Solidangle theory and heart rate adjustment of STsegment depression for the identification and quantification of coronary artery disease.  
MedLine Citation:

PMID: 8122616 Owner: NLM Status: MEDLINE 
Abstract/OtherAbstract:

Determinants of the STsegment response to exercise can be mathematically modeled by solidangle theory, and heart rate adjustment of the magnitude of exerciseinduced STsegment depression can remodel the solidangle relationship to provide a theoretic and practical basis for application of heart rateadjusted indexes of ST depression in exercise electrocardiography. Solidangle theory indicates that the magnitude of ST depression recorded at a surface electrode (epsilon) can be described as the product of spatial and nonspatial determinants: epsilon = (omega/4 pi).(delta Vm).K (equation 1), where omega is the solid angle subtending the boundary of the ischemic territory, delta Vm is the difference in transmembrane voltage between the ischemic and adjacent nonischemic regions, and K is a term correcting for differences in intracellular and extracellular conductivity and changes in endplate conductance. As a consequence, the magnitude of ST depression recorded by a surface electrode will be proportional both to the area of ischemic territory subtended by the recording electrode, which reflects the solid angle, and to the local transmembrane potential difference, which in turn reflects the electric consequences of the metabolic severity of ischemia at the level of the myocardial cell. It follows from equation 1 that the amplitude of ST depression can accurately reflect the area of ischemic boundary only when the severity of ischemia is constant or otherwise controlled, and differences in ST depression will only reflect varying areas of underlying ischemia when similar severity of ischemia is present. During exercise the severity of ischemia is directly proportional to changes in myocardial oxygen demand and coronary blood flow, which in turn are directly related to increasing heart rate (delta HR). Because the change in transmembrane voltage across the ischemic boundary is linearly proportional to delta HR, delta Vm/delta HR remains constant as ischemia develops. Dividing the solidangle relationship in equation 1 by delta HR and making the appropriate substitution for a constant delta Vm/delta HR then indicates that epsilon/delta HR = (omega/4 pi).(c . K) [equation 2], where c is the new constant. Under conditions where changes in conductance are proportional or small, this simplified relationship reduces to delta ST/delta HR = c'.omega [equation 3], where delta ST reflects the magnitude of ST depression recorded by the surface electrode, delta HR the change in heart rate during developing ischemia, and c' the resulting empiric constant. 
Authors:

P M Okin; P Kligfield 
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Publication Detail:

Type: Journal Article; Review 
Journal Detail:

Title: American heart journal Volume: 127 ISSN: 00028703 ISO Abbreviation: Am. Heart J. Publication Date: 1994 Mar 
Date Detail:

Created Date: 19940405 Completed Date: 19940405 Revised Date: 20060227 
Medline Journal Info:

Nlm Unique ID: 0370465 Medline TA: Am Heart J Country: UNITED STATES 
Other Details:

Languages: eng Pagination: 65867 Citation Subset: AIM; IM 
Affiliation:

Department of Medicine, New York HospitalCornell Medical Center, NY 10021. 
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MeSH Terms  
Descriptor/Qualifier:

Coronary Disease
/
diagnosis*,
physiopathology Electrocardiography* Exercise Test Heart Rate / physiology* Humans Models, Cardiovascular Models, Theoretical 
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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