Microcatheters

Microcatheters are slender, highly flexible intravascular catheters designed for selective catheterization of small, distal vessels and for targeted delivery of therapies. They are used in interventional radiology, neuroradiology, and cardiovascular procedures to reach areas that standard catheters cannot access. Typical microcatheters have an outer diameter in the range of about 0.010–0.040 inches and lengths from roughly 65 to 200 cm, with a single lumen or multiple lumens for simultaneous delivery of contrast, drugs, or embolic materials. The distal tip is engineered for navigation through tortuous anatomy and may be straight, curved, or angled; many employ lubricious coatings such as hydrophilic polymers to improve trackability. They are visualized under fluoroscopy with radiopaque markers.

Construction and features: Most microcatheters are built from polyimide or similar polymers, with outer layers of Pebax or nylon, sometimes reinforced with braided or coiled supports to enhance torque control and kink resistance. They may include multiple lumens, detachable-tip options, or designs that allow passage over a microwire while maintaining distal stability. Radiopaque bands along the shaft aid in guidance.

Applications: In neurointerventions, microcatheters enable selective catheterization of cerebral vessels for aneurysm embolization, thrombectomy, or targeted drug delivery. In peripheral and visceral procedures, they facilitate embolization, chemoembolization, or delivery of solvents, contrast, or therapeutic agents to specific vessels or tumors.

Considerations and safety: Selection depends on microwire compatibility, required distal reach, and the desired balance of trackability and support. Distal tip shape and catheter stiffness are chosen for the anatomy treated. Complications include vessel injury, vasospasm, thromboembolism, or dissection; careful technique and imaging mitigate risks.

History and regulation: Microcatheters emerged in the late 20th century as refinements to standard angiographic catheters. They are regulated as medical devices and cleared for specific indications in many regions, with ongoing development aiming to improve flexibility, safety, and compatibility with various wires and embolic materials.