of the two-segment caliber method of CTV (arm vein injection of contrast material) with IVUS. METHODS: In patients who underwent computed tomography assessment of iliac vein segments before IVUS examination during a 5-year period, 91 limbs were analyzed. This is a single-center, retrospective analysis of prospectively collected data. CTV images of CIV and EIV segments were compared individually and in combination with IVUS planimetry images. A caliber diameter of <16 mm for CIV and <14 mm for EIV was considered stenotic with either imaging technique. Bland-Altman plots and receiver operating characteristic curves were used. RESULTS: On IVUS evaluation, 84% of CIVs and 78% of EIVs were stenotic and 16% and 22% were of normal caliber. These provided IVUS positive and negative controls for CTV comparison. On CTV, at least one of the two segments (CIV or EIV) was stenotic in 90% of the limbs, about 10% to 15% higher than single-segment involvement. Mean CTV caliber difference from IVUS was +2.5% for CIV and +7.3% for EIV. On Bland-Altman plot, single-segment diagnostic sensitivity of CTV was 83% and 73% for CIV and EIV, respectively, compared with IVUS. The sensitivity increased to 97% with a positive predictive value and accuracy of 93% and 91%, respectively, when a stenotic caliber in at least one of the two segments was considered diagnostic of iliac vein stenosis. Receiver operating characteristic analysis confirmed increased accuracy of the two-segment method over single-segment assessment with an area under the curve of 0.89 (P < .001). CONCLUSIONS: Caliber diameter of <16 mm for CIV or <14 mm for EIV on routine CTV imaging appears to correlate with IVUS caliber stenosis with good diagnostic metrics of low false positives and false negatives.

Contralateral limb improvement after unilateral iliac vein stenting argues against simultaneous bilateral stenting.

OBJECTIVE: Symptoms of chronic venous insufficiency secondary to obstructive iliofemoral disease are often bilateral. The impact of iliofemoral stenting of the more symptomatic lower extremity on clinical outcomes in the less affected contralateral extremity is not clear. Such benefit, secondary to offloading of collaterals, may potentially be of the magnitude that the contralateral extremity does not require intervention. METHODS: A retrospective review of contemporaneously entered electronic medical record data of 368 patients/limbs with initial unilateral iliocaval stents (240 left and 128 right) placed during a 3-year period from 2015 to 2017 was performed. Patients who underwent simultaneous bilateral stenting or had occlusive disease were excluded. Of the remainder, the impact of stenting on contralateral leg symptoms was evaluated by analyzing visual analog scale (VAS) pain score (1-10), grade of swelling (1-3), and Venous Clinical Severity Score (VCSS). The duration of any improvement and need for intervention on the contralateral side were also appraised. Kaplan-Meier analysis was used to assess stent patency after intervention, whereas paired t-tests were used to examine clinical outcomes. RESULTS: Of the 368 limbs that underwent stenting with a combination of a Wallstent (Boston Scientific, Marlborough, Mass) with a Z stent (Cook Medical, Bloomington, Ind) for stenotic lesions, 304 patients (89 men and 215 women) had contralateral symptoms (200 left and 104 right). The cause was post-thrombotic syndrome in 229 limbs and May-Thurner syndrome or nonthrombotic iliac vein lesion in 75 limbs. In this contralateral group, at 12 months, the VAS pain score improved from 5 to 0 (P < .0001), the grade of swelling went from 3 to 1 (P < .0001), and VCSS went from 5 to 3 (P < .0001) after stenting of the ipsilateral side. During the median follow-up of 20 months, 15 contralateral limbs underwent stenting. Median time to stenting of the contralateral limb after ipsilateral stenting was 9 months. The median VAS pain score, grade of swelling, and VCSS in this group before stenting were 6.5, 2, and 5 compared with 0 (P < .0001), 1 (P = .27), and 3 (P = .0021), respectively, in those members of the contralateral group who did not require stenting. Primary and primary assisted patencies at 12 months after contralateral stenting were 78% and 100%, respectively. There were no stent occlusions after contralateral stenting. CONCLUSIONS: Patients with bilateral obstructive iliofemoral venous lesions often experience improvement of the contralateral limb symptoms (95%) after stenting of the worse ipsilateral limb. Only 15 of 304 (5%) symptomatic contralateral limbs had to undergo stenting during the follow-up period because of a worsening clinical picture. Based on this, a staged approach to iliofemoral stenting in patients with bilateral symptoms focusing initially on the more symptomatic limb is suggested.

Impact of Presence of Inferior Vena Cava Filter on Iliocaval Stent Outcomes.

BACKGROUND: The impact of presence of an IVC filter in patients undergoing stenting for symptomatic femoroiliocaval obstruction has not been explored in detail. This study attempts to fill this gap by evaluating clinical and stent-related outcomes in such patients. The incidence of deep vein thrombosis (DVT) in this setting is also analyzed. METHODS: A retrospective review of contemporaneously entered EMR data on initial iliocaval stents placed in patients with an indwelling IVC filter (or placed after stenting) over a 15-year period from 2000 to 2015 was performed. A separate matched cohort that underwent initial stenting during the time frame, but which did not have an IVC filter, was utilized as the control group. Clinical outcomes were evaluated through use of the venous clinical severity score (VCSS) and visual analog scale (VAS) pain scores. Incidence of deep venous thrombosis after stenting was also reviewed in both groups. The Kaplan-Meier analysis was used to assess stent patency after intervention while t-tests were used to examine preintervention and postintervention outcomes within and in-between groups. RESULTS: A total of 50 limbs (40 patients) underwent placement of a femoroiliocaval stent in the setting of a preexisting (49) or post-stent (1) IVC filter [filter group]. The control group had 156 limbs (155 patients). There was no difference in VCSS, VAS pain score, or grade of swelling at baseline between the 2 groups. Over the median follow-up duration (43 months-filter group; 40 months-control group), VCSS went from 6 to 4 at 12 months (P = 0.0001) in the filter group and from 6 to 4 in the control group (P < 0.0001). VAS pain scores went from 7 to 0 at 12 months (P < 0.0001) in the filter group and from 5 to 0 in the control group (P < 0.0001). There was no significant difference in the VCSS scores or VAS pain score between the 2 groups at 12 months (P > 0.05). Overall, there was a statistically significant increase in the incidence of DVT in the filter group (10%) compared to the control group (3%) [P = 0.03%]. Primary, primary assisted, and secondary patencies in the filter/control groups at 48 months were 64%/65% (P = 0.6), 100%/97% (P = 0.5), and 100%/75% (P = 0.4), respectively. Reintervention from in-stent restenosis was noted in 16% of patients in the filter group compared to 4% in the control group (P = 0.006). CONCLUSIONS: Patients with an IVC filter in the setting of a femoroiliocaval stent tend to have an increased rate of deep venous thrombosis on the stented side. In addition, an increased rate of reintervention secondary to in-stent restenosis was also noted. In light of this, every attempt should be made to remove the IVC filter as soon as the need for the filter no longer exists.