Back to the Basics: Inferior Vena Cava Filters

Inferior vena cava filters are an important therapeutic option for patients with venous thromboembolism and contraindication to anticoagulation. Indications for filter placement have varied over the previous decades. This article discusses the history of inferior vena cava filter use, with a basic overview of technology and specific devices. Finally, this article reviews emerging filter design and technology. Understanding the basics of inferior vena cava filters is critical to building more robust clinical data for the purpose of improving patient outcomes.

Abstract TP251: It’s All in the Wrist - Integrating EMS, Telestroke and Stroke Registry Data Systems

Background: States without a recognized directive for stroke care and transport risk the ability to monitor, assess and review stroke patient movement from first medical contact (FMC) to delivery/and/or transfer to hospitals. We are seeking to determine a new tracking program’s efficacy from emergency medical systems (EMS) to telestroke sites and other receiving hospitals utilizing Get-With-The-Guidelines (GWTG) in data reporting.

Hypothesis: We hypothesized that all three entities (EMS, telestroke sites and other hospitals) would record suspected and positive strokes into their electronic databases and integrate the process into their standard of practice, protocols and guidelines.

Methods: Statewide EMS agencies, receiving hospitals in the Arkansas Stroke Registry and telestroke sites received educational training about placing blue wristbands on all suspected strokes. Stroke bands were to be placed on all patients arriving via EMS or privately owned vehicle. The bands contained a unique number sequence for recording in both EMS and hospital GWTG electronic databases. We retrospectively reviewed all prospectively collected data from January 1, 2019 to May 31, 2019 for wristband placement by the EMS systems and determined the percentage match to hospital emergency department (ED) discharge data using the GWTG data and telestroke data.

Results: From the five months of retrospective analysis of prospectively collected data for 5 months showed, 4,668 strokes were seen in hospitals complying with GWTG. Forty-two% of the positive strokes in hospital (EDs) had stroke bands placed. Of these 8.4% had matching stroke wristband numbers to the EMS database. The telestroke system reported 636 consultations with 95% band placement, 39% placed by EMS. Matching telestroke band ID’s to EMS records was 37%. Wristbands placed by EMS were associated with positive screen tests, pre-notification and shortened Door to CT time (p < 0.0021).

Conclusions: Wrist-bands were associated with improved EMS response and provided informed response to hospital care teams. For consistent tracking of positive stroke patient data from FMC to discharge both prehospital and hospital, systems must undergo additional training followed by surveys to determine informed training.

Abstract WP120: Welcoming the New Kid on the Block; The Phase IIb Prospective, Randomized, Open-Label, Blinded Endpoint (PROBE) Study of NanO 2 TM Neuroprotection in Large Vessel Strokes

Background: NVX-208 (NanO 2 TM ) was recently examined in a completed randomized, placebo-controlled and double-blinded dose escalation Phase Ib/II safety trial in acute ischemic stroke (AIS) patients and was found to be safe in all dosage levels. Exploratory aims indicated early treatment in the highest NanO 2 TM dose cohort improved clinical outcomes of early NIHSS and 90-day mRS. In the current Phase 2b protocol, NanO 2 TM ’s enhanced oxygen delivery from the blood to tissue will be examined in early AIS subjects with large vessel occlusions (LVO). LVO patients will provide the optimal assessment for NanO 2 TM to maintain penumbra tissue viability. The Phase 2b primary objective will be to assess functional recovery and subject independence.

Drug information: NanO 2 TM is an emulsion of 2% dodecafluoropentane (DDFP) in stabilizers (sucrose, PEG-Telomer-B) and phosphate buffered saline (pH 7.0) that is a highly efficient fluorocarbon oxygen transporter. Compared to previously developed fluorocarbon oxygen carriers, NanO 2 TM carries far more oxygen per gram of fluorocarbon. Because DDFP is not metabolized, almost 100% of administered doses was recovered in the subject’s breath as DDFP.

Hypothesis: NanO 2 TM given early to subjects with LVO ischemic stroke will maintain penumbra tissue viability.

Methods: Phase 2b study sites will include multiple stand-alone and hub and spoke systems located across the United States. Central IRB and safety monitors will provide oversight and support coverage. Key methodology includes providing early first dosage administration of NanO 2 TM or placebo (study treatment) to identify and consent LVO AIS subjects with viable penumbra. For drip and ship patients, second and third doses will be given en route or after arrival at the hub hospital and after revascularization procedures, respectively. Following the third dose, all subjects will receive study treatment dosing out to 24 hours, each dose at 90 minute intervals. 24-hour imagery assessments will confirm infarct volume. All final angiograms and 24-hour imaging data will be sent to core labs for blinded confirmatory review. Subject recovery and independence will be assessed throughout the study to 90 days.

Conclusion: Study projected start date is early to mid-2020.

Collaterals: an important determinant of prolonged ischemic penumbra versus rapid cerebral infarction?

Intravenous tissue plasminogen activator is the mainstay for the treatment of acute ischemic stroke in patients presenting within 4.5 h of symptom onset. Studies have demonstrated that treating patients early leads to improved long-term outcomes. MR imaging currently allows quantification of the ischemic penumbra in order to better identify individuals most likely to benefit from intervention, irrespective of “time last seen normal.” Its increasing use in clinical practice has demonstrated individual differences in rate of infarction. One explanation for this variability is a difference in collateral blood flow. We report two cases that highlight the individual variability of infarction rate, and discuss potential underlying mechanisms that may influence treatment decisions and outcomes.

Risk factors for failed transverse sinus stenting in pseudotumor cerebri patients

BACKGROUND

Idiopathic intracranial hypertension (IIH) when no underlying etiology is found, is a clinical syndrome characterized by elevated intracranial pressure (ICP) (>25 cm H2O), which may lead to headaches and visual symptoms. In patients with IIH who are found to have transverse sinus stenosis, placement of a venous stent across the stenosis has been shown to lower ICP and to resolve the symptoms in several case series, with generally favorable results. In this study, we examine common risk factors associated with failure of transvenous stenting for IIH. If venous sinus stenting fails, CSF diversion should be considered as the next line of treatment.

METHODS

We retrospectively reviewed the records of eighteen patients diagnosed with IIH who underwent venous sinus stenting for transverse sinus stenosis with a mean pressure gradient (MPG) of at least 4 mmHg. Fifteen of these patients did not need further treatment. We compared their pre- and post-treatment, neurological and neuro-ophthalmological evaluations to the three patients who went on to have a shunt placement as a second line treatment.

RESULTS

Shunting after stent placement patients (n=3) had a mean age of 30 years and a mean body mass index of 36.6 kg/m(2), whereas the group that underwent stent placement alone (n=15) had a mean age of 40.7 years and a mean body mass index of 33.3 kg/m(2). In the shunting after stent placement group, the mean opening pressure on the most recent lumbar puncture obtained prior to any intervention was 50 cm of H2O, whereas the group that underwent stent placement alone had an opening CSF pressure of 37 cm of H2O which was statistically significant (p<0.05). There were no other significant differences in pre- or post-intervention factors between the two groups.

CONCLUSION

In patients with IIH and documented evidence of venous sinus stenosis with a pressure gradient, venous sinus stenting should be the primary treatment of choice; however, some patients may be refractory to stenting and still require permanent CSF diversion, which can be complicated in these chronically anticoagulated patients. Patients with persistent papilledema post-stenting and highly elevated opening pressure pre-stenting should be followed closely as they are at greatest risk of requiring a shunt and failing stenting.

Diagnostic quality and accuracy of low dose 3D-DSA protocols in the evaluation of intracranial aneurysms

BACKGROUND

3D-DSA is the 'gold standard' imaging technique for the diagnosis and characterization of intracranial aneurysms.

OBJECTIVE

To compare the image quality and accuracy of low dose 3D-DSA protocols in patients with unruptured intracranial aneurysms.

MATERIALS AND METHODS

The standard manufacturer 5 s 0.36 μGy/f protocol and one of three low dose 3D-DSA protocols (5 s 0.10 μGy/f, 5 s 0.17 μGy/f, 5 s 0.24 μGy/f) were performed in 12 patients with unruptured intracranial aneurysms. Three interventional neuroradiologists, two neurosurgeons, and two neurologists rated the image quality of all 3D reconstructions as good, acceptable, or poor. Three interventional neuroradiologists measured two dimensions of each aneurysm for all protocols. The radiation dose metric Ka,r (reference point air kerma, in mGy) was recorded for each 3D-DSA protocol.

RESULTS

The standard 5 s 0.36 μGy/f protocol earned the highest average subjective rating of 2.76, followed by the 5 s 0.24 μGy/f (2.72), and 5 s 0.17 μGy/f (2.59) protocols. The ranges of differences in aneurysm measurements between the 5 s 0.24 μGy/f protocol and the standard were <0.5 mm. The median Ka,r metrics for each protocol were as follows: 5 s 0.36 μGy/f (89.0 mGy), 5 s 0.24 μGy/f (57.7 mGy), 5 s 0.17 μGy/f (45.9 mGy), and 5 s 0.10 μGy/f (27.6 mGy).

CONCLUSIONS

Low dose 3D-DSA protocols with preserved image quality are achievable, and can help reduce exposure of patients and operators to unnecessary radiation. The 5 s 0.24 μGy/f protocol generates one-third smaller radiation dose than the standard 5 s 0.36 μGy/f protocol without compromising diagnostic image quality or accuracy.

Reducing radiation dose while maintaining diagnostic image quality of cerebral three-dimensional digital subtraction angiography: an in vivo study in swine

BACKGROUND

Three-dimensional digital subtraction angiography (3D-DSA) is a modern technique that allows for better appreciation of complex vascular lesions. This study evaluates the impact of various dose reduction strategies on 3D-DSA image quality.

METHODS

The standard manufacturer 5 s 0.36 μGy/frame setting was modified to create lower dose 3D-DSA protocols by varying the acquisition time (5 or 3 s) and/or dose per frame (0.36, 0.24, 0.17, and 0.10 μGy/f). All protocols were evaluated in three swine. Four raters measured a segment of the external carotid artery on two-dimensional multiplanar reconstruction images. The raters were also presented with three-dimensional volume rendered images from all protocols in a blinded manner and asked to choose the superior image. A full model analysis of variance with repeated measure factors was performed to compare mean differences in measurements between protocols.

RESULTS

Measurement differences between the standard and low dose protocols were not clinically significant (<0.5 mm). All raters demonstrated high inter-rater reliability. The 5 s protocols were considered as qualitatively superior to the 3 s protocols. Delivered system doses ranged from 43.8 to 6.5 mGy. The 5 s 0.10 μGy/frame protocols generated 65-68% less delivered dose compared with the 5 s 0.36 μGy/frame setting.

CONCLUSIONS

Low dose 3D-DSA protocols with preserved image quality are achievable, and can help reduce unnecessary radiation exposure to both patients and operators. The 5 s low dose protocols generated clinically acceptable and superior images compared with the 3 s protocols, suggesting a more important role for acquisition time than dose per frame to maintain image quality.

Intra-arterial intraoperative computed tomography angiography guided navigation: a new technique for localization of vascular pathology

BACKGROUND

Precise intraoperative surgical localization of small distal aneurysms, arteriovenous malformations (AVMs), and cranial base dural arteriovenous fistulae may be challenging. Current neuronavigational techniques are based on imaging techniques with limited sensitivity to detect vascular lesions that are small. We introduce the technique of intraoperative computed tomography angiography (iCTA) with an intra-arterial injection for surgical navigation.

OBJECTIVE

To determine whether iCTA integrated with a navigation platform is accurate and useful for precise localization of small vascular lesions that are challenging to treat.

METHODS

This study included 8 patients: 2 with aneurysms, 3 with small cortical AVMs, and 3 with cranial base dural arteriovenous fistulae. iCTA with intra-arterial contrast injection was performed in all patients for precise localization of the small vascular lesion to facilitate craniotomy planning and microsurgical approach. All operative reports, inpatient and outpatient records, and radiographic studies available were reviewed retrospectively.

RESULTS

: The iCTA was used to target 2 aneurysms, 3 small subcortical AVMs, and 3 dural arteriovenous fistulae. This technique was most helpful to localize the 3 AVMs and the distal M4 aneurysm precisely. Craniotomy planning was accurate in all instances; no complications related to the technique were noted, and all patients had uneventful postoperative recoveries.

CONCLUSION

iCTA is an effective and accurate novel technique that can enhance the safety of surgical treatment for small intra-axial vascular pathology.

ABBREVIATIONS

AVM, arteriovenous malformationCTA, computed tomography angiographyDAVF, dural arteriovenous fistulaDSA, digital subtraction angiographyiCTA, intraoperative computed tomography angiographyMCA, middle cerebral arteryMSCT, multislice computed tomographyMRA, magnetic resonance angiography.

Enhanced visualization processing: effect on workflow

RATIONALE AND OBJECTIVES

Soft-copy viewing of digital radiographs allows for image processing to improve visualization of anatomy and lesions, but it can take more time than film-based viewing. Enhanced visualization processing (EVP) was developed to increase the latitude of an image without reducing the vital contrast, potentially reducing the need for the radiologist to manipulate images. This study examined the influence of processing radiographic images with EVP on workflow in a picture archiving and communications system (PACS).

MATERIALS AND METHODS

Portable computed radiographic chest images were obtained and processed either with EVP or without. A security camera with a videocassette recorder was positioned above the PACS workstation. Four radiologists reviewed the images during their normal work schedule. The current diagnostic image was used to determine if the case contained EVP or non-EVP images. The videotapes of the sessions were reviewed to determine diagnostic viewing times and how zoom and/or window and level manipulation was used.

RESULTS

Viewing time was significantly longer for the non-EVP than the EVP cases. The difference occurred with all readers. Window and level manipulation was used on 35% of the EVP and 41% of the non-EVP images. Zoom was used on 64% of the EVP and 69% of the non-EVP images. Average time spent using zoom and window and level manipulation was significantly shorter with the EVP than with the non-EVP images.

CONCLUSION

EVP of chest images displayed on PACS monitors significantly improved workflow as measured by viewing time. EVP decreased use of window and level manipulation and zooming and the amount of time each one was used.