Doppler Ultrasound Surveillance Research Articles

Doppler ultrasound surveillance of recently formed haemodialysis arteriovenous fistula: the SONAR observational cohort study.

Arteriovenous fistulas are considered the best option for haemodialysis provision, but as many as 30% fail to mature or suffer early failure. To assess the feasibility of performing a randomised controlled trial that examines whether, by informing early and effective salvage intervention of fistulas that would otherwise fail, Doppler ultrasound surveillance of developing arteriovenous fistulas improves longer-term arteriovenous fistula patency. A prospective multicentre observational cohort study (the 'SONAR' study). Seventeen haemodialysis centres in the UK. Consenting adults with end-stage renal disease who were scheduled to have an arteriovenous fistula created. Participants underwent Doppler ultrasound surveillance of their arteriovenous fistulas at 2, 4, 6 and 10 weeks after creation, with clinical teams blinded to the ultrasound surveillance findings. Fistula maturation at week 10 defined according to ultrasound surveillance parameters of representative venous diameter and blood flow (wrist arteriovenous fistulas: ≥ 4 mm and > 400 ml/minute; elbow arteriovenous fistulas: ≥ 5 mm and > 500 ml/minute). Mixed multivariable logistic regression modelling of the early ultrasound scan data was used to predict arteriovenous fistula non-maturation by 10 weeks and fistula failure at 6 months. A total of 333 arteriovenous fistulas were created during the study window (47.7% wrist, 52.3% elbow). By 2 weeks, 37 (11.1%) arteriovenous fistulas had failed (thrombosed), but by 10 weeks, 219 of 333 (65.8%) of created arteriovenous fistulas had reached maturity (60.4% wrist, 67.2% elbow). Persistently lower flow rates and venous diameters were observed in those fistulas that did not mature. Models for arteriovenous fistulas' non-maturation could be optimally constructed using the week 4 scan data, with fistula venous diameter and flow rate the most significant variables in explaining wrist fistula maturity failure (positive predictive value 60.6%, 95% confidence interval 43.9% to 77.3%), whereas resistance index and flow rate were most significant for elbow arteriovenous fistulas (positive predictive value 66.7%, 95% confidence interval 48.9% to 84.4%). In contrast to non-maturation, both models predicted fistula maturation much more reliably [negative predictive values of 95.4% (95% confidence interval 91.0% to 99.8%) and 95.6% (95% confidence interval 91.8% to 99.4%) for wrist and elbow, respectively]. Additional follow-up and modelling on a subset (n = 192) of the original SONAR cohort (the SONAR-12M study) revealed the rates of primary, assisted primary and secondary patency arteriovenous fistulas at 6 months were 76.5, 80.7 and 83.3, respectively. Fistula vein size, flow rate and resistance index could identify primary patency failure at 6 months, with similar predictive power as for 10-week arteriovenous fistula maturity failure, but with wide confidence intervals for wrist (positive predictive value 72.7%, 95% confidence interval 46.4% to 99.0%) and elbow (positive predictive value 57.1%, 95% confidence interval 20.5% to 93.8%). These models, moreover, performed poorly at identifying assisted primary and secondary patency failure, likely because a subset of those arteriovenous fistulas identified on ultrasound surveillance as at risk underwent subsequent successful salvage intervention without recourse to early ultrasound data. Although early ultrasound can predict fistula maturation and longer-term patency very effectively, it was only moderately good at identifying those fistulas likely to remain immature or to fail within 6 months. Allied to the better- than-expected fistula patency rates achieved (that are further improved by successful salvage), we estimate that a randomised controlled trial comparing early ultrasound-guided intervention against standard care would require at least 1300 fistulas and would achieve only minimal patient benefit. This trial is registered as ISRCTN36033877 and ISRCTN17399438. This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR135572) and is published in full in Health Technology Assessment; Vol. 28, No. 24. See the NIHR Funding and Awards website for further award information.

Results of a hemodialysis vascular access routine ultrasound surveillance protocol and frequency of surveillance guided pre-emptive access maintenance interventions

Background: To evaluate the implementation of routine surveillance using ultrasound on hemodialysis vascular access (VA) outcomes and determine the number and frequency of corrective, surveillance-guided procedures performed. Methods: Multicenter, prospective, observational study that includes consecutive hemodialysis patients receiving therapy from native arteriovenous fistulae (AVF) or grafts (AVG). Participants were assigned to a routine VA Color Doppler ultrasound surveillance (DUS) protocol from January 2019 to December 2021. Patients were referred for corrective procedures (endovascular or surgical) based on clinical or DUS findings (pre-emptive procedures; PEP). Primary endpoint was the estimation of primary unassisted (PUP) and secondary patency (SP) rates. Secondary endpoints were the determination of the number and frequency of PEP and VA survival rates. Results: In total, 223 patients with 243 VA (192 AVF and 51 AVG) were included. Access PUP and SP rates were 83% and 93% at 12 months, 75% and 88% at 24 months, and 72% and 83% at 36 months follow-up. Autologous fistulae PUP and SP were 89% and 96% at 12 months, 81% and 93% at 24 months, and 80% and 89% at 36 months, respectively. Graft PUP and SP were 56% and 80% at 12 months, 44% and 65% at 24 months, and 39% and 54% at 36 months, respectively. In total, 56 corrective procedures (38/56 PEP; 65.5%) were performed (0.13 procedures/year), of which 34 were in AVF patients (0.09 procedures/year) and 22 in AVG patients (0.40 procedures/year). Overall, 33 VA losses occurred (0.06 failures/year), 17 in AVF (0.04 failures/year), and 16 in AVG patients (0.20 failures/year). Conclusion: The use of DUS resulted in the timely diagnosis of dysfunction, satisfactory overall VA survival, and patency rates, with a low PEP frequency. Randomized controlled trials are required to establish the value of DUS surveillance on access patency and whether DUS-guided interventions could improve VA outcomes.

Periadventitial β-aminopropionitrile-loaded nanofibers reduce fibrosis and improve arteriovenous fistula remodeling in rats.

Arteriovenous fistula (AVF) postoperative stenosis is a persistent healthcare problem for hemodialysis patients. We have previously demonstrated that fibrotic remodeling contributes to AVF non-maturation and lysyl oxidase (LOX) is upregulated in failed AVFs compared to matured. Herein, we developed a nanofiber scaffold for the periadventitial delivery of β-aminopropionitrile (BAPN) to determine whether unidirectional periadventitial LOX inhibition is a suitable strategy to promote adaptive AVF remodeling in a rat model of AVF remodeling. Bilayer poly (lactic acid) ([PLA)-]- poly (lactic-co-glycolic acid) ([PLGA)] scaffolds were fabricated with using a two-step electrospinning process to confer directionality. BAPN-loaded and vehicle control scaffolds were wrapped around the venous limb of a rat femoral-epigastric AVF during surgery. AVF patency and lumen diameter were followed monitored using Doppler ultrasound surveillance and flow was measured before euthanasia. AVFs were harvested after 21 days for histomorphometry and immunohistochemistry. AVF compliance was measured using pressure myography. RNA from AVF veins was sequenced to analyze changes in gene expression due to LOX inhibition. Bilayer periadventitial nanofiber scaffolds extended BAPN release compared to the monolayer design (p < 0.005) and only released BAPN in one direction. Periadventitial LOX inhibition led to significant increases in AVF dilation and flow after 21 days. Histologically, BAPN trended toward increased lumen and significantly reduced fibrosis compared to control scaffolds (p < 0.01). Periadventitial BAPN reduced downregulated markers associated with myofibroblast differentiation including SMA, FSP-1, LOX, and TGF-β while increasing the contractile marker MYH11. RNA sequencing revealed differential expression of matrisome genes. Periadventitial BAPN treatment reduces fibrosis and promotes AVF compliance. Interestingly, the inhibition of LOX leads to increased accumulation of contractile VSMC while reducing myofibroblast-like cells. Periadventitial LOX inhibition alters the matrisome to improve AVF vascular remodeling.

Doppler Ultrasound of Vascular Complications After Pediatric Liver Transplantation: Incidence, Time of Detection, and Positive Predictive Value.

Purpose Doppler ultrasound (DUS) is widely used to detect vascular complications after pediatric liver transplantation (LT). This study aimed to assess the moment of first detection of vascular complications with DUS, and to determine the positive predictive value (PPV) of DUS. Materials and Methods Patients aged 0-18 years who underwent LT between 2015 and 2019 were retrospectively included. 92 LTs in 83 patients were included (median age: 3.9 years, interquartile range: 0.7-10.5). Patients underwent perioperative (intra-operative and immediately postoperative) and daily DUS surveillance during the first postoperative week, and at 1, 3, and 12 months. Vascular complications were categorized for the hepatic artery, portal vein, and hepatic veins. DUS findings were compared to surgical or radiological findings during the 1-year follow-up. Results 52 vascular complications were diagnosed by DUS in 35/92 LTs (38%). 15 out of 52 (28.8%) were diagnosed perioperatively, 29/52 (55.8%) were diagnosed on postoperative days 1-7, and 8/52 (15.4%) after day 7. The PPV for all vascular complications diagnosed with DUS was 92.3%. During the 1-year follow-up, 18/19 (94.7%) hepatic artery complications, 19/26 (73.1%) portal vein complications, and 7/7 (100%) hepatic vein complications were diagnosed perioperatively or during the first week. Conclusion The majority of vascular complications during the first year after pediatric LT were diagnosed by DUS perioperatively or during the first week, with a high PPV. Our findings provide important information regarding when to expect different types of vascular complications on DUS, which might improve DUS post-LT surveillance protocols.

Prevalence and Risk Factors of Arterio-Venous Fistula Obstruction on Patient with Chronic Kidney Disease

Prevalence and Risk Factors of Arterio-Venous Fistula Obstruction on Patient with Chronic Kidney Disease&#x0D; Ismail MT1, Hariawan H1, Wardhani Y2, Puspitasari M2, Artayasa IPA1, Ramadhan G1, Tarigan T1, Triatmaja R1&#x0D; &#x0D; 1Department of Cardiology and Vascular Medicine, Faculty of Medicine, Universitas Gadjah Mada, Yogyakarta, 55284, Indonesia&#x0D; 2Department of Internal Medicine Faculty of Medicine Universitas Gadjah Mada-RSUP Dr. Sardjito Yogyakarta Indonesia&#x0D; &#x0D; ABSTRACT&#x0D; Aim:&#x0D; AV fistula obstruction has become one of the main vascular access complications in patients undergoing haemodialysis. This complications have significant impacts on the morbidity and mortality of dialysis patients while also leading to higher medical costs. Clinical monitoring has been routinely used for early detection of AV fistula stenosis and obstruction, however screening with Doppler ultrasound is still not a routine recommendation. This study aims to know prevalence and risk factors of AV Fistula obstruction detected by Duplex ultrasound examination.&#x0D; &#x0D; Methods:&#x0D; This study was a hospital-based descriptive analytic study with cross sectional design conducted at the haemodialysis center of National General Hospital Dr. Sardjito, Yogyakarta, Indonesia. Patient demographic and clinical risk factor were recorded using direct interview. AV fistula obstruction were assessed using Duplex ultrasound by professional sonographer.&#x0D; &#x0D; Results:&#x0D; Seventy four (74) patients are using AV fistula as entry access for hemodialysis in RSUP dr. Sardjito. It is consist of 39 male (53%) and 35 Female (47%). The mean age of patients is 50 years old. Surveillance using Doppler ultrasound found 20 patients (27%) have stenotic AV Fistula. Smoking habits (OR 5.37, 95% CI, 1.760 - 16.431, p=0.002) and diabetes mellitus (OR 5.00, 95% CI, 1.631 – 15.503, p=0.004) increase risk for having stenotic AV fistula. Only 4 patient (20 %) of all 20 patient with stenotic AV fistula were symptomatic, and needed for further vascular intervention&#x0D; &#x0D; Conclusion:&#x0D; Prevalence of AV fistula obstruction detected by Doppler ultrasound was 27% of all AV fistula patient with only 5% had symptomatic AV fistula failure. Smoking habits and diabetes mellitus are important risk factor for AV fistula obstruction. Asymptomatic AV fistula obstruction often goes undetected by clinical monitoring that can increase of risk of symptomatic AV fistula obstruction in the future. The further study is needed to determine level recommendation of routine AV fistula surveillance with Doppler Ultrasound.&#x0D; &#x0D; Key words: AV Fistula obstruction, CKD, Doppler ultrasound surveillance, Risk factors, Prevalence

The role of Doppler ultrasonography in vascular access surveillance-controversies continue.

Chronic hemodialysis therapy required regular entry into the patient’s blood stream with adequate flow. The use of arteriovenous fistulas and grafts is linked with lower morbidity and mortality than the use of catheters. However, these types of accesses are frequently affected by stenoses, which decrease the flow and lead to both inadequate dialysis and access thrombosis. The idea of duplex Doppler ultrasound surveillance is based on the presumption that in-time diagnosis of an asymptomatic significant stenosis and its treatment prolongs access patency. Details of performed trials are conflicting, and current guidelines do not support ultrasound surveillance. This review article summarizes the trials performed and focuses on the reasons of conflicting results. We stress the need of precise standardized criteria of significant access stenosis and the weakness of the metaanalyses performed.

Prospective Study of Doppler Ultrasound Surveillance for Deep Venous Thromboses in 1000 Plastic Surgery Outpatients.

Current guidelines recommend individual risk stratification, chemoprophylaxis, and risk mitigation to prevent venous thromboembolism. However, the evidence for efficacy is lacking in plastic surgery outpatients. Anticoagulation can cause bleeding. Ultrasound technology offers a highly accurate screening method. A prospective study was undertaken among 1000 consecutive cosmetic surgery outpatients who were scanned at three times: before surgery, the day after surgery, and 1 week after surgery (inclusion rate, 93 percent). Intravenous sedation was used, with no muscle relaxation. Compression, Doppler color flow, and waveform analysis were performed on the deep veins of the lower extremities, including the calves. Affected patients were followed with weekly scans. No chemoprophylaxis was ordered. Sequential compression devices were used during the first half of the study. Nine deep venous thromboses were detected (0.9 percent). Two thromboses were found on scans performed the day after surgery. Six thromboses were detected on the scan approximately 1 week after surgery. One deep venous thrombosis was detected 35 days after surgery. Eight of the nine patients were prescribed oral anticoagulants. All affected patients recovered fully. The mean time to thrombosis resolution was 4.8 weeks. A logistic regression found no deep venous thrombosis risk reduction from sequential compression devices. Patient age was significantly associated with deep venous thromboses (p < 0.05). Ultrasound surveillance offers an effective method for early detection and treatment of postoperative deep venous thromboses. This technology offers an alternative to risk stratification and chemoprophylaxis, which causes iatrogenic bleeding. Sequential compression devices are unnecessary for plastic surgery outpatients undergoing total intravenous anesthesia. Diagnostic, IV.

Discussion: Prospective Study of Doppler Ultrasound Surveillance for Deep Venous Thromboses in 1000 Plastic Surgery Outpatients.

Discussion: Prospective Study of Doppler Ultrasound Surveillance for Deep Venous Thromboses in 1000 Plastic Surgery Outpatients.

Onset of Neurological Deficit During Carotid Clamping With Carotid Endarterectomy Under Regional Anesthesia Is Not a Predictor of Carotid Restenosis

A number of awake patients undergoing carotid endarterectomy (CEA) present from test clamp neurological deficits (NDs) during the procedure. Current guidelines advocate tighter Doppler ultrasound (DUS) surveillance in these patients because of probable higher likelihood of hemodynamic stroke (class 1 grade C), although evidence is lacking regarding benefit. The aim for the study is the assumption that patients who present ND have a higher risk of developing a complete stroke if the ipsilateral carotid artery becomes occluded, and for this reason, surveillance over restenosis of endarterectomy in this group is justifiable; hence, the authors would like to contribute to this matter presenting their experience on restenosis in this specific group of patients. Data were prospectively collected between 2009 and 2018 for patients of a university tertiary referral center who underwent CEA under regional anesthesia and developed alterations in the neurologic monitoring during internal carotid artery (ICA) test clamping. Control patients were consecutively selected as the next patient submitted to the same procedure but who did not develop neurologic alterations. Patients who did not present to the first postoperative evaluation were excluded (4-6weeks). Primary outcome was any restenosis (>30%; >50%; >70%) detected by DUS evaluations between 16 and 30months of follow-up. Clinical adverse events such as stroke, myocardial infarction, acute heart failure, and all-cause death were assessed 30days after the procedure and in the subsequent long-term surveillance period. A multivariate analysis of factors with significant associations to restenosis identified in a univariate analysis was performed by binary logistic regression. Kaplan-Meier analysis and life tables were used to evaluate time-dependent variables. Ninety patients with ND and 94 controls were included. Those with ND had a higher prevalence of obesity, mean age, and scores of American Society of Anesthesiologist physical status, as well as a lower mean degree of ipsilateral stenosis (82.3% vs. 85.8%, P=0.032) and a higher mean degree of contralateral stenosis (67.8% vs. 61.1%, P=0.030). The incidence of restenosis after 2years did not differ significantly between groups. The univariate analysis yielded two significant associations to restenosis >50%, which remained significant after adjustment: ipsilateral stenosis (1.927 + -0.656, P=0.02) and peripheral arterial disease (3.006 + -1.101, P=0.048). NDs were not found to be associated to restenosis (P=0.856). After a median follow-up period of 52months, patients with NDs did not have a higher incidence of stroke (90.6%, standard deviation [SD]: 3.5%; ND: 91.1%, SD: 3.6%, P=0.869), major adverse cardiovascular events (ND: 69.2%, SD: 5.5%; control, 73.6%, SD: 5.2%, P=0.377), or all-cause death (ND: 90.6%, SD: 3.5%; control: 91.1, SD: 3.6%, P=0.981) than controls. The presence of any restenosis was not associated with later stroke rate (ND: 89.5%, SD: 3.2%; control: 100%, P=0.515). Cost-effective DUS surveillance after CEA requires the definition of evidence-based factors associated with restenosis and late stroke. The present study does not support the assumption that patients who presented NDs during the ICA test clamping present a higher risk of developing late stroke. This group of patients also did not present a higher incidence of restenosis. For these reasons, tighter DUS surveillance in this group seems not justifiable. Results from other groups are required to support this position.

Doppler ultrasound surveillance of TIPS-patency in the era of covered stents – retrospective analysis of a large single-center cohort

The purpose of this study was to determine accuracy and necessity of long-term Doppler ultrasound (DU) surveillance of transjugular intrahepatic portosystemic shunt (TIPS) patency after implantation of an ePTFE-covered stent-graft (Viatorr). This single-center retrospective study includes 228 consecutive cirrhotic patients with TIPS implantation due to portal hypertensive complications. Standardized DU surveillance was scheduled 3 - 5 days, 3 months, and 6 months after TIPS implantation and every 6 months thereafter. Portal venography was performed in case of DU findings suspicious of TIPS dysfunction, clinical signs of recurrent portal hypertension, or refractory hepatic encephalopathy. During a mean follow-up of 16.6 ± 23.4 months, 866 DU examinations were performed. Twenty-two cases of TIPS dysfunction were observed in 16 patients with no first dysfunction more than 4 years after implantation. Routine DU in asymptomatic patients had little therapeutic impact (0.75 %). DU and venography were concordant in 39/46 (84.8 %) paired examinations, and 1-, 2-, and 5-year primary TIPS patency was 87.4 %, 83.7 %, and 79.97 %, respectively. Patients with TIPS dysfunction and subsequent successful revision during the first 2 years of follow-up had a significantly higher risk (p = 0.001) of new dysfunction compared to those without TIPS dysfunction. Cumulative 1-, 2-, and 5-year survival was 68.7 %, 61.3 %, and 42.7 %, respectively. Despite acceptable accuracy, scheduled DU surveillance proved to have minor therapeutic impact. Thus, detailed DU surveillance is not useful in asymptomatic patients after 2 years of unremarkable follow-up. In contrast, long-term DU surveilleance should be performed in patients after successful revision of TIPS dysfunction and patients with prothrombotic states (e. g., portal vein thrombosis, Budd-Chiari syndrome).

Intra-operative portal hemodynamics in pediatric LDLT: Doppler ultrasound surveillance.

Doppler ultrasonography is useful in monitoring intra-operative PV flow in LDLT. A retrospective cohort study included 550 pediatric recipients (<18years) who underwent LDLT from October 2006 to August 2016 in our hospital. A total of 33 recipients (incidence 6%) were found to have insufficient intra-operative PV flow after PV reperfusion. The treatments included intra-operative stent placement (n=25), anticoagulation (n=3), thrombectomy and re-anastomosis (n=2), graft repositioning (n=1), collateral ligation (n=1), and replaced PV (n=1). The peak PV velocity, HAPSV, HARI, and HV velocity before and after the interventions were significantly improved 0(0,5.5) cm/s vs. 37.36±15.30cm/s, 38.68±8.92cm/s vs. 62.30±16.97cm/s, 0.55±0.08 vs. 0.76±0.10, and 32.37±10.33cm/s vs. 40.94±15.01cm/s, respectively (P<.01). Insufficient PV flow and decreased HARI are two significant criteria indicating need for intra-operative PV management. Dramatic changes in the hepatic hemodynamics were detected after proper treatment. Immediate resolution of PV flow is feasible in pediatric LDLT.

Outcomes of Percutaneous Portal Vein Intervention in a Single UK Paediatric Liver Transplantation Programme

IntroductionPercutaneous transluminal angioplasty (PTA), with or without stent placement, has become the treatment of choice for portal vein complications (PVC) following liver transplantation. We aimed to assess long-term outcomes of intervention in paediatric transplant recipients, in a single institution.Materials and Methods227 children received 255 transplants between November 2000 and September 2016. 30 patients developed PVC of whom 21 had percutaneous intervention. Retrospective clinical and procedural outcome data on these 21 patients were collected.Results21 patients, with median age 1.7 years (range 0.4–16.2), underwent 42 procedures with PTA with or without stenting. 36 procedures were for PV stenosis and 6 for PV thrombosis. Treatment was with primary PTA, with stenting reserved for suboptimal PTA result or restenosis within 3 months. 28 procedures were performed with PTA and 13 with stenting. Technical success (>50% reduction in mean pressure gradient, absolute pressure gradient ≤4 mmHg or venographic stenosis <30%) was achieved in 41 procedures. Failure to recanalise a thrombosed PV occurred in 1 procedure. There were no major procedural complications. Patients were followed-up with serial Doppler ultrasound surveillance. Kaplan–Meier estimated median primary patency was 9.9 months, with primary-assisted patency of 95% after median follow-up of 45.5 months (range 11.1–171.6).ConclusionWith regular surveillance, excellent patency rates can be achieved following percutaneous intervention for PVC post-paediatric liver transplantation.

A Case of Hepatic Artery Thrombosis after Liver Transplantation

Introduction: Hepatic artery thrombosis (HAT) is the most serious vascular complication after liver transplantation. The most common presentation is elevation of liver function tests. When the diagnosis of hepatic arterial thrombosis is established, prompt intervention should be performed.Case Presentation: In this case report, we present a 37-year-old male with Chronic Hepatitis B infection who underwent a successful liver transplantation, and later developed multiple complications. The most significant of which is hepatic artery thrombosis. He underwent revascularization, supported by heparin and prostaglandin infusion. Succeeding doppler ultrasound surveillance showed patency of right hepatic artery flow. Conclusion: Early identification of hepatic artery thrombosis should be paid attention after liver transplantation to prevent its complications. Once the diagnosis is established, prompt intervention such as retransplantation or revascularization should be performed.

Caprini Scores, Risk Stratification, and Rivaroxaban in Plastic Surgery: Time to Reconsider Our Strategy.

Summary:Limited data are available regarding the pathophysiology of venous thromboembolism in plastic surgery patients. In an effort to identify patients at greater risk, some investigators promote individual risk assessment using Caprini scores. However, these scores do not correlate with relative risk values. Affected patients cannot be reliably predicted (97% false positive rate). Caprini scores make many body contouring patients candidates for chemoprophylaxis, an intervention that introduces risks related to anticoagulation. Caprini has financial conflicts with several companies that manufacture products such as enoxaparin, commonly used for chemoprophylaxis. Rivaroxaban, taken orally, has been used by some plastic surgeons as an alternative to enoxaparin injections. However, this medication is not United States Food and Drug Administration approved for venous thromboembolism prophylaxis in plastic surgery patients, and a reversal agent is unavailable. This article challenges the prevailing wisdom regarding individual risk stratification and chemoprophylaxis. Alternative methods to reduce risk for all patients include safer anesthesia methods and Doppler ultrasound surveillance. Clinical findings alone are unreliable in diagnosing deep venous thromboses. Only by using a reliable diagnostic tool such as Doppler ultrasound are we able to learn more about the natural history of this problem in our patients. Such knowledge is likely to better inform our treatment recommendations.

Comparison study of Doppler ultrasound surveillance of expanded polytetrafluoroethylene‐covered stent versus bare stent in transjugular intrahepatic portosystemic shunt

This prospectively randomized controlled study aimed to assess with Doppler ultrasound (US) the shunt function of expanded polytetrafluoroethylene (ePTFE)-covered transjugular intrahepatic portosystemic shunt (TIPS) stent versus bare stent and to evaluate the usefulness of routine TIPS follow-up of ePTFE-covered stents. Sixty consecutive patients were randomized for bare or covered transjugular TIPS stenting in our institution between April 2007 and April 2009. Data of follow-up Doppler US, angiography, and portosystemic pressure gradient measurements were collected and analyzed. The follow-up period was 8.34 + or - 4.42 months in the bare-stent group and 6.16 + or - 3.89 months in the covered-stent group. Baseline clinical characteristics were similar in both groups. Two hundred three US studies were performed in 60 patients, with a mean of 3.4 per patient, and demonstrated abnormalities in 28 patients (21 bare stents, 7 ePTFE-covered stents), 19 of them (13 in bare-stent group, 6 in covered-stent group) showing no clinical evidence of recurrence. Ten of 13 patients in the bare-stent group underwent balloon angioplasty or additional stent placement, whereas only one of six patients in the covered-stent group needed reintervention for intimal hyperplasia. The average peak velocity in the midshunt of ePTFE-covered stent was 139 + or - 26 cm/s after TIPS creation and 125 + or - 20 cm/s during follow-up, which was significantly higher than the bare-stent group (p < 0.05). The main portal vein and hepatic artery showed higher flow velocities in the ePTFE-covered stent group than in the bare-stent group. ePTFE-covered stents maintained lower portosystemic pressure gradient than bare stents (9.5 + or - 2.9 versus 13.2 + or - 1.5 mmHg, p < 0.05). ePTFE-covered stents resulted in higher patency rates and better hemodynamics than bare stents. Routine US surveillance may not be necessary in patients with ePTFE-covered TIPS stent.

Evaluation of third trimester uterine artery flow velocity indices in relationship to perinatal complications

Objective. Uterine artery Doppler is becoming a routine part of pregnancy surveillance in high-risk pregnancies. Which blood flow velocity waveform index to measure is debated and the ‘notch’ in early diastole is not widely accepted, as it is a subjective measure. The aim of the present study was to evaluate the different indices in the prediction of adverse outcome of pregnancies suspected for intrauterine fetal growth restriction (IUGR).Methods. Uterine artery blood flow was recorded in 217 pregnancies admitted for Doppler ultrasound surveillance due to suspected IUGR. The median gestational age at examination was 38 weeks (range 25–42 weeks). Only cases having bilateral uterine artery notching were included in the evaluation. The uterine artery Doppler spectrum was analyzed for different indices, including evaluation of notch and end-diastolic velocities. Umbilical artery Doppler velocimetry was also performed. The outcome variables chosen were: a small-for-gestational-age (SGA) newborn, preterm birth, and abdominal delivery. ROC-curve calculations were used to compare the different indices.Results. The uterine artery blood velocity pulsatility index (PI) and resistance indices (RI) were the best predictors of adverse outcome of pregnancy. Apart from premature birth, the systolic/end-diastolic ratio was less predictive of adverse outcome. The indices including only diastolic blood velocities were the least predictive of adverse outcome. The group with notch velocity above end-diastolic velocity was compared with those having notch velocity below the end-diastolic velocity. No difference in outcome was seen between the two groups.Conclusions. RI and PI as measures of third trimester utero-placental vascular impedance are the best predictors of adverse outcome of IUGR-suspected pregnancies.

Thrombosis in the portal venous system after elective laparoscopic splenectomy.

The occurrence of thrombosis in the portal system is an underappreciated complication of splenectomy. Presenting symptoms are usually mild and nonspecific. The short hospital stay associated with the laparoscopic approach could delay the early diagnosis of this condition unless routine imaging controls are planned after discharge. The records of 40 patients who underwent laparoscopic splenectomy at our institution were reviewed for clinical signs of thrombosis in the portal system and associated factors. All patients were also enrolled in a color Doppler ultrasound surveillance program. Nine patients (22.5%) developed thrombosis of the splenic vein, progressing to the portal vein in five cases (12.5%). Six patients (15%) were symptomatic. Thrombosis occurred even as late as 4 months after splenectomy. Spleen weight was the only significant factor predictive of postoperative thrombosis. The combination of splenomegaly and an elevated preoperative platelet count was associated with a 75% incidence of this complication. The high risk of thrombosis after the laparoscopic resection of large spleens should prompt strict postoperative imaging surveillance, combined with a more aggressive anticoagulation prophylaxis.

Prospective evaluation of the role of quantitative Doppler ultrasound surveillance in liver transplantation.

Doppler ultrasound (DUS) is able to measure parameters of blood flow within vessels of transplanted organs, and vascular complications are associated with abnormal values. We analyzed the findings of 51 consecutive patients who underwent DUS on 2 occasions in the first postoperative week following liver transplantation for cirrhosis to determine the range of values in patients following liver transplantation. Three patients developed early vascular thromboses that were detected by the absence of a Doppler signal. In patients making an uneventful recovery, the arterial velocity tended to increase and the resistive index (RI) to decrease during the first postoperative week. All recipients were shown to have high-velocity segments within the hepatic artery, without an increase in flow resistance. Assessment of the portal vein revealed narrowing at the anastomosis, associated with a segmental doubling of flow velocity, and the mean portal venous flow decreased by approximately 20% in the first postoperative week. In conclusion, a wide range of abnormalities occurs in the vessels of liver transplant recipients, which were not associated with the development of vascular complications or affect patient management.

Femorodistal Bypass Using Cryopreserved Venous Allografts for Limb Salvage

Critical ischemia due to extensive femoropopliteal occlusive disease often leads to amputation in patients in whom an autologous vein is unavailable for reconstruction. The purpose of this nonrandomized prospective study is to evaluate the usefulness of cryopreserved venous allografts (CPVA) as an arterial substitute in these cases. Between October 1990 and March 1993, long bypass to a tibial or a foot artery using a CPVA was performed in 25 consecutive patients with ulcerations or gangrene. There were 19 women and six men with a mean age of 72 years (range: 51-90). The indication for allograft reconstruction was absence (17 cases) or unsuitability (eight cases) of an autologous vein graft. Greater saphenous vein allografts were harvested from multiple organ donors and frozen at -80 degrees C with 12% dimethylsulfoxide (DMSO). Sixteen patients had undergone one or more previous unsuccessful limb salvage attempts. The plantar arch was absent or incomplete in 16 patients (64%). Patients were followed up prospectively for a mean of 21 months (range: 3-32). One patient died early (32 days) and three patients died late with patent bypasses. Cumulative survival rate was 77% at 1 year and 72% at 2 years. Cumulative secondary patency rate (Kaplan-Meier) was 88% at 1 months, 72% at 6 months, and 52% at 1 year. The cumulative limb salvage rate was 78% at 2 years. When an autologous vein is unavailable, long bypass using a CPVA is a simple, quick, minimally traumatic, economical, and effective method to achieve limb salvage in patients with severe distal arterial occlusive disease. However, CPVA causes immunoreaction and there is a risk of proximal postanastomotic stenosis. Doppler ultrasound surveillance of a subcutaneous graft allows accurate assessment and repair of the abnormalities with no increase in mortality or morbidity.