氧化应激对心房颤动犬心房肌细胞凋亡及凋亡相关蛋白影响的研究

目的 观察普罗布考(probucol)对长期心房快速起搏诱发心房颤动(房颤)犬心房肌细胞凋亡及凋亡相关蛋白表达的影响,探讨氧化应激在房颤心房结构重构中的作用.方法 杂种犬20只,随机分为假手术组(n=6)、对照组(n=7)和普罗布考组(n=7).无菌条件下开胸后在犬右心房缝植4对心外膜记录电极,电极尾端经皮下由犬背部穿出;在右心耳缝植螺旋型起搏电极,连接实验用AOO高频起搏器(400次/min),心房快速起搏6周,建立房颤犬模型;假手术组犬仅缝植心外膜记录电极和起搏电极但不起搏;对照组及普罗布考组犬心房快速起搏6周;普罗布考组于起搏前一周开始服用普罗布考(100 mg·kg-1·d-1),直至起搏结束.TUNEL法检测心房肌细胞凋亡情况;免疫组化方法及免疫印记法检测凋亡相关蛋白caspase-3、bcl-2和bax表达情况;免疫组化方法检测calpain Ⅰ表达;比色法检测心房肌总抗氧化能力(T-AOC)、丙二醛(MDA)和抗超氧阴离子(抗O2-)水平;于起搏前、起博6周后,经心外膜电极记录各组犬房颤诱发情况.结果 与假手术组犬相比,对照组犬左、右心房肌凋亡细胞数量显著增加[(44.3±9.7)% vs (1.36±0.70)%,(42.1±11.9)% vs (1.07±0.50)%,P＜0.01],心房肌caspase-3、bax和calpain Ⅰ表达明显上调(P＜0.01),bcl-2表达显著下调(P＜0.01).与对照组犬相比,普罗布考组犬左、右心房肌凋亡细胞数量明显减少[(21.4±5.8)% vs (44.3±9.7)%,(20.1±6.1)% vs (42.1±11.9)%,P＜0.01],calpain Ⅰ、caspase-3和bax表达显著下调(P＜0.01),bcl-2表达增加(P＜0.05).与假手术组犬相比对照组犬心房肌MDA水平明显增加(P＜0.01),T-AOC、抗O2-水平明显降低(P＜0.01);与对照组犬相比,普罗布考组犬心房肌MDA水平显著降低(P＜0.05),T-AOC、抗O2-水平显著增加(P＜0.01).对照组和普罗布考组起搏后房颤诱发率和平均持续时间均较起搏前显著增加(P＜0.05);起搏后普罗布考组房颤诱发率较对照组降低(P＜0.05),房颤平均持续时间显著减少(P＜0.01).结论 普罗布考可能通过抑制氧化应激,增加bcl-2表达,降低calpain Ⅰ、caspase-3和bax表达,阻止长期心房快速起搏诱发房颤犬心房肌细胞凋亡,对房颤心房结构重构防治有益,能够减少房颤发生.     

心房颤动患者心房肌动作电位时程频率适应性研究

目的　研究阵发性孤立性心房颤动 (房颤 )患者及对照组心房肌动作电位时程 (APD)频率适应性的差异 ,阐明其与房颤发生有关的可能机制。方法　应用同时具有起搏功能的Ag AgCl电极记录单向动作电位 (MAP) ,房颤组和对照组各入选 11例患者 ,在逐渐递减的 9个起搏周长分别记录MAP并测量APD90 、APD90 50 。所有房颤患者MAP记录前 1个月无房颤发作史 ,以排除电重塑影响。结果　在较长起搏周长 (6 0 0、5 5 0、5 0 0ms) ,房颤组APD90 显著短于对照组 (P <0 0 5 ) ;在较短起搏周长(340、30 0、2 80ms) ,房颤组APD90 又显著长于对照组 (P <0 0 5 )。同样APD90 50 在较长起搏周长 (6 0 0、5 5 0、5 0 0、4 6 0ms) ,房颤组显著短于对照组 (P <0 0 5 ) ;而较短起搏周长 (340、30 0、2 80ms)两组无差别。结论　心房肌APD频率适应性曲线在阵发性孤立性房颤组与对照组有所不同 ,其可能与房颤的最初发生和维持有关 ,机制存在于离子通道水平。     

原代心房肌细胞培养及快速起搏细胞模型的建立

目的:利用原代培养的心房肌细胞建立快速起搏模型,对心房颤动(房颤)早期的重构现象进行初步研究。方法:原代培养大鼠心房肌细胞,并建立快速电场刺激起搏细胞模型,利用全细胞膜片钳技术记录刺激前后心房肌细胞的动作电位周期,透射电镜观察细胞超微结构的变化。结果:培养至第4天,细胞生长密度可以达到瓶底70%左右,数目可达(2~3)×109/L,经免疫细胞化学鉴定,90%以上培养细胞α-肌动蛋白抗体染色阳性;全细胞膜片钳记录了培养心房肌细胞及经电场刺激(600次/min,1·5V/cm)24h后的心房肌细胞的动作电位周期,动作电位周期分别为(64·2±4·6)ms和(56·6±4·1)ms,刺激前后差异有统计学意义(P<0·05)。透射电镜观察到刺激后心房肌细胞超微结构发生去分化改变。结论:经快速起搏24h后,心房肌细胞发生了电及结构重构;利用原代培养的心房肌细胞建立快速起搏的房颤模型,可以对房颤早期的重构机制进行研究。     

犬慢性快速心房起搏心房颤动模型的建立

报道犬慢性快速心房起搏心房颤动 (简称房颤 )模型的建立方法。取杂种犬 13只 ,安置实验用埋藏式高频率心脏起搏器快速起搏 ( 3 70～ 4 0 0次 /分 )心房 8～ 10周。于起搏前及起搏 8～ 10周后行经胸超声心动图、心房程序电刺激和burst刺激。 10只犬完成实验。快速起搏前所有犬均未能用心房程序刺激诱发出持续性房颤 ( >15min) ,2只 ( 2 0 %)可用burst刺激诱发出非持续性房颤。起搏 8～ 10周后 ,3只 ( 3 0 %)犬不需诱发即出现房颤。 8只 ( 80 %)可经程序刺激诱发出持续性房颤 ,其平均持续时间为 5 3± 11min。 10只犬 ( 10 0 %)均可用burst刺激诱发出持续性房颤。超声心动图检查显示快速起搏后犬心房面积显著增大 (左房 :6.4± 1.3cm2 vs 11.1± 1.8cm2 ;右房 :4 .2± 1.1cm2 vs 7.8± 1.3cm2 ,P均 <0 .0 0 1)。结论 :犬慢性快速心房起搏房颤模型具有房颤诱发率高、持续时间长、重复性好等特点。     

心房细胞的电重构与逆向电重构的研究

目的采用经典的玻璃微电极技术,观察快速起搏及自主神经递质、β受体阻滞剂和钙通道阻滞剂对心房肌细胞跨膜动作电位及其恢复过程的影响,探讨观察房性快速性心律失常中的电重构(ER)和逆向电重构(RER)现象。方法健康豚鼠35只取出心脏,剪下左心耳,取大约2×5mm大小的肌条。用充满3mol/L氧化钾的玻璃微电极插入心房肌,记录动作电位。观察复极30%、50%、90%时的动作电位时程(APD30、APD50、APD90)、有效不应期(ERP)、动作电位振幅(APA)、静息电位(RMP)。灌流台氏液中分别加入丙基肾上腺素(ISO)、乙酰胆碱(Ach)、去甲肾上腺素(NA),艾司洛尔(Esm)和地尔硫卓(Dil)平衡20min后记录上述指标并观察其恢复过程。结果快速心房刺激可出现明显的心房电重构,心房快速刺激终止后电重构特性逐步恢复,表现为逆向电重构。乙酰胆碱和丙基肾上腺素可延长快速起搏后动作电位和有效不应期的恢复。艾司洛尔和地尔硫卓均可改善短时间快速刺激后动作电位的恢复。我们提出的心脏电学顿抑是心脏的重要电生理特性之一。     

普罗布考对快速起搏心房犬心房颤动发生与心房结构的影响及机制探讨

目的研究普罗布考对快速起搏犬心房颤动(AF)发生及心房结构的影响,并探讨其机制。方法 21只杂种犬被随机分为假手术组(n=7)、起搏组(n=7)和普罗布考组(n=7)。起搏组和普罗布考组犬行心房400次/分快速起搏6周。普罗布考组于起搏前1周给予普罗布考(100 mg·kg-1·d-1)直至起搏结束。起搏前和起搏6周后,分别测定各组犬AF诱发率和持续时间;TUNEL法观察心房肌细胞凋亡;Masson染色观察心房间质纤维化;比色法检测丙二醛(MDA)和总抗氧化能力(T-AOC)。免疫组化法和Western-blot法检测心房肌聚ADP核糖聚合酶-1(PARP-1)和凋亡诱导因子(AIF)蛋白表达。结果与假手术组比较,起搏组AF诱发率和持续时间较起搏前显著增加(P0.01),心房肌细胞凋亡指数和心房肌纤维化程度显著增加(P0.01);起搏组MDA水平显著增加,T-AOC水平明显地下降(P0.05),心房肌PARP-1和AIF表达明显增加(P0.001)。与起搏组比较,普罗布考组AF诱发率降低,AF持续时间缩短,MDA水平降低和T-AOC水平提高,心房肌细胞凋亡数量和心房肌纤维化程度减少,PARP-1和AIF蛋白表达下调。结论普罗布考可降低氧化应激程度,下调心房肌PARP-1表达,延缓电重构和心房结构重构,减少AF发生。     

培哚普利联合醛固醇受体拮抗剂对心房纤颤犬心房结构重构的影响

目的:观察培哚普利和螺内酯及二者联用对长期心房快速起搏诱发心房纤颤(房颤,AF)犬心房结构和功能重构的影响。方法:实验犬24只,随机分为4组,即对照组、培哚普利组(P组)、螺内酯组(S组)和二者联用组(P+S组)。各组心房快速起搏8周,建立AF犬模型。分别于起搏前、起搏4周及8周测定血浆血管紧张素II(AngII)和醛固酮(Ald)水平;起搏前及起搏后8周,测定左心房结构和功能变化;起搏8周后停止起搏,观察各组犬AF维持的例数及AF自行持续时间;Masson染色检测各组犬心房肌胶原容积分数(CVF)改变。结果:与对照组相比,P组、S组和P+S组犬起搏4周和8周后血浆AngII及Ald水平明显降低,起搏8周后左心房左右径、上下径、收缩末期容积和舒张末期容积明显减小,左心房射血分数显著增大,停止起搏后AF维持率明显减少,AF平均持续时间明显缩短,CVF值明显降低。而3个用药组相比差异无统计学意义。结论:培哚普利和醛固酮受体拮抗剂(螺内酯)能够阻止长期心房快速起搏AF犬心房结构功能的改变及心房纤维化,减少AF发生率及持续时间,但二者联用效果并不优于单药。     

牛磺酸对甲亢豚鼠心室肌细胞电生理特性的影响

目的观察牛磺酸(Taurine T)对甲状腺机能亢进(以下简称甲亢)豚鼠离体心室肌细胞动作电位的影响,探讨牛磺酸对甲亢豚鼠心室肌细胞电活动的影响及其机制.方法采用微电极技术,引导心室肌细胞动作电位,观察在甲亢状态下牛磺酸对心室肌细胞动作电位各参数的影响.结果 (1)甲亢组豚鼠心室肌细胞动作电位时程(APD20, APD50, APD90, APD)及有效不应期(ERP)显著缩短,甲亢豚鼠心室肌细胞动作电位幅度(APA),零期最大除极速率(Vmax)无显著性变化;(2)加入牛磺酸后,甲亢豚鼠心室肌细胞动作电位时程APD50, APD90, APD显著延长,而APD20及动作电位幅度(APA)无显著变化 ,零期最大除极速率(Vmax)显著降低,ERP显著延长;(3)给甲状腺功能正常组加入牛磺酸后,豚鼠心室肌细胞动作电位时程APD20, APD50, APD90显著缩短,APD亦有缩短,但无显著性差别,ERP显著延长,APA无显著性变化,Vmax显著性降低.结论 (1)较高浓度的牛磺酸可能对甲亢豚鼠的离体心室肌细胞膜的外向(主要是K )电流具有一定的抑制作用;(2)对甲状腺功能正常豚鼠的心室肌细胞,一定程度上,可能促进钾外流;(3)无论是正常组还是甲亢组,在加入牛磺酸后,Vmax均出现显著降低,提示较高浓度的牛磺酸对心室肌细胞的INa也有影响.     

依那普利和厄贝沙坦及血管紧张素-(1-7)对快速心房起搏犬心房肌瞬时外向钾电流及L型钙电流的影响

目的研究依那普利、厄贝沙坦及血管紧张素-(1-7)[Ang-(1-7)]对快速心房起搏犬心房肌瞬时外向钾电流(Ito)、L型钙电流(ICa-L)及其基因表达的影响。方法普通杂种犬30只,分为假手术(S)组、心房起搏对照(C)组、依那普利(EN)组、厄贝沙坦(IB)组及Ang-(1-7)(A)组,每组6只。C组以特制起搏器维持500次/分右房起搏2周,S组安置起搏器但不予起搏刺激。EN组、IB组和A组,右房起搏同时分别给予依那普利、厄贝沙坦、Ang-(1-7)治疗至实验结束。观察心房肌细胞Ito、ICa-L和动作电位时程(APD)的变化,以及ItoKv4.3亚单位和ICa-Lα1C亚单位mRNA在心房组织的表达。结果与S组比较,心房起搏后,各刺激频率下C组和EN组APD复极达90%时程(APD90)显著缩短。IB组和A组,APD90缩短不显著。S组、IB组、A组,随着刺激频率增加APD90缩短,C组、EN组无此特征。除EN组外,不同刺激频率下,各组复极达50%时程(APD50)变化均不显著。与S组比较,C组、IB组Ito最大电流密度显著降低(P0.05),EN组显著升高(P0.01);C组、EN组、IB组ICa-L最大电流密度低于S组(P0.01)。C组、IB组Kv4.3mRNA转录水平低于S组(P0.01),EN组显著升高(P0.01)。C组、EN组、IB组、A组ICa-Lα1CmRNA转录水平较S组显著降低(P0.01)。结论依那普利、厄贝沙坦和Ang-(1-7)对快速心房起搏犬心房肌Ito、ICa-L及APD的影响不同。     

犬心房颤动时T型钙通道在心房电重塑中的作用及机制探讨

目的探讨犬心房颤动(房颤)时T型钙通道在心房电重塑中的作用及机制。方法将2002年2月至2006年10月北京大学人民医院动物实验的杂种犬15条,分为3组,每组5条,分别为正常对照组、单纯房颤组和房颤 mibefradil组。房颤组在右心房植入起搏器进行快速起搏建立犬慢性房颤模型;房颤 T型钙通道阻滞剂mibefradil组在起搏术后第2天开始给mibefradil(术后稳定24h)。正常对照组不植入起搏器。采用电生理检查方法测定房颤的持续时间和心房有效不应期;胶原酶Ⅱ型分离心房肌细胞,激光共聚焦显微镜检测Ca2 通道阻滞剂对细胞内Ca2 浓度变化的影响。结果(1)术前的心房有效不应期为280/90~110ms。起搏24周时,房颤 mibefradil组的心房有效不应期延长为2000/1400~1700ms。起搏24周时单纯房颤组中有75%的犬呈自身持续性房颤,而房颤 mibefradil组有20%呈持续性房颤,其余犬在给予短阵猝发刺激(500/min)时可诱发出房颤,持续时间为1~6min。(2)正常对照组的心房肌细胞在阻滞L型Ca2 通道后细胞内Ca2 浓度没有明显改变(1.17±0.09OD比值),单纯房颤组在阻滞L型Ca2 通道后细胞内Ca2 浓度明显升高(2.35±1.05OD比值),与正常对照组比较差异有显著性意义(P<0.05),而房颤 mibefradil组在阻滞L型Ca2 通道后细胞内Ca2 浓度比单纯房颤组下降30%(2.05±0.90OD比值)。(3)正常对照组、单纯心房颤动组和房颤 mibefradil组的心房肌细胞在阻滞T型Ca2 通道后细胞内Ca2 浓度均增高(1.49±0.17,1.53±0.33和1.38±0.35OD比值),且3组间比较差异均无显著性意义。结论(1)T型Ca2 通道阻滞剂能够明显延长房颤时的心房有效不应期,并能缩短房颤的持续时间,但并不能阻止房颤的发生;(2)房颤时心房肌细胞的T型Ca2 电流增加,而L型Ca2 电流减少,提示T型Ca2 通道可能在房颤时的心房肌细胞内Ca2 超载机制中起主要作用。     

应用单相动作电位研究房颤模型心房电重构的发生机制

目的应用单相动作电位(MAP)技术检测心房颤动模型电生理参数改变的特点,探讨房颤电重构发生的分子机制。方法健康杂种犬17只,随机分为房颤组(n=11)和对照组(n=6)。房颤组安装固定频率起搏器,以350~430次/min的频率快速心房起搏,对照组行假手术。于起搏前和8周后测量右房有效不应期(AERP)和单相动作电位,测量单相动作电位振幅(MAPA)、单相动作电位时限(MAPD)、复极90%时动作电位时限(MAPD90)、复极50%时动作电位时限(MAPD50)、复极90%动作电位时限与复极50%动作电位时限之差(MAPD90-50)。原子发射光电直读光谱法测定心房肌组织Ca2+含量。RT-PCR法检测心房肌浆网Ca2+-ATP酶和L型钙通道mRNA转录水平。结果对照组MAP时相明显。房颤组MAP形态发生改变。与对照组相比,房颤组MAPA有下降趋势;MAPD,MAPD90,MAPD50,MAPD90-50分别缩短13.79%,19.65%,13.59%和31.25%。MAPD,MAPD90,MAPD90-50与右房心肌Ca2+呈显著负相关;MAPD90-50与L型钙通道显著正相关。上述指标与肌浆网钙ATP酶均无相关性。结论 MAP是研究房颤电重构的可靠手段,心房肌细胞膜L型钙通道和肌浆网Ca2+-ATP酶mRNA表达改变可能是电重构的分子机制之一     

Effect of 60 Minutes of Rapid Atrial Pacing on Atrial Action Potential Duration in the In-Situ Canine Heart

Right atrial monophasic action potentials were recorded before and after 60 minutes of rapid atrial pacing (pacing cycle length (CL); 127 ± 10 ms) in 12 closed-chest dogs. The right atrial (RA) monophasic action potential (MAP) duration at 90% repolarization (RAMAPD) was measured at CLs of 400 ms and 250 ms. CL-dependent changes in RAMAPD (CL 400 ms – 250 ms) before and after rapid atrial pacing were 24 ± 1 ms and 16 ± 5 ms, respectively (p < 0.02). RAMAP was recorded at each atrial pacing CL starting at 240 ms decreasing by 10-ms increments. RAMAPD alternans was observed in 10 of 12 dogs at a CL of 163 ± 17 ms before and in 10 of 12 dogs at s CL of 198 ± 29 ms (p < 0.01) after rapid atrial pacing. Sustained atrial fibrillation (AF) (>5 minutes) was induced in 1 of 12 dogs at a pacing CL of 130 ms before rapid atrial pacing and in 4 of 12 dogs at a pacing CL of 135 ± 17 ms after rapid atrial pacing. Onset of AF was always preceded by the RAMAPD alternans. Sixty minutes of rapid atrial pacing leads to diminution of rate adaptation of atrial action potential duration (APD) and appearance of APD alternans of greater magnitude at longer CL, both of which may contribute to the initiation and perpetuation of AF during its early phase.     

Action potential duration restitution kinetics in human atrial fibrillation

OBJECTIVES: We undertook this study to determine whether human atrial fibrillation (AF) relates to steeply sloped action potential duration restitution (APDR) kinetics and whether the spatial nonuniformity of APDR promotes persistence of AF. BACKGROUND: A steeply sloped APDR curve is known to be an important determinant of the induction of more complex action potential duration (APD) dynamics and fibrillation. METHODS: Patients with chronic atrial fibrillation (CAF) (n = 18), paroxysmal atrial fibrillation (PAF) (n = 14) and normal control subjects (n = 9) were studied. The monophasic action potential duration at 90% repolarization (APD(90)) and the effective refractory period (ERP) were measured at six sites in the right atrium. After AF was electrically converted, APDR was assessed by delivering a single extrastimulus after a train of stimuli at a cycle length of 600 ms (S(1)S(2)) at six different sites of the right atrium, as well as rapid pacing at cycle lengths that induced APD alternans. RESULTS: The APD(90) and ERP in patients with CAF were shorter than those in patients with PAF and control subjects (p < 0.05); however, the dispersions of APD(90) and ERP in each group were similar. The maximal slopes of APDR by S(1)S(2) and rapid pacing in patients with CAF (1.2 +/- 0.4 and 1.7 +/- 0.2) and PAF (1.1 +/- 0.4 and 1.3 +/- 0.4) were higher than those in control subjects (0.5 +/- 0.3 and 0.8 +/- 0.2, respectively; p < 0.01). The maximal slope obtained by S(1)S(2) did not differ from that obtained by rapid pacing in any group. The inter-regional difference of the maximal slope in patients with CAF (1.6 +/- 0.4, p < 0.05) was greater than that in patients with PAF (1.2 +/- 0.3, p = NS vs. control) and control subjects (0.4 +/- 0.2). CONCLUSIONS: Atrial fibrillation was related to steeply sloped (>1) APDR kinetics. The spatial dispersion of APDR in patients with chronic AF was greater than that of patients with paroxysmal AF and control subjects, indicating that the heterogeneity of APDR of the atrium plays an important role in the persistence of AF.     

Age-associated changes in electrophysiologic remodeling: a potential contributor to initiation of atrial fibrillation

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.     

迷走神经和肺静脉刺激对心房肌动作电位和乙酰胆碱激活钾电流的影响

目的研究迷走神经和肺静脉快速刺激对心房肌动作电位和乙酰胆碱激活钾电流的影响。方法24只犬随机分为3组,每组8只犬。对照组：采用20Hz频率和0．2ms波宽刺激迷走神经,观察诱发心房颤动（房颤）情况。左上肺静脉（LSPV）刺激组：快速刺激LSPV4h,观察刺激前后左有心房和LSPV动作电位时限（APD）的变化,随后行迷走神经刺激,观察诱发房颤情况。迷走神经干预组：先采用5Hz频率、0．2ms波宽和5～10V电压刺激迷走神经30min,然后快速刺激LSPV4h,观察刺激前后APD的变化,冉迷走神经刺激观察诱发房颤情况。所有犬在电生理检测后开胸取心脏,分离LSPV和左右心房肌细胞,采用膜片钳技术观察乙酰胆碱激活钾电流（IK,ACh）变化。结果LSPV刺激组,APD。明显缩短,动作电位时限高散度（dAPD90）明显增加[（5±3）msVS（14±5）ms,P〈0．05]。迷走神经干预组,APD。无明显变化,但APD90-d明显增加[（6±3）mvs vs（12±5）ms,P〈0．05]。与对照组相比,LSPV刺激组细胞Ik、ACh明显增加,但对照组与迷走神经干预组相比,IK．ACh差异无统计学意义。结论APD缩短是胆碱能房颤诱发的基础,肺静脉快速刺激可增加IK．ACh密度,快速刺激前行迷走神经能阻止电重构的发生。     

Heterogeneous pulmonary vein myocardial cell repolarization implications for reentry and triggered activity

BACKGROUND: Myocardial cells in the pulmonary veins (PVs) are thought to play a major role in the initiation and maintenance of atrial arrhythmias, including atrial fibrillation. However, systematic single-cell microelectrode recordings from different regions in intact PV-atrial tissues are lacking. OBJECTIVES: The purpose of this study was to determine the transmembrane action potential properties of myocardial cells in different regions of the PV and the left atrium (LA) and assess their arrhythmogenic potential during perfusion with isoproterenol (ISO) and rapid atrial pacing. METHODS: Glass microelectrode recordings of action potentials were made from the left PV and the LA in Langendorff-perfused young (3-4 month) male rats (Fisher344) (n = 9). RESULTS: Action potential duration (APD) of atrial and PV cells had similar duration at a pacing cycle length (CL) of 200 ms. However, shortening of the pacing CL to 100 ms led to heterogeneous repolarization of PV cells. Mid-PV cells had a significantly higher maximum slope of APD restitution than atrial or other PV sites. Intra-PV conduction block developed at rates when LA and proximal PV cells manifested 1:1 capture. Perfusion of ISO and rapid atrial pacing promoted the emergence of early afterdepolarization (EAD) and triggered beats in two out of nine tissues, causing premature atrial activation. No difference in resting potential or AP amplitude could be detected among the PV and LA cells. CONCLUSIONS: PV myocardial cells develop marked heterogeneity in repolarization, and there is a slight ease of developing EAD and triggered activity in response to rapid pacing and ISO infusion.     

Remodeling of Ca(2+)-handling by atrial tachycardia: evidence for a role in loss of rate-adaptation

BACKGROUND: Loss of rate-dependent action potential (AP) duration (APD) adaptation is a characteristic feature of atrial tachycardia-induced remodeling (ATR). ATR causes sarcolemmal ion-channel remodeling (ICR) and changes in Ca(2+)-handling. The present studies were designed to quantify Ca(2+)-handling changes and then to apply a mathematical AP model to assess the contributions of Ca(2+)-handling abnormalities and ICR to loss of APD rate-adaptation. METHODS: Indo-1 fluorescence was used to measure intracellular Ca(2)-transients and whole-cell patch-clamp to record APs in atrial myocytes from control dogs and dogs subjected to atrial pacing at 400/min for 6 weeks. A previously developed ionic model of the canine atrial AP was modified to reproduce measured Ca(2+)-transients of control and ATR myocytes. RESULTS: In control, APD to 95% repolarization (APD(95)) decreased by 91 ms experimentally and by 88 ms in the model over the 1-6 Hz range. In ATR myocytes, APD(95) failed to decrease over the 1-6 Hz range. Ca(2+)-handling abnormalities in ATR myocytes included slowed upstroke, decreased amplitude and strong single-beat post-rest potentiation. Unaltered Ca(2+)-handling properties included caffeine-releasable Ca(2+)-stores and Ca(2+)-transient relaxation before and after exposure to the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor cyclopiazonic acid (CPA). Including ICR alone in the model accounted for loss of APD(50) rate-adaptation; however, KR alone reduced APD(95) rate-adaptation by only 19% to 71 ms. When both ICR and Ca(2+)-handling changes were incorporated, APD(95) rate-adaptation decreased to 6 ms, accounting for experimental observations. CONCLUSION: ICR alone does not fully account for loss of APD rate-adaptation with atrial remodeling: Ca(2+)-handling changes appear to contribute to this clinically significant phenomenon.     

心房颤动中钙耦联蛋白表达的实验研究

采用逆转录聚合酶链式反应 (RT PCR)方法研究起搏房颤 (AF)模型心房肌钙耦联蛋白———L型钙通道α1c亚基和肌浆网Ca2 + ATP酶的基因表达情况以及药物的干预作用。选择成年杂种犬 15条 ,随机分为起搏组 (P组 )、起搏及口服维拉帕米组 (PV组 )和对照组 (C组 )。采用心房猝发刺激诱发AF。其中P组和PV组的犬在诱发AF后置入起搏脉冲发生器作心房快速 ( 4 0 0次 /分 )起搏 7天。PV组的犬于起搏第 2天起给予维拉帕米缓释剂 12 0mg/天口服。第 7天再次诱发AF后将动物处死 ,于左、右心房和房间隔部位取材进行RT PCR扩增。结果 :心房快速起搏 7天后 ,阵发性AF和持续性AF的发生率明显增加。而加用维拉帕米后AF的发生率和起搏前没有差异。以 β actin为内参照的RT -PCR结果显示起搏组心房肌的L型钙通道α1c亚基和肌浆网Ca2 + ATP酶的mRNA水平明显降低(和C组相比分别降低 4 3 %和 4 0 %,P <0 .0 1)。而PV组第 7天心房肌L型钙通道α1c亚基和Ca2 + ATP酶的mRNA水平和C组相比则没有显著差异 (P >0 .0 5 )。心房不同部位之间的mRNA水平没有差异。结论 :心房起搏AF模型中心房肌细胞钙耦联蛋白L型钙通道α1c亚基和肌浆网Ca2 + ATP酶的基因表达明显下调 ;钙通道阻断剂维拉帕米可预防心房电重构和心房肌钙耦联蛋白的下调。     

快速心房起搏对犬心房功能的影响

应用声学定量技术评价心房颤动 (简称房颤 )犬心房功能。通过建立犬快速心房起搏房颤模型 ,应用声学定量技术记录 8只犬起搏前 ,起搏 1,4 ,8周时停止起搏后的左右房容量 时间曲线 ,并计算相关指标。结果 :左房储存器容积在起搏过程中无明显改变 ;管道容积在起搏 8周后较起搏前及起搏 1周时显著增加 (P均 <0 .0 1) ;左房射血分数在起搏 1,4 ,8周时较起搏前显著下降 (P分别 <0 .0 1,<0 .0 1,<0 .0 0 1) ;左房心室收缩末期容积、快速排空末期容积、心室舒张末期容积 ,心房排空容积在起搏 1周 ,4周时较起搏前增加 ,起搏 8周时较起搏前及起搏 1周时增加 ;峰值心房排空率在起搏 4周时下降 ,起搏 8周时较起搏前及起搏 1周时显著降低。右房储存器容积 ,管道容积在起搏过程中无明显变化 ;右房射血分数起搏 8周后较起搏前及起搏 1周时显著降低 (P分别 <0 .0 0 1,<0 .0 1) ;右房心室收缩末期容积 ,快速排空末期容积 ,心室舒张末期容积在起搏 4周时增加 ,起搏 8周时较起搏前及起搏 1周时增加 ;峰值心房排空率在起搏 8周时较起搏前及起搏 1周时下降。结论 :快速心房起搏使左、右房助力泵功能受损 ,左房管道功能增强 ,而对双房储存器功能无明显影响。     

持续快速心房起搏对犬肺静脉肌袖组织结构的影响

探讨持续快速心房起搏对犬肺静脉肌袖组织结构的影响。 1 4条杂种犬 ,其中起搏犬 8只 ,对照犬 6只。起搏犬以 40 0次 /分的频率持续起搏右心房 9～ 1 0周 ,对照犬仅放置起搏导线及起搏器 ,但不起搏。 9～ 1 0周后对所有犬均进行心房颤动 (简称房颤 )的诱发 ,并取其肺静脉组织进行HE染色、Masson′s染色和电镜检查。结果 :终止起搏后起搏犬的持续房颤 ( >1 5min)诱发率为 87.5 % ( 7/8) ,显著高于对照犬 ( 0 % ,P <0 .0 1 )。起搏犬肺静脉肌袖组织的光镜特征为心肌细胞变性 ,胶原组织大量增生 ;电镜下变性心肌细胞的超微结构异常主要累及线粒体和肌原纤维。对照犬肺静脉肌袖组织的形态学未见明显病理改变。结论 :持续快速心房起搏可导致犬的肺静脉肌袖组织发生显著的形态学重构 ,后者可能与该模型房颤的机制有关。