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Acta Physiologica Congress

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Acta Physiologica 2011; Volume 203, Supplement 686
Joint Congress of FEPS and Turkish Society of Physiological Sciences
9/3/2011-9/7/2011
Istanbul, Turkey


CHANGES IN PATTERNS OF MONOPHASIC ACTION POTENTIAL MORPHOLOGY DURING ALTERNATING ATRIAL FLUTTER AND FIBRILLATION ELICITED BY ACETYLCHOLINE AND RAPID PACING IN ANESTHETIZED RABBITS
Abstract number: PC049

Aidonidis1 Isaac, Konstantinos1 Doulas, Makantasis1 Ioannis, Adam Molyvdas1 Paschalis

1Dept. of Physiology, Medical School of Larissa, University of Thessaly, Greece

Objective: 

The mechanisms of spontaneous conversions of flutter to fibrillation and inversely still remain an area of investigation. We aimed to assess changes in local atrial repolarization during the transition periods from one arrhythmia form to the other.

Methods: 

For that purpose, combination PACING/RECORDING monophasic action potential (MAP) catheters were used in 9 closed-chest ketamine-thiopental scheme anesthetized rabbits. Intravenous acetylcholine was intermittently infused at 0.02 mg/Kg/min to facilitate inducibility of either AF or AFL by rapid burst pacing. MAP recordings were manually analyzed during sustained (>30 s) episodes of the inducible arrhythmia to evaluate changes in action potential frequency and shape preceding the conversion of flutter to fibrillation and inversely. Recordings were made from a stable area during the entire experiment.

Results: 

We studied 16 episodes of the conversion between AFL and AF. Conversion of flutter into fibrillation was almost always accompanied by 3–5 faster atrial MAPs (115±11 vs. 75±10 ms cycle length, stable AFL vs. transition period). In 12/16 episodes a short interval of zero excitability (isoelectric line) was observed prior to flutter transformation. The transition of fibrillation into flutter was more complex showing a marked diversity of MAP characteristics. In the majority of cases (10/16), however, a period of flutter-like MAP transformation (slower fibrillatory waves more regular in shape) was preceded the onset of stable typical flutter.

Conclusions: 

These observations indicate distinct changes in atrial repolarization during alternating AFL/AF, presumably forming one mechanism for functional conduction block leading to either fibrillatory conduction (AFL into AF) or termination of fibrillatory conduction enabling a single reentrant circuit to recover (AF into AFL).

To cite this abstract, please use the following information:
Acta Physiologica 2011; Volume 203, Supplement 686 :PC049

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