Document Detail

Interaction of oscillatory processes: the effects of subthreshold A.C. current on sinoatrial nodal rhythm.
MedLine Citation:
PMID:  870579     Owner:  NLM     Status:  MEDLINE    
In this study of interactions occurring within the heart, isolated superfused strips of rabbit atria, containing the sinoatrial (s.a.) node, were subjected to sinusoidal subthreshold current pulses of varied frequencies and intensities. A.C. current from an R.C. oscillator was applied through a Grass stimulation isolation unit, push-pull connection, and non-polarizing (Ag-AgCl-KCl-Tyrode Agar-Agar) electrodes. A Grass polygraph and tachometer were used to record the applied pulses and nodal firing rates; simultaneous magnetic tape recordings were obtained and used for data analysis. Suction electrode recordings and oscilloscope displays were used to determine how the cyclic impulses affected cellular activity. The s.a. nodal rhythm was modified by subthreshold A.C. current applications; when frequencies were low, firing rates of the node were modulated by the A.C. and mean rates were reduced. As frequencies were progressively increased, slow waxings and wanings in heart rate were produced. These periodic fluctuations were not readily correlated with either the A.C. frequency nor the intrinsic nodal rate, but were representative of the difference between the two. As applied current frequency neared the pacemaker's intrinsic rate, a synchronization occurred and the discharges locked in at a specific phase of the applied current alternation. This synchronization maintained during slight further increases in A.C. frequency but above a critical rate this relationship broke down and the waxing and wanings in frequency of pacemaker rate again developed. It was concluded that pacemaker action of the s.a. node is effected by integration of cellular activity through electron coupling.
J Ushiyama; C M Brooks
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Publication Detail:
Type:  In Vitro; Journal Article    
Journal Detail:
Title:  Journal of electrocardiology     Volume:  10     ISSN:  0022-0736     ISO Abbreviation:  J Electrocardiol     Publication Date:  1977 Apr 
Date Detail:
Created Date:  1977-06-30     Completed Date:  1977-06-30     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0153605     Medline TA:  J Electrocardiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  165-70     Citation Subset:  IM    
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MeSH Terms
Action Potentials
Electric Stimulation*
Sinoatrial Node / physiology*

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

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