Remote Navigation and Contact-Force Control of Radiofrequency Ablation Catheters

Atrial fibrillation (AF), the most common and clinically significant heart rhythm disorder, is characterized by rapid and irregular electrical activity in the upper chambers resulting in abnormal contractions. Radiofrequency (RF) cardiac catheter ablation is a minimally invasive curative treatment that aims to electrically correct signal pathways inside the atria to restore normal sinus rhythm. Successful catheter ablation requires the complete and permanent elimination of arrhythmogenic signals by delivering transmural RF ablation lesions contiguously near and around key cardiac structures. These procedures are complex and technically challenging and, even when performed by the most skilled physician, nearly half of patients undergo repeat procedures due to incomplete elimination of the arrhythmogenic pathways. This thesis aims to incorporate innovative design to improve catheter stability and maneuverability through the development of robotic platforms that enable precise placement of reproducibly durable ablation lesions. The first part of this thesis deals with the challenges to lesion delivery imposed by cardiorespiratory motion. One of the main determinants of the delivery of durable and transmural RF lesions is the ability to define and maintain a constant contact force between the catheter tip electrode and cardiac tissue, which is hampered by the presence of cardiorespiratory motion. To address this need, I developed and evaluated a novel catheter contact-force control device. The compact electromechanical add-on tool monitors catheter-tissue contact force in real-time and simultaneously adjusts the position of a force-sensing ablation catheter within a steerable sheath to compensate for the change in contact force. In a series of in vitro and in vivo experiments, the contact-force control device demonstrated an ability to: a) maintain an average force to within 1 gram of a set level; b) reduce contact-force variation to below 5 grams (2-8-fold improvement over manual catheter intervention); c) ensure the catheter tip never lost contact with the tissue and never approached dangerous force levels; and importantly, d) deliver reproducible RF ablation lesions regardless of cardiac tissue motion, which were of the same depth and volume as lesions delivered in the absence of tissue motion. In the second part of the thesis, I describe a novel steerable sheath and catheter robotic navigation system, which incorporates the catheter contact-force controller. The robotic platform enables precise and accurate manipulation of a remote conventional steerable sheath and permits catheter-tissue contact-force control. The robotic navigation system was evaluated in vitro using a phantom that combines stationary and moving targets within an in vitro model representing a beating heart. An electrophysiologist used the robotic system to remotely navigate the sheath and catheter tip to select targets and compared the accuracy of reaching these targets performing the same tasks manually. Robotic intervention resulted in significantly higher accuracy and significantly improved the contact-force profile between the catheter tip and moving tissue-mimicking material. Our studies demonstrate that using available contact-force information within a robotic system can ensure precise and accurate placement of reliably transmural RF ablation lesions. These robotic systems can be valuable tools used to optimize RF lesion delivery techniques and ultimately improve clinical outcomes for AF ablation therapy

FROM CONCEPT, TO DESIGN, EVALUATION AND FIRST IN VIVO DEMONSTRATION OF A TELE-OPERATED CATHETER NAVIGATION SYSTEM

Percutaneous transluminal catheter (PTC) intervention is a medical technique used to assess and treat vascular and cardiac diseases, including electrophysiological conditions. A Interventional specialists use the vasculature as a passageway to guide the catheter to the site of interest, using fluoroscopic x-ray imaging for image-guidance. Common PTC procedures include: vascular angiography, inflating balloons and stents, depositing coils, and the treatment of cardiac arrhythmia via catheter ablation. Catheter ablation has gained prevalence over the last two decades, as the treatment success rate for atrial fibrillation reaches 100%. The close proximity between the interventionalist and the radiation source combined with the increased number of procedures performed annually has lead to increased lifetime exposure; escalating the interventionalist probability of developing cancer, cataracts or passing genetic defects to offspring. Furthermore, the lead garments that protect the interventionalist can lead to musculoskeletal injury. Both these factors have lead to increased occupational risk. Catheter navigation systems are commercially available to reduce these risks. Lack of intuitive design is a common failing among these systems. iii This thesis presents the design and validation of a remote catheter navigation system (RCNS) that utilizes dexterous skills of the interventionalist during remote navigation, by keeping the catheter in their hands of the interventionalist during remote navigation. For remote catheter manipulation, the interventionalist pushes, pulls, and twists an input catheter, which is placed inside an electromechanical sensor (CS). Position changes of the input catheter are transferred to a second electromechanical (CM) that replicates the sensed motion with a second, remote catheter. Design of this system begins with understanding the dynamic forces applied to the catheter during intravascular navigation. These dynamics were quantified and then used as operating parameters in the mechanical design of the CM. In a laboratory setting, motion sensed and replicated by the RCNS was found to be 1 mm in the axial direction, 1° in the radial direction, with a latency of 180 ms. In a multi-operator, comparative study using a specially constructed multi-path vessel phantom, comparable navigation efficacy was demonstrated between the RCNS and conventional catheter manipulation, with the RCNS requiring only 9s longer to complete the same tasks. Finally, remote navigation was performed in vivo to fully demonstrate the application of this system towards the diagnosis and treatment of cardiac arrhythmia

Design, development and evaluation of a compact telerobotic catheter navigation system.

BACKGROUND: Remote catheter navigation systems protect interventionalists from scattered ionizing radiation. However, these systems typically require specialized catheters and extensive operator training. METHODS: A new compact and sterilizable telerobotic system is described, which allows remote navigation of conventional tip-steerable catheters, with three degrees of freedom, using an interface that takes advantage of the interventionalist\u27s existing dexterity skills. The performance of the system is evaluated ex vivo and in vivo for remote catheter navigation and ablation delivery. RESULTS: The system has absolute errors of 0.1 ± 0.1 mm and 7 ± 6° over 100 mm of axial motion and 360° of catheter rotation, respectively. In vivo experiments proved the safety of the proposed telerobotic system and demonstrated the feasibility of remote navigation and delivery of ablation. CONCLUSION: The proposed telerobotic system allows the interventionalist to use conventional steerable catheters; while maintaining a safe distance from the radiation source, he/she can remotely navigate the catheter and deliver ablation lesions. Copyright © 2015 John Wiley & Sons, Ltd

Modeling and Control of Steerable Ablation Catheters

Catheters are long, flexible tubes that are extensively used in vascular and cardiac interventions, e.g., cardiac ablation, coronary angiography and mitral valve annuloplasty. Catheter-based cardiac ablation is a well-accepted treatment for atrial fibrillation, a common type of cardiac arrhythmia. During this procedure, a steerable ablation catheter is guided through the vasculature to the left atrium to correct the signal pathways inside the heart and restore normal heart rhythm. The outcome of the ablation procedure depends mainly on the correct positioning of the catheter tip at the target location inside the heart and also on maintaining a consistent contact between the catheter tip and cardiac tissue. In the presence of cardiac and respiratory motions, achieving these goals during the ablation procedure is very challenging without proper 3D visualization, dexterous control of the flexible catheter and an estimate of the catheter tip/tissue contact force. This research project provides the required basis for developing a robotics-assisted catheter manipulation system with contact force control for use in cardiac ablation procedures. The behavior of the catheter is studied in free space as well in contact with the environment to develop mathematical models of the catheter tip that are well suited for developing control systems. The validity of the proposed modeling approaches and the performance of the suggested control techniques are evaluated experimentally. As the first step, the static force-deflection relationship for ablation catheters is described with a large-deflection beam model and an optimized pseudo-rigid-body 3R model. The proposed static model is then used in developing a control system for controlling the contact force when the catheter tip is interacting with a static environment. Our studies also showed that it is possible to estimate the tip/tissue contact force by analyzing the shape of the catheter without installing a force sensor on the catheter. During cardiac ablation, the catheter tip is in contact with a relatively fast moving environment (cardiac tissue). Robotic manipulation of the catheter has the potential to improve the quality of contact between the catheter tip and cardiac tissue. To this end, the frequency response of the catheter is investigated and a control technique is proposed to compensate for the cardiac motion and to maintain a constant tip/tissue contact force. Our study on developing a motion compensated robotics-assisted catheter manipulation system suggests that redesigning the actuation mechanism of current ablation catheters would provide a major improvement in using these catheters in robotics-assisted cardiac ablation procedures

imaged-based tip force estimation on steerable intracardiac catheters using learning-based methods

Minimally invasive surgery has turned into the most commonly used approach to treat cardiovascular diseases during the surgical procedure; it is hypothesized that the absence of haptic (tactile) feedback and force presented to surgeons is a restricting factor. The use of ablation catheters with the integrated sensor at the tip results in high cost and noise complications. In this thesis, two sensor-less methods are proposed to estimate the force at the intracardiac catheter’s tip. Force estimation at the catheter tip is of great importance because insufficient force in ablation treatment may result in incomplete treatment and excessive force leads to damaging the heart chamber. Besides, adding the sensor to intracardiac catheters adds complexity to their structures. This thesis is categorized into two sensor-less approaches: 1- Learning-Based Force Estimation for Intracardiac Ablation Catheters, 2- A Deep-Learning Force Estimator System for Intracardiac Catheters. The first proposed method estimates catheter-tissue contact force by learning the deflected shape of the catheter tip section image. A regression model is developed based on predictor variables of tip curvature coefficients and knob actuation. The learning-based approach achieved force predictions in close agreement with experimental contact force measurements. The second approach proposes a deep learning method to estimate the contact forces directly from the catheter’s image tip. A convolutional neural network extracts the catheter’s deflection through input images and translates them into the corresponding forces. The ResNet graph was implemented as the architecture of the proposed model to perform a regression. The model can estimate catheter-tissue contact force based on the input images without utilizing any feature extraction or pre-processing. Thus, it can estimate the force value regardless of the tip displacement and deflection shape. The evaluation results show that the proposed method can elicit a robust model from the specified data set and approximate the force with appropriate accuracy

FROM CONCEPT, TO DESIGN, EVALUATION AND FIRST IN VIVO DEMONSTRATION OF A TELE-OPERATED CATHETER NAVIGATION SYSTEM

Percutaneous transluminal catheter (PTC) intervention is a medical technique used to assess and treat vascular and cardiac diseases, including electrophysiological conditions. Interventional specialists use the vasculature as a passageway to guide the catheter to the site of interest, using fluoroscopic x-ray imaging for image-guidance. Common PTC procedures include: vascular angiography, inflating balloons and stents, depositing coils, and the treatment of cardiac arrhythmia via catheter ablation. Catheter ablation has gained prevalence over the last two decades, as the treatment success rate for atrial fibrillation reaches 100%. The close proximity between the interventionalist and the radiation source combined with the increased number of procedures performed annually has lead to increased lifetime exposure; escalating the interventionalist probability of developing cancer, cataracts or passing genetic defects to offspring. Furthermore, the lead garments that protect the interventionalist can lead to musculoskeletal injury. Both these factors have lead to increased occupational risk. Catheter navigation systems are commercially available to reduce these risks. Lack of intuitive design is a common failing among these systems. iii This thesis presents the design and validation of a remote catheter navigation system (RCNS) that utilizes dexterous skills of the interventionalist during remote navigation, by keeping the catheter in their hands of the interventionalist during remote navigation. For remote catheter manipulation, the interventionalist pushes, pulls, and twists an input catheter, which is placed inside an electromechanical sensor (CS). Position changes of the input catheter are transferred to a second electromechanical (CM) that replicates the sensed motion with a second, remote catheter. Design of this system begins with understanding the dynamic forces applied to the catheter during intravascular navigation. These dynamics were quantified and then used as operating parameters in the mechanical design of the CM. In a laboratory setting, motion sensed and replicated by the RCNS was found to be 1 mm in the axial direction, 1° in the radial direction, with a latency of 180 ms. In a multi-operator, comparative study using a specially constructed multi-path vessel phantom, comparable navigation efficacy was demonstrated between the RCNS and conventional catheter manipulation, with the RCNS requiring only 9s longer to complete the same tasks. Finally, remote navigation was performed in vivo to fully demonstrate the application of this system towards the diagnosis and treatment of cardiac arrhythmia

MR Safe Robotic Manipulator for MRI-Guided Intracardiac Catheterization

This paper introduces a robotic manipulator to realize robot-assisted intracardiac catheterization in magnetic resonance imaging (MRI) environment. MRI can offer high-resolution images to visualize soft tissue features such as scars or edema. We hypothesize that robotic catheterization, combined with the enhanced monitoring of lesions creation using MRI intraoperatively, will significantly improve the procedural safety, accuracy, and effectiveness. This is designed particularly for cardiac electrophysiological (EP) intervention, which is an effective treatment of arrhythmia. We present the first MR Safe robot for intracardiac EP intervention. The robot actuation features small hysteresis, effective force transmission, and quick response, which has been experimentally verified for its capability to precisely telemanipulate a standard clinically used EP catheter. We also present timely techniques for real-time positional tracking in MRI and intraoperative image registration, which can be integrated with the presented manipulator to im prove the performance of teleoperated robotic catheterization

Anatomical targets and expected outcomes of catheter-based ablation of atrial fibrillation in 2020.

Anatomical-based approaches, targeting either pulmonary vein isolation (PVI) or additional extra PV regions, represent the most commonly used ablation treatments in symptomatic patients with atrial fibrillation (AF) recurrences despite antiarrhythmic drug therapy. PVI remains the main anatomical target during catheter-based AF ablation, with the aid of new technological advances as contact force monitoring to increase safety and effective radiofrequency (RF) lesions. Nowadays, cryoballoon ablation has also achieved the same level of scientific evidence in patients with paroxysmal AF undergoing PVI. In parallel, electrical isolation of extra PV targets has progressively increased, which is associated with a steady increase in complex cases undergoing ablation. Several atrial regions as the left atrial posterior wall, the vein of Marshall, the left atrial appendage, or the coronary sinus have been described in different series as locations potentially involved in AF initiation and maintenance. Targeting these regions may be challenging using conventional point-by-point RF delivery, which has opened new opportunities for coadjuvant alternatives as balloon ablation or selective ethanol injection. Although more extensive ablation may increase intraprocedural AF termination and freedom from arrhythmias during the follow-up, some of the targets to achieve such outcomes are not exempt of potential severe complications. Here, we review and discuss current anatomical approaches and the main ablation technologies to target atrial regions associated with AF initiation and maintenance.This work was supported by the European Regional Development Fund, the Spanish Ministry of Science and Innovation (SAF2016- 80324-R), and the Fundación Interhospitalaria para la Investigación Cardiovascular (FIC). The Centro Nacional de Investigaciones Cardiovasculares (CNIC) is supported by the Spanish Ministry of Science and Innovation and the Pro-CNIC Foundation, and is a Severo Ochoa Center of Excellence (SEV-2015-0505). Giulio La Rosa has received a fellowship grant from the joint program between the Heart Rhythm Association of the Spanish Society of Cardiology (ARC) and CNIC.S