持续性心房颤动患者心房肌内向整流钾电流的研究

目的研究不同病程持续性心房颤动(房颤)患者心房肌内向整流钾电流(IK1)的变化,探讨其与房颤自我发展的可能关系。方法采用急性酶消化法分离单个心房肌细胞。以窦性心律(窦律)的风湿性心脏病患者为对照,应用膜片钳全细胞技术记录房颤≤6个月和>6个月的风湿性心脏病患者心房肌IK1。结果与窦律组相比,在-50~-100mV之间,房颤≤6个月组心房肌IK1密度无明显改变,房颤>6个月组心房肌IK1密度绝对值明显增大(P<0.05)。与房颤≤6个月组相比,房颤>6个月组心房肌IK1密度绝对值也明显增大(P<0.05)。在-100mV,IK1密度绝对值在窦律组为(4.05±0.96)pA/pF(n=18),房颤≤6个月组为(4.35±0.49)pA/pF(n=18),房颤>6个月组为(8.94±0.15)pA/pF(n=18)。结论心房肌IK1在持续性房颤自我发展过程的表现不同,IK1的这种表现可能有利于房颤的自我发展。     

持续性心房颤动患者心房肌细胞L型钙通道电流变化的研究

目的比较窦性心律(窦律)患者和持续性心房颤动(房颤)患者心房肌细胞L-型钙通道电流密度及通道电压依赖的激活和失活特性变化。方法应用两步酶解法获得单个人体心房肌细胞,采用常规全细胞膜片钳技术记录L-型钙通道电流,观察18例窦律患者和12例持续房颤患者右心房肌L-型钙通道电流密度及动力学特性变化。结果(1)持续房颤组与窦律组相比,L-型钙通道电流密度降低,测试脉冲从-40~0mV时的L-型钙通道电流密度分别为(-4.58±0.39)pA/pF(n=21)和(-1.32±0.19)pA/pF(n=12),两组比较P<0.01。(2)动力学特性:窦律组与持续房颤组比较,通道激活曲线参数半数最大激活电压(V1/2)、斜率因子(K)以及失活曲线参数半数最大失活电压(V1/2)、斜率因子(K)差异均无统计学意义。结论持续房颤患者心房肌细胞L-型钙通道电流密度明显降低,其通道动力学特性变化差异无统计学意义。L-型钙通道电流密度的变化是房颤时“心房电生理重构”离子机制之一。     

心房颤动心房肌细胞短暂外向钾电流的特点

观察心房颤动 (AF)心房肌细胞的电生理特点 ,探讨短暂外向钾电流 (Ito)与AF电重构的关系。采用组织块酶消化法分离 7例AF(AF组 )和 14例非AF(非AF组 )患者的右心耳心房肌细胞 ,利用全细胞记录技术观察单个心房肌细胞的Ito。在各钳制电位下 ,AF组的Ito值均明显低于对照组。钳制电位在 + 60mV时AF组的Ito值 ( 14 2 .87±4 2 .2 5pA)与非AF组 ( 4 80 .12± 3 9.2 4pA)相比 ,减少 70 .2 4 %(P <0 .0 0 1)。在各钳制电位下 ,AF组的稳态电流 (Isus)均高于非AF组。钳制电位在 + 60mV时AF组的Isus值 ( 83 1.88± 72 .90pA)与非AF组 ( 5 4 3 .93± 65 .3 4pA)相比 ,增加 5 2 .94 %(P <0 .0 1)。随着刺激频率的增加 ,AF与非AF患者心房肌细胞在钳制电位 + 60mV时的Ito强度逐渐降低 ,与非AF组不同的是 ,AF组心房肌细胞的Ito在刺激频率 1～ 2Hz间电流改变的差异具有显著性。结论 :AF心房肌不应期的缩短与Ito的降低有关 ,Ito可能是AF电重构的离子机制 ,Isus可能也参与了电重构的发生。     

心房颤动患者心房肌细胞离子重塑及缬沙坦的干预研究

目的研究心房颤动(房颤)患者心房肌电生理重塑机制并探讨缬沙坦在房颤患者治疗中的作用及可能机制. 方法经典两步酶解法分离单个心房肌细胞,膜片钳全细胞法记录离子电流,并分别观察缬沙坦(10 μmol/L)对房颤组和窦性心律(窦律)组心房肌细胞各离子电流的影响. 结果 (1)与窦律组比较房颤组心房肌细胞L型钙电流(ICa-L)密度降低(P<0.001),瞬间外向钾电流(Ito1)密度降低(P<0.001),内向整流性钾电流(IK1)在超极化状态密度增加(P<0.05).两组超速激活延迟整流性钾电流(IKur)和快速内向钠电流(INa)差异无显著性.(2) 缬沙坦灌流前后两组心房肌细胞各离子电流自身前后对比以10 μmol/L缬沙坦灌流后,房颤组心房肌细胞INa密度峰值减少65.68%(P<0.001),膜电位+50 mV时IKur密度减少30.70%(P<0.05),膜电位-120 mV时IK1密度减少23.32% (P<0.05);窦律组心房肌细胞仅INa密度峰值减少59.49%(P<0.001),IKur和IK1无显著改变.缬沙坦对房颤和窦律组心房肌细胞Ito1及ICa-L无显著影响. 结论心房肌细胞ICa-L、Ito1密度降低而超极化状态时IK1密度增加,是房颤患者心房肌电生理重塑的重要离子基础;缬沙坦对房颤患者心房肌细胞离子电流表现出异于窦律患者的作用,可能有利于改善房颤导致的心房电重塑.     

慢性心房颤动患者心房肌细胞超快速激活钾电流的研究

目的　研究风湿性心脏病 (RHD)慢性心房颤动 (房颤 )使心房肌细胞膜超快速激活钾电流 (IKur)的变化 ,探讨离子通道改变在房颤时心房电重构 (AER)中的作用。方法　采集 2 3例RHD患者(房颤组 12例 ,窦性心律组 11例 )心房肌标本 ,采用急性酶解法 ,将组织块分解以获得游离的心房肌细胞 ;应用膜片钳全细胞技术 ,记录两组患者心房肌细胞膜IKur电流 ,并对比分析两组的电流 电压曲线以及稳态激活和失活的动力学特性。结果　在钳制电位 + 10mV～ + 50mV时 ,房颤组IKur密度明显低于窦性心律组 (P <0 0 5) ;其中 ,除极化至 + 50mV时 ,密度分别为 (4 92± 1 48)pA/pF(n =19个细胞 )和 (9 3 1± 1 44) pA /pF(n =2 1个细胞 ,P <0 0 1)。房颤组右心房细胞IKur的激活最大电导较窦性心律组明显降低 ,分别为 (2 75± 0 55)nS(n =2 1个细胞 )和 (4 74± 0 63 )nS(n =2 1个细胞 ,P <0 0 1)。房颤组在 + 50mV时的失活率为 56% ,低于窦性心律组 (P <0 0 5) ,而两组的稳态激活和失活特征的差异无显著性。结论　现有数据显示 ,IKur密度的改变可能是慢性房颤时AER中多种离子通道重构的重要机制之一 ,可能与房颤时心肌细胞的传导性、不应期等改变有关 ,与房颤发生和持续的关系和潜在的治疗性意义尚需进一步研究阐明     

心肌小电导钙激活钾通道及与心房颤动关系的研究进展

小电导钙激活钾通道在哺乳动物心肌组织中高度表达,参与心肌细胞动作电位复极末期,对动作电位时程和形态有重要影响。小电导钙激活钾通道在维持心脏正常功能活动中起重要作用。现就心肌组织小电导钙激活钾通道及与心房颤动的关系作一综述。     

人心房肌细胞钠通道的增龄性变化

目的 通过观察人心房肌细胞钠通道的增龄性变化,探讨心房颤动(房颤)发病率随年龄增加的原因.方法 23例接受换瓣手术的患者按年龄分为成年组和老年组,所有患者均为正常窦性心律,采用全细胞膜片钳技术记录右心耳细胞的钠电流.结果 两组的钠电流密度和时间依赖性恢复动力学差异均无统计学意义,但老年组电压依赖性失活曲线向更正的方向偏移.结论 增龄对钠通道电流和恢复动力学无影响,老年组患者房颤发病率增高可能与钠通道无关.     

蛋白激酶C对心房颤动患者心房肌小电导钙激活钾通道的影响

目的:比较心房颤动(AF)时蛋白激酶C(PKC)对小电导钙激活钾通道(SK)电流的影响,探讨人AF时PKC途径对SK2通道的调节作用。方法:取行体外循环手术患者新鲜的右心耳组织,采用改良的酶分离法获得单个心房肌细胞,全细胞膜片钳模式且电极液中游离钙离子浓度为5×10-7 mol/L时记录SK2通道电流。比较正常的窦性心律组(SR组)和AF组患者心房肌细胞SK2通道电流密度,观察PKC特异性激活剂PMA对SK2通道电流的影响。结果:1AF组SK2通道电流密度明显大于SR组,且AF组SK2通道电流在混合内向电流中所占的比例明显增加;在-130mV膜电压下,SR组和AF组SK2通道电流密度分别(-5.10±0.32)pA/pF(nSR=5)和(-10.71±0.73)pA/pF(nAF=5),P0.05;SR组和AF组SK2通道电流在混合内向电流中所占的比例分别为(23.20±1.09)%和(32.87±1.81)%(nSR=5,nAF=6),P0.05。2PKC激活剂PMA降低SR组和AF组SK2通道电流密度及其在混合电流中所占的比例,AF组的抑制比大于SR组;在-130mV电压下,PMA对SK2通道电流的抑制比分别为(8.39±0.80)%和(20.9±0.70)%。结论:AF时SK2通道功能增强,激活PKC后可下调SK2通道电流,且对AF患者SK2的调节作用更显著,推测PKC相关途径对SK2通道的调控参与了心房电重构过程。     

心房颤动时心房肌钾、钙离子通道重构

心房颤动（ａｔｒｉａｌ ｆｉｂｒｉｌｌａｔｉｏｎ,ＡＦ）是临床上最常见的心律失常之一,可严重影响患者生活质量。ＡＦ诱发和持续的电生理基础是动作电位时限（ａｃｔｉｏｎ ｐｏｔｅｎｔｉａｌ ｄｕｒａｔｉｏｎ,ＡＰＤ）和有效不应期（ｅｆｆｅｃｔｉｖｅ ｒｅｆｒａｃｔｏｒｙ ｐｅｉｏｄ,ＥＲＰ）缩短,以及不应期的不均一性增加［１］,ＡＰＤ和ＥＲＰ缩短与钾、钙通道重构导致膜电位复极加快有关。深入研究离子通道重构,充分认识ＡＦ的离子基础,是向通过药物抑制通道重构治疗ＡＦ迈出的重要一步,因而通道重构是ＡＦ研究的热…     

心房颤动患者小电导钙激活钾通道及蛋白激酶C对其调控的研究进展

心房颤动(atrial fibrillation,AF)是临床上最为常见而复杂的心律失常,容易引起心房内血栓、脑栓塞等严重并发症而导致脑卒中、痴呆和心力衰竭.引起房颤的原因有很多,小电导钙激活钾通道(small conductance calcium-activatedpotassium channels,SK channels) 是引起房颤的新的离子通道,由于它具有心房选择性特点,从而作为新的药物治疗靶点,对SK 通道的调控可能成为治疗某些疾病的新途径[ 1 ].人类SK 通道上存在蛋白激酶C(PKC)磷酸化氨基酸序列[ 2 ],同时PKC 参与了体内多种物质的生物合成,是重要的信号传导介质.本文对近年来心房颤动患者小电导钙激活钾通道与PKC 对其调控因素的研究进展作一综述.     

SK4通道和BK通道对心脏起搏功能的影响

钙离子激活的钾离子通道根据其电导的大小主要分为三种类型：小电导钙离子激活的钾离子通道SK（SK1-3）,中电导钙离子激活的钾离子通道(IK或SK4)和大电导钙离子激活的钾离子通道(BK)。既往研究已表明SK、SK4和BK在心律失常,高血压,心肌再灌注损伤等的发生发展中发挥重要作用。最近研究提示SK4和BK具有调节心脏起搏的功能。本文旨在综述这两种离子通道在心脏起搏中的作用和机制及构建生物起搏的潜在可能     

心房颤动患者右心房肌细胞瞬间外向钾电流的变化

目的　比较心房颤动 (AF)和正常窦性心律 (NSR)患者右心房肌细胞瞬间外向钾电流 (Itol)的变化。方法　用膜片钳全细胞记录法研究了风湿性心脏病AF心律 (AF组 )和NSR心律 (NSR组 )患者右心房肌细胞Itol的变化。两步酶解法得到单个心肌细胞 ,分别对比了两组细胞的电流 电压曲线、激活曲线、失活曲线、失活后再激活的恢复过程及电流失活速度。结果　AF患者右心房肌细胞Itol密度比NSR患者的Itol密度明显降低 ,除极化至 +6 0mV时分别为 (4 2 5± 0 86 )pA/pF(n =2 0个细胞 )和(8 5 3± 0 6 8) pA/pF(n =11细胞 ) ,P <0 0 0 1。两组Itol失活速度均无电压依赖性 ,两组细胞Itol电流的失活速度、激活与失活特征及失活后再恢复常数差异均无显著性。结论　AF和NSR患者右心房肌细胞的Itol除电流密度明显降低外 ,激活曲线参数、失活曲线参数、失活后再激活的恢复时间常数及电流失活速度差异均无显著性 ,这是AF患者离子通道重构机制之一。     

L-type calcium currents in atrial myocytes from patients with persistent and non-persistent atrial fibrillation

Objective. In patients with persistent atrial fibrillation (AF), the atrial myocardium is characterized by a reduced contractile force, by a shortened duration of the action potential and a recently demonstrated reduction of the L-type Ca²⁺ currents. We analyzed potential effects on L-type Ca²⁺ currents of the patients' medication and of the duration of AF. Methods and results. Human atrial myocytes were prepared from the right auricles of patients undergoing open-heart surgery. Three groups of patients were studied: a control group with sinus rhythm (SR, n = 26 patients) and a group with persistent AF (> 3 months duration; n = 10), a group with non-persistent AF (3 patients with SR but with documented episodes of AF in their history). L-type Ca²⁺ currents were measured during depolarizing pulses from a holding potential of −70mV to a test potential of +10mV and are given as mean ±SEM of current densities (currents normalized to the cell capacitance). Ca²⁺ current densities were significantly (p < 0.0001) smaller in cells from patients with persistent AF than in control cells (0.54 ± 0.08 pA/pF vs. 1.96 ± 0.12 pA/pF). No indication was found that these changes were caused by medication with Ca²⁺ channel antagonists, β blockers, or digitalis. Stimulation with the dihydropyridine Bay K 8644 (1 μM) or with isoproterenol (0.1 μM) increased Ca²⁺ currents in control cells 3.5 ± 0.2 and 3.5 ± 0.3-fold. In persistent AF, this increase was significantly larger (6.0 ± 0.5 and 5.2 ± 0.6-fold) but stimulated currents were still significantly lower than in control cells. Patients with non-persistent AF exhibited Ca²⁺ currents well within the control range. Conclusion. A reduction in Ca²⁺ currents, due to a reduction in number as well as a depression of L-type channels, is a characteristic and pathophysiologically important part of the myocardial remodeling during long-lasting atrial fibrillation. It is not present in patients with non-persistent AF and not caused by medication. Received: 27 September 2000, Returned for revision: 9 October 2000, Revision received: 8 November 2000, Accepted: 9 November 2000     

Why atrial fibrillation recurs in patients who obtained current ablation endpoints with longstanding persistent atrial fibrillation

Purpose

Although several techniques for modification of atrial fibrillation (AF) substrate, such as linear ablation and complex fractionated atrial electrograms (CFAEs) ablation, have been proposed for longstanding persistent AF (LS-AF) and improved the outcome, there was still a certain recurrence rate, even if current ablation endpoints of these techniques were completely achieved. The purpose of this study was to describe the determinants of recurrent AF in patients who obtained current ablation endpoints with LS-AF.

Methods and results

In all, 208 consecutive patients who obtained current ablation endpoints with LS-AF were studied. The current ablation endpoints were defined as complete pulmonary vein isolation, bidirectional block of lines, and disappearance of CFAEs. After a follow-up of 19.9?±?4.1 months, the patients were classified as AF recurrence group and non-AF recurrence group (including patients with sinus rhythm and atrial tachycardia), and 34 (16 %) patients were in the AF recurrence group. The patients in AF recurrence group had higher rates of right atrium (RA) enlargement (67.7 vs. 45.4 %, p?=?0.018) and ≥2 procedure times (58.8 vs. 27.0 %, p?<?0.001), longer AF duration (82.4?±?44.8 vs. 50.8?±?42.8 months, p?<?0.001), and larger left atrium (LA) diameter (49.4?±?6.2 vs. 46.5?±?5.3 mm, p?=?0.007). In the multivariate analysis, RA enlargement, ≥2 procedure times, and AF duration were independent predictors of AF recurrence.

Conclusion

RA enlargement, ≥2 procedure times, and AF duration played important roles in AF recurrence in patients who obtained current ablation endpoints. For these patients with AF recurrence who had already underwent ≥2 procedure times, enlarged RA may contribute to other AF foci and/or substrate, and the ablation strategy may be transformed from LA to RA in the next ablation procedures.     

Demonstration of calcium-activated transient outward chloride current and delayed rectifier potassium currents in Swine atrial myocytes

Cellular electrophysiology is not fully understood in the atrium of pig heart. The objective of the present study was to determine whether transient outward current (I(to)), ultra-rapid delayed rectifier potassium current (I(Kur)), and rapid and slow delayed rectifier K(+) currents (I(Kr) and I(Ks)) were present in pig atrium. The whole-cell patch technique was applied to record membrane currents and action potentials in myocytes isolated from pig atrium. It was found that an I(to) was activated upon depolarization voltage steps to between -10 and +60 mV from -50 mV in pig atrial cells, and the I(to) was sensitive to the inhibition by the blockade of L-type calcium (Ca(2+)) current, showed a "bell-shaped" I-V relationship, typical of I(to2) (i.e. I(Cl.Ca)). The I(to2) was inhibited by the chloride (Cl(-)) channel blocker anthracene-9-carboxylic acid (9-AC, 200 micromol/l) or 4,4'-diisothiocyanostilben-2,2'disulfonic acid (200 micromol/l), and by Cl(-) substitution in the superfusate. I(Kur) was found in pig atrial myocytes, and the current showed properties of weak inward rectification and use- and frequency-dependent reduction. I(Kur) was resistant to tetraethylammonium, but sensitive to inhibition by 4-aminopyridine (4-AP) (IC(50) = 71.7 +/- 3.5 micromol/l). In addition, E-4031-sensitive I(Kr) and chromanol 293B-sensitive I(Ks) were observed in pig atrial myocytes. Blockade of I(to2), I(Kur), I(Kr) or I(Ks) with corresponding blockers significantly prolonged atrial action potentials. These results indicate that Ca(2+)-activated I(to2), 4-AP-sensitive I(Kur), E-4031-sensitive I(Kr), and 293B-sensitive I(Ks) are present in pig atrial myocytes, and these currents play important roles in action potential repolarization of pig atria.     

心房颤动演变过程中人心房肌细胞短暂外向钾电流重构的研究

本研究以人心房肌细胞为研究对象，观察心房颤动(房颤)不同的演变阶段，短暂外向钾电流(transient outward potassium carrent，I16)动态变化的特点。     

心房颤动患者心房肌乙酰胆碱兴奋钾电流通道基因和蛋白的表达

目的:探讨心房颤动(房颤)患者心房肌乙酰胆碱兴奋钾电流(Ik,Ach)通道基因和蛋白表达变化,以了解Ik,Ach通道在房颤发生中的可能作用机制.方法:入选行心脏瓣膜病手术患者作研究对象,其中并发房颤者9例(房颤组),窦性心律者13例(对照组).所有入选患者于开胸行心脏手术时切取右心耳组织,房颤组患者同期加取左心耳组织.用RT-PCR和Western-Blot检测不同心房肌组织中人Kir3.4基因及蛋白水平的表达.结果:房颤组患者IK,Aeh通道蛋白mRNA表达水平及蛋白含量均较对照组患者减少(P＜0.05).结论:Ik,Ach通道蛋白mRNA表达水平及蛋白含量较少可能是慢性房颤患者发病机制之一.