Linked Life Data

8184945

Source:http://linkedlifedata.com/resource/pubmed/id/8184945

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4 Pt 2
pubmed:dateCreated
1994-6-10
pubmed:abstractText
Discrete theoretical methods, compatible with the discrete features of the beating heart, are used together with experimental study to attain a quantitative understanding of the transient response to a volume perturbation and of sustained mechanical alternans (SMA) in the beating heart. This is done in three stages. In stage A, a first-order difference equation describes the stroke volume (SV) response due to the Frank-Starling mechanism. It is shown that the value of gamma, the slope of the SV-end-diastolic volume curve, determines the type of response obtained because of a perturbation: 1) nonoscillatory decay for gamma < 1,2) oscillatory decay for 1 < gamma < 2, 3) SMA for gamma = 2, and 4) chaotic response for gamma > 2. In stage B, when the effect of each SV change on the successive end-diastolic aortic pressure (P) is considered, SV response to a perturbation is determined by a second-order difference equation. The solution of this equation shows that the response is determined by gamma and by the afterload factor lambda 1 = alpha 1.delta, where alpha 1 = delta Pj + 1/delta SVj and delta = delta SVj + 1/delta Pj + 1. The responses are a nonoscillatory decay for lambda 1 < 1 - gamma (type 1), oscillatory decay for 1 - (gamma/2) > lambda 1 > 1 - gamma (type 2), SMA for lambda 1 = 1 - gamma/2 (type 3), and 2:1 electrical-mechanical response for lambda 1 > 1 - gamma/2 (type 4). In stage C, a single volume perturbation, delta SVj, will directly affect not only Pj + 1 but also the subsequent values of P. Filling volume perturbations performed with a mitral valve occluder in eight anesthetized dogs led only to type 1 and 2 responses. The responses predicted by the model (using the experimental values of gamma and lambda 1) in each of the eight open-chest dogs are compatible with the experimental responses, suggesting that it is unlikely that SMA is initiated and maintained by variations in preload and afterload.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0002-9513
pubmed:author
pubmed:issnType
Print
pubmed:volume
266
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
H1657-71
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1994
pubmed:articleTitle
Modeling the transient response to volume perturbations in the beating heart by the difference equation method.
pubmed:affiliation
Department of Biomedical Engineering, Hadassah University Hospital, Ein Kerem, Jerusalem, Israel.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.