Contact force management has been proven to have a positive effect on the outcome of cardiac ablation procedures. However, no method exists that allows maintaining a constant contact force within a required and effective range. This work aims to develop and evaluate such a constant force mechanism for use in an ablation catheter. A passive constant force mechanism was designed based on a tape loop. The tape loop consists of two tapered springs that work in parallel. A finite element analysis was carried out to verify the behavior and performance of the design. A design based on requirements for a constant force ablation tip showed an average force of about 7.8×10-2 N±8×10-3 N over 20 mm in simulation. A scaled prototype was built and evaluated to prove the validity of the concept; this prototype provides an average force of 1.3×10-1 N±1.6×10-2 N over 35 mm. The mechanism allows for controlled delivery of contact force within a desired and effective range. Based on these findings, it can be concluded that the approach is successful but needs to be optimized for future applications. Being able to control the delivery of contact force in a constant range may increase the effectivity of cardiac ablation procedures and improve clinical outcomes.

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Positioning and stabilizing a catheter at the required location inside a vessel or the heart is a complicated task in interventional cardiology. In this review we provide a structured classification of catheter stabilization mechanisms to systematically assess their challenges during cardiac interventions. Commercially available, patented, and experimental prototypes of catheters were classified with respect to their stabilizing mechanisms. Subsequently, the classification was used to define requirements for future cardiac catheters and persisting challenges in catheter stabilization. The classification showed that there are two main stabilization mechanisms: surface-based and volume-based. Surface-based mechanisms apply attachment through surface anchoring, while volume-based mechanisms make use of locking through shape or force against the vessel or cardiac wall. The classification provides insight into existing catheter stabilization mechanisms and can possibly be used as a tool for future design of catheter stabilization mechanisms to keep the catheter at a specific location during an intervention. Additionally, insight into the requirements and challenges for catheter stabilization inside the heart and vasculature can lead to the development of more dedicated systems in the future, allowing for intervention- and patient-specific instrument manipulation.

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The aim of this research is to integrate spectral tissue sensing technology inside a cardiac bioptome for real-time measurements of tissue characteristics. Bioptome tip and handle components were designed and manufactured to house and guide optical fibers. The designed components were assembled on a cardiac bioptome together with optical fibers. A technical feasibility test was carried out to study the functionality of the instrument and the effect of the optical technology on the biopsy performance. Biopsy samples were taken from five different tissue types in a porcine heart and the resulting optical spectra were compared. Spectral tissue sensing fibers were successfully integrated inside a conventional cardiac bioptome. The integrated instrument allowed differentiation between ventricular tissue, blood, and cardiac fat tissue based on blood and fat percentage and amount of scattering. Moreover, differences between scarred and nonscarred tissue were clearly visible. A first step has been made in the use of spectral tissue sensing for the detection of different tissue structures for endo-myocardial biopsy (EMB). The instrument was able to differentiate between various tissues, as well as between healthy and diseased cardiac tissues. Future research should focus on measurements of naturally diseased cardiac tissue, repeated measurements with statistical value, and improvements to the instrument design. Having the ability to measure tissue characteristics prior to acquiring a biopsy sample will not only allow easier positioning of the bioptome at the correct location but can also prevent sampling undesired tissue or scar tissue from previous biopsies.

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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.

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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

This work focuses on the design of a new device (called ChoRe) to place artificial chords in the mitral valve structure during a trans-catheter procedure. The aim of the device is to restore the correct functionality of the valve and solve mitral valve regurgitation, that is, a common consequence of chordae tendineae rupture. An analysis of the requirements was carried out and used to design and develop a first functional prototype. The resulting device was able to connect artificial chords at the posterior leaflet of the mitral valve and at the apex of the left ventricle, also allowing the control of the artificial chord length. The ChoRe was tested ex-vivo in bovine hearts. The qualitative assessment of the ChoRe focused on the performance of the device and preliminary evaluation of the procedure time. Results demonstrated that the device is able to create a top and bottom fixation in an average time of 3.45 ± 1.44 min. Future improvements will focus on enhancing the connection at the leaflet, as well as the overall functionality, in order to guarantee better control of the artificial chord length. This work shows future potentials for more patient-specific treatments in trans-catheter scenarios for mitral valve repair.

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Even though technological advances have increased the application area of minimally invasive surgery (MIS), there are still hurdles to allow for widespread adoption for more complex procedures. The development of steerable instruments, in which the surgeon can alter the tip orientation, has increased the application area of MIS, but they are bulky, which limits their ability to navigate through narrow environments, and complex, which complicates miniaturization. Furthermore, they do not allow for navigating through complex anatomies. In an effort to improve the dexterity of the MIS instruments, while minimizing the outer dimensions, the previously developed cable-ring mechanism was redesigned, resulting in the thinnest, Ø2mm (Ø 1mm lumen), eight degrees-of-freedom (DOF) multisteerable tip for MIS to date. The multisteerable tip consists of four steerable segments of 2DOF stackable elements allowing for ±90 deg articulation, as well the construction of complex shapes, actuated by 16 Ø0.2mm stainless steel cables. In a proof-of-principle experiment, an ultrasound transducer and optical shape sensing (OSS) fiber were inserted in the lumen, and the multisteerable tip was used to perform scanning motions in order to reconstruct a wire frame in three-dimensional (3D). This configuration could in future be used to safely navigate through delicate environments and allow for tissue characterization. Therefore, the multisteerable tip has the potential to increase the application area of MIS in future, as it allows for improved dexterity, the ability to guide several tip tools toward the operation area, and the ability to navigate through tight anatomies.

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In interventional cardiology catheters are routinely used to access and treat defects and diseases in the heart. Image guidance using forward-looking (FL)ultrasound transducers at the tip of the catheter could give the physician visual feedback during complex procedures such as valve replacement or transseptal puncture. In this work, we investigate FL 3D imaging by integrating a 7 MHz single-element ultrasound transducer at the tip of a novel multi-steerable intracardiac catheter together with an optical shape sensing fiber (OSS). We tested the imaging capability of the integrated device on an ex-vivo pig heart. By acquiring ultrasound A-lines at different locations while steering the catheter tip, a sparse 3D image is obtained. To reconstruct a volumetric image from the sparse data we implemented an adaptive Normalized Convolution (NC)algorithm were the dimension, orientation and angle of the 3D anisotropic kernel changes dynamically according to the scanning path. We acquired ultrasound A-lines of the tricuspid valve and we computed the 3D image using NC with both an isotropic kernel and an anisotropic kernel. We successfully interpolated the sparse data obtaining 3D volumes of the heart. By using an anisotropic kernel better 3D reconstruction is achieved with higher detail information compared to the reconstruction obtained using an isotropic kernel. This pilot experiment demonstrates the potential of FL image guidance during intracardiac procedures using a single-element transducer integrated in a steerable catheter with an OSS fiber.

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To overcome the challenges presented by complex 3-dimensional shapes and tortuous vasculature in the cardiovascular environment, we previously developed a prototype of a multi-steerable catheter having 4 DOFs controlled by two joysticks [1]. However, it remains unknown whether the added steering possibilities are beneficial in the cardiovascular anatomy. With this research we aimed to investigate the effect of 0-DOF, 2-DOF, and 4-DOF catheter systems on surgical performance in a cardiovascular model.@en

Objective: This review aims to provide a structured classification of the underlying steering mechanisms in steerable catheters and to assess their future challenges. Methods: Existing, patented, and experimental designs of steerable catheters are classified with respect to their steerability. Subsequently, the classification is used as a tool for defining future requirements and challenges for steerable cardiac catheters. Results: The results of the classification provide two categories of steering at a fundamental level: 1) Force generation in the tip and 2) force transmission to the tip. The former group consists of force generating steering mechanisms as a result of 1) electric, 2) thermal, and 3) magnetic actuation. The latter group comprises force transmitting steering mechanisms as the result of 4) hydraulic chamber actuation or 5) mechanic cable actuation. Each category can be further subdivided into multiple subcategories. Future requirements and challenges are found for steering and positioning capabilities, cardiac applications and safety, and miniaturization potential. Conclusion: A structured classification is presented which identifies the different steering mechanisms in steerable catheters. The classification proves to be a useful tool in determining future requirements and challenges, being invaluable for future application-driven design. Significance: Using the applied classification as a tool for future design will not only provide insight into previously applied steering technology, it will identify new and unexplored options too. Additionally, insight into the requirements and challenges for catheter steering toward and inside the heart, will allow more dedicated systems, allowing intervention- and patient-specific instrument manipulation.@en