A microcatheter is a very small-diameter, flexible catheter — typically below 3 French (1 mm) — designed to reach vessels that standard catheters cannot enter, from cerebral arteries to distal tumor-feeding branches. Microcatheters are used coaxially: they travel inside a larger guiding catheter or sheath and track over a fine guidewire to the target, where they deliver embolic coils, liquid embolics, stents, or contrast. This guide walks through the anatomy of a microcatheter from hub to tip, explains how steerable sheaths and deflectable catheters differ, and summarizes how physicians choose among them.
What Is a Microcatheter?
A microcatheter is defined by three characteristics: a very low outer diameter (commonly 1.7–2.9 French at the distal segment), a graduated shaft that transitions from a firmer proximal section to a soft, trackable tip, and an inner lumen sized for micro-guidewires and therapeutic payloads. Reinforcement — braided or coiled wire embedded in the catheter wall — preserves the lumen through tight curves and prevents kinking. Hydrophilic coatings reduce friction during navigation. In neurovascular work, coronary intervention, and peripheral embolization, the microcatheter is the final delivery conduit for treatment.
What Is a Microcatheter Hub?
The microcatheter hub is the rigid connector at the proximal (physician) end of the catheter. It provides the luer-lock interface for syringes, rotating hemostatic valves (RHVs), and injection lines, and it is where the operator applies torque and push. A strain-relief segment just distal to the hub protects the shaft from kinking at the transition between the rigid connector and the flexible catheter body. Hub design matters in practice: a secure luer connection prevents leakage during high-pressure contrast injection or liquid embolic delivery, and clear hub labeling (catheter length, inner diameter, tip configuration) lets staff verify compatibility with wires and devices during a procedure.
What Is a Steerable Sheath?
A steerable sheath is an access sheath whose distal segment can be actively deflected by a control handle at the hub — pull-wires inside the sheath wall curve the tip in one or two planes. Instead of relying solely on pre-shaped curves, the operator dials in the angle needed to present devices coaxially to a branch vessel or chamber. Steerable sheaths are widely used in structural heart and electrophysiology procedures and increasingly in complex endovascular navigation. INVAMED's SteerCATH steerable catheter applies this deflection principle, and the JaGuar guiding sheath covers fixed-curve guiding support; both are detailed in our overview of steerable catheter deflection mechanisms and control systems.
Deflectable Catheter vs Steerable Sheath: What Is the Difference?
The terms overlap, but the distinction is functional. A deflectable catheter is itself the working device — its articulating tip carries electrodes, delivers devices, or performs mapping. A steerable sheath is a conduit: it deflects to create a stable, angled pathway through which other catheters and devices are advanced. In practice, a steerable sheath provides the adjustable platform, and the catheter passing through it does the therapeutic work. Choosing between a deflectable device and a steerable-sheath-plus-standard-catheter combination depends on the procedure's need for tip precision versus device exchange flexibility.
Brain Catheters: Microcatheters for Neurovascular Access
Catheters intended for the cerebral circulation — often loosely called brain catheters — face the most demanding navigation environment in the body: long distances from the access site, sequential tight curves, and fragile vessel walls. Neurovascular microcatheters therefore prioritize distal softness, shapeable or pre-shaped tips, and stable positioning for coil or liquid embolic delivery. INVAMED's MicroCATH Neurovascular Catheter Family is designed for coiling, liquid embolic infusion, and distal exploration, complementing stroke devices such as the KinG intracranial revascularization device within the neurovascular interventions portfolio. Engineering detail is covered in our article on neurovascular microcatheter design.
How Physicians Select a Microcatheter
Selection starts from the payload and works backward: the coil, stent, or embolic agent defines the minimum inner diameter; the target anatomy defines the required tip flexibility and length; and the guiding catheter or sheath defines the maximum outer diameter. Additional criteria include tip shapeability, radiopaque marker configuration for precise positioning, coating behavior in tortuous anatomy, and hub compatibility with the planned injection setup. For complex cases, our review of advanced microcatheter selection discusses material trade-offs in depth.
Frequently Asked Questions
What is the difference between a microcatheter and a standard catheter?
Size and role. Standard diagnostic and guiding catheters (4–8 French) establish access and support; microcatheters (below 3 French) travel through them to reach small, distal, or tortuous vessels and deliver therapy there.
What connects to a microcatheter hub?
Syringes, contrast injection lines, and rotating hemostatic valves connect to the hub's luer-lock fitting. The hub is also where the operator torques and advances the catheter, with a strain-relief section protecting the shaft behind it.
Can a steerable sheath replace a guiding catheter?
In many procedures, yes — a steerable sheath can serve as the supporting conduit while adding adjustable tip angulation. The choice depends on the required support level, vessel size, and the devices to be delivered through it.
Why are neurovascular microcatheters different from peripheral ones?
Cerebral vessels are smaller, more tortuous, and more fragile, so neurovascular microcatheters emphasize distal softness and atraumatic tips over the pushability prioritized in peripheral embolization catheters.
Related on INVAMED
Further reading: single and double-lumen microcatheters, microcatheter selection for embolization, and the comprehensive catheter and guidewire systems portfolio.
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