Document Detail

Effects of tachycardia on the adequacy of subendocardial oxygen delivery in experimental aortic stenosis.
MedLine Citation:
PMID:  1155327     Owner:  NLM     Status:  MEDLINE    
We studied the interaction of tachycardia and aortic stenosis on the adequacy of subendocardial oxygen delivery. In 18 open-chest dogs with acute supravalvular aortic stenosis, we produced subendocardial ischemia by increasing either heart rate (artrial pacing) or the severity of aortic stenosis. Ischemia was determined from ST-elevation of the intracavitary electrocardiogram. Subendocardial oxygen supply was assessed by measuring subendocardial flow (radioactive microspheres, 8 to 10 microns) and arterial oxygen content, and related to simultaneous oxygen demand [estimated from the tension time index (TTI)]. The adequacy of the supply/demand relationship in the subendocardium was estimated from the ratio DPTI times 02 content (supply)/TTI (demand). Subendocardial ischemia occurred at aortic gradients ranging from 30 to 100 mm. Hg and heart rates from 120 to 180 beats per minute. Ischemic hearts were characterized by (1) redistribution of coronary flow away from the subendocardium (endo/epi flow ratio less than 1.0), (2) reduced subendocardial oxygen delivery per unit of demand (TTI) (p less than 0.01), (3) failure to lower left ventricular end-diastolic pressure with tachycardia, and (4) supply/demand ratios (DPTI times 02 content/TTI) below 15 ( less than 0.01). These findings suggest that (1) the principal determinant of subendocardial ischemia in aortic stenosis is the unfavorable alteration of the supply/demand relationship caused by the interaction between heart rate and severity of stenosis, rather than absolute heart rate or aortic gradient and (2) the adequacy of subendocardial oxygen delivery can be assessed from readily obtained measurements of blood pressure and oxygen content.
J R Brazier; G D Buckberg
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  American heart journal     Volume:  90     ISSN:  0002-8703     ISO Abbreviation:  Am. Heart J.     Publication Date:  1975 Aug 
Date Detail:
Created Date:  1975-11-01     Completed Date:  1975-11-01     Revised Date:  2007-11-15    
Medline Journal Info:
Nlm Unique ID:  0370465     Medline TA:  Am Heart J     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  222-30     Citation Subset:  AIM; IM    
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MeSH Terms
Aortic Valve Stenosis / metabolism*
Blood Flow Velocity
Blood Pressure
Cardiac Output
Cardiac Volume
Catecholamines / metabolism
Coronary Circulation
Coronary Disease / metabolism
Heart Rate
Myocardium / metabolism*
Oxygen Consumption*
Tachycardia / metabolism*
Reg. No./Substance:

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

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