Lab Updates (ECG Lab)Bioengineering 6000 -- SystemsPhysiology ILab Report CommentsLab III: ECG Measurement and AnalysisBIOEN 6000Spring 2011Lab Updates (ECG Lab)Bioengineering 6000 -- SystemsPhysiology IMethods• Define the three dimensional coordinate system employed• For each system:– Electrode locations– Polarity of leads– This is best described concisely with a figure (example at right taken from a classmate)Lab Updates (ECG Lab)Bioengineering 6000 -- SystemsPhysiology IGeneral Elements• Nomenclature (do not interchange):– Limb Leads: Lead I, II, or III– Frank Leads: Kpx, Kpy, Kpz – Precordial Leads: V1-6.• Unipolar vs. Bipolar• Above all else understand the figure at right:Lab Updates (ECG Lab)Bioengineering 6000 -- SystemsPhysiology IResultsDerivation of Hx and Hy• Several Approaches• Trick was noting sign conventions– Lead II: •+Hx ! +LII •+Hy ! -LII– Lead III: •+Hx ! -LIII•+Hy ! -LIII ! LII= cos(60) " Hx# cos(30) " Hy(1)LIII= # cos(60) " Hx# cos(30) " Hy(2)! Hx= LI= LII" LIII(3)Hy= "13(LII+ LIII) (4)Lab Updates (ECG Lab)Bioengineering 6000 -- SystemsPhysiology IResultsVector Loop Plots• Consistent scaling • Compare loop morphology across various lead systems.• Compare planes[B]Lab Updates (ECG Lab)Bioengineering 6000 -- SystemsPhysiology IDiscussion• Suitability of representing heart’s electrical activity as a dipole– A gross oversimplification (as many of you correctly noted in context of differences btw/ systems and the complexity that arose with BSPM)– Not without its merits… a valuable clinical diagnostic• Differences between vector loop plots of various systems– Primary cause: different electrode placement on torso• Influence of physical orientation on BSPM– Shift in heart position– Shift in additional tissues/fluid that serves as volume conductor– Which positions caused the greatest changes?Lab Updates (ECG Lab)Bioengineering 6000 -- SystemsPhysiology ISpecifics, Specifics, Specifics…• If you are presenting a result with any room for interpretation…CLARIFY– Leads selected to define the precordial xz plane (why should you choose leads off of torso instead of heart?)– Leads selected to define planes for BSPM
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