Design of a sensorized guiding catheter for in situ laser fenestration of endovascular stent

Abstract

Purpose: The in situ fenestration of a standard endograft is currently limited by difficulties in targeting the fenestration site under fluoroscopic control and by the lack of a safe method to perforate the graft. Evidence in the literature suggests the use of a 3 D electromagnetic navigator to accurately guide the endovascular instruments to the target and a laser to selectively perforate the graft. The aim of this work is to provide design guidelines to develop a sensorized catheter to guide the laser tool to the fenestration site and conduct preliminary testing of the feasibility of the proposed solution. Matherials and methods: Different catheter designs were delineated starting from engineering considerations, then prototypes were preliminarily tested to collect surgeon opinions and to steer the design process toward the preferred solution reported by the user. Finally, mechanical simulations were performed with CathCAD, a design software system for the development of composite tubing for endovascular catheters. Results: Based on surgeon feedback, a 9-French steerable catheter with a stabilization system was designed. CathCAD simulations allowed us to define the construction parameters (e.g., materials and geometric constrains) for the fabrication of composite tubes with mechanical properties (flexural, axial, and torsional rigidities) compatible with target values in the literature for guiding catheters. Conclusion:The presented results preliminarily demonstrate the clinical reasonability and feasibility of the designed tool in terms of mechanical properties. Further mechanical tests and extensive in vitro clinical trials are required prior to animal testing.

An Experimental Study of Laser in situ Fenestration of Current Aortic Endografts

“…A tri-dimensional fusion technique, sensorised guiding, and electromagnetically navigated devices could be helpful in this setting. 21,22 Regarding fabric strength modification, a significant mechanical strength loss was observed following both MISF and LISF. In fact, the hole creates a zone where there is a lack of fabric material, which corresponds to (i) the material degraded with the fenestration and (ii) the cutting balloon enlargement.…”

In situ diode laser fenestration: An ex‐vivo evaluation of irradiation effects on human aortic tissue

“…A 3D computer‐aided guidance system and/or a robotic platform can be employed to minimize accidental irradiation risks due an incorrect targeting of the fenestration site. In we have proposed a sensorization strategy, based on electromagnetic (EM) coils, to track in real time the position and the orientation of the endovascular laser fenestration tool.…”

“…This procedure requires a great deal of technical skill and precision. In addition, several changes and readjustments of the C‐Arm position/orientation are necessary to determine the best viewing direction, which results in prolonged fluoroscopic exposure times . Moreover, these customized grafts are expensive and not available for acute syndromes (their fabrication requires several days).…”

Novel EM Guided Endovascular Instrumentation for In Situ Endograft Fenestration

“…The steerable catheter can be easily rotated to appropriately orient the fenestration tool in the direction of the target site. To perform a perfect fenestration, this tool and the steerable catheter tip, should be perpendicular to the graft surface [24], [25]. For this reason, the catheter was designed to allow for a 90 • articulation.…”

“…Both the stabilizer and the steerable catheter feature a multi-lumen, braided structure made of 304V stainless steel, an austenitic non-ferromagnetic steel, chosen to avoid EM interference with the NDI Aurora tracking device. The internal structure of the metal allows the catheter to meet torqueability and pushability specifications [24]. The torqueability is the capability of a catheter to transmit twisting forces without kinking allowing the rotation of its distal end by turning its proximal portion; whereas the pushability is the capability of a catheter to transmit the force along its main axis for an easy advancement into the vascular system.…”