Superior Vena Cava Syndrome

Superior vena cava (SVC) syndrome comprises a constellation of clinical signs and symptoms caused by obstruction of blood flow through the SVC. The management of patients with life-threatening SVC syndrome is evolving from radiation therapy to endovascular therapy as the first-line treatment. There is a paucity of data and societal guidelines with regard to the management of SVC syndrome. This paper aims to update the practicing interventionalists with the contemporary and the evolving therapeutic approach to SVC syndrome. In addition, the review will focus on endovascular techniques, including catheter-directed thrombolysis, angioplasty, and stenting, and their associated complications.

Management of inferior vena cava thrombosis with the FlowTriever and ClotTriever systems

OBJECTIVE

Although inferior vena cava (IVC) thrombosis is infrequently encountered, it carries a significant risk of post-thrombotic syndrome and pulmonary embolus. Recent studies show no difference in the incidence of post-thrombotic syndrome in patients with iliofemoral deep venous thrombosis (DVT) treated with pharmacothrombolysis vs anticoagulation alone; however, there is an associated increased risk of bleeding. The treatment of IVC thrombosis is less well-studied and the hemodynamic changes may be more significant with pharmacothrombolysis, although the bleeding risk remains. The ClotTriever and FlowTriever systems remove thrombus from veins without the use of thrombolytics. Our study evaluates outcomes of patients undergoing mechanical thrombectomy for the treatment of IVC thrombosis using the ClotTriever and FlowTriever devices.

METHODS

A retrospective chart review was performed to identify consecutive patients who underwent mechanical thrombectomy for the treatment of IVC thrombosis using the ClotTriever and/or FlowTriever systems from November 2018 to January 2020 at four data-sharing institutions. The decision of which device(s) to use was at the discretion of the surgeon. Patient demographics, symptomatology, and imaging characteristics were captured at presentation and follow-up.

RESULTS

A total of 15 patients met the inclusion criteria; 10 were male, and the average age was 59 years. The majority of patients were symptomatic at presentation (n = 14), had a prior history of DVT (n = 13), and had a preexisting IVC filter (n = 8). Eleven patients presented with acute onset (<1 week) of symptoms, whereas three patients had subacute (1-4 weeks) symptoms. Most patients had an associated iliofemoral DVT (n = 13) and were treated with both ClotTriever and FlowTriever (n = 8); others were treated with either ClotTriever or FlowTriever alone (n = 5 and n = 2, respectively). Technical success was achieved in all but two patients, one who had a nonocclusive thrombus densely adherent to a preexisting IVC filter and another who had a chronic rubbery clot in the IVC that could not be cleared. No patient required concomitant lytic therapy or a postoperative stay in the intensive care unit. Furthermore, there were no postoperative bleeding events, myocardial infarctions, pulmonary emboli, renal impairments, or deaths. The median length of stay was 3 days (range, 1-37 days). Patients underwent postoperative follow-up (n = 7) as well as extended follow-up (>6 months; n = 8). All patients who achieved technical success were asymptomatic without evidence of reocclusion of the IVC on follow-up imaging.

CONCLUSIONS

In our multicenter series of 15 patients, The ClotTriever and FlowTriever showed promise in the treatment of IVC thrombosis without the use of fibrinolytic drugs, with no bleeding events and no requirement for intensive care unit stay.

Pulmonary embolism response teams: Purpose, evidence for efficacy, and future research directions

Pulmonary embolism (PE) is a major cause of morbidity and mortality in the United States. Although new therapeutic tools and strategies have recently been developed for the diagnosis and treatment of patients with PE, the outcomes for patients who present with massive or high-risk PE remain dismal. To address this crisis, pulmonary embolism response teams (PERTs) are being created around the world in an effort to immediately and simultaneously engage multiple specialists to determine the best course of action and coordinate the clinical care for patients with acute PE. The scope of this review is to describe the PERT model and purpose, present the structure and organization, examine the available evidence for efficacy and usefulness, and propose future directions for research that is needed to demonstrate the value of PERT and determine if this multidisciplinary approach represents a new standard of care.

Improved fluorescence of indocyanine green in vitro and in vivo after simple cooling procedures

Indocyanine green (ICG) is a contrast agent used for detecting angiogenesis with optical imaging (OI). The purpose of this study was to investigate whether cooling procedures increase the signal yield of ICG with OI. Test samples of 0.05 and 0.02 mM ICG in 40% DMSO and 60% DMEM underwent OI at four different temperatures (5, 37, 55 and 75 degrees C). In addition, six athymic rats with an antigen-induced arthritis of the knee and ankle joints underwent OI before and after injection of ICG (10 mg/ml, dose 15 mg/kg) on two separate days with and without cooling of the joints. The fluorescent signals of the test samples and arthritic joints were measured and evaluated for significant differences before and after cooling with a t-test. In vitro studies showed a strong negative correlation between ICG temperature and fluorescent signal. The mean fluorescent signal of arthritic joints (measured in efficiency) was 0.345 before ICG-injection, 4.55 after ICG-injection and before cooling and 9.71 after ICG-injection and after cooling. The fluorescent signal enhancement of arthritic joints with ICG-enhanced OI images increased significantly after cooling (p = 0.02). The signal yield of ICG can be significantly increased by cooling the target pathology. The primary underlying cause of the temperature dependence of ICG is enhanced collisional quenching with increasing temperature. This simple cooling method may be immediately helpful to increase the fluorescence signal yield in current ICG-enhanced OI-studies in patients.

Optical imaging of cellular immunotherapy against prostate cancer

The purpose of this study was to track fluorophore-labeled, tumor-targeted natural killer (NK) cells to human prostate cancer xenografts with optical imaging (OI). NK-92-scFv(MOC31)-zeta cells targeted to the epithelial cell adhesion molecule (EpCAM) antigen on prostate cancer cells and nontargeted NK-92 parental cells were labeled with the near-infrared dye DiD (1,1'-dioctadecyl-3,3,3',3'-tetramethylindodicarbocyanine). The fluorescence, viability, and cytotoxicity of the labeled cells were evaluated. Subsequently, 12 athymic rats with prostate cancer xenografts underwent OI scans before and up to 24 hours postinjection of DiD-labeled parental NK-92 cells or NK-92-scFv(MOC31)-zeta cells. The tumor fluorescence intensity was measured and compared between pre- and postinjection scans and between both groups using t-tests. OI data were confirmed with fluorescence microscopy. In vitro studies demonstrated a significant increase in the fluorescence of labeled cells compared with unlabeled controls, which persisted over a period of 24 hours without any significant change in the viability. In vivo studies demonstrated a significant increase in tumor fluorescence at 24 hours postinjection of tumor-targeted NK-92-scFv(MOC31)-zeta cells but not parental NK cells. Ex vivo OI scans and fluorescence microscopy confirmed a specific accumulation of NK-92-scFv(MOC31)-zeta cells but not parental NK cells in the tumors. Tumor-targeted NK-92-scFv(MOC31)-zeta cells could be tracked to prostate cancer xenografts with OI.