Catheter Directed Thrombolysis for Not Immediately Threatening Acute Limb Ischaemia: Systematic Review and Meta-Analysis.

OBJECTIVE: This systematic review and meta-analysis reports the outcomes of catheter directed thrombolysis (CDT) in patients with not immediately threatening (Rutherford I) acute lower limb ischaemia (ALI). DATA SOURCES: PubMed, Embase, and the Cochrane Library. REVIEW METHODS: A systematic search of PubMed, Embase, and the Cochrane Library was performed to identify observational studies and trials published between 1990 and 2022 reporting on the results of CDT in patients with Rutherford I ALI. A meta-analysis was performed using a random effects model with 95% confidence intervals (CIs). The outcomes of interests were treatment duration, angiographic success, bleeding complications, amputation and mortality rates, primary and secondary patency, and functional outcome expressed as pain free walking distance. RESULTS: Thirty-nine studies were included, comprising 1 861 patients who received CDT for not immediately threatening ALI. Funnel plots showed an indication of publication bias, and heterogeneity was substantial. Data from 5 to 13 studies were included in the meta-analysis. The pooled treatment duration was 2 days (95% CI 1 - 2), with an angiographic success rate of 80% (95% CI 73 - 86) and a 30 day freedom of amputation rate of 98% (95% CI 92 - 100). The major bleeding rate was 5% (95% CI 2 - 14), with a 30 day mortality rate of 3% (95% CI 1 - 5). The amputation free survival rate was 71% (95% CI 62 - 80) at the one year and 63% (95% CI 51 - 73) at the three year follow up. Long term patency rates were retrieved from four studies: 48% at one year (95% CI 27 - 70). No data could be retrieved on patient walking distance. CONCLUSION: Although CDT in the treatment of not immediately threatening ALI showed high angiographic success, the long term outcomes were relatively poor, with low patency and a substantial risk of major amputation. Further research is required to interpret the outcome of CDT in the context of potential confounders such as age and comorbidities.

Major Bleeding During Thrombolytic Therapy for Acute Lower Limb Ischaemia: Value of Laboratory Tests for Clinical Decision Making, 17 Years of Experience.

OBJECTIVE: Regular measurement of fibrinogen as dose guidance in catheter directed thrombolysis (CDT) for acute limb ischaemia (ALI) has recently been dropped from European guidelines based on inconsistent literature. This study aimed to determine whether low fibrinogen levels and high activated partial thromboplastin time (APTT) are associated with an increased major bleeding risk during CDT. METHODS: All consecutive patients treated with CDT for ALI in two Dutch hospitals between January 2004 and April 2021 were analysed retrospectively. Patients were treated with two dosing regimens (low dose: 50 000 IU/hour; high dose: 100 000 IU/hour) of urokinase and, after 2018, with a single low dose regimen of alteplase (rtPA) due to urokinase manufacturing problems. The incidence of major bleeding and associated APTT and fibrinogen levels were reviewed from patient charts. RESULTS: Of the 443 included cases, 277 underwent CDT with urokinase and 166 with rtPA. The incidence of major bleeding in the whole cohort was 7%. Patients with a fibrinogen levels < 1.0 g/L developed more major bleeding than those in whom the fibrinogen level did not drop below 1.0 g/L (15% vs. 6%; p = .041). Systemic heparinisation during CDT or high (> 80 seconds) APTT were not significantly associated with major bleeding. Angiographic success (47% vs. 72%; p = .003) and 30 day amputation free survival (53% vs. 82%; p < .001) were lower for cases with major bleeding. Older age (odds ratio [OR] 1.06, 95% confidence interval [CI] 1.02 - 1.11), cardiac history (OR 3.35, 95% CI 1.39 - 8.06), high dose regimens (≥ 75 000 IU/hour urokinase; OR 2.67, 95% CI 1.18 - 6.04), and fibrinogen values < 1.0 g/L (OR 5.59, 95% CI 1.98 - 15.77) were independent predictors for major bleeding during CDT. CONCLUSION: High dose thrombolytic regimens and fibrinogen levels of ≤ 1.0 g/L are associated with more major bleeding during thrombolytic therapy. Major bleeding significantly worsened the clinical outcome. A prospective comparative study is needed to assess the benefit of monitoring fibrinogen levels.

Feasibility of Microbubble-Accelerated Low-Dose Thrombolysis of Peripheral Arterial Occlusions Using an Ultrasound Catheter.

PURPOSE: Intra-arterial administration of microbubbles (MBs) through an ultrasound (US) catheter increases the local concentration of MBs into the thrombus and may further enhance outcomes of contrast-enhanced sonothrombolysis (CEST). The objective of this study was to evaluate the feasibility and lytic efficacy of intra-arterial infusion of MBs during US-enhanced thrombolysis in both in vitro and in vivo peripheral arterial occluded models. MATERIALS AND METHODS: SonoVue and Luminity MBs were infused at a flow rate of 20 mL/h through either the drug delivery lumen of the US catheter (DDC, n=20) or through the tube lumen of the vascular phantom (systematic infusion, n=20) during thrombolysis with a low-dose urokinase (UK) protocol (50 000 IU/h) with(out) US application to assess MB survivability and size by pre-treatment and post-treatment measurements. A human thrombus was placed into a vascular phantom of the flow system to examine the lytic effects of CEST by post-treatment D-dimer concentrations measurements of 5 treatment conditions (saline, UK, UK+US, UK+US+SonoVue, and UK+US+Luminity). Thrombolytic efficacy of localized MBs and US delivery was then investigated in vivo in 5 porcine models by arterial blood flow, microcirculation, and postmortem determined thrombus weight and remaining length. RESULTS: US exposure significantly decreased SonoVue (p=0.000) and Luminity (p=0.000) survivability by 37% and 62%, respectively. In vitro CEST treatment resulted in higher median D-dimer concentrations for the SonoVue (0.94 [0.07-7.59] mg/mL, p=0.025) and Luminity (0.83 [0.09-2.53] mg/mL, p=0.048) subgroups when compared with thrombolysis alone (0.36 [0.02-1.00] mg/mL). The lytic efficacy of CEST examined in the porcine model showed an improved median arterial blood flow of 21% (7%-79%), and a median thrombus weight and length of 1.02 (0.96-1.43) g and 2.25 (1.5-4.0) cm, respectively. One allergic reaction and 2 arrhythmias were observed due to the known allergic reaction on lipids in the porcine model. CONCLUSION: SonoVue and Luminity can be combined with an US catheter and could potentially accelerate thrombolytic treatment of peripheral arterial occlusions. CLINICAL IMPACT: Catheter-directed thrombolysis showed to be an effective alternative to surgery for acute peripheral arterial occlusions, but this technique is still associated with several limb and life-threatening complications. The effects of thrombolysis on clot dissolution may be further enhanced by intra-arterial administration of microbubbles through an ultrasound catheter. This study demonstrates the feasibility and lytic efficacy of intra-arterial infusion of microbubbles during US-enhanced thrombolysis in both in vitro and in vivo peripheral arterial occluded models.

Microbubbles and Ultrasound Accelerated Thrombolysis for Peripheral Arterial Occlusions: The Outcomes of a Single Arm Phase II Trial.

OBJECTIVE: Acute peripheral arterial occlusions can be treated by catheter directed thrombolysis (CDT). However, CDT is time consuming and accompanied by the risk of bleeding complications. The addition of contrast enhanced ultrasound and microbubbles could improve thrombus susceptibility to thrombolytic agents and potentially shorten treatment time with a lowered risk of bleeding complications. This article reports the outcomes of the safety and feasibility of this novel technique. METHODS: In this single arm phase II trial, 20 patients with acute lower limb ischaemia received CDT combined with an intravenous infusion of microbubbles and locally applied ultrasound during the first hour of standard intra-arterial thrombolytic therapy. The primary endpoint was safety, i.e., occurrence of serious adverse events (haemorrhagic complications and/or amputation) and death within one year. Secondary endpoints included angiographic and clinical success, thrombolysis duration, additional interventions, conversion, and quality of life. RESULTS: The study included 20 patients (16 men; median age 68.0 years; range, 50.0 - 83.0; and 40% native artery and 60% bypass graft). In all patients, the use of microbubble contrast enhanced sonothrombolysis could be applied successfully. There were no serious adverse events related to the experimental treatment. Duplex examination showed flow distal from the occlusion after 23.1 hours (range 3.1 - 46.5) with a median thrombolysis time of 47.5 hours (range 6.0 - 81.0). The short term ABI and pain scores significantly improved; however, no changes were observed before or after thrombolysis in the microcirculation. Overall mortality and amputation rates were both 2% within one year. The one year patency rate was 55%. CONCLUSION: Treatment of patients with acute peripheral arterial occlusions with contrast enhanced sonothrombolysis is feasible and safe to perform in patients. Further research is necessary to investigate the superiority of this new treatment over standard treatment.

Catheter Directed Thrombolysis Protocols for Peripheral Arterial Occlusions: a Systematic Review.

OBJECTIVE: Catheter directed thrombolysis (CDT) for peripheral arterial occlusions is a well established alternative to thrombo-embolectomy in patients with (sub)acute limb ischaemia. However, protocols are heterogeneous and need optimisation to improve results and lower bleeding risks. The objective was to review the results and outcomes of different CDT protocols for patients with peripheral arterial occlusions. DATA SOURCES: Electronic information sources (MEDLINE, Embase, Cochrane) and reference lists were searched to identify studies reporting results of CDT of peripheral arterial occlusions. METHODS: Two independent observers performed study selection, quality assessment and data extraction. Primary outcomes were treatment duration, success rates, and bleeding complications. Secondary outcomes were mortality and amputation rates. RESULTS: One hundred and six studies were included: 19 randomised controlled trials (RCTs), 38 prospective studies, 48 retrospective studies, and one mixed cohort study. The studies comprised a total number of 10,643 cases of which 9877 received CDT for lower extremity arterial occlusion, with a mean treatment duration of 21.4 h (95% confidence interval [CI] 21.0-21.8), an angiographic patency of 75% (95% CI 74.6-75.1), and freedom from amputation rate of 91% (95% CI 90.3-90.7). Pooled results showed a thrombolysis duration with high dose protocols of 21.9 h (95% CI 21.4-22.5) and 32.7 h with low dose protocols, with bleeding rates of 16.7% (95% CI 16.3-17.1) and 13.4% (95% CI 12.8-14.0), respectively. Weighted mean results for all RCTs and prospective cohorts of >100 cases analysed separately, showed comparable results to all observational cohorts pooled. Bleeding complications occurred in 18% (95% CI 17.8-18.3) of patients and remain an important risk of CDT. CONCLUSION: CDT is an effective treatment for peripheral arterial occlusions, the main concern is bleeding complications. Although no formal meta-analysis could be performed, the pooled results suggest that lower doses of fibrinolytics lead to similar success rates at a cost of longer treatment duration but with less bleeding. There is large variation in treatment protocols and the available literature suffers from absence of reporting standards and high heterogeneity.

Efficacy versus Complications in Arterial Thrombolysis.

BACKGROUND: Acute peripheral arterial occlusions threaten life and limb. Thrombolysis is an established, minimally invasive alternative treatment for surgical thromboembolectomy. Yet, there is no consensus regarding an optimal thrombolysis protocol, and current knowledge is largely based on studies from the 1990s. This study reviews a contemporary cohort of patients treated with thrombolysis and aims to evaluate the treatment results and to identify possible predictors for outcome and (bleeding) complications. METHODS: The electronic health record data of all consecutive patients who underwent thrombolysis for acute limb ischemia due to thromboembolic lower extremity arterial occlusions between April 2006 and June 2012 were analyzed. End points were change in clinical stage of ischemia, incidence of bleeding complications, duration of thrombolysis, predictors of outcome and complications, and mortality and amputation-free rates after 30-day and 6-months follow-up. RESULTS: In total, 109 cases were included. Clinical improvement was observed in 79%. Amputation-free rates at 30 days and 6 months were 94% and 90%, respectively. The incidence of major bleeding complications was 13%. Median duration of thrombolysis was 27 (4-68) hr. Mortality rates at 30 days and 6 months were 7% and 16%, respectively; none bleeding related. In addition to age, popliteal artery occlusions and a progressed chronic vascular stage are predictive for a worse outcome. Age, female sex, and cardiac history were risk factors for bleeding. CONCLUSIONS: Treatment of peripheral arterial occlusions with high-dose thrombolysis on an intensive-care unit yields high clinical success rates, but major bleeding complications are often observed. Strict clinical observation remains essential since intensive monitoring of hemostatic parameters during thrombolysis does not predict bleeding complications.

Intravenous Targeted Microbubbles Carrying Urokinase versus Urokinase Alone in Acute Peripheral Arterial Thrombosis in a Porcine Model.

BACKGROUND: Standard therapy in acute peripheral arterial occlusion consists of intra-arterial catheter-guided thrombolysis. As microbubbles may be used as a carrier for fibrinolytic agents and targeted to adhere to the thrombus, we can theoretically deliver the thrombolytic medication locally following simple intravenous injection. In this intervention-controlled feasibility study, we compared intravenously administered targeted microbubbles incorporating urokinase and locally applied ultrasound, with intravenous urokinase and ultrasound alone. METHODS: In 9 pigs, a thrombus was created in the left external iliac artery, after which animals were assigned to either receive targeted microbubbles and urokinase (UK + tMB group) or urokinase alone (UK group). In both groups, ultrasound was applied at the site of the occlusion. Blood flow through the iliac artery and microcirculation of the affected limb were monitored and the animals were euthanized 1 hr after treatment. Autopsy was performed to determine the weight of the thrombus and to check for adverse effects. RESULTS: In the UK + tMB group (n = 5), median improvement in arterial blood flow was 5 mL/min (range 0-216). Improvement was seen in 3 of these 5 pigs at conclusion of the experiment. In the UK group (n = 4), median improvement in arterial blood flow was 0 mL/min (-10 to 18), with slight improvement in 1 of 4 pigs. Thrombus weight was significantly lower in the UK + tMB group (median 0.9383 g, range 0.885-1.2809) versus 1.5399 g (1.337-1.7628; P = 0.017). No adverse effects were seen. CONCLUSIONS: Based on this experiment, minimally invasive thrombolysis using intravenously administered targeted microbubbles carrying urokinase combined with local application of ultrasound is feasible and might accelerate thrombolysis compared with treatment with urokinase and ultrasound alone.

Therapeutic application of contrast-enhanced ultrasound and low-dose urokinase for thrombolysis in a porcine model of acute peripheral arterial occlusion.

BACKGROUND: The addition of local ultrasound (US) with a contrast agent to standard intra-arterial thrombolysis can accelerate the thrombolytic treatment of stroke and myocardial infarction. The contrast agent consists of microsized gas-filled bubbles that collapse when exposed to US, causing destabilization of the clot and making the clot surface more susceptible to fibrinolytics. In this study, we investigated the effect of additional US and microbubbles on standard low-dose intra-arterial thrombolysis in a porcine model of extensive peripheral arterial occlusion. METHODS: Extensive arterial thrombosis was induced in 10 pigs in the 4-cm external iliac artery by clamping and injection of 100 IU of bovine thrombin. A transcutaneous laser Doppler flow probe and an ultrasonic perivascular flow probe assessed microcirculation and arterial flow respectively. The urokinase-only (UK) group (n = 4) received standard thrombolytic therapy: intra-arterial bolus injection of 500,000 IU, followed by a continuous low-dose urokinase (50,000 IU/h) infusion through an intra-arterial catheter and local intermittent application of US, 1 second on, 5 seconds off, to visualize vascular patency during the first hour of therapy and to ensure microbubbles replenished the proximal portion of the occluded artery. The urokinase plus microbubbles (UK+) group (n = 6) received the same urokinase therapy with a concomitant intravenous infusion of microbubbles and local intermittent application of US. The contrast infusion protocol consisted of a bolus of two vials of 5 mL in the first 15 minutes and then three times 5 mL slowly hand-injected continuously during the next 45 min. After 3 hours of therapy, the animals were euthanized, and thrombi were harvested and weighed. All organs were cut in thin slices and macroscopically inspected for potential (hemorrhagic) adverse events, and tissue samples were taken. RESULTS: Median thrombus weights were 1.1 g (range, 0.8-1.3 g) in the UK+ group vs 1.6 g (range, 1.3-1.9 g) in the UK group (P = .01). Arterial blood flow increased in four of six pigs in the UK+ group by a mean 61% vs in one of four in the UK group, with 1%. Microcirculation and lower limb arterial pressure levels improved after the start of therapy in the UK+ group, contrary to a trend of decline in the UK group. No signs of bleeding complications were observed in either group. CONCLUSIONS: In this experimental pilot study, the addition of contrast-enhanced US accelerated the thrombolytic effect of low-dose intra-arterial thrombolysis in peripheral arterial occlusions. Further clinical studies are warranted.

CAVA (Ultrasound-Accelerated Catheter-Directed Thrombolysis on Preventing Post-Thrombotic Syndrome) Trial: Long-Term Follow-Up Results.

Background The CAVA (Ultrasound-Accelerated Catheter-Directed Thrombolysis Versus Anticoagulation for the Prevention of Post-Thrombotic Syndrome) trial did not show a reduction of post-thrombotic syndrome (PTS) after additional ultrasound-accelerated catheter-directed thrombolysis in patients with acute iliofemoral deep vein thrombosis at 1-year follow-up. This prespecified analysis of the CAVA trial aimed to determine the impact of additional thrombolysis on outcomes of PTS at long-term follow-up. Methods and Results Patients aged 18 to 85 years with a first-time acute iliofemoral deep vein thrombosis were included and randomly assigned (1:1) to either standard treatment plus ultrasound-accelerated catheter-directed thrombolysis or standard treatment alone. The primary outcome was the proportion of PTS (Villalta score ≥5 on 2 occasions ≥3 months apart or venous ulceration) at the final follow-up visit. Additionally, PTS according to the International Society on Thrombosis and Haemostasis (ISTH) consensus definition was assessed to allow external comparability. Major bleedings were the main safety outcome. At a median follow-up of 39.0 months (interquartile range, 23.3-63.8), 120 patients (79.8%) participated in the final follow-up visit: 62 from the intervention group and 58 from the standard treatment group. PTS developed in 19 (30.6%) versus 26 (44.8%) patients, respectively (odds ratio [OR], 0.54; 95% CI, 0.26 to 1.15 [P=0.11]), with an absolute difference between groups of -14.2% (95% CI, -32.0% to 4.8%). Using the ISTH consensus definition, a significant reduction in PTS was observed (29 [46.8%] versus 40 [69.0%]) (OR, 0.40; 95% CI, 0.19-0.84 [P=0.01]) with an absolute difference between groups of -22.2% (95% CI, -39.8% to -2.8%). No new major bleedings occurred following the 12-month follow-up. Conclusions The impact of additional ultrasound-accelerated catheter-directed thrombolysis on the prevention of PTS was found to increase with time. Although this study was limited by its sample size, the overall findings indicate a reduction of mild PTS without impact on quality of life. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT00970619.

Dataset of the vascular e-Learning during the COVID-19 pandemic (EL-COVID) survey.

This dataset supports the findings of the vascular e-Learning during the COVID-19 pandemic survey (the EL-COVID survey). The General Data Protection Regulation (GDPR) of the European Union was taken into consideration in all steps of data handling. The survey was approved by the institutional ethics committee of the Primary Investigator and an online English survey consisting of 18 questions was developed ad-hoc. A bilingual English-Mandarin version of the questionnaire was developed according to the instructions of the Chinese Medical Association in order to be used in mainland People's Republic of China. Differences between the two questionnaires were minor and did affect the process of data collection. Both questionnaires were hosted online. The EL-COVID survey was advertised through major social media. All national and regional contributors contacted their respective colleagues through direct messaging on social media or by email. Eight national societies or groups supported the dissemination of the EL-COVID survey. The data provided demographics information of the EL-COVID participants and an insight on the level of difficulty in accessing or citing previously attended online activities and whether participants were keen on citing these activities in their Curricula Vitae. A categorization of additional comments made by the participants are also based on the data. The survey responses were filtered, anonymized and submitted to descriptive analysis of percentage.

Association of Successful Ultrasound-Accelerated Catheter-Directed Thrombolysis with Postthrombotic Syndrome: A Post Hoc Analysis of the CAVA Trial.

BACKGROUND: The CAVA trial did not show the anticipated risk reduction for postthrombotic syndrome (PTS) after thrombus removal via additional ultrasound-accelerated catheter-directed thrombolysis (UACDT) in patients with acute iliofemoral deep vein thrombosis (IFDVT). Difficulties in achieving an effective degree of recanalization through thrombolysis may have influenced outcomes. We therefore assessed whether successful UACDT (restored patency ≥ 90%) did reduce the development of PTS. METHODS: This CAVA trial post hoc analysis compared the proportion of PTS at 1-year follow-up between patients with successful UACDT and patients that received standard treatment only. In addition, clinical impact as well as determinants of successful thrombolysis were explored. RESULTS: UACDT was initiated in 77 (50.7%) patients and considered successful in 41 (53.2%, interrater agreement κ = 0.7, 95% confidence interval 0.47-0.83). PTS developed in 15/41 (36.6%) patients in the successful UACDT group versus 33/75 (44.0%) controls (p = 0.44). In this comparison, successful UACDT was associated with lower Venous Clinical Severity Score (3.50 ± 2.57 vs. 4.82 ± 2.74, p = 0.02) and higher EuroQOL-5D (EQ-5D) scores (40.2 ± 36.4 vs. 23.4 ± 34.4, p = 0.01). Compared with unsuccessful UACDT, successful UACDT was associated with a shorter symptom duration at inclusion (p = 0.05), and higher rates of performed adjunctive procedures (p < 0.001) and stent placement (p < 0.001). CONCLUSION: Successful UACDT was not associated with a reduced proportion of PTS 1 year after acute IFDVT compared with patients receiving standard treatment alone. There was, however, a significant reduction in symptom severity and improvement of generic quality of life according to the EQ-5D. Better patient selection and optimization of treatment protocols are needed to assess the full potential of UACDT for the prevention of PTS. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov number, NCT00970619.

Ultrasound-accelerated catheter-directed thrombolysis versus anticoagulation for the prevention of post-thrombotic syndrome (CAVA): a single-blind, multicentre, randomised trial.

BACKGROUND: Early thrombus removal might prevent post-thrombotic syndrome by preserving venous function and restoring flow. Previous trials comparing additional catheter-directed thrombolysis to standard treatment showed conflicting outcomes. We aimed to assess the benefit of additional ultrasound-accelerated catheter-directed thrombolysis for the prevention of post-thrombotic syndrome compared with standard therapy in patients with iliofemoral deep-vein thrombosis. METHODS: We did a multicentre, randomised, single-blind, allocation-concealed, parallel group, superiority trial in 15 hospitals in the Netherlands. Patients aged 18-85 years with a first-time acute iliofemoral deep-vein thrombosis and symptoms for no more than 14 days were randomly assigned (1:1) to either standard treatment with additional ultrasound-accelerated catheter-directed thrombolysis or standard treatment alone. Randomisation was done with a web-based automatic programme and a random varying block size (2-12), stratified by age and centre. Standard treatment included anticoagulant therapy, compression therapy (knee-high elastic compression stockings; 30-40 mmHg), and early ambulation. Additional ultrasound-accelerated catheter-directed thrombolysis was done with urokinase with a starting bolus of 250 000 international units (IU) in 10 mL NaCl followed by a continuous dose of 100 000 IU/h for a maximum of 96 h through the Ekos Endowave-system. Adjunctive percutaneous transluminal angioplasty, thrombosuction, or stenting was performed at the discretion of the physician who performed the intervention. The primary outcome was the proportion of patients with post-thrombotic syndrome at 12 months diagnosed according to the original Villalta criteria-a Villalta-score of at least 5 on two consecutive occasions at least 3 months apart or the occurrence of venous ulceration-and was assessed in a modified intention-to-treat population of all randomly assigned patients who passed screening and started treatment. The safety analysis was assessed in the same modified intention-to-treat population. This study is complete and is registered at ClinicalTrials.gov, NCT00970619. FINDINGS: Between May 28, 2010, and Sept 18, 2017, 184 patients were randomly assigned to either additional ultrasound-accelerated catheter-directed thrombolysis (n=91) or standard treatment alone (n=93). Exclusion because of screening failure or early withdrawal of informed consent resulted in 77 patients in the intervention group and 75 in the standard treatment group starting allocated treatment. Median follow-up was 12·0 months (IQR 6·0-12·0). 12-month post-thrombotic syndrome occurred in 22 (29%) patients allocated to additional treatment versus 26 (35%) patients receiving standard treatment alone (odds ratio 0·75 [95% CI 0·38 to 1·50]; p=0·42). Major bleeding occurred in four (5%) patients in the intervention group, with associated neuropraxia or the peroneal nerve in one patient, and no events in the standard treatment group. No serious adverse events occurred. None of the four deaths (one [1%] in the intervention group vs three [4%] in the standard treatment group) were treatment related. INTERPRETATION: This study showed that additional ultrasound-accelerated catheter-directed thrombolysis does not change the risk of post-thrombotic syndrome 1 year after acute iliofemoral deep-vein thrombosis compared with standard therapy alone. Although this trial is inconclusive, the outcome suggests the possibility of a moderate beneficial effect with additional ultrasound-accelerated catheter-directed thrombolysis. Further research is therefore warranted to better understand this outcome in the context of previous trials, preferably by combining the available evidence in an individual patient data meta-analysis. FUNDING: The Netherlands Organisation for Health Research and Development (ZonMw), Maastricht University Medical Centre, BTG-Interventional Medicine.

Microbubbles and UltraSound-accelerated Thrombolysis (MUST) for peripheral arterial occlusions: protocol for a phase II single-arm trial.

INTRODUCTION: Acute peripheral arterial occlusions can be treated with intra-arterial catheter-directed thrombolysis as an alternative to surgical thromboembolectomy. Although less invasive, this treatment is time-consuming and carries a significant risk of haemorrhagic complications. Contrast-enhanced ultrasound using microbubbles could accelerate dissolution of thrombi by thrombolytic medications due to mechanical effects caused by oscillation; this could allow for lower dosages of thrombolytics and faster thrombolysis, thereby reducing the risk of haemorrhagic complications. In this study, the safety and practical applicability of this treatment will be investigated. METHODS AND ANALYSIS: A single-arm phase II trial will be performed in 20 patients with acute peripheral arterial occlusions eligible for thrombolytic treatment. Low-dose catheter-directed thrombolysis with urokinase will be used. The investigated treatment will be performed during the first hour of thrombolysis, consisting of intravenous infusion of 4 Luminity phials (6 mL in total, diluted with saline 0.9% to 40 mL total) of microbubbles with the use of local ultrasound at the site of occlusion. Primary end points are the incidence of complications and technical feasibility. Secondary end points are angiographic and clinical success, duration of thrombolytic infusion, treatment-related mortality, amputations, additional interventions and quality of life. ETHICS AND DISSEMINATION: Ethical approval for this study was obtained in 2015 from the Medical Ethics Committee of the VU University Medical Center, Amsterdam, the Netherlands. A statement of consent for this study was given by the Dutch national competent authority. Data will be presented at national and international conferences and published in a peer-reviewed journal. TRIAL REGISTRATION NUMBERS: Dutch National Trial Registry: NTR4731; European Clinical Trials Database of the European Medicines Agency: 2014-003469-10; Pre-results.