Catheter-directed thrombolysis (CDT) delivers a fibrinolytic drug directly into a thrombus through a multi-side-hole catheter placed within the clot, rather than infusing it systemically. The rationale is simple and powerful: a high local drug concentration dissolves clot faster and with a fraction of the systemic dose, lowering — though not eliminating — bleeding risk. In selected deep vein thrombosis (DVT) and pulmonary embolism (PE), CDT and its ultrasound-assisted variant are core tools of the interventional response. This article outlines how CDT works, where it fits, and the devices that deliver it.
How CDT Works
Under imaging guidance, a catheter with multiple side holes is embedded along the length of the thrombus, and a thrombolytic is infused over hours directly into the clot. Because the drug is concentrated where it is needed, the total dose is far lower than systemic thrombolysis. Ultrasound-assisted CDT (the EKOS approach) adds high-frequency ultrasound from the catheter, which disaggregates fibrin strands to expose more surface area to the drug — accelerating lysis at low drug doses. Many contemporary programs also combine CDT with mechanical thrombectomy in a "pharmacomechanical" strategy to shorten infusion times.
CDT in DVT: Preserving the Vein
In extensive proximal (iliofemoral) DVT, the goal beyond relieving acute symptoms is preventing post-thrombotic syndrome — the chronic swelling, pain, and ulceration that follow valve damage from a clot left in place. CDT aims to restore flow and preserve valve function in appropriately selected patients, particularly younger patients with extensive iliofemoral clot and low bleeding risk. It frequently uncovers an underlying iliac vein compression (May-Thurner) lesion that then needs venous stenting. Patient selection is central: CDT is not for every DVT, and guidelines reserve it for specific scenarios.
CDT in PE: The Intermediate-High-Risk Middle Ground
Pulmonary embolism care is risk-stratified. Massive (high-risk) PE with shock may need systemic thrombolysis or aggressive intervention; low-risk PE is treated with anticoagulation alone. The difficult middle — intermediate-high-risk PE with right-ventricular strain but preserved pressure — is where catheter-based therapy has grown, offering clot reduction and right-heart offloading at lower bleeding risk than full-dose systemic lysis. Catheter-directed and ultrasound-assisted approaches are options here alongside mechanical aspiration.
Devices Behind CDT
Delivery hardware matters: the infusion catheter must distribute drug along the whole clot, and in pharmacomechanical strategies it pairs with aspiration or maceration. INVAMED's INCA thrombolysis catheter and Viper Ultra thrombolysis catheter serve this role within the DVT portfolio, complemented by aspiration systems such as the DOVI aspiration catheter. Device and strategy selection follow the clinical scenario and the Instructions for Use.
Frequently Asked Questions
What is the difference between catheter-directed and systemic thrombolysis?
Systemic thrombolysis infuses the drug into a peripheral vein to circulate everywhere; CDT delivers it directly into the clot through a catheter, achieving faster local lysis at a much lower dose and lower bleeding risk.
What is EKOS / ultrasound-assisted thrombolysis?
A CDT variant that adds catheter-based ultrasound to loosen fibrin and expose more clot to the drug, enabling effective lysis at low thrombolytic doses.
Who should get CDT for DVT?
Typically selected patients with extensive iliofemoral DVT, good functional status, and low bleeding risk, where preserving vein valves to prevent post-thrombotic syndrome is a priority.
Is catheter-directed thrombolysis used for pulmonary embolism?
Yes, particularly for intermediate-high-risk PE with right-ventricular strain, as a lower-bleeding-risk alternative to full systemic thrombolysis.
Related on INVAMED
Companions: catheter-based PE treatment, IVC filters. Portfolio: DVT and pulmonary embolism management.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.