Electrophysiologic Characterization of the Arrhythmogenic Substrate in Reentrant Atrial and Ventricular Arrhythmias Insights from the Clinical and Experimental Electrophysiology Laboratories

This thesis encompasses an overview and critical analysis of 11 publications of clinical and translational cardiac electrophysiology research that has been executed over the last seven years. The focus of this dissertation and the selected papers is on the use of electroanatomic mapping technology to define the arrhythmogenic substrate in patients with structural heart disease and ventricular arrhythmias. Such advancements in elucidating the mechanisms and pathophysiology underlying scar-related ventricular tachycardia have yielded improved clinical outcomes for patients with drug-refractory ventricular arrhythmias. Chapter 1 describes the epidemiologic background and introduces the concept of intracardiac mapping and the technological evolution that has provided the basis for this current body of work. Chapter 2 and Chapter 3 provide a detailed description of how electroanatomic mapping studies have provided critical insight into disease pathogenesis in patients with dilated nonischemic cardiomyopathy arrhythmogenic right ventricular cardiomyopathy (ARVC). The clinical impact and relevance of these studies are discussed based on conventional electroanatomic mapping technologies to define abnormal physiological substrates. Chapter 3 also addresses important considerations regarding percutaneous epicardial mapping and ablation that have been derived from extensive clinical experience. Chapter 4 and Chapter 5 describe the evolution of mapping technologies and the use of high-resolution mapping system technologies. These chapters discuss the potential clinical advantages of these technologies during substrate and activation mapping, particularly in post-infarct ventricular scar and VT. Finally, Chapter 6 concludes this thesis with final thoughts on the broader context of the lessons that have been learned from the studies that are presented in this thesis and implications for future work

Instrument Tracking and Visualization for Ultrasound Catheter Guided Procedures

We present an instrument tracking and visualization system for intra-cardiac ultrasound catheter guided procedures, enabled through the robotic control of ultrasound catheters. Our system allows for rapid acquisition of 2D ultrasound images and accurate reconstruction and visualization of a 3D volume. The reconstructed volume addresses the limited field of view, an inherent problem of ultrasound imaging, and serves as a navigation map for procedure guidance. Our robotic system can track a moving instrument by continuously adjusting the imaging plane and visualizing the instrument tip. The overall instrument tracking accuracy is 2.2mm RMS in position and 0.8◦ in angleEngineering and Applied Science

Three-dimensional holographic visualization of high-resolution myocardial scar on HoloLens.

Visualization of the complex 3D architecture of myocardial scar could improve guidance of radio-frequency ablation in the treatment of ventricular tachycardia (VT). In this study, we sought to develop a framework for 3D holographic visualization of myocardial scar, imaged using late gadolinium enhancement (LGE), on the augmented reality HoloLens. 3D holographic LGE model was built using the high-resolution 3D LGE image. Smooth endo/epicardial surface meshes were generated using Poisson surface reconstruction. For voxel-wise 3D scar model, every scarred voxel was rendered into a cube which carries the actual resolution of the LGE sequence. For surface scar model, scar information was projected on the endocardial surface mesh. Rendered layers were blended with different transparency and color, and visualized on HoloLens. A pilot animal study was performed where 3D holographic visualization of the scar was performed in 5 swines who underwent controlled infarction and electroanatomic mapping to identify VT substrate. 3D holographic visualization enabled assessment of the complex 3D scar architecture with touchless interaction in a sterile environment. Endoscopic view allowed visualization of scar from the ventricular chambers. Upon completion of the animal study, operator and mapping specialist independently completed the perceived usefulness questionnaire in the six-item usefulness scale. Operator and mapping specialist found it useful (usefulness rating: operator, 5.8; mapping specialist, 5.5; 1-7 scale) to have scar information during the intervention. HoloLens 3D LGE provides a true 3D perception of the complex scar architecture with immersive experience to visualize scar in an interactive and interpretable 3D approach, which may facilitate MR-guided VT ablation

Catheter ablation of ventricular fibrillation: importance of left ventricular outflow tract and papillary muscle triggers

Background: Monomorphic ventricular premature depolarizations (VPDs) have been found to initiate ventricular fibrillation (VF) or polymorphic ventricular tachycardia (PMVT) in patients with and without structural heart disease. Objective: The purpose of this study was to describe and characterize sites of origin of VPDs triggering VF and PMVT. Methods: The distribution of mapping-confirmed VPDs, electrophysiology laboratory findings, and results of radiofrequency catheter ablation were analyzed. Results: Among 1132 consecutive patients who underwent ablation for ventricular arrhythmias, 30 patients (2.7%) with documented VF/PMVT initiation were identified. In 21 patients, VF/PMVT occurred in the setting of cardiomyopathy; in 9 patients, VF/PMVT was idiopathic. The origin of VPD trigger was from the Purkinje network in 9, papillary muscles in 8, left ventricular outflow tract in 9, and other low-voltage areas unrelated to Purkinje activity in 4. Each distinct anatomic area of origin was associated with VF/PMVT triggers in patients with and without heart disease. Acute VPD elimination was achieved in 26 patients (87%), with a decrease in VPDs in another 3 patients (97%). During median follow-up of 418 days (interquartile range [IQR] 144-866), 5 patients developed a VF/PMVT recurrence after a median of 34 days (IQR 1-259). Rare recurrence was noted in patients with and without structural disease and from each distinct anatomic origin. The total burden of VF/PMVT episodes/shocks was reduced from a median of 9 (IQR 2.5-22.5) in the 3 months before ablation to 0 (IQR 0-0, total range 0-2) during follow-up (

Iron imaging in myocardial infarction reperfusion injury

Restoration of coronary blood flow after a heart attack may lead to reperfusion injury and pathologic iron deposition. Here, the authors perform magnetic susceptibility imaging showing its association with iron in a large animal model of myocardial infarction during wound healing, and showing feasibility in acute myocardial infarction patients undergoing percutaneous coronary intervention