Document Detail

Preload reserve and mechanisms of afterload mismatch in normal conscious dog.
MedLine Citation:
PMID:  3953839     Owner:  NLM     Status:  MEDLINE    
Preload reserve and mechanisms of afterload mismatch were examined in 10 normal conscious dogs. The left ventricular (LV) pressure, wall thickness, and external major and minor axis diameters (sonomicrometry) were measured during sinus rhythm, and beat-averaged pressure-volume loops were generated. With maximum angiotensin II infusion, LV end-diastolic volume (EDV) increased by 13 +/- 2% (SEM), LV peak pressure (LVSP) increased by 44 +/- 6%, and stroke volume decreased by 12 +/- 3% (P less than 0.01), demonstrating an apparent descending limb of LV performance. With volume load alone, EDV increased by 9 +/- 2% from control (P less than 0.01), and stroke volume increased by 13 +/- 2%; mean wall stress during ejection was not increased, and heart rate and end-systolic pressure-volume relations showed no changes. To test whether the descending limb of function was due to maximum use of preload reserve or to inadequate venous return, angiotensin infusion was repeated during volume load. The descending limb relating LVEDV to stroke volume was always shifted upward and to the right after volume load, and the stroke volume at a comparable wall stress was 12 +/- 3% higher than during control angiotensin infusion (P less than 0.01). During pressure loading plus volume loading, the maximum EDV increase was 16 +/- 2%, and assuming unchanged afterload and end-systolic volume, an average maximum stroke volume reserve of 31 +/- 4% is calculated. 1) We conclude that sizable preload and stroke volume reserves exist in the normal resting dog; and 2) we describe a mechanism for the descending limb of LV performance curves produced by pressure loading in the intact circulation, which is related to inadequate venous return.
J D Lee; T Tajimi; J Patritti; J Ross
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  The American journal of physiology     Volume:  250     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1986 Mar 
Date Detail:
Created Date:  1986-04-18     Completed Date:  1986-04-18     Revised Date:  2003-11-14    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H464-73     Citation Subset:  IM    
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MeSH Terms
Angiotensin II / pharmacology
Blood Pressure / drug effects
Blood Volume
Heart / physiology*
Heart Rate / drug effects
Heart Ventricles
Stroke Volume / drug effects
Reg. No./Substance:
11128-99-7/Angiotensin II

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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