From the SIR Residents and Fellows Section

Teaching Topic: Influence of different flush methods on transfemoral cerebral angiography 

Lee HJ, Yang PS, Lee SB, et al. The influence of flush methods on transfemoral catheter cerebral angiography: continuous flush versus intermittent flush. J Vasc Interv Radiol. 2016; 27:651-657.

Click here for abstract

This manuscript compares different flush methods on transfemoral cerebral angiography (TFCA) in a single-blind randomized trial. Fifty patients were allocated to intermittent-flush (n = 25) and continuous-flush (n = 25). Researchers evaluated differences in procedure duration, amounts of contrast and heparinized saline used, , heparin dose, blood loss, fluoro time, radiation dose, and development of new embolic signal (NES) on diffusion-weighted imaging (DWI). There were noted differences in procedure duration, amount of contrast used, wasted heparinized saline, and aspirated blood. However, there were no differences in the occurrence of NES on DWI between the treatment groups.

Clinical Pearls

What is a new embolic signal (NES)?

NES identifies an area of brain hyperacutely affected by microembolism during a neurovascular, angiographic procedure. Diffusion-weighted imaging (DWI) is the gold standard to confirm these lesions. A new, diffusion-prolonged, foci can be considered a procedure-related embolic signal. Alternatively, transcranial Doppler (TCD) can be performed at the bedside and is easily repeated. Flushing with heparinized saline during TFCA is mandatory for protecting against thromboembolic complications.

What are the most common complications of cerebral angiography?

Access-site hematoma is the most common complication overall (4.2%), neurologic complications are seen in 2.63% with 0.14% being strokes with permanent disability. Factors associated with increased risk of neurologic complication include the indication of atherosclerotic cerebrovascular disease, indication of subarachnoid hemorrhage, and the comorbidity of frequent TIAs. Conversely, involvement of a trainee in the cerebral angiogram decreased the risk of complication1.



Figure

Preparation of the diagnostic catheter in each group. (a) The diagnostic catheter was connected to a 10-mL syringe filled with heparinized saline via a one-way connector in the intermittent-flush group. (b) The diagnostic catheter was connected to a Y connector in the continuous-flush group. The side arm of the Y connector was connected to the pressurized flushing line (A) and a connecting line (B) via a three-way connector. Another three-way connector was connected to the connecting line of the mechanical power injector (C) and a syringe for manual injection (D).

Questions to Consider

What types of flushing methods can be used?

Heparinized saline (5,000 U/L) was used for the flushes during TFCA in this study. A conventional continuous flushing system through a vascular sheath is formed by connecting the sheath to a plastic bag of heparinized saline surrounded by a pressure cuff inflated to 300 mmHg. A reducer permits a rate of 1 drop/sec into the sheath and catheter system. Some operators believe that the use of a continuous flushing method reduces the possibility of air embolism compared to intermittent flushing during the procedure, which requires blood aspiration into the flush syringe to ensure air bubbles are removed from the catheter prior to injection. It is generally accepted that intermittent flushing be performed whenever wires and catheters are removed and exchanged during the procedure.

How may the flush method affect the procedure?

Depending on the type of flush method used, procedure duration, amounts of contrast medium and heparinized saline used, heparin dose, blood loss, fluoroscopy time, radiation dose, and occurrence of new embolic signal (NES) on diffusion-weighted imaging (DWI) may differ and were monitored in this study. The authors found that although it is time-consuming to set up the more complex continuous-flush system, total procedure time in the continuous-flush group was significantly shorter than the total procedure time in the intermittent-flush group. Three NESs on DWI occurred in three of the 27 patients who underwent DWI in this study (11%). All lesions were asymptomatic and occurrence was lower than the previously reported prevalence (15%–26%). The amount of heparinized saline wasted, contrast used, contrast wasted, and blood aspirated were also significantly lower in the continuous-flush group.

Additional Citations:

Kaufmann TJ, Huston J, Mandrekar JN, Scleck CD, Thielen KR, Kallmes DF. Complications of diagnostic cerebral angiography: evaluation of 19,826 consecutive patients. Radiology. 2007; 243: 812-9.

Post Author:
Rajat Chand, MD
Diagnostic Radiology Resident, PGY-2
John H. Stroger Hospital of Cook County

Predictors of Recanalization for Incompetent Great Saphenous Veins Treated with Cyanoacrylate Glue

Summary

In recent years, several promising non-thermal endovenous ablation techniques have been introduced which do not require tumescent anesthesia. These include mechanochemical ablation (ClariVein; Vascular Insights, Quincy, Massachusetts), VariClose (Biolas, Ankara, Turkey), polidocanol endovenous microfoam (Varithena; BTG International, London, United Kingdom), and VenaSeal Closure System (Medtronic, Gorway, United Kingdom). Long-term outcomes following ablation with these non-thermal techniques remains limited compared to the mature evidence base underlying endovenous thermal ablation. This study from Chan et al is a retrospective series of 108 legs in 55 consecutive patients with saphenofemoral junction (SFJ) or great saphenous vein (GSV) incompetence which aimed to identify predictors of great saphenous vein (GSV) recanalization following treatment with VenaSeal. The included patients had Clinical-Etiology-Anatomy-Pathophysiology (CEAP) 3 (60%) or higher disease. Patients underwent VenaSeal with concurrent microphlebectomy and were followed with clinical evaluation and duplex ultrasound at 1-week, 1-month, 6-months, and 24-months post-procedure. VenaSeal was deposited 4 cm distal to the SFJ and at 3-cm intervals along the entire course of the targeted GSV (median treatment length: 28 cm). On follow-up, GSV closure rates were 97% (1 week), 94% (1 month), 89% (6 months), and 76% (12 months). The majority of recanalization occurred at one year and developed from the SFJ rather than segmentally within ablated areas. Cox regression for predictors of GSV recanalization found only GSV diameter ³6.6 mm as a significant predictor (p=0.016). Other evaluated variables, which were not found to be significant, included GSV length, presence of incompetent thigh perforators, clinical severity at presentation, and operator experience. The study also observed low pain and mild ecchymosis following the procedure as well as significant improvements in validated vein symptom scores post-procedure.



Figure 2B. Kaplan-Meier curve showing significantly lower closure rates in GSV ³ 6.6 mm (log-rank test, p=0.002)

Commentary

The treatment of saphenous vein insufficiency has been revolutionized in the last two decades with the development of endovenous ablation techniques using radiofrequency ablation (RFA) and endovenous laser ablation (EVLA) which offer high rates of technical success at far less morbidity than traditional surgical vein stripping. These techniques; however, do have some disadvantages including the requirement of tumescent anesthesia and ecchymosis and pain during the recovery period. Several new non-thermal endovenous ablation techniques have been developed to address these (and other) limitations of thermal ablation techniques and include cyanoacrylate based compounds (VenaSeal and Variclose), polidocanol foam (Varithena), and mechanochemical ablation (ClariVein). Similar to prior studies, this series demonstrated that VenaSeal has very low associated post-procedural pain which is a benefit over thermal ablation techniques. The prior VeCLose trial for Venaseal demonstrated 99% GSV closure rate at 3-months, but longer term follow-up with VenaSeal is limited. This study demonstrated an increasing rate of GSV recanalization at 12-months follow-up (24% patients from 11% patients at 6 months), highlighting the importance of long-term outcomes data. Notably, the study had substantial drop-off in number of patients who completed duplex follow-up at the later time points, with only 58% patients at 6 months, and 34% patients at 12 months. The authors suggested that the American patient population in the VeClose trial had smaller mean GSV diameters than those seen in the Asian population, but the median GSV diameter in the current study was 6.6 mm, similar to the 6.3 mm mean proximal GSV diameter in VeClose. The Cox regression finding of GSV diameter ³6.6 mm as a significant predictor for GSV recanalization provides useful data for counseling patients who are considering VenaSeal. Prior studies on endovenous thermal ablation techniques have also found larger GSV diameter as significant predictor for recanalization. Insurance reimbursement for VenaSeal remains challenging in many geographic areas and patients may be paying out-of-pocket so management of expectations and advising alternative modalities may be appropriate in patients with larger GSV diameters. The authors mention another series describing the use of larger VenaSeal volumes to achieve durable results in larger caliber GSVs, but definitive long-term outcomes data are lacking. Lastly, all patients in this study wore full-length compression stockings for at least one month post-procedure which is not a universal protocol (one of the marketed benefits of VenaSeal is the lack of need for post-procedure compression stockings) and may therefore affect the generalizability of the results. Non-thermal GSV closure techniques remain an exciting and growing area in the treatment of GSV reflux and more studies like this one are needed to elucidate the optimal technique and algorithm with which to apply these novel modalities.

Click here for abstract

Chan YC, Law Y, Cheung GC, Cheng SW. Predictors of Recanalization for Incompetent Great Saphenous Veins Treated with Cyanoacrylate Glue. J Vasc Interv Radiol 2017; 28:665-71.

Post Authors:
Jeffrey Forris Beecham Chick, MD, MPH, DABR
Assistant Professor of Vascular and Interventional Radiology
Vice Quality Assurance and Safety Officer
Venous Health Program Faculty
University of Michigan Health System
Michigan Medicine

James X. Chen, MD
Resident in Radiology
Hospital of the University of Pennsylvania