Document Detail


Effects of afterload on regional left ventricular torsion.
MedLine Citation:
PMID:  8759247     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
OBJECTIVE: To determine if left ventricular torsion, as measured by magnetic resonance tissue tagging, is afterload dependent in a canine isolated heart model in which neurohumoral responses are absent, and preload is constant. METHODS: In ten isolated, blood perfused, ejecting, canine hearts, three afterloads were studied, while keeping preload constant: low afterload, high afterload (stroke volume reduced by approx. 50% of low afterload), and isovolumic loading (infinite afterload). RESULTS: There were significant effects of afterload on both torsion (P < 0.05) and circumferential shortening (P < 0.0005). Between low and high afterloads, at the anterior region of the endocardium only, where torsion was maximal, there was a significant reduction in torsion (15.1 +/- 2.2 degrees to 7.8 +/- 1.8 degrees, P < 0.05). Between high afterload and isovolumic loading there was no significant change in torsion (7.8 +/- 1.8 degrees to 6.2 +/- 1.5 degrees, P = NS). Circumferential shortening at the anterior endocardium was significantly reduced both between low and high afterload (-0.19 +/- 0.02 to -0.11 +/- 0.02, P < 0.0005), and also between high afterload and isovolumic loading (-0.11 +/- 0.02 to 0.00 +/- 0.02, P < 0.05). Plots of strains with respect to end-systolic volume demonstrated a reduction in both torsion and shortening with afterload-induced increases in end-systolic volume. Torsion, but not circumferential shortening, persisted at isovolumic loading. CONCLUSIONS: Maximal regional torsion of the left ventricle is afterload dependent. The afterload response of torsion appears related to the effects of afterload on end-systolic volume.
Authors:
G A MacGowan; D Burkhoff; W J Rogers; D Salvador; H Azhari; P S Hees; J L Zweier; H R Halperin; C O Siu; J A Lima; J L Weiss; E P Shapiro
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Cardiovascular research     Volume:  31     ISSN:  0008-6363     ISO Abbreviation:  Cardiovasc. Res.     Publication Date:  1996 Jun 
Date Detail:
Created Date:  1996-10-11     Completed Date:  1996-10-11     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0077427     Medline TA:  Cardiovasc Res     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  917-25     Citation Subset:  IM    
Affiliation:
Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD 21224, USA.
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MeSH Terms
Descriptor/Qualifier:
Animals
Computers
Dogs
Heart / anatomy & histology,  physiology*
Heart Ventricles
Magnetic Resonance Imaging
Models, Cardiovascular
Perfusion
Stroke Volume / physiology*
Torsion Abnormality
Grant Support
ID/Acronym/Agency:
R01-HL-38324/HL/NHLBI NIH HHS; R01-HL-43722/HL/NHLBI NIH HHS; R01-HL-46223/HL/NHLBI NIH HHS

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