老龄兔心房电生理特征及其与心房颤动的易感性

The stdudy of electrophysiological characteristics and susceptibility on atrial fibrillation in aging hearts of rabbits

目的探讨老龄兔心房电生理特征及其与心房颤动(AF)的易感性。方法记录青龄(青龄组,n=15)和老龄(老龄组,n=15)兔清醒状态下模拟II导联心电图,测量P波间期和离散度,PR、RR和QT间期以及心率。麻醉开胸暴露心脏,记录在体心房肌组织单相动作电位,测量复极化恢复到10%、20%和90%时程(APD_(10)、APD_(20)和APD_(90))、平台期电位(plateau P)、最大上升速率(Max_(dv/dt))。以基础刺激周长为300 ms、200 ms和150 ms测量心房肌组织的有效不应期(AERP)及其离散度(dERP)和频率自适应性(fERP),Burst刺激诱发AF的起搏间期和诱发率。酶解法分离两组的单个心房肌细胞,全细胞膜片钳技术记录各组心房肌细胞短暂外向钾电流(I_(to))及其电流-电压(I-V)相关性曲线。结果与青龄组比较,老龄组P波间期、P波离散度、PR间期、RR间期和QT间期均显著延长,心率变慢(P均<0.05)。另外,老龄组的APD_(10)和APD_(20)缩短,平台期电位减小,APD_(90)延长以及Max_(dv/dt)加快均更显著(P均<0.05)。且ERP和fERP缩短,dERP和诱发AF的BCL延长均更明显(P<0.01),AF诱发率增加(P<0.05)。在电压钳制方案下,老龄组兔心房肌细胞I_(to)明显减小,I-V曲线下移。当钳制电位为+50 mV时,老龄组兔心房肌细胞I_(to)为(12.8±0.9)pA/pF明显小于青龄组的(16.8±0.7)pA/pF(P<0.001)。结论老龄兔的心脏电生理特征发生了明显的电重构,增加了AF的易感性而易于诱发AF。

Objective To investigate the electrophysiological characteristics and susceptibility on atrial fibrillation(AF)in aging hearts of rabbits.Methods The experimental animals were composed by young and old male New Zealand rabbits.The young rabbits were participated young goup(n=15),and the old rabbits were taken part in old group(n=15).The some main electrical parameters in 2 groups were recorded such as P duration,PR interval,and P wave dispersion from normalⅡlead electrocardiogram,and plateau potential(plateau P),action potential duration of 10%,20%and 90%(APD_(10),APD_(20),APD_(90))from recording of monophasic action potential(MAP),as well as atrial effective refractory period(AERP),dispersion and frequency self adaptation of AERP(dERP,fERP),inducibility and duration of AF by recording with 300 ms,200 ms and 150 ms of basic cycle length(BCLs)and Burst-pacing in left atrium tissue of rabbits in vivo.The Transient outward potassium current(I_(to))was recorded via whole-cell patch clamp technique in enzymatically dissociated single rabbit atrial myocytes in young and old age goup.Results Compared with young group,some main data with normalⅡlead electrocardiogram were notably modified in old goup,such as P wave duration and dispersion,PR interval,RR duration and QT ineterval were respectively prolongated,as well as heart rate was significant slower(all P<0.05).Moreover,compared with young group,APD_(10) and APD_(20) were significantly shortened,Max_(dv/dt) and Plateau V were obviously decreased,APD_(90) was completedly prolongated in rabbits of old group(all P<0.05).Otherwise,the AERP and fERP was significantly shortened,and dERP was increased,as well as BCL value was prolongated,at last the induced rate of AF was obviously increased in rabbit atrium of old group(all P<0.05).At last and with voltage clamp model,the I_(to) was significantly decreased,and the I-V correlationship curve was obviously downward with different command potential in atrial cells of old group ompared with that of young group.When holding potential was-50 mV and command potential was+50 mV,the current densities of I_(to) were significantly decreased much more in old goup than that in young group[(16.8±0.7)pA/pF vs(12.8±0.9)pA/pF,P<0.01].Conclusion The atrial electrical remodeling in aged atrium of rabbits might be increased to facilitate susceptibility of AF,which might contribute to occurrence of AF in old rabbit.[Chinese Journal of Cardiac Pacing and Electrophysiology,2021,35(2):163-167]