Age-associated changes in electrophysiologic remodeling: a potential contributor to initiation of atrial fibrillation.
Cardiovasc Res
; 66(2): 353-63, 2005 May 01.
Article
em En
| MEDLINE
| ID: mdl-15820204
ABSTRACT
OBJECTIVE:
Although the incidence of atrial fibrillation (AF) increases with age, the cellular electrophysiological changes that render the atria of aged individuals more susceptible to AF remain poorly understood. We hypothesized that dispersion of atrial repolarization increases with aging, creating a substrate for initiation of AF.METHODS:
Four groups of dogs were studied adult and old dogs in normal sinus rhythm (SR) and adult and old dogs with chronic AF (CAF) induced by rapid atrial pacing. In each dog, action potentials (AP) were recorded with microelectrodes from isolated endocardial preparations of four regions of right atrium and three regions of left atrium. Two indices of AP duration (APD) heterogeneity were obtained in each dog by calculating standard deviation (SD) and the coefficient of variation (COV=[SD/mean] x 100%).RESULTS:
In SR groups, APD averaged across all regions was significantly longer in old than in adult tissues. Both indices of APD heterogeneity were higher in old dogs in comparison to adult. At both ages, CAF was associated with significant APD shortening and a decrease in APD adaptation to rate. While CAF significantly increased both indices of APD heterogeneity in adult dogs, it significantly decreased them in old dogs.CONCLUSIONS:
The increase of spatial variability in repolarization in old atria may contribute to the initiation of AF in the aged. CAF-induced APD shortening and a decrease in APD adaptation appear to be important for the maintenance of sustained AF in both adult and old atria. The CAF-induced increase in dispersion of repolarization may be important for AF stabilization in adults, while previously reported fibrosis and slowed conduction of premature beats may be important in the old for both AF initiation during SR and subsequent stabilization of AF.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Fibrilação Atrial
/
Envelhecimento
/
Coração
Tipo de estudo:
Risk_factors_studies
Limite:
Animals
Idioma:
En
Revista:
Cardiovasc Res
Ano de publicação:
2005
Tipo de documento:
Article
País de afiliação:
Estados Unidos