Experimental study of the atrial septal puncture, linear ablation, and monophasic action potential contact force resulting in proposed medical device enhancements to improve ablation procedure outcomes

Abstract

Background: This thesis presents novel research relative to medical device enhancements used to improve the treatment of atrial fibrillation. Specifically, atrial septal punctures, mitral isthmus linear ablations, and the recording of monophasic action potentials all retain important roles in overall procedure success for the clinical intervention of atrial fibrillation using an ablative therapy. The fundamental premise for these medical device innovations is to improve procedural safety and therapeutic outcomes. The continued development of clinical tools and approaches for such procedures will require medical device innovators to understand variability in underlying patient anatomies. I believe this thesis provides critical insights on underling anatomic features and engineering parameters that could dictate how such innovations could be advanced. Approach: My thesis is composed of a series of studies that focus on: 1) characterizing device efficacy for transseptal puncture; 2) improvements in device utilization for the creation of linear lesions in the region of the mitral isthmus; 3) detailed descriptions of proposed ablation procedural approaches that provide critical insights as to potential effect on adjacent anatomies; and 4) applications of innovative monitoring tools to collect monophasic action potentials and associated contact forces, thereby enhancing detection of arrnythmogenic myocardium therapeutic targets and resultant lesion formations. Specifically, fossa ovalis anatomy was evaluated using swine and human specimens; direct assessments of fossa ovalis biomechanical properties were performed and means to perform transseptal puncture procedures were identified. To accomplish this, I developed novel methodologies for assessing both puncture and tear. I also sought to determine the relative utility of employing the swine fossa ovalis as a predictive indicator for human tissue responses. Further, novel approaches were evaluated against a set of clinically available puncture devices, e.g., those that use either mechanical or radiofrequency puncture approaches. The specimens were also subjected to different sized sheath devices as another means to better understand the relative properties of the given species’ septal anatomy for eliciting punctures and/or tearing. In another set of studies described within my thesis, using human cardiac tissue, a new procedural technique (with currently available clinical devices) was developed as a means to potentially augment a physician’s ability to generate effective linear lesions in the regional anatomy of the mitral isthmus; it was possible to assess such approaches within human cardiac specimens as well. Additionally, magnetic resonance imaging was employed on multiple perfusion-fixed human specimens to provide detailed associated anatomies of the mitral isthmus and coronary sinus, as a means to provide important insights to both clinicians and medical device designers regarding improved procedural approaches taking into consideration collateral structures as well as next generation ablative devices. Finally, I have described experimental approaches to record monophasic action potential contact force data using custom constructed catheters. It was shown that this approach allowed me to evaluate how varied cardiac anatomies may affect a user’s ability to collect reproducible monophasic action potentials as a means to obtain important clinical information during a clinical ablative procedure. Summary: In this thesis, I have shown that the fossa ovalis anatomy of the swine can serve as a useful surrogate, within the range of responses that one may encounter clinically in humans. Furthermore, I have also shown what the impact may be of utilizing various methods for performing transseptal puncture procedures, as well as, the relative impact of employing a range of delivery catheter sizes. I consider that the results of the novel studies I describe here will contribute to the future of individuals working in this field, to develop safe transseptal devices that will also reduce damage of associated anatomies. Further, I describe unique ablative procedural techniques as well as various device improvements which could specifically improve therapeutic outcomes for creating linear mitral isthmus ablation lines. Finally, I describe the required contact forces and other recording parameters that would be needed to appropriately collect monophasic action potentials in various locations throughout cardiac anatomies (endocardial and epicardial). This information should provide novel clinical insights that could then be used to design future tools and/or techniques that may even change how a given ablative procedure is conducted. Therefore, the overall described experimental outcomes within my thesis will increase one’s understanding of associated cardiac anatomy relative to therapeutic approaches for treating atrial fibrillation and the procedures to do so, and also inspire novel clinical approaches and/or the next generation of catheter-based detection of arrhythmogenic tissue and lesion generation.