Alterations in atrial electrophysiology associated with chronic atrial fibrillation in man

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Abstract
Background The purpose of this study was to determine the changes in atrial electrophysiology associated with chronic persistent atrial fibrillation in man. Methods and Results Atrial monophasic action potential duration at 90% repolarization and the effective refractory period were measured in 13 patients with chronic persistent atrial fibrillation after low-energy endocardial cardioversion, and compared to eight controls without a history of atrial fibrillation. Measurements were made at the right atrial appendage and midlateral right atrial wall at basic, 600ms and 400ms drive cycle lengths. In control patients, the effective refractory periods were significantly longer at the atrial appendage than the lateral wall at 600ms (right atrial appendage 265ms, midlateral right atrial wall 228ms, PPP0·001) reached statistical significance. Effective refractory period dispersion was significantly greater in controls than in patients with atrial fibrillation (cycle length 600ms: controls 36, atrial fibrillation 13, P=0·01; cycle length 400ms: controls 54, atrial fibrillation 18, PConclusions In patients without a history of atrial fibrillation, the refractory period at the right atrial appendage is significantly longer than at the midlateral right atrial wall. This ‘normal’ pattern of atrial refractory dispersion is lost in patients with chronic persistent atrial fibrillation, with marked shortening of the effective refractory period at the right atrial appendage. This may explain the high risk of recurrence of atrial fibrillation following successful electrical cardioversion.

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