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This Article Full Text Full Text (PDF) All Versions of this Article: 291/5/H2547    most recent 01248.2005v2 01248.2005v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Ninio, D. M. Articles by Saint, D. A. Search for Related Content PubMed PubMed Citation Articles by Ninio, D. M. Articles by Saint, D. A.

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Passive pericardial constraint protects against stretch-induced vulnerability to atrial fibrillation in rabbits

School of Molecular and Biomedical Science, University of Adelaide, Adelaide, South Australia, Australia

Submitted 28 November 2005 ; accepted in final form 18 June 2006

Atrial fibrillation is more common in conditions with elevated atrial pressure and can be induced experimentally with acute increases in atrial pressure. We examined the effect of increased atrial pressure with and without pericardial constraint to better separate the effects of increased pressure and atrial stretch. In Langendorff-perfused rabbit hearts with intact pericardium, after ligating the pulmonary and caval veins, intra-atrial pressures were increased in a stepwise manner by adjusting the pulmonary outflow cannula. Rapid burst pacing was applied to induce atrial fibrillation at increasing intra-atrial pressures from 0 to 24 cmH₂O. The atrial refractory period was recorded at each pressure using a single extra stimulus. The protocol was repeated after the pericardium was removed. When the pericardium was intact, atrial stretch was limited by passive constraint, and sustained atrial fibrillation could not be induced despite atrial pressures in excess of 20 cmH₂O. In contrast, when the pericardium was removed, atrial fibrillation could be reliably induced when atrial pressure exceeded 15 cmH₂O. This suggests that the electrophysiological effects of acute atrial volume loading rely on atrial stretch rather than increased atrial pressure alone.

atrial refractory period; mechanoelectric feedback; Langendorff

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