Flow Complexity Estimation in Dysfunctional Arteriovenous Dialysis Fistulas using Vector Flow Imaging

Non-invasive assessment is preferred for monitoring arteriovenous dialysis fistulas (AVFs). Vector concentration assesses flow complexity, which may correlate with stenosis severity. We determined whether vector concentration could assess stenosis severity in dysfunctional AVFs. Vector concentration was estimated in four stenotic phantoms at different pulse repetition frequencies. Spectral Doppler peak velocity and vector concentration were measured in 12 patients with dysfunctional AVFs. Additionally, 5 patients underwent digital subtraction angiography (DSA). In phantoms, vector concentration exhibited an inverse relationship with stenosis severity and was less affected by aliasing in severe stenoses. In nine stenoses of 5 patients undergoing DSA, vector concentration correlated strongly with stenosis severity (first stenosis: r = -0.73, p = 0.04; other stenoses; r = -0.69, p = 0.02) and mid-stenotic diameter (first stenosis: r = 0.87, p = 0.006; other stenoses: r = 0.70, p = 0.02) as opposed to peak velocities (p > 0.05). Vector concentration is less affected by aliasing in severe stenoses and correlates with DSA in patients with dysfunctional AVF.

The use of tissue plasminogen activator as continuous infusion into an arteriovenous hemodialysis access in the hemodialysis unit: a case series

BACKGROUND

Thrombolytics such as tissue plasminogen activator are often used by interventional radiologists in the radiology suite to salvage thrombosed hemodialysis arteriovenous fistulae. Thrombolytics are also commonly used in dialysis facilities as a dialysis catheter lock solution or as an infusion into a dialysis catheter when dysfunctional. However, the use of tissue plasminogen activator as a continuous infusion into an arteriovenous fistula in the dialysis facility to treat clot burden is not commonly done.

OBJECTIVE

The aim of our case series is to demonstrate the successful use of tissue plasminogen activator to decrease clot burden in an arteriovenous fistula in the dialysis unit.

DESIGN

Observational case series.

SETTING

An outpatient dialysis facility in a tertiary care hospital.

PATIENTS

Three non- consecutive patients were diagnosed with an acute thrombosed arteriovenous fistula either on physical exam or by imaging.

MEASUREMENTS

A thrombosed fistula as well as successful resolution of clot was illustrated by either physical exam, fistulogram or ultrasound. A functioning fistula demonstrated successful continuation of dialysis and adequate access flow measurements in follow up.

METHOD

This is a case series that describes the technique of using an infusion of tissue plasminogen activator into an arteriovenous fistula on the dialysis unit by vascular access nurses to treat or diminish clot burden.

RESULTS

We have described three separate cases where treatments with tissue plasminogen activator infusions on the dialysis unit resulted in objective evidence of decrease in clot burden on ultrasound or fistulogram.

LIMITATIONS

The small numbers of our case series requires that the results need to be verified in a larger study. Inclusion and exclusion criteria need to be defined before widespread application of this technique.

CONCLUSIONS

To our knowledge this small case series is the first to describe the procedure whereby low dose tissue plasminogen activator is directly infused into the fistula by the vascular access nurse in the dialysis unit during dialysis and not in the interventional suite. This provides additional information to the existing literature that there is an alternative option for dialysis units to diminish clot burden until a more permanent solution is established through angioplasty.