In recent years, steerable catheters have been developed to combat the effects of the dynamic cardiac environment. Mechanically actuated steerable catheters appear the most in the clinical setting; however, they are bound to a number of mechanical limitations. The aim of this research is to gain insight in these limitations and use this information to develop a new prototype of a catheter with increased steerability. The main limitations in mechanically steerable catheters are identified and analysed, after which requirements and solutions are defined to design a multi-steerable catheter. Finally, a prototype is built and a proof-of-concept test is carried out to analyse the steering functions. The mechanical analysis results in the identification of five limitations: (1) low torsion, (2) shaft shortening, (3) high unpredictable friction, (4) coupled tip-shaft movements, and (5) complex cardiac environment. Solutions are found to each of the limitations and result in the design of a novel multi-steerable catheter with four degrees of freedom. A prototype is developed which allows the dual-segmented tip to be steered over multiple planes and in multiple directions, allowing a range of complex motions including S-shaped curves and circular movements. A detailed analysis of limitations underlying mechanically steerable catheters has led to a new design for a multi-steerable catheter for complex cardiac interventions. The four integrated degrees of freedom provide a high variability of tip directions, and repetition of the bending angle is relatively simple and reliable. The ability to steer inside the heart with a variety of complex shaped curves may potentially change conventional approaches in interventional cardiology towards more patient-specific and lower complexity procedures. Future directions are headed towards further design optimizations and the experimental validation of the prototype.@en

Purpose: In previous studies we developed two mechanical prototypes of steerable catheters: the Sigma, which uses joysticks to actuate two steerable tip segments, and the Epsilon, which has a handle that is an enlarged version of the tip. In this study, we present a first performance evaluation of the prototypes in the cardiac environment. The evaluation was carried out by an expert user, an electrophysiologist with over 20 years of experience, to obtain insight in clinically relevant factors. Methods: Two experiments were conducted. In the first experiment, the Sigma was used in a passive beating heart setup connected to pumps with a saline solution and camera visualization, and compared with the expert’s past experience with conventional steerable catheters. In the second experiment, the Sigma was used in an active beating heart setup with blood perfusion through the coronary arteries and echo visualization, and compared with the Epsilon prototype. The prototype was evaluated through questionnaires on task performance, catheter usability, and workload. After each of the experiments, the catheter characteristics were evaluated via a survey and followed by an in-depth interview. Results & Conclusions: The expert user found the passive beating heart setup to more successful than the active beating heart setup for the purpose of this experiment, with insightful visualization while the heart was in beating condition. The steerability of the prototypes was experienced as useful and clinically relevant. Based on the questionnaires and interview we were able to identify future design improvements and developments for the steerable catheter prototypes.@en