Document Detail

Developmental changes in myocardial contractile reserve in the lamb.
MedLine Citation:
PMID:  4047765     Owner:  NLM     Status:  MEDLINE    
We have assessed serial changes in myocardial contractility and reserve in the normal lamb over the first month of life using an in vivo adaptation of the endsystolic pressure-volume relationship. Via a left thoracotomy, we insert a catheter tip pressure transducer into the left ventricle, affix an echo transducer onto the left ventricular epicardium, place an electromagnetic flow transducer around the pulmonary artery, and insert catheters for monitoring and infusions. We measure contractility by generating left ventricular wall stress-volume index (the cube of dimension) curves, at the same time increasing afterload by infusing phenylephrine. The slope of the endsystolic wall stress-volume index relationship is our index of contractility. Weekly studies were performed at rest and during isoproterenol infusion in 12 animals, and after propranolol administration in four. The data showed a progressive decrease in resting contractility but no change in maximal contractility during isoproterenol infusion over the 4 wk. Taking each week separately, the average increase in contractility during isoproterenol infusion was small at 1 wk (13%), moderate at 2 and 3 wk (24 and 26%, respectively), and large at 4 wk (79%). beta-Adrenergic blockade with propranolol caused a significant decrease in contractility in three of four animals studied at 1 wk, in only one of four animals at 2 wk, and in none of four animals at 3 or 4 wk. Thus, the newborn lamb shows a limited reserve in contractility that increases progressively with age; the limited reserve appears secondary to a high resting beta-adrenergic state.
D F Teitel; D Sidi; T Chin; C Brett; M A Heymann; A M Rudolph
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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:  Pediatric research     Volume:  19     ISSN:  0031-3998     ISO Abbreviation:  Pediatr. Res.     Publication Date:  1985 Sep 
Date Detail:
Created Date:  1985-11-06     Completed Date:  1985-11-06     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0100714     Medline TA:  Pediatr Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  948-55     Citation Subset:  IM    
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MeSH Terms
Animals, Newborn / growth & development*
Cardiac Output
Cardiac Pacing, Artificial
Heart / anatomy & histology
Heart Rate
Isoproterenol / pharmacology
Myocardial Contraction* / drug effects
Propranolol / pharmacology
Regression Analysis
Sheep / growth & development*
Grant Support
Reg. No./Substance:
525-66-6/Propranolol; 7683-59-2/Isoproterenol

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

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