T-type calcium channel effects on atrial electrical remodelling and an approach to its mechanisms during atrial fibrillation / 中国实用内科杂志

ABSTRACT

Objective To inquire into T-type calcium channel effects on atrial electrical remodelling and its mechanisms during atrial fibrillation.Methods Animal experiment was performed in Peking University Pepole's Hospital from Feb.2002 to Oct.2006.Fifteen adult cross-bred dogs were used in the experiment.Ten dogs underwent continuous rapid atrial pacing(500 beats/min)for twenty-four weeks to create persistent atrial fibrillation.In five rapidly-paced dogs,50mg pure powder/day of mibefradil dihydrochloride was given from the second day after pacemaker implantation and continued until the twenty-fourth week.A group of size-matched dogs(n=5)without being given mibefradil was used as a pure atrial fibrillation group.Another group of size-matched dogs(n=5)without pacemaker implantation was used as a control group.Atrial fibrillation duration was determined by electrophysiological study.Canine atrial myocytes were isolated by enzymatic dissociation and intracellular Ca2+ cytosolic transient was studied with confocal imaging.Results (1)The preoperation atrial effective refractory period was 280/90~110 ms.In the twenty-fourth week after rapid atrial pacing,atrial effective refractory period was obviously extended(2000/1400~1700 ms)in the T-type Ca2+ channel blocker group compared with the preoperation one.In the twenty-fourth week,the induced rate of persistent atrial fibrillation was 75% in atrial fibrillation group,whereas the persistent atrial fibrillation occurred in only one case(20%)in the T-type Ca2+ channel blocker group.(2)Intracellular Ca2+ concentration of atrial myocytes was unremarkably changed in control group after blocking L-type Ca2+ channel(1.17?0.09 OD ratio),whereas the intracellular Ca2+ concentration was obviously enhanced(2.35?1.05 OD ratio)(P