טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentMeiry Gideon
SubjectElectrical Properties of Altered Activation
Patterns in Neonatal Rat Ventricular Myocytes
Cultures; Model and Implications
DepartmentDepartment of Medicine
Supervisor Professor Emeritus Ofer Binah
Full Thesis textFull thesis text - English Version


Abstract

The heart is a rhythmic electromechanical pump, the function of which depends on action potential excitation and propagation causing contraction, followed by relaxation and a period of refractoriness until the next impulse is generated. However, normal beat-to-beat excitation sequence may be altered during pathological conditions, leading to impaired cardiac activation (arrhythmias). Consequently, cardiac pumping efficacy may be reduced and patients may suffer from inadequate circulation. The mechanisms that promote alterations in the normal cardiac excitation sequence are diverse, and not fully understood. Hence, the purpose of this Thesis was to develop a model for studying altered activation patterns in cardiomyocytes networks.

Dissociated neonatal rat ventricular myocytes (NRVM) which forms confluent beating networks were grown on a Micro Electrode Array (MEA) and their electrical activity was recorded. This unique setup was new and therefore not established. Thus, model developing required building a variety of tools, including tools for cultures maintenance, data acquisition and data analysis. The model was validated by studying the effects of altered activation patterns on the waveform shape, the activation patterns and the pacemaker(s) behavior.

To enhance culture stability and activity we developed a novel 'out-of-the-incubator' perfusion system which constantly provides the culture with fresh medium while maintaining constant pH and sterility. Recording modes alternated automatically between full raw data and activation timing giving data for activation patterns and beat-rate-variability analyses (respectively). In addition, the model was designed to support a verity of clinical and practical studies, e.g., hypoxia conditions and new pharmacologic compounds. All analyses were conducted by special Matlab® tools we designed and wrote.

Our results demonstrated that altered activation pattern (given by pacing) is more likely to remain dominant in the culture after pacing termination if it mimics a formally observed pattern. Also we found that beat-to-beat variations studied by using non-linear dynamics (fractals) analyses methods remained similar regardless of the discrete pacemaker which was beating. Finally, our findings demonstrated that the model we developed is stable, and supports well controlled long term (> one week) in vitro studies of NRVM networks electrophysiological properties.