Document Detail

Effects of asynchrony on myocardial relaxation at rest and during exercise in conscious dogs.
MedLine Citation:
PMID:  3364585     Owner:  NLM     Status:  MEDLINE    
The effect of left ventricular asynchrony induced by right ventricular pacing on relaxation indexes was studied at rest and during exercise in seven conscious dogs instrumented for chronic measurements of left ventricular pressure, coronary blood flow, and arterial pressure and with right atrial and ventricular pacing electrodes. Increasing heart rate with atrial pacing resulted in an increase in both left ventricular maximum and minimum rates of pressure development, LV dP/dtmax and LV dP/dtmin, respectively, as well as in a decrease in the relaxation constant T. In contrast, increasing heart rate with ventricular pacing resulted in a decrease in LV dP/dtmax, a small increase in LV dP/dtmin, and a significant decrease in T. During exercise with heart rate kept constant with atrial pacing, both LV dP/dtmax and LV dP/dtmin increased and T decreased to the same extent as during exercise in sinus rhythm. In contrast, exercising during right ventricular pacing resulted in a significant increase in T, expressing a slowing of relaxation. It is concluded that increasing heart rate alone in the presence of asynchrony of LV contraction induced by abnormal electrical activation results in a depressed contractile response, while the relaxation phase is not significantly affected. However, during sympathetic stimulation, a condition where synchronization should be improved, the relaxation phase is considerably lengthened.
G R Heyndrickx; P J Vantrimpont; M F Rousseau; H Pouleur
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of physiology     Volume:  254     ISSN:  0002-9513     ISO Abbreviation:  Am. J. Physiol.     Publication Date:  1988 May 
Date Detail:
Created Date:  1988-06-09     Completed Date:  1988-06-09     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0370511     Medline TA:  Am J Physiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  H817-22     Citation Subset:  IM    
Department of Physiology, State University of Ghent, Belgium.
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MeSH Terms
Adaptation, Physiological
Coronary Circulation
Heart Rate
Myocardial Contraction*
Physical Exertion*

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

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