Date of Award
Spring 2005
Document Type
Thesis - Restricted
Degree Name
Master of Science (MS)
Department
Biomedical Engineering
First Advisor
Ropella, Kristina M.
Second Advisor
Euler, David E.
Third Advisor
Audi, Said H.
Abstract
If the heart is activated by a pair of closely coupled depolarizations, the following beat shows augmented contractility. This phenomenon has been observed in both isolated cardiac muscle and intact hearts and has been termed postextrasystolic potentiation (PESP). 1-3 When paired or coupled pacing is used to evoke a premature beat after every beat in the intact heart, the positive inotropic response is sustained.4,5 Since the premature beats do not develop enough pressure to open the aortic valve and eject blood from the ventricles, the mechanical heart rate (pulse rate) is half of the electrical heart rate. Dual chamber coupled pacing (DCCP) is a new method of coupled pacing involving atrial and ventricular premature stimuli coupled to the intrinsic ventricular event. The coupling interval between the ventricular sensed event and the ventricular coupled pace is called the extrasystolic interval (ESD. Maximum potentiation is observed when the ventricle is just outside of the effective refractory period (ERP), and the degree of potentiation decreases nonlinearly as the ESI increases. 2-4, 6-9. A clear understanding of ventriculo-arterial coupling, how the arterial system responds to the enhanced myocardial performance, is necessary in determining the clinical or therapeutic usefulness of dual chamber coupled pacing. Since ventricular power relates to both contractility and afterload, it is in a sense a measure of coupling between the heart and the arterial system. 10 The primary objective of this thesis is to assess the effects of dual chamber coupled pacing and extrasystolic interval on external afterload and hydrodynamic efficiency of left ventricular energy transfer (a measure of ventriculo-arterial coupling). This will be accomplished by calculating aortic input impedance and left ventricular power components from aortic pressure and flow measurements in acutely instrumented canines during dual chamber coupling pacing at a range of ESIs. Chapter 1 reviews the concept of ventriculo-arterial coupling as well as the mechanisms of action and clinical relevance of postextrasystolic potentiation. The chapter concludes with the underlying hypothesis and motivation for this thesis. A description of the experimental procedure, protocol, and biomedical engineering data analysis methods is contained in Chapter 2. Key components of the analysis include correction of pressure and flow phase delay, normalization of ESI, and the calculation of aortic input impedance and hydrodynamic efficiency. In Chapter 3, the results showing the effects of dual chamber coupled pacing and extrasystolic interval on external afterload and hydrodynamic efficiency are detailed. Chapter 4 discusses these results and reflects on the implications of this work. Potential areas of future investigation are also presented.
Recommended Citation
Jaye, Deborah A., "The Hydrodynamic Efficiency of Left Ventricular Energy Transfer During Dual Chamber Coupled Pacing" (2005). Master's Theses (1922-2009) Access restricted to Marquette Campus. 4849.
https://epublications.marquette.edu/theses/4849