Effect Of Valsartan On Atrial Electrical Remodeling And Ultrastructure Changes Induced By Rapid Atrial Pacing

Objective: Atrial fibrillation is the most common cardiac arrhythmia. It has relatively high mortality and can easily lead to chronic disability. So far the mechanism of atrial fibrillation is not completely known, and it is difficult to prevent and treat this disease now. During the last few years, the mechanism research gets big progress, and the management strategy of atrial fibrillation must be changed to intervene in the mechanism. Now the effect of renin-angiotensin system on atrial remodeling has been emphasized. This study is to investigate the effect of rapid atrial pacing on atrial electrophysiological characteristics, to evaluate the effect of valsartan on atrial electrical remodeling and ultrastructure changes induced by rapid atrial pacing.Methods: Twenty-four New Zealand big ear rabbits were randomly divided into three groups :normal control group (distilled water 10ml/d,n=8) and rapid atrial pacing group(distilled water 10ml/d,n=8) and valsartan group (valsartan 10mg/kg·d, in distilled water 10ml, n=8). After two weeks' pretreatment, each rabbit of the rapid atrial pacing group and valsartan group was paced with the rate of 600 per minute for 8 hours. The atrial effective refractory period (AERP) was measured with S1S2 programmed electrical stimulation at pre-pacing (after autonomic blockade), during pacing (0.5, 1, 2, 4, 6, 8 hours) and post-pacing(10min,30min). To determine the rate adaptation , the AERPs were measured in the right atrial appendage at 3 pacing cycle lengths (250,200,150ms) respectively. At last, the right atrial appendage tissue specimen was fixated and examined by electron microscope in order to observe the ultrastructure. Ca²⁺ content was measured by biochemical technique. Results: The AERPs was shortened and the rate adaptation of AERP was lost...