Noninvasive measurement of ambulatory venous pressure via column interruption duration in chronic venous disease.

BACKGROUND: Column interruption duration (CID) is a noninvasive surrogate for venous refill time (VFT), a parameter used in ambulatory venous pressure measurement. CID is more accurate than invasive VFT measurement because it avoids errors involved with indirect access of the deep system through the dorsal foot vein. The aim of this retrospective single center study is to analyze the clinical usefulness of CID in assessment of chronic venous disease (CVD). METHODS: A total of 1551 limbs (777 patients) were referred with CVD symptoms over a 5-year period (2018-2023); CID, air plethysmography, and duplex reflux data were analyzed. Of these limbs, 679 had supine venous pressure data as well. The pathology was categorized as obstruction if supine peripheral venous pressure was >11 mm Hg and as reflux if duplex reflux time in superficial or deep veins was >1 second. CID was measured via Doppler monitoring of flow in the great saphenous vein (GSV) and one of the paired posterior tibial (PT) veins near the ankle in the erect posture. The calf is emptied by rapid inflation cuff. CID is the time interval in seconds when cephalad venous flow in great saphenous vein and posterior tibial veins reappear after calf ejection. A CID <20 seconds in either vein is abnormal similar to the threshold used in VFT measurement. RESULTS: Thirty-two percent of the limbs had obstruction, 17% had reflux, and 37% had a combination; 14% had neither. Higher clinical-etiology-anatomy-pathophysiology (CEAP) clinical classes (C4-6) were prevalent in 44% of pure reflux, significantly less (P < .0001) than in pure obstruction (73%) or obstruction plus reflux subsets (72%), partly reflecting distribution of pathology. There is a progressive increase in supine venous pressure and abnormal CID (P < .0001 and P < .0001, respectively) in successive CEAP clinical class. No such correlation between CEAP and any of the reflux severity grading methods (reflux segment score, Venous Filling Index, and Kistner axial grading) was observed. Abnormal CID (55%) was more prevalent in higher CEAP classes (>4) (P < .0001) than in lesser clinical classes (0-2) or limbs with neither obstruction nor reflux (P < .01). CONCLUSIONS: Obstruction seems to be a more dominant pathology in clinical progression among CEAP clinical classes than reflux. CID is abnormal in both obstructive and refluxive pathologies and may represent a common end pathway for similar clinical manifestations (eg, ulcer). These data suggest a useful role for CID measurement in clinical assessment of limbs with CVD.

Conduit design with expanding diameter for enhanced flow.

Conduits are commonly used for treating lesions in arteries and veins. The conventional stents are cylindrical in shape, which increases flow resistance with length. This study presents a design of stents and conduits where the conduit caliber expands gradually to reduce resistance while avoiding flow separation. Inflow was provided from a header tank at two different pressures (i.e., 10 and 25 mm Hg pressure) into a cylindrical or expanding conduit. The initial conduit calibers were 2-, 3-, 4-, and 5-mm and 160-, 310-, and 620-mm lengths in each case. The flow rates of expanding caliber conduits (at a rate of r4-6/cm where r is the initial conduit radius) were compared to traditional cylindrical conduits of constant radius. The expanded caliber yields a significantly increased flow of 16-55% for R4/L expansion, 9-44% for R5/L expansion, and 1-28% for R6/L expansion. Simulated flow models using computational fluid dynamics (CFD) were used to validate and expand the experimental findings. Flow separation was detected for certain simulations by flow pathlines and wall shear stress (WSS) calculations. The results showed that a caliber expansion rate of r6/cm is the optimal rate of expansion for most potential applications with minimum flow separation, lower resistance, and increased flow.

Iliac vein stent failure in community practice and results of corrective reinterventions.

OBJECTIVE: The goal of endovenous stenting is to relieve venous obstruction and reduce peripheral venous hypertension by using large caliber venous stents in the presence of adequate venous inflow and outflow for the stented conduit. The aim of this report is to describe the technical reasons and outcomes for reinterventions in a subset of patients who had a history of iliac vein stenting and were now referred to us at a specialty venous clinic for further care. METHODS: From January 2016 to December 2021, records of all patients who were referred to us with a history of iliac vein stenting performed at an outside facility and who had a reoperation performed at our center were retrospectively analyzed. RESULTS: A total of 149 limbs underwent a deep venous reintervention after a failure of a trial of conservative therapy. The mean age of the sample was 57 ± 16 years. The ratio of non-thrombotic iliac vein lesions to post-thrombotic lesions was 1:2.5. The majority of the patients (84%) were CEAP class C4 or higher. The most common reason for reintervention was stent occlusion (74%), followed by iatrogenic stenosis (53%) and in-stent restenosis/shelving (38%). There was a trend for improvement in all clinical parameters (venous clinical severity score, visual analog scale for pain, and edema grade) after the reintervention. Poor inflow was present in 70% of limbs with stent occlusion. The median diameters of stented common femoral vein, external iliac vein, and common iliac vein prior to reintervention were 12, 12, and 13 mm, respectively. The median diameters of stented common femoral vein, external iliac vein, and common iliac vein after reintervention were 14, 15, and 16 mm, respectively. Eighty-eight percent of limbs required at least one further reintervention after initial reoperation. CONCLUSIONS: Venous reoperations are generally infrequent and required in a small number of patients. Poor inflow appeared to be a common cause of stent occlusion. Iatrogenic stenosis is another common reason for venous reoperation and is difficult to fully rectify through current endovascular techniques and tools. Use of intravascular ultrasound planimetry routinely in every deep venous intervention and thorough knowledge of the principles of venous stenting outlined in this report may help forestall the need for reoperative deep venous surgery in some cases.

Clinical tolerance of untreated reflux after iliac vein stent placement.

BACKGROUND: We have recently demonstrated in a large patient cohort that the prevalence and severity of reflux will improve in most limbs after stenting and that most limbs will not develop new-onset reflux. In the present report, we have focused on the long-term clinical outcomes associated with untreated reflux in the same patient cohort who had undergone iliofemoral venous stenting without correction of residual reflux. METHODS: The clinical outcomes data from 1379 limbs treated with only iliac vein stenting without correction of superficial or deep reflux from 1997 to 2018 were analyzed (23-year follow-up period). Of the 1379 limbs, 632 (46%) had had preexisting reflux before stenting and 747 (54%) had did not. The reflux data (reflux segmental score, air plethysmography, ambulatory venous pressure) for these patients have been previously reported in detail. The subsets were compared perioperatively with each other using the following variables: grade of swelling, visual analog scale for pain score, venous clinical severity score, venous stasis dermatitis, ulceration, and quality of life measures. RESULTS: Both groups demonstrated improvements in the venous clinical severity score, grade of swelling, visual analog scale score, and quality of life. No differences were found in ulcer healing (5% vs 3% for limbs with and without prestent reflux, respectively) and resolution of dermatitis (6% vs 5% for limbs with and without prestent reflux, respectively) between the two groups. Of the 632 limbs with preexisting reflux, 218 (34%) had had axial reflux and 414 had had nonaxial reflux (66%). The clinical outcomes were similar between the two groups. Using a multisegment reflux score, the limbs with prestent reflux (n = 632) were divided into two groups. A segmental score of ≥3 indicated severe reflux and a score of <3 indicated moderate reflux. Of these 632 limbs, 161 (25%) had severe reflux and 471 (75%) had moderate reflux. The two groups demonstrated similar outcomes for most clinical parameters. The post-thrombotic limbs and nonthrombotic limbs also showed similar outcomes. CONCLUSIONS: The long-term follow-up of patients after iliac vein stenting showed that uncorrected reflux is well tolerated by most patients across most clinical measures.

Long-term improvement of limb reflux prevalence and severity after iliac vein stent placement.

BACKGROUND: The effect of iliac vein stenting on ipsilateral limb reflux is unknown and has remained a matter of speculation. It has been suggested that the propensity for reflux might worsen when proximal stenosis is corrected. This could allow for retrograde flow with coughing and the Valsalva maneuver, stressing the valve. We examined this hypothesis by an analysis of the long-term effects of iliac vein stenting on limb reflux using a single-center, retrospective analysis of prospectively collected data. METHODS: Reflux data from duplex ultrasound of 1387 limbs in 1228 patients who had undergone iliac vein stenting from 1997 to 2018 were analyzed. Of the 1387 limbs, 632 (46%) had had ipsilateral duplex ultrasound-determined valve reflux before stenting, and 747 limbs (54%) had not had reflux; data were missing for 8 limbs. Reflux status before and after stenting was available for seven individual segments for each limb in the database for analysis (total, 9653 segments). The stented patients were examined for reflux at least annually during the follow-up period (range, 1-26 years). Segmental reflux prevalence was detected using duplex ultrasound. We have referred to this as "duplex reflux" or simply "reflux." Reflux severity was graded using (1) a reflux segmental score, assigning one point each for refluxing segments in the limb; (2) air plethysmography (venous filling index [VFI90]); and (3) ambulatory venous pressure (venous filling time [VFT]). RESULTS: Prestent duplex reflux was present in a combination of superficial, deep, and perforator segments. Reflux prevalence ranged from 7% of deep femoral segments to 51% at the popliteal segment. Post-stent reflux resolution varied from 21% at the femoral vein segment to 58% at the perforator segments. Reflux had completely resolved in 23% of the limbs. New-onset reflux was rare, with a median incidence of 7% for all segments at risk, with cumulative improvement (Kaplan-Meier curve) in reflux severity (segment score, VFI90, and VFT) for most limbs. These metrics were unimproved, with residual reflux in only 18%, 11%, and 6% (segment score, VFI90, and VFT, respectively) of the limbs at long-term follow-up. CONCLUSIONS: Long-term follow-up of limbs after iliac vein stenting has shown that the associated ipsilateral reflux prevalence and severity will improve in most limbs over time.