What is catheter-directed therapy? (EKOS)

Catheter-directed lysis therapy delivers thrombolytics (like tPA) via a catheter. Consider it for extensive DVT or submassive or massive PE when you have concerns about bleeding risks.

EKOS (EndoWave Catheter Infusion System) is a device that is supposed to enhance catheter-directed therapy with the use of ultrasonic waves. Ooh! There are several parts of the EKOS experience to be aware of:

  • Control unit–the pump. Can adjust settings and infusion rates. Beeps at you when there are problems.
  • Catheter/drug delivery device–infuses the thrombolytic at a set rate
  • Ultrasound core–supposedly increases thrombolytic efficacy, decreases fibrin clotting
  • Coolant (usually normal saline or heparin-infused normal saline)–to prevent the ultrasound core from overheating/causing tissue damage

A video is worth a thousand pictures: check out the EKOS inservice video on YouTube.

This review goes into some of the nitty-gritty of managing EKOS. The thrombolytic of your choice is usually set to an infusion rate of 1-5 mg/hour. The catheter usually stays in for 18-24 hours. Consider stopping thrombolysis once a maximum dose has been given (like 18-24 mg), 18-24 hours has passed, or repeat ECHO or CTA shows improvement. Once the clinical goal is achieved, the catheters may be removed without repeat imaging. Trend fibrinogen levels: most conservative protocols would reduce or stop the infusion when fibrinogen <200 mg/dL.

While there are studies proving the efficacy and relative safety of EKOS (such as SEATTLE II), there are no high-quality studies that compare EKOS with other kinds of catheter-directed therapy, or against the oldie goodie systemic tPA. Therefore, EKOS seems promising, but people are reluctant to recommend it over other kinds of therapy.

Tangent: not all contraindications to tPA are created equal; see this review on the absolute and relative contraindications to thrombolytics. In addition, even when there are contraindications to tPA, you might still be able to use it and get lucky, as in this interesting case report.

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