Document Detail

Transmural coronary vasodilator reserve and flow distribution during severe exercise in ponies.
MedLine Citation:
PMID:  6874488     Owner:  NLM     Status:  MEDLINE    
Transmural distribution of myocardial blood flow and coronary vasodilator reserve (15-microns-diam radionuclide-labeled microspheres) was studied in 11 adult, healthy ponies at rest and during moderate and severe exercise performed on a treadmill (heart rate 56 +/- 4, 154 +/- 3, and 225 +/- 7 beats . min-1, respectively.). Exercise resulted in a marked increase in cardiac output, mean aortic pressure, right ventricular (RV) systolic and end-diastolic pressure, left ventricular (LV) end-diastolic pressure, and the maximum rate of rise of LV pressure LV (dP/dtmax). Accompanying these changes was a pronounced increase in transmural myocardial perfusion. During severe exercise, subendocardial/subepicardial (endo/epi) perfusion ratio for the LV (0.99 +/- 0.02) decreased significantly from control value (1.27 +/- 0.03) but it was not significantly different from 1.00. With adenosine infusion during severe exercise, transmural myocardial blood flow throughout the cardiac ventricles was able to increase significantly further (delta from severe exercise to severe exercise with adenosine, 75% for LV, 68% for septum, and 57% for RV) despite the fact that heart rate, aortic pressure, and RV and LV end-diastolic pressures were unaltered. During severe exercise with adenosine, endo:epi perfusion ratios were 1.11 +/- 0.15 and 1.32 +/- 0.10 for LV and RV, respectively. In the LV, the coronary vasodilator reserve was found to be the least in papillary muscles, where the increment in blood flow during severe exercise with adenosine was only 46% above severe exercise without adenosine. Coronary vasodilator reserve was largest in the middle layers of the LV myocardium (88%). With adenosine infusion during severe exercise, coronary vascular resistance in both LV and RV decreased significantly from that observed during severe exercise alone (27 +/- 2 and 30 +/- 2 mmHg . ml-1 . min . g, respectively) to levels observed during maximal coronary vasodilation induced by adenosine infusion at rest (20 +/- 2 and 18 +/- 2 mmHg . ml-1 . min . g, respectively). These data clearly demonstrate that there remains a marked coronary vasodilator reserve transmurally in the pony myocardium during severe exercise.
C M Parks; M Manohar
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of applied physiology: respiratory, environmental and exercise physiology     Volume:  54     ISSN:  0161-7567     ISO Abbreviation:  J Appl Physiol Respir Environ Exerc Physiol     Publication Date:  1983 Jun 
Date Detail:
Created Date:  1983-09-20     Completed Date:  1983-09-20     Revised Date:  2013-09-26    
Medline Journal Info:
Nlm Unique ID:  7801242     Medline TA:  J Appl Physiol Respir Environ Exerc Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1641-52     Citation Subset:  IM    
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MeSH Terms
Adenosine / pharmacology
Coronary Circulation* / drug effects
Coronary Vessels / physiology*
Hemodynamics / drug effects
Physical Exertion*
Reg. No./Substance:

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

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