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Atrial Fibrillation in the Goat Induces Changes in Monophasic Action Potential and mRNA Expression of Ion Channels Involved in Repolarization
Author(s) -
VELDEN HUUB M.W.,
ZEE LUCIE,
WIJFFELS MAURITS C.E.F.,
LEUVEN CARLO,
DORLAND RICK,
VOS MARC A.,
JONGSMA HABO J.,
ALLESSIE MAURITS A.
Publication year - 2000
Publication title -
journal of cardiovascular electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.193
H-Index - 138
eISSN - 1540-8167
pISSN - 1045-3873
DOI - 10.1046/j.1540-8167.2000.01262.x
Subject(s) - medicine , repolarization , atrial action potential , atrial fibrillation , cardiology , effective refractory period , cardioversion , electrophysiology , anesthesia
MAP Changes and Ion Channel Expression in Goat AF. Introduction: Sustained atrial fibrillation (AF) is characterized by a marked shortening of the atrial effective refractory period (AKRP) and a decrease or reversal of its physiolonic adaptation to heart rate. The aim of the present study was to investigate whether the AF‐induced changes in AKKP in the goat are associated with changes in the atrial monophasic action potential (MAP) and whether an abnormal expression of specific ion channels underlies such changes. Methods and Results: Following thoracotomy, MAPs were recorded from the free wall of the right atrium hoth before induction of AF (control) and after cardioversion of sustained AF (>2 months) in chronically instrumented goats. In control goats. MAP duration at 80% repolarization (MAPD 80 ) shortened (P < 0.01) from 132 ± 4 msec during slow pacing (400‐msec interval) to 86 ± 10 msec during fast pacing (180 msec). After cardioversion of sustained AF, the MAPD 80 , during slow pacing was as short as 67 ± 5 msec (electrical remodeling). Increasing the pacing rate resulted in prolongation (P = 0.02) of the MAPD 80 to 91 ± 6 msec. Also. MAPD 20 (20% repolarization) shortened (P = 0.05) from 32 ± 4 msec (400 msec) to 14 ± 7 msec (180 msec) in the control goats, whereas it prolonged (P = 0.03) from 20 ± 3 msec (400 msec) to 33 ± 5 msec (180 msec) in sustained AF, mRNA expression of the L‐type Ca 2+ channel α1c gene and Kv1.5 potassium channel gene, which underlie Ic a , and I kur respectively, was reduced in sustained.AF compared with sinus rhythm hy 32% (P = 0.01) and 45% (P < 0.01). respectively. No significant changes were found in the mRNA levels of the rapid Na + channel, the Na + /Ca 2+ exchanger, or the Kv4.2/4.3 channels responsible for I 10 . Conclusion: AF‐induced electrical remodeling in the goat comprises shortening of MAPD and reversal of its physiologic rate adaptation. Changes in the time course of reploarization of the action potential are associated with changes in mRNA expression of the α subunit genes of the L.‐type Ca 2+ channel and the Kvl.5 potassium channel.