Document Detail

Toward consistent definitions for preload and afterload.
MedLine Citation:
PMID:  11824209     Owner:  NLM     Status:  MEDLINE    
Significant differences exist among textbook definitions for the terms preload and afterload, leading to confusion and frustration among students and faculty alike. Many faculty also chose to use in their teaching simple terms such as "end-diastolic volume" or "aortic pressure" as common-usage approximations of preload and afterload, respectively, but these are only partial representations of these important concepts. Straightforward definitions both of preload and afterload that are concise yet still comprehensive can be developed using the Law of LaPlace to describe the relationships among chamber pressure, chamber radius, and wall thickness. Within this context, the term "preload" can be defined as all of the factors that contribute to passive ventricular wall stress (or tension) at the end of diastole, and the term "afterload" can be defined as all of the factors that contribute to total myocardial wall stress (or tension) during systolic ejection. The inclusion of "wall stress" in both definitions helps the student appreciate both the complexities of cardiac pathophysiology and the rationale for therapeutic intervention.
J M Norton
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Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Advances in physiology education     Volume:  25     ISSN:  1043-4046     ISO Abbreviation:  Adv Physiol Educ     Publication Date:  2001 Dec 
Date Detail:
Created Date:  2002-02-04     Completed Date:  2002-07-11     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  100913944     Medline TA:  Adv Physiol Educ     Country:  United States    
Other Details:
Languages:  eng     Pagination:  53-61     Citation Subset:  IM    
Department of Physiology and Pharmacology, University of New England, College of Osteopathic Medicine, Biddeford, Maine 04005, USA.
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MeSH Terms
Heart / physiology*
Myocardial Contraction / physiology*
Osteopathic Medicine / education*
Terminology as Topic*
Comment In:
Adv Physiol Educ. 2003 Dec;27(1-4):44-5; author reply 89-90   [PMID:  12594075 ]

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