Assessment of flow mechanics in the lower extremity venous system.

BACKGROUND: The Reynolds number (Re) is a dimensionless parameter that describes fluid flow mechanics. Veins are compliant and collapsible vascular conduits that can accommodate large volume changes in response to small pressure changes. However, only sparse information is available about flow parameters such as the Re in the venous system. METHODS: Bilateral duplex ultrasound examination of 15 healthy volunteers (30 limbs) was performed before and after exercise (four flights of stairs) of the veins of the lower extremity (left and right sides) and inferior vena cava. These volunteers had been confirmed to not have any signs or symptoms of lower extremity venous disease via focused history and physical examination findings. RESULTS: Most of the volunteers were women (73%). Their mean age was 37 ± 12.8 years. The Re was highest in the inferior vena cava among all the veins examined (470 ± 144 before exercise and 589 ± 205 after exercise; P = .04). The association between the change in Re before and after exercise and the specific vein examined was also significant for the right and left external iliac veins, right and left common femoral veins, right and left profunda femoris veins, right and left femoral veins, and right common iliac vein. Resistance and velocity maps for the lower extremity venous system were also created. The velocity increased and the resistance decreased as one moved up the venous tree toward the right atrium. CONCLUSIONS: The Re increased for most of the lower extremity veins after exercise in our healthy volunteers. However, the critical value for turbulent flow was not reached despite the exercise.

Female Gender is a Predictor of Lower Iliac Vein Stenting Patency Rates.

BACKGROUND: Iliac venous stenting (IVS) for thrombotic and nonthrombotic venous disease is increasingly used as evidence of the safety, efficacy and durability of these interventions increases. Female gender has been implicated as a predictor of failure in arterial endovascular interventions. We hypothesize that female gender could be predictive of patency rates of iliac vein stenting. METHODS: Consecutive patients who underwent IVS for thrombotic or nonthrombotic venous disease at our institution from 2007 until 2019 were identified and divided into groups based on gender. Operative notes, venograms, and the electronic health record were then queried to obtain operative details, co-morbid conditions, postoperative outcomes and stent patency. Study outcome was long term patency rate. The data was analyzed using chi-square, logistic regression, and Kaplan-Meier analysis as appropriate. RESULTS: A total of 200 consecutive patients (231 limbs) were identified in our retrospective analysis, with a mean age of 48.8 ± 17.3, and BMI of 31.6 ± 8.6. Of those, 119 (59.5%) patients, (131 [56.8%] limbs) were female. Comparisons between the gender groups revealed no difference in age, BMI, or preoperative comorbidities. There was no difference in type of venous disease between male (85% thrombotic, 15% nonthrombotic) and female (84% thrombotic, 16% nonthrombotic), P= 0.830. The male cohort was more likely to present with leg ulceration (17% vs. 4.6%, P = 0.002), and the female cohort was more likely to present with leg edema (98.5% vs. 93.0%, P= 0.03). The male cohort had a higher rate of caval (48% vs. 33.6%, P= 0.027) and infrainguinal stent extension. (11% vs. 6.9%, P= 0.02). Females had a higher rate of left sided stenting (80.9% vs. 66/0%, P= 0.010). There was no difference in the median stent diameter used between the cohorts. Primary patency at 5 years was significantly higher for the male cohort (94.1% vs. 74.4%, P= 0.01) On adjusted multivariable cox regression female gender was a predictor of loss of primary patency within 5 years (HR, 4.04; P= 0.007). CONCLUSIONS: In this single center retrospective analysis of IVS, male patients were found to have better primary stent patency compared to female.

Non-enhanced multimodal magnetic resonance imaging in assessment of iliac vein obstruction with or without thrombosis.

OBJECTIVE: To evaluate the diagnostic accuracy of a contrast-free multimodal magnetic resonance (MR) protocol (including M2DIPEAR, THRIVE, BTFE-SPAIR, and FLAIR sequences) in the detection of iliac vein obstruction with or without thrombosis. MATERIALS AND METHODS: From May 1st, 2015, to May 1st, 2016, a total of 73 patients (aged 51.33 ± 4.21 years) who received both digital subtraction angiography (DSA) and the multimodal MR imaging were included. The protocol of the multimodal MR included M2DIPEAR and BTFE-SPAIR for presenting iliac vein obstruction, and THRIVE and FLAIR for revealing the co-existed thrombosis. Three observers who were blinded to clinical and DSA results independently analyzed all multimodal MR datasets. Per-patient evaluations on presence or absence of iliac vein obstruction were performed to calculate the diagnostic performance of MR imaging (DSA regarded as gold reference) in terms of overall accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). Capability to display the co-existing venous thrombus was also evaluated per-MR sequence using a 3-point scale system. RESULTS: Iliac vein obstruction was depicted with DSA in 64 patients. In per-patient evaluation, the multimodal MR imaging yielded accuracy of 95.9% (70/73), sensitivity of 96.9% (62/64), specificity of 88.9% (8/9), positive predictive value of 98.4% (62/63), and negative predictive value of 80% (8/10), respectively. In the multimodal MR sequences, balanced turbo field echo-spectral attenuated inversion recovery (BTFE-SPAIR) sequence was superior to other sequences in depicting the iliac vein configuration, but fluid attenuated inversion recovery (FLAIR) and T1 high-resolution isovolumetric examination (THRIVE) seemed superior in detecting co-existing venous thrombosis. CONCLUSIONS: M2DIPEAR and BTFE-SPAIR sequence can reveal iliac vein obstruction while THRIVE and FLAIR can detect the co-existed thrombosis. The proposed multimodal MR protocol can accurately depict the iliac vein obstruction and accurately detect the co-existing venous thrombosis comparable with that of DSA.

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.

Individual Choice for the Aspiration Thrombectomy Treatment of Acute Iliofemoral Deep Venous Thrombosis.

OBJECTIVE: To compare clinical efficacy, safety and cost of AngioJet rheolytic thrombectomy (ART) plus catheter-directed thrombolysis (CDT) and manual aspiration thrombectomy (MAT) plus CDT for acute iliofemoral deep venous thrombosis (DVT). METHODS: This was a retrospective study. A total of 126 DVT patients met the inclusion criteria. Sixty-one patients were included in the ART group and sixty-five in the MAT group. Clinical parameters were used to compare the groups. Clinical outcomes, complications and various medical expenses were analyzed. RESULTS: Technical success rates were 100% in ART and MAT group. There was no significant difference in the rate of thrombus clearance (lysis grades II and III) between ART group (98.36%) and MAT group (100%) (P = 0.311). The incidence of venous damage was slightly higher in the MAT group (4.6%) than in the ART group (0%) (P = 0.245). The cost of the ART group ($8,291.7 ± 471.4) was significantly higher than that of the MAT group ($4,632.5 ± 441.7) (P < 0.001). CONCLUSIONS: ART and MAT appear similar with good clinical outcomes for acute iliofemoral DVT. MAT substantially lowers mean cost per patient compared to ART.

Overlooked guide wire: a multicomplicated Swiss Cheese Model example. Analysis of a case and review of the literature.

Objectives: Central venous catheter (CVC) implementation is now usual in emergency department. The most common complications are misplacement, bleeding, pleural perforation, thrombosis and sepsis. Forgetting a guide wire in the patient's body after catheterization is an underestimated complication of this procedure; only 76 cases are described. Even if the majority of patients remained asymptomatic, severe complications can happened even years later. This article's aim is to identify the sequence of elements that led to the event occurrence and to suggest recommendations of good practice to minimize complications related to central catheter placement.Method: After reviewing all the complications related to central venous catheterization and their frequencies, we analyse from a case report and a review of the literature the sequence of elements that led to the medical error. We use an Ishikawa diagram to show our results and the links between them.Results: Our Ishikawa diagram shows that material, human resources, procedural and radiological involvement factors are the main elements on which we can act to reduce the complications rate after central venous catheterization. We advocate for the establishment of standardized procedures before, during and after the technical gesture.Conclusions: Because of human nature, errors will always be possible when taking care of a patient. However, we propose good practice recommendations to avoid the repetition of a forgetting guide wire after central venous catheterization.

Single- versus multiple-stage catheter-directed thrombolysis for acute iliofemoral deep venous thrombosis does not have an impact on iliac vein stent length or patency rates.

BACKGROUND: Incomplete venous thrombolysis and residual nonstented iliac vein disease are known predictors of recurrent deep venous thrombosis (DVT). Controversy exists as to whether the number of thrombolysis sessions affects total stent treatment length or stent patency. The goal of this study was to evaluate the outcomes of patients who underwent single vs multiple catheter-directed lysis sessions with regard to stent extent and patency. METHODS: Consecutive patients who underwent thrombolysis and stenting for acute iliofemoral DVT between 2007 and 2018 were identified and divided into two groups on the basis of the number of treatments performed (one vs multiple sessions). Operative notes and venograms were reviewed to determine the number of lytic sessions performed and stent information, including size, location, total number, and length treated. End points included total stent length, 30-day and long-term patency, and post-thrombotic syndrome (Villalta score ≥5). The χ2 comparisons, logistic regression, and survival analysis were used to determine outcomes. RESULTS: There were 79 patients who underwent lysis and stenting (6 bilateral interventions; mean age, 45.9 ± 17 years; 48 female). Ten patients (12 limbs) underwent single-stage treatment with pharmacomechanical thrombolysis, and the remaining 69 (73 limbs) had two to four operating room sessions combining pharmacomechanical and catheter-directed thrombolysis. Patients who underwent a single-stage procedure were older and more likely to have a malignant disease. These patients received less tissue plasminogen activator compared with the multiple-stage group (17.2 ± 2.2 mg vs 27.6 ± 11.6 mg; P = .008). Average stent length was 8.8 ± 5.2 cm for the single-stage group vs 9.2 ± 4.6 cm for the multiple-stage group (P = .764). Patients who underwent a single-stage procedure had no difference in average length of stay from that of patients who underwent multiple sessions (8.5 days vs 5.9 days; P = .269). The overall 30-day rethrombosis rate was 7.3%. Two-year patency was 72.2% and 74.7% for the single and multiple stages, respectively (P = .909). The major predictors for loss of primary patency were previous DVT (hazard ratio [HR], 5.99; P = .020) and incomplete lysis (HR, 5.39; P = .014) but not number of procedures (HR, 0.957; P = .966). The overall post-thrombotic syndrome rate was 28.4% at 5 years and was also not associated with the number of treatment sessions. CONCLUSIONS: Single- vs multiple-stage thrombolysis for DVT is not associated with a difference in extent of stent coverage. Patency rates remain high for iliac stenting irrespective of the number of lytic sessions, provided lysis is complete and the diseased segments are appropriately stented.

Fast-track thrombolysis protocol: A single-session approach for acute iliofemoral deep venous thrombosis.

OBJECTIVE: Catheter-directed thrombolysis in the treatment of acute iliofemoral deep venous thrombosis (IFDVT) often requires more than one interventional session to yield successful outcomes. Catheter-directed thrombolysis is generally expensive, requiring prolonged hospital stay that may be associated with increased local and systemic hemorrhagic complications. We developed the fast-track thrombolysis protocol (FTTP) to address these issues. The goal of FTTP is to restore patency during the initial session of thrombolysis, thereby minimizing costs and complications associated with prolonged thrombolysis. METHODS: A retrospective analysis of 38 patients treated for acute IFDVT using FTTP at our institution from January 2014 to February 2019 was performed. The protocol includes periadventitial injection of lidocaine at the venipuncture site under ultrasound guidance, contrast venography of the entire target segment, pharmacomechanical rheolytic thrombectomy of the occluded venous segment, tissue plasminogen activator infusion along the occluded segment, balloon maceration of the thrombus, and, if indicated, venous stent placement in areas of significant (≥50%) stenosis refractory to thrombolysis and balloon angioplasty. Once the thrombus was cleared, patients were prescribed oral antithrombotic therapy. RESULTS: Thirty-eight primary FTTPs (45 total interventions) were performed in 38 patients. The median age was 66 years (range, 39-93 years); 60.5% were female. Initial venous access was most often obtained through the popliteal vein, followed by the femoral and great saphenous veins. The mean operative time was 122 minutes (range, 59-249 minutes), and the median volume of tissue plasminogen activator infused was 10 mg (range, 4-20 mg). The median cost per procedure, including devices and medication, was $5374.45. Median postoperative length of stay was 1 day (range, 1-45 days). Successful single-session FTTP, as determined by completion venography, was accomplished in 81.5% (n = 31/38) of cases. The remaining seven cases (18.5%) required one additional session. Of the 38 patients, 30 (79%) required iliac vein stenting. Periprocedural complications consisted of one patient with retroperitoneal hemorrhage that was managed conservatively. No patients experienced rethrombosis within 30 days of FTTP. During the 5-year study period, there were no cases of pulmonary embolism, significant local or systemic hemorrhage, limb loss, or mortality. CONCLUSIONS: FTTP, as presented herein, appears to be a safe, effective, and cost-effective technique in the resolution of acute IFDVT.

Application of computed tomography venography in the diagnosis and severity assessment of iliac vein compression syndrome: A retrospective study.

The objectives are to evaluate the application of computed tomography venography (CTV) in the diagnosis of iliac vein compression syndrome (IVCS), and to assess the factors related to the incidence and development of IVCS and the recurrence of varicose veins.Imaging data of 120 patients with chronic venous disease (CVD) of the lower extremity and 68 subjects without CVD (control) were retrospectively reviewed by radiologists blinded to the groups. CTV, conventional venography, and Doppler ultrasound were compared in the diagnosis and contributing factors for IVCS were also analyzed.CTV required less procedure time than venography or color ultrasonography (P < .001). The rate of iliac venous compression diagnosed by CTV was higher in the CVD group (53.3%) than in the control group (22.1%) (χ = 17.425, P < .001). Risk factors for IVCS included gender, hyperlipidemia, and course of disease (P < .05). Development of femoral vein collateral was more common in patients with IVCS (P < .05). The duration of disease was positively associated with the severity of iliac vein compression (r = 0.321, P < .001). IVCS was an important contributing factor for varicose vein recurrence (51.2%). In patients with IVCS and venous ulcer (C5-C6), the healing time of the ulcer treated with stent was significantly shorter compared with those without stent treatment (P < .001).CTV is accurate for the diagnosis and severity evaluation of IVCS. IVCS might be a contributing factor for varicose vein recurrence. Iliac vein stent implantation as a safe and effective interventional therapy promotes the healing of venous ulcer caused by IVCS.

Managing iliofemoral deep venous thrombosis of pregnancy with a strategy of thrombus removal is safe and avoids post-thrombotic morbidity.

BACKGROUND: Extensive deep venous thrombosis (DVT) during pregnancy is usually treated with anticoagulation alone, risking significant post-thrombotic syndrome (PTS) in young patients. Catheter-directed thrombolysis (CDT) and operative venous thrombectomy have been safely and effectively used in nonpregnant patients, demonstrating significant reduction in post-thrombotic morbidity. This report reviews short- and long-term outcomes of 13 patients with extensive DVT of pregnancy treated with a strategy of thrombus removal. METHODS: From 1999 to 2013, 13 patients with iliofemoral DVT during pregnancy were offered CDT, pharmacomechanical thrombolysis (PMT), and/or venous thrombectomy. Gestational age ranged from 8 to 34 weeks. Fetal monitoring was performed throughout hospitalization. Radiation exposure was minimized with pelvic lead shields, focal fluoroscopy, and limited angiographic runs. Follow-up included objective vein evaluation using venous duplex and PTS assessment using the Villalta scale. RESULTS: CDT and/or PMT were used in 11 patients. Two patients underwent venous thrombectomy alone, and one patient had operative thrombectomy as an adjunct to CDT and PMT. Each patient had complete or near-complete thrombus resolution and rapid improvement in clinical symptoms. Eight of 11 having CDT or PMT underwent venoplasty and stenting of the involved iliac veins. Twelve of the 13 delivered healthy infants at term. One patient opted for termination of her pregnancy. Mean patient and gestational ages were 26 years and 26 weeks, respectively. Mean follow-up was 1.3 years, with only one recurrence. Duplex ultrasonography demonstrated patent veins in all but one patient and normal valve function in 10 patients. Eleven patients had Villalta scores <5 (considered normal), with a mean score of 0.7. CONCLUSIONS: Extensive DVT of pregnancy can be effectively and safely treated with a strategy of thrombus removal, resulting in a patent venous system, normal valve function in many, prevention of PTS, and reduction in recurrence.

Contrast-enhanced US in the assessment of the ilio-caval axis in deep venous thrombosis.

PURPOSE: To assess the feasibility and the accuracy of a new technique in the evaluation of deep venous thrombosis (DVT) in the ilio-caval axis. MATERIALS AND METHODS: Thirty-eight patients with suspected DVT were prospectively examined with unenhanced and enhanced colour-Doppler ultrasonography, and ascending contrast venography. Thirty-five out of 38 patients underwent US phlebography, consisting in manual injection of Levovist (Schering Ag, Berlin, Germany) through a 21-G cannula in a suitable dorsal vein of the foot ipsilateral to the suspected DVT. Three patients in whom it was not possible to cannulate a dorsal vein of foot underwent contrast-enhanced US after injection of Levovist through an antecubital vein, but where excluded from the present study. A contrast venogram was nonetheless carried out in all out three patients for comparison with the US-phlebography findings. RESULTS: US-phlebography allowed better definition of the presence and extension of deep vein thrombosis in all patients, when compared to conventional color-Doppler US. In the evaluation of suspected acute thrombosis, the comparative efficacy of Doppler-US and US phlebography compared with ascending phlebography as the gold standard, was as follows: sensitivity of 85.7% and 90%, specificity of 71.4 and 100%, accuracy of 80.9 and 95.2%, PPV of 85.7, and 100%, and NPV of 71.4, and 75%, respectively. In the assessment of chronic thrombosis, US and US phlebography achieved a sensitivity of 90% and 100%, a specificity of 75% and 100%, an accuracy of 85.7% and 100%, a PPV of 100, 100%, a NPV of 87.5, 100%, respectively. No complications related to US phlebography were observed. CONCLUSIONS: US-phlebography is a promising tool in the assessment of deep vein thrombosis, being highly accurate and feasible. However, further studies based on larger series are mandatory to confirm our promising results and establish a standardised role for this new technique.

Two-dimensional time-of-flight MR venography: assessment with detection of chronic deep venous thrombosis in combination with magnetization transfer contrast.

PURPOSE: The purpose of this study was to determine the optimum imaging parameters for 2D-TOF MR venography (MRV) of the pelvis and suprapopliteal deep venous system in combination with off-resonance magnetization transfer constant (MTC) and to evaluate the use of MRV in patients suspected of having chronic deep venous thrombosis (DVT) by comparing its accuracy with that of conventional venography (CV). METHOD: MRV was performed in 10 normal subjects to determine the optimum imaging parameters. Systematically varied scan parameters included flip angles ranging from 30 to 120 degrees by 10 degrees increments. Best TR was calculated by using the theoretical relation between the optimal TR and flow velocity. We then evaluated the use of MRV in 26 patients (total 52 deep venous systems) suspected of having chronic DVT by comparing its accuracy in evaluating the intrapelvic and suprapopliteal deep venous system with that of CV. RESULTS: The optimal imaging parameters for intrapelvic and suprapopliteal venous system MRV were found to be a flip angle of 60 degrees and a pulse sequence of 35/6.9 (TR ms/TE ms) combined with an off-resonance MTC technique. All the main veins of the intrapelvic and suprapopliteal venous systems were clearly demonstrated in each subject. The sensitivity of MRV was 100% and its specificity was 100% for diagnosis of pelvic venous stenosis. The collateral vessels were demonstrated with MRV in all patients. CONCLUSION: 2D-TOF off-resonance MTC MRV of the pelvis and the suprapopliteal lower extremities is suitable for evaluation of intrapelvic branches and suprapopliteal deep venous system and chronic DVT.

Accuracy of clinical assessment of deep-vein thrombosis.

The clinical diagnosis of deep-vein thrombosis is generally thought to be unreliable. From experience, we hypothesised that this widely held view might be incorrect. We developed a clinical model and prospectively tested its ability in three tertiary care centres to stratify symptomatic outpatients with suspected deep-vein thrombosis into groups with high, moderate, or low probability groups of deep-vein thrombosis. We evaluated our clinical model in combination with venous ultrasonography to determine the potential for an improved and simplified diagnostic approach in patients with suspected deep-vein thrombosis. All patients were clinically assessed to determine the probability for deep-vein thrombosis before they had ultrasonography and venography. All tests were performed and interpreted by independent observers. In 529 patients, the clinical model predicted prevalence of deep-vein thrombosis in the three categories: 85% in the high pretest probability category, 33% in the moderate, and 5% in the low category. There was no statistical difference in the performance of the model in the three centres. The model demonstrated excellent interobserver reliability (Kappa = 0.85). There were important differences with ultrasonography between the high and low pretest probability groups for both positive predictive values (100% (95% CI, 94-100%) vs (63% [35-85%], respectively). Thus, use of the clinical model combined with ultrasonography would decrease the number of false positive and negative diagnosis if venography were done when the ultrasound result and pretest probability were discordant. The diagnostic process could be simplified by excluding those patients with low pretest probability and normal ultrasound results from serial testing.