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Synergistic Action of Atrial Dilation and Sodium Channel Blockade on Conduction in Rabbit Atria
Author(s) -
EIJSBOUTS SABINE C.M.,
HOUBEN RICHARD P.M.,
BLAAUW YURI,
SCHOTTEN ULRICH,
ALLESSIE MAURITS A.
Publication year - 2004
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.1540-8167.2004.04326.x
Subject(s) - crista terminalis , flecainide , medicine , cardiology , refractory period , atrium (architecture) , blockade , dilation (metric space) , electrophysiology , anesthesia , sodium channel , atrial fibrillation , sodium , catheter ablation , receptor , chemistry , mathematics , combinatorics , organic chemistry
The aim of this study was to investigate the interaction of atrial dilation and blockade of the rapid sodium channel on atrial conduction and degree of anisotropy. Methods and Results: The right atrium was acutely dilated by increasing intra‐atrial pressure from 2 to 9 cm H 2 O in 14 isolated rabbit hearts. A rectangular mapping array of 240 electrodes (spatial resolution 0.5 mm) was positioned on the free wall of the right atrium during pacing from four different directions at intervals of 240 and 140 msec. In nondilated atria, 0.5 and 1.0 mg/L of the use‐dependent I Na blocker flecainide prolonged the total conduction time under the mapping electrode by 15% to 75%. In dilated atria, flecainide depressed conduction by 24% to 89% (P < 0.05). The incidence of intra‐atrial conduction block increased from 0.6%–0.8% to 3.3%–7.2% in nondilated atria and from 3.9%–4.6% to 13%–21% in dilated atria (P < 0.05). The direction of activation relative to the crista terminalis and major pectinate muscles was of major importance for occurrence of conduction block. During rapid pacing, the degree of anisotropy in conduction increased by the combination of atrial dilation and flecainide (1.0 mg/L) from 1.7 ± 0.1 to 2.2 ± 0.4 (P < 0.05). The effects of dilation and flecainide on conduction were clearly synergistic. The effect of flecainide on the atrial refractory period also was enhanced by atrial dilation. Conclusion: In dilated atria, blockade of the rapid sodium channels caused a higher degree of local conduction delay and intra‐atrial conduction block than in nondilated atria.