Challenge: Current procedures for minimally invasive access to the epicardium surrounding the heart have proven to run the risk of puncturing the right ventricle up to 30% of the time during catheter and pacer lead insertion. Software had been developed at a well renowned academic institution that could interpret the pressures required to pass a needle through different tissues. Our challenge was to refine the design of a retractable needle that could carry a sensor that would measure the pressure differentials during the puncture of the varied muscle structures surrounding the heart. Surgeons would then have better awareness of their tools' positions and be alerted when they might risk puncturing a ventricle.
Design Concept: The initial concept was a dual lumen needle that would carry the pressure sensor. A readily available and appropriately sized MEMs-based pressure sensor was sourced and the refinement of the design and manufacturing process development was accelerated. Initial concepts included an overmolded handle which needed to provide clearance for pass-through of a fiber optic cable and a Luer connection so that liquid could be flushed through the non-coring needle.
Solution: Final design iterations included human factors considerations for needle length and handle configuration. The configuration for pressure sensor placement and bonding to the inner tube were detailed. The inner cannula was to be fastened by laser welds. The laser weld process required welds at its proximal and distal points to properly secure the inner tube to strict tolerance requirements as the pressure sensor had be fastened a known distance from the needle tip. The pressure sensor was bonded in place after laser welding. The overmolding of the handle was then addressed. The pilot manufacturing phase revealed occlusions flowing into the needle lumen during the over molding process. Plastic tooling and mold flow processes were altered to alleviate the forming of occlusions. The device was tested and performed as required.