Critical left main coronary artery stenosis presenting as cardiac arrest in coarctation of the aorta patient.

Congenital coronary artery stenosis coexisting with aortic coarctation in nonsyndromic patients has not previously been reported. This report describes a nonsyndromic aortic coarctation patient who experienced intraoperative cardiac arrest due to a previously undiagnosed critical left main coronary artery stenosis. The patient was successfully resuscitated, underwent patch coronary ostioplasty, and was discharged home. He remains well for four months following repair.

Novel application of the Diabolo technique to restrict pulmonary blood flow in a single ventricle patient with a right ventricle to pulmonary artery conduit.

Balancing pulmonary and systemic circulations in single ventricle patients with a conduit after Stage 1 palliation is challenging. A transcatheter intervention for excessive pulmonary blood flow would provide benefit. We report a case of a critically ill single ventricle patient with symptoms of excessive pulmonary blood flow after Stage 1 despite maximal medical therapy. The patient underwent percutaneous intraluminal downsizing of the right ventricle to pulmonary artery conduit using a novel application of the Diabolo-covered stent technique, with subsequent clinical improvement. A second catheterization was performed during the interstage period with successful dilation of the stent to achieve appropriate saturations. The Diabolo technique can be successfully employed in this population to restrict pulmonary blood flow and has the advantage of being adjusted during placement and in subsequent interventions.

Calculating Relative Lung Perfusion Using Fluoroscopic Sequences and Image Analysis: The Fluoroscopic Flow Calculator.

BACKGROUND: Maldistribution of pulmonary blood flow in patients with congenital heart disease impacts exertional performance and pulmonary artery growth. Currently, measurement of relative pulmonary perfusion can only be performed outside the catheterization laboratory. We sought to develop a tool for measuring relative lung perfusion using readily available fluoroscopy sequences. METHODS: A retrospective cohort study was conducted on patients with conotruncal anomalies who underwent lung perfusion scans and subsequent cardiac catheterizations between 2011 and 2022. Inclusion criteria were nonselective angiogram of pulmonary vasculature, oblique angulation ≤20°, and an adequate view of both lung fields. A method was developed and implemented in 3D Slicer's SlicerHeart extension to calculate the amount of contrast that entered each lung field from the start of contrast injection and until the onset of levophase. The predicted perfusion distribution was compared with the measured distribution of pulmonary blood flow and evaluated for correlation, accuracy, and bias. RESULTS: In total, 32% (79/249) of screened studies met the inclusion criteria. A strong correlation between the predicted flow split and the measured flow split was found (R2=0.83; P<0.001). The median absolute error was 6%, and 72% of predictions were within 10% of the true value. Bias was not systematically worse at either extreme of the flow distribution. The prediction was found to be more accurate for either smaller and younger patients (age 0-2 years), for right ventricle injections, or when less cranial angulations were used (≤20°). In these cases (n=40), the prediction achieved R2=0.87, median absolute error of 5.5%, and 78% of predictions were within 10% of the true flow. CONCLUSIONS: The current study demonstrates the feasibility of a novel method for measuring relative lung perfusion using conventional angiograms. Real-time measurement of lung perfusion at the catheterization laboratory has the potential to reduce unnecessary testing, associated costs, and radiation exposure. Further optimization and validation is warranted.

Transcatheter Ductus Arteriosus Stenting for Acute Pediatric Pulmonary Arterial Hypertension is Associated with Improved Right Ventricular Echocardiography Strain.

BACKGROUND: Interventional therapies for severe pulmonary arterial hypertension (PAH) can provide right ventricular (RV) decompression and preserve cardiac output. Transcatheter stent placement in a residual ductus arteriosus (PDA) is one potentially effective option in critically ill infants and young children with PAH. We sought to assess recovery of RV function by echocardiographic strain in infants and young children following PDA stenting for acute PAH. METHODS: Retrospective review of patients < 2 years old who underwent PDA stenting for acute PAH. Clinical data were abstracted from the electronic medical record. RV strain (both total and free wall components) was assessed from echocardiographic images at baseline and 3, 6, and 12 months post-intervention, as well as at last echocardiogram. RESULTS: Nine patients underwent attempted ductal stenting for PAH. The median age at intervention was 38 days and median weight 3.7 kg. One-third (3of 9) of patients had PAH associated with a congenital diaphragmatic hernia. PDA stents were successfully deployed in eight patients. Mean RV total strain was - 14.9 ± 5.6% at baseline and improved to - 23.8 ± 2.2% at 6 months post-procedure (p < 0.001). Mean free wall RV strain was - 19.5 ± 5.4% at baseline and improved to - 27.7 ± 4.1% at 6 months (p = 0.002). Five patients survived to discharge, and four patients survived 1 year post-discharge. CONCLUSION: PDA stenting for severe, acute PAH can improve RV function as assessed by strain echocardiography. The quantitative improvement is more prominent in the first 6 months post-procedure and stabilizes thereafter.

Safety and Short-Term Outcomes for Infants < 2.5 kg Undergoing PDA Device Closure: A C3PO Registry Study.

To evaluate short-term procedural outcomes and safety for infants < 2.5 kg who underwent catheterization with intended patent ductus arteriosus (PDA) device closure in a multi-center registry, as performance of this procedure becomes widespread. A multi-center retrospective review was performed using data from the Congenital Cardiac Catheterization Project on Outcomes (C3PO) registry. Data were collected for all intended cases of PDA closure in infants < 2.5 kg from April 2019 to December 2020 at 13 participating sites. Successful device closure was defined as device placement at the conclusion of the catheterization. Procedural outcomes and adverse events (AE) were described, and associations between patient characteristics, procedural outcomes and AEs were analyzed. During the study period, 300 cases were performed with a median weight of 1.0 kg (range 0.7-2.4). Successful device closure was achieved in 98.7% of cases with a 1.7% incidence of level 4/5 AEs, including one periprocedural mortality. Neither failed device placement nor adverse events were significantly associated with patient age, weight or institutional volume. Higher incidence of adverse events associated with patients who had non-cardiac problems (p = 0.017) and cases with multiple devices attempted (p = 0.064). Transcatheter PDA closure in small infants can be performed with excellent short-term outcomes and safety across institutions with variable case volume.

Predictors of Serious Adverse Events and High-Level Cardiorespiratory Support in Patients Undergoing Transcatheter Pulmonary Vein Interventions.

Patients with pulmonary vein stenosis (PVS) often require frequent transcatheter pulmonary vein (PV) interventions for management of restenosis. Predictors of serious adverse events (AEs) and need for high-level cardiorespiratory support (mechanical ventilation, vasoactive support, and/or extracorporeal membrane oxygenation) 48 h after transcatheter PV interventions have not been reported. This is a single-center retrospective cohort analysis of patients with PVS who underwent transcatheter PV interventions from 3/1/2014 to 12/31/2021. Univariate and multivariable analyses were performed using generalized estimating equations to account for within-patient correlation. 240 patients underwent 841 catheterizations involving PV interventions (median 2 catheterizations per patient [1,3]). At least one serious AE was reported in 100 (12%) cases, the most common of which were pulmonary hemorrhage (n = 20) and arrhythmia (n = 17). There were 14 severe/catastrophic AEs (1.7% of cases) including three strokes and one patient death. On multivariable analysis, age less than 6 months, low systemic arterial saturation (< 95% in patients with biventricular [BiV] physiology, < 78% in single ventricle [SV] physiology), and severely elevated mean PA pressure (≥ 45 mmHg in BiV, ≥ 17 mmHg in SV) were associated with SAEs. Age less than 1 year, hospitalization prior to catheterization, and moderate-severe RV dysfunction were associated with high-level support after catheterization. Serious AEs during transcatheter PV interventions in patients with PVS are common, although major events such as stroke or death are uncommon. Younger patients and those with abnormal hemodynamics are more likely to experience serious AEs and require high-level cardiorespiratory support after catheterization.

Early Postoperative Congenital Cardiac Catheterization Outcomes: A Multicenter Study.

BACKGROUND: Early postoperative catheterizations (EPOCs) within 6 weeks after a congenital heart surgical procedure can treat residual lesions and provide important clinical information. However, EPOCs are often assumed to impose additional risk on a vulnerable patient population. This study aimed to describe the EPOC population, evaluate procedural safety, compare EPOC patients with procedure-matched non-EPOC patients, and determine risk factors for poor outcomes using data from the Congenital Cardiac Catheterization Project on Outcomes registry. METHODS: In a retrospective cohort, demographic, clinical, and procedural characteristics were analyzed for diagnostic and interventional catheterizations performed in 13 participating institutions from January 2014 to December 2017, excluding patients after heart transplant. The primary outcome was a high-severity adverse event (AE). Three distinct analyses included (1) describing the full cohort and EPOC patients, (2) comparing EPOC patients with and without a high-severity AE, and (3) comparing EPOC patients with controls matched on case type. RESULTS: This study included 17,776 catheterizations, with 1399 EPOCs. The high-severity AE rate was 6.4% overall, 8.9% in the EPOC cohort, and 8.4% in matched controls (P = .74). The association between EPOC status and high-severity AE was not significant in a multivariable model (P = .17). In EPOCs with a high-severity AE, median procedure duration was 30 minutes longer (P < .001), and median time from surgical procedure to catheterization was 3 days longer (P = .05). CONCLUSIONS: EPOC was not associated with additional risk. Individual patient characteristics of size and hemodynamic vulnerability may serve as informative predictors. Timely catheterization may preempt further clinical deterioration, and intraprocedure duration optimization may correlate with improved outcomes.

Hemodynamic and anatomic changes after fetal aortic valvuloplasty are associated with procedural success and postnatal biventricular circulation.

BACKGROUND: There are minimal data characterizing the trajectory of left heart growth and hemodynamics following fetal aortic valvuloplasty (FAV). METHODS: This retrospective study included patients who underwent FAV between 2000 and 2019, with echocardiograms performed pre-FAV, immediately post-FAV, and in late gestation. RESULTS: Of 118 fetuses undergoing FAV, 106 (90%) underwent technically successful FAV, of which 55 (52%) had biventricular circulation. Technically successful FAV was associated with improved aortic valve growth (p < 0.001), sustained antegrade aortic arch (AoA) flow (p = 0.02), improved mitral valve (MV) inflow pattern (p = 0.002), and favorable patent foramen ovale (PFO) flow pattern (p = 0.004) from pre-FAV to late gestation. Compared to patients with univentricular outcome, patients with biventricular outcome had less decrement in size of the left ventricle (LV) (p < 0.001) and aortic valve (p = 0.005), as well as more physiologic PFO flow (p < 0.001) and antegrade AoA flow (p < 0.001) from pre-FAV to late gestation. In multivariable analysis, echocardiographic predictors of biventricular outcome were less decline in LV end diastolic dimension (p < 0.001), improved PFO flow (p = 0.004), and sustained antegrade AoA flow (p = 0.002) from pre-FAV to late gestation. CONCLUSION: Stabilization of left heart growth and improved hemodynamics following successful FAV through late gestation are associated with postnatal biventricular circulation.

Definitive Closure of the Patent Ductus Arteriosus in Preterm Infants and Subsequent Short-Term Respiratory Outcomes.

A persistent patent ductus arteriosus (PDA) can have significant clinical consequences in preterm infants, depending on the degree of left-to-right shunting, its impact on cardiac performance, and associated perinatal risk factors that can mitigate or exacerbate the shunt. Although the best management strategy remains contentious, PDAs that have contraindications to, or have failed medical management have historically undergone surgical ligation. Recently smaller occluder devices and delivery systems have allowed for minimally invasive closure in the catheterization laboratory even in extremely premature infants. The present review summarizes the pathophysiologic manifestations, treatment options and management of hemodynamically significant PDA in preterm infants. Additionally, we review the available literature surrounding the respiratory support and outcomes of preterm infants following definitive PDA closure.

Lung and Pleural Findings of Children with Pulmonary Vein Stenosis with and without Aspiration: MDCT Evaluation.

Purpose: To retrospectively compare the lung and pleural findings in children with pulmonary vein stenosis (PVS) with and without aspiration on multidetector computed tomography (MDCT). Materials and Methods: All consecutive children (≤18 years old) with PVS who underwent thoracic MDCT studies from August 2004 to December 2021 were categorized into two groups: children with PVS with aspiration (Group 1) and children with PVS without aspiration (Group 2). Two independent pediatric radiologists retrospectively evaluated thoracic MDCT studies for the presence of lung and pleural abnormalities as follows: (1) in the lung (ground-glass opacity (GGO), consolidation, nodule, mass, cyst(s), interlobular septal thickening, and fibrosis) and (2) in the pleura (thickening, effusion, and pneumothorax). Interobserver agreement between the two reviewers was evaluated by the proportion of agreement and the Kappa statistic. Results: The final study population consisted of 64 pediatric patients (36 males (56.3%) and 43 females (43.7%); mean age, 1.7 years; range, 1 day−17 years). Among these 64 patients, 19 patients (29.7%) comprised Group 1 and the remaining 45 patients (70.3%) comprised Group 2. In Group 1 (children with PVS with aspiration), the detected lung and pleural MDCT abnormalities were: GGO (17/19; 89.5%), pleural thickening (17/19; 89.5%), consolidation (16/19; 84.5%), and septal thickening (16/19; 84.5%). The lung and pleural MDCT abnormalities observed in Group 2 (children with PVS without aspiration) were: GGO (37/45; 82.2%), pleural thickening (37/45; 82.2%), septal thickening (36/45; 80%), consolidation (3/45; 6.7%), pleural effusion (1/45; 2.2%), pneumothorax (1/45; 2.2%), and cyst(s) (1/45; 2.2%). Consolidation was significantly more common in pediatric patients with both PVS and aspiration (Group 1) (p < 0.001). There was high interobserver agreement between the two independent reviewers for detecting lung and pleural abnormalities on thoracic MDCT studies (Kappa = 0.98; CI = 0.958, 0.992). Conclusion: Aspiration is common in pediatric patients with PVS who undergo MDCT and was present in nearly 30% of all children with PVS during our study period. Consolidation is not a typical radiologic finding of PVS in children without clinical evidence of aspiration. When consolidation is present on thoracic MDCT studies in pediatric patients with PVS, the additional diagnosis of concomitant aspiration should be considered.

Pleuropulmonary MDCT Findings: Comparison between Children with Pulmonary Vein Stenosis and Prematurity-Related Lung Disease.

Purpose: To retrospectively compare the pleuropulmonary MDCT findings in children with pulmonary vein stenosis (PVS) and prematurity-related lung disease (PLD). Materials and Methods: All consecutive infants and young children (≤18 years old) who underwent thoracic MDCT studies from July 2004 to November 2021 were categorized into two groups­children with PVS (Group 1) and children with PLD without PVS (Group 2). Two pediatric radiologists independently evaluated thoracic MDCT studies for the presence of pleuropulmonary abnormalities as follows­(1) in the lung (ground-glass opacity (GGO), triangular/linear plaque-like opacity (TLO), consolidation, nodule, mass, cyst(s), interlobular septal thickening, and fibrosis); (2) in the airway (bronchial wall thickening and bronchiectasis); and (3) in the pleura (thickening, effusion, and pneumothorax). Interobserver agreement between the two reviewers was evaluated with the Kappa statistic. Results: There were a total of 103 pediatric patients (60 males (58.3%) and 43 females (41.7%); mean age, 1.7 years; range, 2 days−7 years). Among these 103 patients, 49 patients (47.6%) comprised Group 1 and the remaining 54 patients (52.4%) comprised Group 2. In Group 1, the observed pleuropulmonary MDCT abnormalities were­pleural thickening (44/49; 90%), GGO (39/49; 80%), septal thickening (39/49; 80%), consolidation (4/49; 8%), and pleural effusion (1/49; 2%). The pleuropulmonary MDCT abnormalities seen in Group 2 were­GGO (45/54; 83%), TLO (43/54; 80%), bronchial wall thickening (33/54; 61%), bronchiectasis (30/54; 56%), cyst(s) (5/54; 9%), pleural thickening (2/54; 4%), and pleural effusion (2/54; 4%). Septal thickening and pleural thickening were significantly more common in pediatric patients with PVS (Group 1) (p < 0.001). TLO, bronchial wall thickening, and bronchiectasis were significantly more frequent in pediatric patients with PLD without PVS (Group 2) (p < 0.001). There was high interobserver kappa agreement between the two independent reviewers for detecting pleuropulmonary abnormalities on thoracic MDCT angiography studies (k = 0.99). Conclusion: Pleuropulmonary abnormalities seen on thoracic MDCT can be helpful for distinguishing PVS from PLD in children. Specifically, the presence of septal thickening and pleural thickening raises the possibility of PVS, whereas the presence of TLO, bronchial wall thickening and bronchiectasis suggests PLD in the pediatric population.

Anesthesia in Children With Pulmonary Hypertension: Clinically Significant Serious Adverse Events Associated With Cardiac Catheterization and Noncardiac Procedures.

OBJECTIVES: To determine the incidence of clinically significant serious adverse events in a contemporary population of pediatric patients with pulmonary hypertension who require anesthesia and identify factors associated with adverse outcomes. DESIGN: A retrospective, cross-sectional study. SETTING: A single-center quaternary-care freestanding children's hospital in the northeastern United States. PARTICIPANTS: Pediatric patients with pulmonary hypertension based on hemodynamic criteria on cardiac catheterization during a 3-year period from 2015 to 2018. INTERVENTIONS: Anesthesia care for cardiac catheterization, noncardiac surgery, and diagnostic imaging. MEASUREMENTS AND MAIN RESULTS: Two hundred forty-nine children underwent 862 procedures, 592 for cardiac catheterization and 278 for noncardiac surgery and diagnostic imaging. The median age was 1.6 years, and the weight was 9.5 lbs. On index catheterization, median pulmonary artery pressure was 36 mmHg, and the pulmonary vascular resistance was 5.1 indexed Wood units. Ten percent of anesthetics were performed with a natural airway, and 80% used volatile anesthetics. Serious adverse events occurred in 26% of procedures (confidence interval [CI], 22%-30%). The rate of periprocedural cardiac arrest was 8 per 1,000 anesthetic administrations. In multivariate analysis, younger age (adjusted odds ratio [aOR], 1.4 per year; CI, 1.1-1.9; p = 0.01), location in the catheterization laboratory (aOR, 5.1; CI, 1.7-16; p = 0.004), and longer procedure duration (aOR, 1.3 per 30 minutes; CI, 1.1-1.4; p = 0.001) were associated with serious adverse events. Patients with a tracheostomy in place were less likely to experience an adverse event (aOR, 0.1; CI, 0.04-0.5; p = 0.001). The primary anesthetic technique was not associated with adverse events. Interventional cardiac catheterization was associated with an increased incidence of adverse events compared with diagnostic catheterization (42% v 21%; OR, 2.23; CI, 1.5-3.3; p < 0.001). CONCLUSIONS: Serious adverse events were common in this cohort. Careful planning to minimize anesthesia time in young children with pulmonary hypertension should be undertaken, and these factors considered in designing risk mitigation strategies.

Phenotyping respiratory decompensation following definitive closure of the patent ductus arteriosus in preterm infants.

OBJECTIVE: To identify risk factors associated with high-frequency ventilation (HFV) following definitive closure of the patent ductus arteriosus (PDA). METHODS: We performed a retrospective study of premature infants (<37 weeks) who were mechanically ventilated before and after surgical or transcatheter PDA closure. Primary outcome was HFV requirement within 24 h of procedure. Logistic regression was used to estimate clinical associations with post procedure HFV requirement. RESULTS: We identified 110 infants who were mechanically ventilated before PDA closure, of which 48 (44%) escalated to HFV within 24 h after closure. In the multivariable model, surgical ligation (OR 21.5, 95% CI 1.6-284), elevated Respiratory Severity Score (RSS) 1 h post-procedure (OR 1.78, 95% CI 1.07-2.99) and 12 h post-procedure (OR 2.12, 95% CI 1.37-3.26) were independent predictors of HFV. CONCLUSION: Surgical ligation and elevated RSS values over the first 12 h after PDA closure are risk factors for HFV.

Pulmonary vein stenosis: Anatomic considerations, surgical management, and outcomes.

OBJECTIVE: The study objective was to evaluate outcomes of pulmonary vein stenosis repair in a large single-center cohort. METHODS: Clinical data from a pulmonary vein stenosis registry were retrospectively reviewed identifying patients who underwent pulmonary vein stenosis repair. The primary/index operation was defined as the patient's first pulmonary vein stenosis operation during the study period. RESULTS: Between January 2007 and August 2019, 174 patients underwent pulmonary vein stenosis repair. Bilateral pulmonary vein stenosis occurred in 111 patients (64%); 71 patients (41%) had 4-vessel disease. Fifty-nine patients (34%) had primary pulmonary vein stenosis. Median age was 9 months (interquartile range, 5-27) and weight was 6.5 kg (4.7-10.2). Surgical techniques evolved and included ostial resection, unroofing, reimplantation, sutureless, modified sutureless, and a newer anatomically focused approach of pulmonary vein stenosis resection with lateralization or patch enlargement of the pulmonary vein-left atrium connection. Twenty-three patients (13%) required reoperation. Cumulative 2-year incidence of postoperative transcatheter intervention (balloon dilation ± stenting) was 64%. One-, 2-, and 5-year survivals were 71.2%, 66.8%, and 60.6%, respectively. There was no association between surgery type and reoperation rate (hazard ratio, 2.38, P = .25) or transcatheter intervention (hazard ratio, 0.97, P = .95). The anatomically focused repair was associated with decreased mortality on univariate (hazard ratio, 0.38, P = .042) and multivariable analyses (hazard ratio, 0.19, P = .014). Antiproliferative chemotherapy was also associated with decreased mortality (hazard ratio, 0.47, P = .026). CONCLUSIONS: This large single-center surgical pulmonary vein stenosis experience demonstrates encouraging midterm results. A new anatomically focused repair strategy aims to alleviate pulmonary vein angulation to minimize turbulence and shows promising early outcomes. Continued follow-up is required to understand longer-term outcomes for this surgical approach.

Secondary Pulmonary Vein Stenosis Due to Total Anomalous Pulmonary Venous Connection Repair in Children: Extravascular MDCT Findings.

PURPOSE: To evaluate extravascular findings on thoracic MDCT angiography in secondary pulmonary vein stenosis (PVS) due to total anomalous pulmonary venous connection (TAPVC) repair in children. MATERIALS AND METHODS: All patients aged ≤18 years with a known diagnosis of secondary PVS after TAPVC repair, confirmed by echocardiography, conventional angiography, and/or surgery, who underwent thoracic MDCT angiography studies between July 2008 and April 2021 were included. Two pediatric radiologists independently examined MDCT angiography studies for the presence of extravascular thoracic abnormalities in the lung, pleura, and mediastinum. The location and distribution of each abnormality (in relation to the location of PVS) were also evaluated. Interobserver agreement between the two independent pediatric radiology reviewers was studied using kappa statistics. RESULTS: The study group consisted of 20 consecutive pediatric patients (17 males, 3 females) with secondary PVS due to TAPVC repair. Age ranged from 2 months to 8 years (mean, 16.1 months). In children with secondary PVS due to TAPVC repair, the characteristic extravascular thoracic MDCT angiography findings were ground-glass opacity (19/20; 95%), septal thickening (7/20; 35%), pleural thickening (17/20; 85%), and a poorly defined, mildly heterogeneously enhancing, non-calcified soft tissue mass (17/20; 85%) which followed the contours of affected pulmonary veins outside the lung. There was excellent interobserver kappa agreement between two independent reviewers for detecting extravascular abnormalities on thoracic MDCT angiography studies (k = 0.99). CONCLUSION: Our study characterizes the extravascular thoracic MDCT angiography findings in secondary pediatric PVS due to TAPVC repair. In the lungs and pleura, ground-glass opacity, interlobular septal thickening, and pleural thickening are common findings. Importantly, the presence of a mildly heterogeneously enhancing, non-calcified mediastinal soft tissue mass in the distribution of the PVS is a novel characteristic thoracic MDCT angiography finding seen in pediatric secondary PVS due to TAPVC repair.

The Role of Elevated Wall Shear Stress in Progression of Pulmonary Vein Stenosis: Evidence from Two Case Studies.

Pulmonary vein stenosis is a serious condition characterized by restriction or blockage due to fibrotic tissue ingrowth that develops in the pulmonary veins of infants or children. It is often progressive and can lead to severe pulmonary hypertension and death. Efforts to halt or reverse disease progression include surgery and catheter-based balloon dilation and stent implantation. Its cause and mechanism of progression are unknown. In this pilot study, we propose and explore the hypothesis that elevated wall shear stress at discrete pulmonary venous sites triggers stenosis. To assess this theory, we retrospectively analyzed cardiac catheterization, lung scan, and X-ray computed tomography data to estimate wall shear stress in the pulmonary veins at multiple time points during disease progression in two patients. Results are consistent with the existence of a level of elevated wall shear stress above which the disease is progressive and below which progression is halted. The analysis also suggests the possibility of predicting the target lumen size necessary in a given vein to reduce wall shear stress to normal levels and remove the trigger for stenosis progression.