Document Detail

If in left human atrium: a potential contributor to atrial ectopy.
MedLine Citation:
PMID:  15485684     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: The left human atrium plays an important role in initiation of atrial fibrillation (AF) and the hyperpolarization activated cation current (I(f)) is a candidate for contributing to abnormal automaticity. However, electrophysiological data concerning I(f) are not available in this cardiac region and we therefore investigated I(f) in human left atrial tissue. METHODS: Human atrial myocytes were isolated from the left atrial appendage (LAA) and the left atrial wall (LAW) obtained from patients undergoing open heart surgery. I(f) was measured with the whole-cell patch-clamp technique. RESULTS: I(f) densities between -70 and -110 mV were found to be significantly higher in LAA than in LAW cells. Furthermore, in the group of LAA cells the half maximal activation potential (V(1/2)) was found to be less negative (V(1/2) of -84.3+/-1.9 mV, n=14/9) compared to LAW cells (V(1/2) of -97.8+/-2.1 mV, n=28/9). Beta-adrenergic receptor stimulation with isoproterenol (1 microM) caused an acceleration of current activation and a V(1/2) shift to more positive potentials in cells of both regions (LAA: 8.8+/-2.3 mV, n=6/4 and LAW: 8.9+/-2.6 mV, n=6/4). Simulations using a mathematical model of the human atrial myocyte demonstrated that I(f) was able to induce spontaneous activity in the model at a regular rhythm due to the interplay of I(f), Na(+)/Ca(2+) exchange current and Ca(2+) release of the sarcoplasmic reticulum (SR). CONCLUSIONS: Our study revealed the presence of I(f) in left atrial myocytes and showed that I(f) parameters depend on atrial region. I(f) current densities were sufficient to convert the mathematical model of a quiescent human atrial cell into a "pacemaker cell". These data support the hypothesis of I(f) as a contributor to abnormal automaticity in human atrial tissue.
Klaus Zorn-Pauly; Peter Schaffer; Brigitte Pelzmann; Petra Lang; Heinrich Mächler; Bruno Rigler; Bernd Koidl
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Cardiovascular research     Volume:  64     ISSN:  0008-6363     ISO Abbreviation:  Cardiovasc. Res.     Publication Date:  2004 Nov 
Date Detail:
Created Date:  2004-10-15     Completed Date:  2005-01-10     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0077427     Medline TA:  Cardiovasc Res     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  250-9     Citation Subset:  IM    
Institut für Medizinische Physik und Biophysik, Medizinische Universität Graz, Harrachgasse 21, A-8010 Graz, Austria.
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MeSH Terms
Adrenergic beta-Agonists / pharmacology
Atrial Premature Complexes / physiopathology*
Computer Simulation*
Electric Stimulation
Heart Atria
Ion Channels / physiology*
Isoproterenol / pharmacology
Models, Cardiovascular*
Myocytes, Cardiac / metabolism*
Patch-Clamp Techniques
Reg. No./Substance:
0/Adrenergic beta-Agonists; 0/Cations; 0/Ion Channels; 7683-59-2/Isoproterenol
Comment In:
Cardiovasc Res. 2004 Nov 1;64(2):195-7   [PMID:  15485677 ]

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