Cardiovascular disease is one of the most prevalent causes of death which has a high mortality rate. If identified early and treated appropriately, the mortality in patients with cardiovascular disease can be hugely reduced. For several decades, 12-Lead ECG has been the standard technique used to identify ischemia, and recent studies have shown that intracardiac electrogram has many benefits over external monitoring such as holter. ST Monitoring feature has been added to St. Jude Medical intracardiac cardioverter defibrillators (ICD) to leverage the ECG technology for identifying cardiovascular disease. This algorithm monitors the intracardiac electrogram to detect and report patterns which could be related to ischemic events. This feature is expected to enhance the process of identifying ischemia and infarction, and provides long-term management of the disease. In order to support the new implantable devices with ST Monitoring capability, the programmer software was updated to support this new feature in the device. This thesis discusses the work on the programmer. Chapter 1 begins with a background of how monitoring technology in an implantable device can benefit the patients facing high risk of myocardial infarction. Chapter 2 states the objective for the work on the programmer. Chapter 3 describes the implementation and the application of this feature. Conclusion and future development are discussed in Chapter 5.

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on February 18, 2010. Major professor: Lily Laiho, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Engineering, with Specializations in Biomedical Engineering." "January 2010." Includes bibliographical references (p. 40-42).

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on May 3, 2010. Major professor: Robert S. Crockett, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Engineering, with a Specialization in Biomedical Engineering." "March 2010." Includes bibliographical references (p. 39-41).

During development and testing of the pacemaker and defibrillator device functionality, engineers in the cardiac rhythm management industry use a patient simulator to ensure device functionality properly before device is tested with an animal or a human. The patient simulator is also used in the formal device product testing. In St. Jude Medical, a patient simulator called Simulation Test Tool (STT) has been developed and used by engineers in the company. While the Heart Simulator (HS) feature based on physiological heart model in the STT has been served as a main cardiac rhythm simulation feature, there has been an increasing need of a new feature in the STT for engineers to create heart rhythm scenarios more easily and effectively. This thesis covers the design and implementation of the new STT feature, called Event Stream, which allows users to create heart rhythm scenarios using simple text string based syntax for testing device functionality.

The performance of the heart after a valve replacement operation will greatly depend on the flow character downstream the mitral valve thus a better understanding of the flow character is essential. Most in vitro studies of the flow downstream of a MHV have been conducted with the valve in the aortic position. Researchers reported detailed measurements most of which were obtained by Laser Doppler Velocimetry (LDV) in rigid models of the aorta. Digital Particle Image Velocimetry (DPIV) has also been utilized to reveal intricate patterns of interacting shed vortices downstream of the aortic valve. The orientation of the valves may considerably affect the flow development and slight difference may produce significant differences in the ventricular flow fields. Two orientations, respectively anatomical and anti-anatomical, of the St. Jude Medical (SJM) bileaflet valve are presented and compared with the SJM Biocor porcine valve, which served to more closely represent the natural valve. In this effort, we employ a powerful tool to monitor the velocity field in a flexible, transparent LV and study the evolution of large eddies and turbulence through a complete cardiovascular cycle. Both time average and instantaneous results of velocity, vorticity, and turbulent kinetic energy distributions are presented. The presence and location of vortical structures were deduced as well as the level of coherence of these structures. The presence of three distinct flow patterns were identified, by the location of vortical structures and level of coherence, for the three configurations corresponding to significant differences in the turbulence level distribution inside the LV. / Master of Science

Native heart valves that have limited functionality due to cardiovascular disease or congenital birth defects are commonly replaced by prosthetic heart valves. Bileaflet mechanical heart valves (BMHV) are the most commonly implanted valve design due to their long-term durability. However, their unnatural hemodynamics promote thrombosis and thromboembolic events. Clinical reports and in vitro experiments suggest that the thrombogenic complications in bileaflet valves are related to the stress imposed on blood by the valves during the closing phase. Additionally, animal and clinical studies have shown that BMHV in the aortic position demonstrate reduced failure rates compared to identical valves in the mitral position. The present study aimed to investigate the leakage, hinge, and near hinge flow fields of two BMHV under simulated physiologic aortic flow conditions and to compare these results with previous findings in the mitral position to better understand how the implant location influences the valve performance and the subsequent risk of blood damage. Two and three-component Laser Doppler Velocimetry techniques were used to quantify the velocity and turbulent shear stress fields in both the hinge and the upstream leakage flow regions. The study focused on the 23 mm St. Jude Medical Regent (SJM) and the 23 mm CarboMedics (CM) valves. Although they were tested under similar physiologic conditions, shape and location of the leakage jets were dependent on valve design. Nevertheless, turbulent shear stress levels recorded within all jets were well above the threshold shear stress for the onset of blood cell damage. Within the hinge region, the flow fields were complex and unsteady. The angulated hinge recess of the CM valve appeared to promote blood damage while the streamlined geometry of the SJM valve contributed to better washout of the hinge region. Animations of the velocity flow fields are given in QuickTime or MPEG format. Comparison of the present findings with previously published results for the mitral position suggests that the superior clinical results of the mechanical valves in the aortic position may be due to less severe leakage flow upon valve closure as well as to enhanced hinge washout during the forward flow phase.

Merlin.net Patient Care Network is a St. Jude Medical product that is used for remote patient management. The basic concept of Merlin.net is to allow the physician to view patient device follow-up information as well as general patient and device information on a web application. The Merlin.net system also interfaces with the patient and will send them notification if they miss a follow-up. All device information will be collected automatically while the patient is sleeping. This information is sent through a telephone line to a Merlin.net server to process a report package and display the collected information on the Merlin.net web application. The Merlin.net verification team ensures that all reports generated by the Merlin.net servers are processed and outputted correctly. There are currently 296 device parameters supported by Merlin.net, and the manual extraction and comparison of the expected parameter values takes several hours for each patient follow-up session. Currently there are 250 patient follow-up sessions used for verification testing. Each new release will continue to create additional patient follow-up sessions. Merlin.net releases are approximately 6 months apart, and each new release adds approximately 30-50 new patient follow-up records to support the new devices. In order to meet aggressive project deadlines, while ensuring that the Merlin.net system is processing and outputting patient follow-up data correctly, it is necessary to come up with an automated process to verify the contents of the processed data is correct. This will save a tremendous amount of time as well as improve on the quality of the verification process by eliminating human error and rework. It is critical for patient safety that the patient device follow-up information is processed and outputted correctly. In this thesis an automated process was developed to verify the correct content of the Merlin.net server generated reports for each patient follow-up session. This process leveraged different tools and scripting languages to achieve automation. TDE (Test Development Environment) tool was used to extract the device parameters from the patient follow-up sessions. The TDE script was written to extracts the desired parameter values from the patient follow-up session and automatically populates parameters in a device parameters spreadsheet. Once all the device parameter values are extracted in the spreadsheet, they are passed through a set of mapping rules, which form the expected values. The mapping rules were implemented as VBA (Visual Basic for Application) macros, one macro for each report. The VBA macros write the expected values back to the spreadsheet to form an “expected values spreadsheet”. The patient follow-up session is then sent to the Merlin.net server to process, which generates a processed patient follow-up session that contains a reports package in .zip format. A perl script was then written to compare the parameter values in the Merlinet.net generated reports with the corresponding expected values from the expected values spreadsheet. The perl script generates a comparison report displaying the discrepancies between the actual and the expected values.

Mechanical heart valve (MHV) flows are characterized by high shear stress, regions of recirculation, and high levels of turbulent fluctuations. It is well known that these flow conditions are hostile to blood constituents, which could lead to thromboembolism. In the ongoing effort to reduce long-term complications and morbidity, it is imperative that we better understand the flow characteristics of the natural valve as well as that of the mechanical valve. In this study, we overcome many of the limitations imposed by other measurement techniques by employing a powerful, high-speed Time-Resolved Digital Particle Image Velocimetry (TRDPIV) system to map the flow field. We compare the flows downstream from a St. Jude Medical bileaflet MHV, a porcine mitral valve (MV), and a combination of both valves to simulate the technique of chordal preservation. Instantaneous velocity fields and vorticity maps are presented, which provide detailed information about the development of the flow. Time-averaged velocity, vorticity, and turbulent kinetic energy measurements are also discussed. Asynchronous leaflet behavior was observed in all cases involving the mechanical valve. Extensive vortex formation and propagation are present distal to the MHV, which leads to high levels of jet dispersion. The porcine mitral jet exhibits lateral oscillatory behavior, but it does not disperse like the MHV. In the MHV/porcine combination system, the native tissue limits vortex propagation and jet dispersion. The results presented provide insight on the hemodynamic characteristics of natural and MHVs, reveal the detrimental character of asynchronous leaflet opening, document the mechanism of vortex formation and interaction distal to the valve, and illustrate the importance of chordal preservation. These results may improve MHV replacement clinical practice and/or motivate and aid the design of MHVs that better mimic natural mitral flow patterns. / Master of Science

Software testing, specifically in the medical device field, has become increasingly complex over the last decade. Technological enhancements to simulate clinical scenarios and advancements in communicating to medical devices have created the need for better testing strategies and methodologies. Typical medical device companies have depended on manual testing processes to fulfill Food and Drug Administration (FDA) submission requirements specifically Class III devices which are life supporting, life sustaining devices. At St. Jude Medical, software testing of Class III devices such as implantable cardioverter-defibrillators (ICDs), pacemakers, and pacing analyzers are given top priority to ensure the highest quality in each product. High emphasis is made on improving software testing for ease of use and for catching more software errors in each device. A significant stride in testing has automated the process and has provided software verification teams with the tools they need to successfully test and deliver high quality products. By creating software libraries which interact with communication to the other interfaces needed to test medical devices, test engineers can focus on fully testing device requirements and will not be concerned with how each test will interact with the device or any other testing tools. The main focus will be a specific St. Jude Medical device known as the Pacing System Analyzer (PSA). The PSA device will be used to demonstrate how verification engineers are able to benefit from software libraries and allow the testing process and test development to be fully automated. New technologies and standards will be created to simulate clinical scenarios and to communicate to new devices. The goal is to use software engineering principles to create standard test libraries which sustain these changes while still allowing testers to focus on finding issues for each device.

Medical devices used for surgical or therapeutic purposes require a high degree of safety and effectiveness. Software is critical component of many such medical devices. The software architecture of a system defines organizational structure and the runtime characteristic of the application used to control the operation of the system and provides a set of frameworks that are used to develop that. As such, the design of software architecture is a critical element in achieving the intended functionality, performance, and safety requirements of a medical device. This architecture uses object-oriented design techniques, which model the underlying system as a set of objects that interact to achieve their goals. The architecture includes a number of frameworks comprised of a set of classes that can be extended to achieve different functionality required for a medical device. The Input/ Output (IO) framework includes a number of core classes that implement periodic and a periodic input output with varying priority requirements, provides a hardware neutral interface to the application logic, and a set of classes that can be extended to both meet the hardware IO specifics of a target platform and create new sensor and actuator types for client applications. The Devices framework provides a blueprint to develop the controller logic of the medical device in terms of abstractions that parallel the hardware components of the medical device. The Configuration framework allows creation and configuration of a medical device from an XML (Extensible Markup Specification) specification that specifies the configuration of the device based on abstract factories that can be extended to meet requirements of a specific medical device. The Controller is the component of the architecture that defines classes that implement reception of commands from and transmission of status and data to a local or remote client and dictate the structure of threads, thread priorities and policies for this purpose. The Diagnostics package of the architecture defines a framework for developing components that monitor the health of the system and detect emergency conditions. The architecture is implemented in C++ and runs on a real-time LINUX operating system. At this time, the architecture is used in development of two of the St. Jude Medical Atrial Fibrillation Division’s medical devices; one of these has FDA class III and the other class II classification.