Alterations in atrial electrophysiology associated with chronic atrial fibrillation in man.

BACKGROUND: The purpose of this study was to determine the changes in atrial electrophysiology associated with chronic persistent atrial fibrillation in man. METHODS AND RESULTS: Atrial monophasic action potential duration at 90% repolarization and the effective refractory period were measured in 13 patients with chronic persistent atrial fibrillation after low-energy endocardial cardioversion, and compared to eight controls without a history of atrial fibrillation. Measurements were made at the right atrial appendage and midlateral right atrial wall at basic, 600 ms and 400 ms drive cycle lengths. In control patients, the effective refractory periods were significantly longer at the atrial appendage than the lateral wall at 600 ms (right atrial appendage 265 ms, midlateral right atrial wall 228 ms, P<0.05), and 400 ms cycle lengths (right atrial appendage 270 ms, midlateral right atrial wall 218 ms, P<0.05), but this was not evident in patients with atrial fibrillation. The monophasic action potentials and effective refractory periods at both atrial sites were shorter in the atrial fibrillation patients compared to controls; however, only the effective refractory periods at atrial appendage at 600 ms (atrial fibrillation 210 ms, controls 265 ms, P<0.001), and 400 ms cycle lengths (atrial fibrillation 200 ms, controls 270 ms, P>0.001) reached statistical significance. Effective refractory period dispersion was significantly greater in controls than in patients with atrial fibrillation (cycle length 600 ms: controls 36, atrial fibrillation 13, P=0.01; cycle length 400 ms: controls 54, atrial fibrillation 18, P<0.01). CONCLUSIONS: In patients without a history of atrial fibrillation, the refractory period at the right atrial appendage is significantly longer than at the midlateral right atrial wall. This 'normal' pattern of atrial refractory dispersion is lost in patients with chronic persistent atrial fibrillation, with marked shortening of the effective refractory period at the right atrial appendage. This may explain the high risk of recurrence of atrial fibrillation following successful electrical cardioversion.     

Simultaneous occurrence of atrial fibrillation and atrial flutter

INTRODUCTION: Early reports suggested that some patients with "atrial fibrillation/flutter" might have atrial fibrillation in one atrium and atrial flutter in the other. However, more recent conceptions of atrial fibrillation/flutter postulate that the pattern is due to a relatively organized (type I) form of atrial fibrillation. We report the occurrence and ECG manifestations of simultaneous atrial fibrillation and flutter in patients undergoing attempted catheter ablation of atrial flutter. METHODS AND RESULTS: In patients undergoing radiofrequency ablation for atrial flutter, an attempt was made to entrain atrial flutter by pacing in the right atrium. The arrhythmias observed occurred following attempts at entrainment, or spontaneously in one case. Twelve transient episodes of simultaneous atrial fibrillation and flutter were observed in five patients. The atrial fibrillation was localized to all or a portion of one atrium, during which the other atrium maintained atrial flutter. In each case, the surface 12-lead ECG reflected the right atrial activation pattern. No patients had interatrial or intra-atrial conduction block during sinus rhythm, suggesting functional intra-atrial block as a mechanism for simultaneous atrial fibrillation/flutter. CONCLUSION: In certain patients, the occurrence of transient, simultaneous atrial fibrillation and flutter is possible. In contrast to prior studies in which it was suggested that left atrial or septal activation determines P wave morphology, the results of the present study show that P wave morphology is determined by right atrial activation. Functional interatrial block appears to be a likely mechanism for this phenomenon.     

左房异常与心房颤动的关系

目的探讨左房异常与心房颤动发生的关系。方法应用心电图和动态心电图进行,持续性房颤患者为A组,阵发性房颤、房扑患者为B组,仅有心电图P波增宽的患者为C组,A、B、C三组各40例。所有入选患者均经超声心动图检测左房大小,观察患者窦性心律时心电图P波时限、切迹和P波离散度,并分析与房颤发生的关系。结果房颤男性多于女性,年龄大于60岁者94例(占78.3%),三组中86.7%的患者存在器质性心脏病(104例)。心电图P波切迹明显、P波离散度大者快速房颤发生率高;超声心动图检测左房直径大者房颤发生率高,持续性房颤比阵发性房颤患者左房直径大(p<0.05)。结论左房扩大、房内阻滞及P波离散度增大的患者易发生房颤。     

Typical atrial flutter ablation and the risk of postablation atrial fibrillation.

Typical atrial flutter is readily abolished by creating a line of block along the isthmus between the tricuspid annulus and the inferior vena cava. However, postablation atrial fibrillation occurs frequently, and its occurrence increases during the follow-up. Preablation atrial fibrillation is the most important risk factor for postablation atrial fibrillation occurrence. Among patients with preablation atrial fibrillation, patients with drug-induced atrial flutter present a lower risk of postablation atrial fibrillation than patients with spontaneous preablation atrial fibrillation. Patients with preablation lone atrial flutter also present a significant risk of atrial fibrillation development as time passes. Hence, they must be advised of the risk of recurrent symptoms and late atrial fibrillation, and closely followed up despite successful transisthmic ablation. Patients with atrial fibrillation after transcatheter isthmus ablation should be offered catheter-based pulmonary vein isolation, particularly if atrial fibrillation occurs despite continuation of antiarrhythmic drug therapy.     

Left atrial appendage function in patients with atrial flutter.

OBJECTIVE: To determine whether echocardiographic markers thromboembolic risk differ between patients with pure atrial flutter and patients with atrial flutter and intermittent atrial fibrillation. DESIGN: Patients with atrial flutter were followed up prospectively for 12 months to identify intermittent atrial fibrillation. After the follow up period, transthoracic and multiplane transoesophageal echocardiography were performed to assess left atrial chamber and appendage size, peak emptying velocities, and emptying fraction of the left atrial appendage. The presence of spontaneous echo contrast was also determined. SETTING: Tertiary cardiac care centre. PATIENTS: 20 consecutive patients with atrial flutter; 11 healthy subjects in sinus rhythm served as controls. RESULTS: Intermittent atrial fibrillation was documented in 11 patients by Holter monitoring or surface ECG; atrial fibrillation was not found in the other nine patients. Compared with the patients with pure atrial flutter, patients with atrial flutter and intermittent atrial fibrillation had larger left atrial chamber (mean (SD) 4.5 (0.6) v 3.8 (0.5) cm; 95% confidence interval 0.2 to 1.2; P = 0.01) and appendage areas (6.7 (2.2) v 4.8 (4.9) cm; 95% CI 0.4 to 3.5; P = 0.02), lower left atrial appendage emptying fractions (33 (11)% v 52 (11)%; 95% CI 8 to 29; P = 0.008), and also lower left atrial appendage emptying velocities (0.44 (0.21) v 0.79 (0.27) m/s; 95% CI 0.13 to 0.56; P = 0.005). In addition, a higher incidence of spontaneous echo contrast (11% v 36%) was observed in patients with atrial flutter and intermittent atrial fibrillation. CONCLUSIONS: Left atrial appendage function is depressed and spontaneous echo contrast more frequent in patients with atrial flutter and intermittent atrial fibrillation, as opposed to patients with pure atrial flutter. These data support the concept that patients with atrial flutter and intermittent atrial fibrillation have an increased risk of thromboembolic events and should therefore receive adequate anticoagulant treatment.     

The use of atrial pacing to induce atrial fibrillation and flutter

We studied the clinical and electrophysiological significance of induction of atrial fibrillation or atrial flutter by atrial electrical stimulation. Our atrial fibrillation/flutter induction protocol included incremental atrial pacing up to a rate of 200 beats/min, ramp up to 250 and 300 beats/min, and bursts up to 600 beats/min. The end point was sustained atrial fibrillation/flutter induction (30 sec). We performed a provocative study on 72 subjects previously divided into three groups: the first was the control group; the second comprised patients with spontaneous paroxysmal atrial fibrillation/flutter; the third comprised patients without spontaneous atrial fibrillation/flutter, but with pathologies assumed to put them at risk for atrial fibrillation/flutter. We were unable to induce sustained atrial fibrillation/flutter in the control group, but were able to induce these arrhythmias in 95% of the subjects with spontaneous atrial fibrillation/flutter. Thus the methods have a sensitivity of 95% and a specificity of 100%. We were also able to induce atrial fibrillation/flutter in 57% of patients at risk for atrial fibrillation/flutter, that is a lower incidence than patients with spontaneous episodes. When sustained atrial fibrillation/flutter could be induced, it was well tolerated and stopped spontaneously in less than 24 hours without treatment. The technique thus involves no risk and demonstrates that antiarrhythmic therapy is usually superfluous in interrupting induced atrial fibrillation/flutter.     

心房颤动的家谱分析

目的：探讨心房颤动发病的遗传性。方法：对13例心房颤动进行家谱调查，每个家谱进行3－4代人调查，调查包括对房颤患者进行心电图、心动超声图第一系列检查，其中一部分家庭成员采血进行了DNA分析。结果：本组房颤均于40岁以后（年龄45－81岁）发病，房颤包括持续性与阵发性房颤。除1例外，男性房颤均有10年以上的吸烟史，第1家谱中；第二代有4例房颤患者，第8、10个家谱中第二代分别各有3例房颤。结论：本组房颤均于成年发病，房颤病例见于2－3代发病，推测部分房颤的发病病因与基因有关，尚待进一步扩大病例深入研究。     

左心耳封堵术对于房颤患者防治卒中的作用

心房颤动（Atrial fibrillation,AF),简称房颤,是最常见的持续性心律失常。随着人口的普遍老龄化,人群中房颤患病率呈显著上升趋势。预计到2050年房颤患病人口将在目前患病人数水平上增加一倍。而对于房颤患者,卒中的预防是房颤治疗的首要目标。据统计,房颤患者发生卒中的风险约为窦性心律失常人群的5倍。目前,对于房颤患者的卒中治疗预防主要是应用口服抗凝药物。最新研究表明,左心耳封堵术对于房颤患者的卒中预防有着显著疗效。本文将综述左心耳封堵术对于房颤患者防治卒中的作用,为临床应用提供依据。     

Incidence and predictive factors of atrial fibrillation after ablation of typical atrial flutter

Although cavotricuspid isthmus radiofrequency catheter ablation is considered curative therapy for typical atrial flutter, many patients develop an atrial fibrillation after ablation. The purpose of our study was to determine the incidence and the predictive factors of post-ablation atrial fibrillation. One hundred and forty eight consecutive patients underwent cavotricuspid isthmus ablation for the treatment of typical atrial flutter between January 2004 and December 2005 in our electrophysiological department. Complete cavotricuspid isthmus block was successfully obtained in 96.6% of the patients. At the end of the electrophysiological study a sustained atrial fibrillation was inducible in 20 patients (13.5%). During an average follow-up of 21.3 ± 8.2 months, atrial fibrillation occurred in 27% of the patients. Univariate analysis identified four parameters correlated with post-ablation atrial fibrillation among the 21 parameters tested: the young age of the patients, a prior history of atrial fibrillation, an inducible atrial fibrillation, and a paroxysmal atrial flutter. Only inducible atrial fibrillation and paroxysmal atrial flutter were independent factors linked to atrial fibrillation after ablation. In our study the incidence of atrial fibrillation after cavotricuspid isthmus radiofrequency catheter ablation is 152 per 1,000 patient-years, i.e. 25 times higher than the incidence of atrial fibrillation in the general population of the same age. Twenty five percent of the patients who had neither prior history of atrial fibrillation nor structural heart disease suffered from atrial fibrillation during a mean follow-up of 21.3 ± 8.2 months. All these results suggest that atrial flutter and fibrillation could be manifestations of a more general electrophysiologic disease. They emphasize the need for all these patients to benefit from regular, long-term cardiological follow-up after cavotricuspid isthmus ablation because of the high incidence of atrial fibrillation. Treatment with antiarrhythmic and antithrombotic agents should also be adapted to these factors.     

左心房追踪技术评价高血压心房颤动和孤立性心房颤动患者左心房功能

目的应用左心房追踪技术(LAVT)评价高血压心房颤动(房颤)和孤立性房颤患者左心房功能。方法实验组为50例房颤患者,分为孤立性房颤组24例,高血压房颤组26例,对照组为25例健康成人,用M型超声测量左心室舒张末期内径(LVEDD)、左心室收缩末期内径(LVESD)、舒张末期室间隔厚度(IVSTd)、舒张末期左心室后壁厚度(LVPWTd),用校正立方体积法(Teich)计算左心室射血分数(LVEF);二维超声测量患者收缩末期左心房前后径(LAD1)、上下径(LAD2)、横径(LAD3),收缩末期右心房上下径(RAD1)、横径(RAD2),应用LAVT测量左心房最大面积(LAAmax)、左心房最大容积(LAVmax)、最小容积(LAVmin)、收缩期左心房充盈速率峰值(dv/dtS)、舒张早期左心房排空速率峰值(dv/dtE)及舒张晚期左心房排空速率峰值(dv/dtA),并计算左心房排空分数(LAEF)。比较左心房的收缩及舒张功能。结果孤立性房颤组LAD1:(42.43±4.24)mm、LAD2:(60.22±5.79)mm、LAD3:(47.90±4.86)mm、RAD1:(55.04±5.06)mm、RAD2:(43.25±2.56)mm、LAAmax、LAVmax、LAVmin、dv/dtE与正常对照组LAD1:(33.81±2.96)mm、LAD2:(47.29±6.79)mm、LAD3:(39.04±3.53)mm、RAD1:(44.34±4.12)mm、RAD2:(36.06±3.16)mm、LAAmax、LAVmax、LAVmin、dv/dtE比较均明显升高(均为P<0.05),孤立性房颤组LAEF、dv/dtS、dv/dtA与正常对照组比较均明显减低(均为P<0.05),LVEDD、LVESD、IVSTd、LVPWTd、LVEF与正常对照组比较差异均无统计学意义(均为P>0.05)。与正常对照组比较,高血压房颤组的LAD1:(45.47±7.33)mm、LAD2:(61.35±7.39)mm、LAD3:(49.27±5.25)mm、RAD1:(56.18±4.36)mm、RAD2:(45.13±3.21)mm、LAAmax、LAVmax、LAVmin、dv/dtE均明显升高,LAEF、dv/dtS、dv/dtA均明显减低(均为P<0.05),LVEDD、LVESD、IVSTd、LVPWTd、LVEF差异均无统计学意义(均为P>0.05)。与孤立性房颤组相比,高血压房颤组LAAmax、LAVmax、LAVmin均明显升高(均为P<0.05),LAEF、dv/dtS、dv/dtE、dv/dtA均明显减低(均为P<0.05),LVEDD、LVESD、IVSTd、LVPWTd、LVEF、LAD1、LAD2、LAD3、RAD1、RAD2差异均无统计学意义(均为P>0.05)。结论 AF患者左心房功能明显下降高血压房颤患者左心房功能损害较孤立性房颤患者明显。LAVT能准确、快速的反映房颤患者左心房大小及功能的变化,在评价左心房功能方面有较高的重复性。     

Catheter ablation of atrial flutter due to amiodarone therapy for paroxysmal atrial fibrillation.

AIMS: Antiarrhythmic drug treatment for atrial fibrillation can cause atrial flutter-like arrhythmias. The aim of this study was to clarify the effect of catheter ablation of the tricuspid annulus-vena cava inferior isthmus on amiodarone-induced atrial flutter and to determine the incidence of atrial fibrillation after catheter ablation of amiodarone-induced atrial flutter in comparison to regular typical flutter. METHODS AND RESULTS: Among 92 consecutive patients with typical atrial flutter who underwent isthmus ablation 28 patients had atrial flutter without a history of previous atrial fibrillation (group I), 10 patients had atrial flutter following the initiation of amiodarone therapy for paroxysmal atrial fibrillation (group II) and 54 patients had atrial flutter and atrial fibrillation (group III). Atrial cycle length during atrial flutter in amiodarone-treated patients (group II) (277+/-24 ms) was significantly longer as compared to the cycle length of atrial flutter in group I (247+/-33 ms) and group III patients (235+/-28 ms). The rate of successful transient entrainment and overdrive stimulation to sinus rhythm was not different between patients with (60%) or without amiodarone therapy (group I: 71%, group III: 53%). Successful isthmus ablation with bidirectional conduction block eliminating right atrial flutter was achieved in 90% of amiodarone-treated patients and 93% of patients without amiodarone therapy. In the amiodarone-treated patient group atrial conduction times during pacing in sinus rhythm were significantly prolonged by 20-30% before and after ablation in all regions of the reentrant circuit. During a mean follow-up of 8+/-3 months post-ablation, atrial fibrillation recurred in two of 10 patients on continued amiodarone therapy after successful isthmus ablation. Thus, successful catheter ablation of atrial flutter due to amiodarone therapy was associated with a markedly lower recurrence rate of paroxysmal atrial fibrillation (20%) as compared to patients with atrial flutter plus preexisting paroxysmal atrial fibrillation (76%) and was similar to the outcome of patients with successful atrial flutter ablation without preexisting atrial fibrillation (25%). CONCLUSION: These data suggest that isthmus ablation with bidirectional block and continuation of amiodarone therapy is an effective therapy for the treatment of atrial flutter due to amiodarone therapy for paroxysmal atrial fibrillation.     

Enhanced atrial ECG and its characteristics in atrial fibrillation

A method of recording intensified atrial ECG (IAECG) is described. A total of 150 subjects were examined by this technique including 60 with the normal sinus rhythm and 90 with atrial fibrillation. A certain homogeneity between P atrial waves and the intensified waves of atrial fibrillation was observed over time in the same patients in the presence of prominent heterogeneity of individual types of atrial fibrillation. Characteristic features of the atrial complexes revealed in patients with atrial fibrillation may be of importance for the differential diagnosis, as well as for the assessment and prediction of therapy efficacy. They also appear to be essential in solving a number of theoretical questions concerned with the genesis of both atrial fibrillation and other heart rhythm irregularities.     

阵发性房颤患者房颤发作时心房电极植入的可行性

目的　探讨阵发性房颤患者在房颤发作时植入心房电极的方法和可靠性。方法　对 10例房颤发作时植入心房电极的患者与同期窦律下植入心房电极患者的植入时间、术中以及术后心房电极的感知、起搏功能进行对比随访观察。结果　阵发房颤患者恢复窦性心律后测定心房感知和起搏功能良好 ,房颤发作时所测得的房颤波振幅与窦性心律时所测心房波振幅有相关性 ,其手术时间和X线曝光时间与窦律下植入起搏器的患者无明显差异。结论　房颤发作时植入心房电极临床上是可行的     

房颤心房纤维化相关研究的文献计量学分析

目的 分析近20年房颤心房纤维化相关领域的研究现状、热点及趋势。 方法 以Web of Science核心合集数据库为数据来源,利用可视化分析软件CiteSpace对近20年房颤心房纤维化相关研究进行可视化分析,探讨相关研究的作者、国家/机构分布、期刊分布状况以及对关键词进行分析。 结果 纳入1 468篇SCI文章,发文量最高的作者是Nattel S,引文量最高的是Burstein B。美国和中国为该领域研究的主要国家,美国犹他大学、约翰霍普金斯大学是房颤心房纤维化研究的重要机构,载文量最多的期刊是《Journal of cardiovascular electrophysiology》,被引频次最高的期刊是《Circulation》,主要的研究热点是①心力衰竭/心肌梗死并发心房颤动与心房纤维化研究;②心房纤维化评估在心房颤动导管消融/基质消融中的应用③炎症及氧化应激在房颤心房纤维化中的作用机制研究。研究的前沿方向主要有①关于房颤患者的患病率、复发率和死亡率的研究;②房颤患者中风的预防;③基于心肌成纤维细胞探讨房颤相关机制的研究;④房颤患者的管理;⑤通过延迟增强MRI评估心房组织纤维化程度。 结论 本研究为了解房颤心房纤维化相关研究提供了一个视角,为研究者识别潜在的合作者和合作机构、热点话题和研究前沿提供了有价值的信息。     

Curative catheter ablation for atrial fibrillation

Optional statement With the recent advances in the understanding of the mechanisms of atrial fibrillation, radiofrequency catheter ablation has emerged as an effective therapeutic modality for patients with atrial fibrillation. Techniques for catheter ablation evolved from elimination of triggers that often originate within the pulmonary veins and initiate atrial fibrillation, to additional left atrial ablation using a variety of approaches to also eliminate the mechanisms that play a role in perpetuation of atrial fibrillation. With the current ablation strategies, atrial fibrillation can be eliminated in approximately 85% of patients with paroxysmal, and in approximately 70% of patients with chronic, atrial fibrillation with a low incidence of significant complications. In symptomatic patients with paroxysmal or chronic atrial fibrillation who have failed antiarrhythmic drug therapy, catheter ablation is an effective treatment strategy for maintenance of sinus rhythm.     

The role of atrial ectopics in initiating paroxysmal atrial fibrillation.

AIMS: To characterize the nature and timing of atrial ectopics preceding clinical episodes of paroxysmal atrial fibrillation. METHODS AND RESULTS: Holter recordings (n= 177, 60 patients, 58% male, mean age 61.7 +/- 11.5 years) were performed on patients with paroxysmal atrial fibrillation. These were subjected to standard analysis and recordings containing atrial fibrillation episodes suitable for analysis were identified (n = 74). Beat interval files differentiating sinus rhythm from atrial fibrillation were generated and atrial ectopics were identified. Atrial ectopics preceding atrial fibrillation were found to be more frequent (5.07 +/- 7.39 min(-1)) and more premature (ratio of coupling interval to that of surrounding sinus cycles = 0.56 +/- 0.08) compared to ectopics occurring remote from atrial fibrillation episodes (frequency = 3.60 +/- 7.32 min(-1) P = 5 x 10(-24), prematurity ratio = 0.60 +/- 0.10, P = 2 x 10(-73)). Atrial ectopic coupling interval frequency histograms were generated and analysed visually and by an automated statistically based test. Many ectopics were seen to occur at one coupling interval in 27 recordings (in eight this occurred only preceding atrial fibrillation onset, while in a further 19 cases this was also seen remote from atrial fibrillation onset). Overall 45% of ectopics preceding atrial fibrillation episodes occurred in isolation, 13% as part of a bigeminal rhythm, 22% as couplets and 20% as runs. This pattern did not differ from that seen remote from atrial fibrillation episodes. CONCLUSION: Paroxysmal atrial fibrillation is preceded by ectopics of a fixed coupling interval in a significant proportion of patients. If, as seems likely, this is a marker of 'focally mediated' atrial fibrillation, then Holter techniques may provide a useful screening tool with which to identify patients suitable for fuller electrophysiological assessment.     

Effect of cibenzoline on atrial vulnerability and value of electrophysiological methods in the treatment of paroxysmal atrial fibrillation

The effects of intravenous cibenzoline (1,5 mg/kg) on atrial vulnerability and electrophysiology were assessed in 25 patients with documented paroxysmal atrial fibrillation, in whom sustained (greater than 30 s) atrial fibrillation/-flutter was induced by programmed atrial stimulation. In seven patients atrial fibrillation persisted despite the application of cibenzoline; in eight patients induction of atrial fibrillation was not prevented. In 10 patients the induction of sustained atrial fibrillation was prevented by cibenzoline. Intraatrial conduction time and shortest ventricular cycle length during atrial fibrillation were increased by cibenzoline (p less than or equal to 0.01). The effective refractory period of the right atrium was not significantly affected. Eight patients with frequent episodes of paroxysmal atrial fibrillation received oral cibenzoline (320 mg/day) for control of paroxysmal atrial fibrillation irrespective of the efficacy of intravenous cibenzoline. Prevention of stimulation-induced atrial fibrillation predicted successful treatment of paroxysmal AF. In conclusion, cibenzoline might be effective in the treatment of atrial tachyarrhythmias. Programmed atrial stimulation seems to be helpful in the prediction of the efficacy of an antiarrhythmic treatment of paroxysmal atrial fibrillation.     

Episodes of atrial fibrillation and atrial vulnerability after successful radiofrequency catheter ablation in patients with Wolff-Parkinson-White syndrome.

Episodes of atrial fibrillation occur in patients with WPW syndrome but frequently disappear after successful radiofrequency ablation. AIMS: To analyze the incidence of atrial fibrillation before and after successful ablation and the presence of increased atrial vulnerability. METHODS AND RESULTS: Fifty-four of 183 WPW patients had at least one documented episode of atrial fibrillation before ablation. During a follow-up of 24 +/- 12 months 13/54 patients (24%) experienced atrial fibrillation. At baseline, the patients with atrial fibrillation were more often men (74%) vs 53%, P=0.007), were older (45 +/- 15 vs 34 +/- 16 years, P=0.0001), more often had pre-excitation during sinus rhythm (87% vs, 73%, P=0.04) and had increased atrial vulnerability (41%, vs 18%, P<0.001). Only patients with atrial fibrillation before, developed atrial fibrillation after ablation. The 13 (of 54) patients who relapsed were also older (53 +/- 13 vs 42 +/- 15 years, P= 0.03), had increased atrial vulnerability at baseline (77% vs 29%, P=0.002), and were more symptomatic, (13 +/- 21 vs 1 +/- 3 arrhythmia attacks/month, P=0001). No patient without atrial fibrillation before ablation developed atrial fibrillation after treatment. CONCLUSIONS: The accessory pathway was important for the development of atrial fibrillation. Frequent tachycardias seem to promote an electrical remodelling and an increased atrial vulnerability to atrial fibrillation, whereas after successful ablation the majority of patients remain free of atrial fibrillation.     

Paradoxical atrial undersensing due to inappropriate atrial noise reversion of atrial fibrillation in dual-chamber pacemakers

Paradoxical atrial undersensing. BACKGROUND: Paradoxical atrial undersensing at high atrial sensing levels was described as false atrial noise reversion of dual-chamber pacemakers during atrial fibrillation in a sheep model. It is unknown whether this phenomenon occurs in humans. METHODS: In total, 71 patients with implanted dual-chamber pacemakers and atrial fibrillation were tested for the occurrence of paradoxical atrial undersensing. After determination of the sensing threshold of atrial fibrillation (30 seconds of continuous mode switch), the atrial sensing level was stepwise increased. If, after correct mode switch behavior at insensitive levels, loss of mode switch occurred at higher sensing levels and if the pacing mode was consistent with atrial noise reversion, paradoxical atrial undersensing was assumed. RESULTS: Paradoxical atrial undersensing could be provoked in 9 of 71 (13%) patients at a median sensing level of 0.4 (range 0.15-2.0) mV. Six different pacemaker models of five different manufacturers were affected. The occurrence of paradoxical atrial undersensing was significantly associated with the sensing threshold of atrial fibrillation (2.7+/-1.5 mV for patients with paradoxical undersensing compared to 1.6+/-1.3 mV for those without, P=0.02). Decreasing the atrial sensing level avoided paradoxical undersensing in 8 of 9 patients while maintaining an adequate safety margin for the detection of atrial fibrillation. CONCLUSION: Paradoxical atrial undersensing is inherent to all current dual-chamber pacemakers. The incidence is about 13% when using very high atrial sensing levels. Inappropriate atrial noise reversion can be resolved in most of the cases by decreasing atrial sensing levels and knowledge of this phenomenon is important to avoid unwarranted atrial lead revisions.     

Operations for atrial fibrillation

Atrial fibrillation is the most common of all sustained cardiac arrhythmias, yet it has no effective medical or surgical therapy. During the past decade, multipoint computerized electrophysiological mapping systems were used to map both experimental and human atrial fibrillation. On the basis of these studies, a new surgical procedure was developed for atrial fibrillation. Between September 25, 1987, and May 1, 1991, this procedure was applied in 22 patients with either paroxysmal atrial flutter (n = 2), paroxysmal atrial fibrillation (n = 11), or chronic atrial fibrillation (n = 9) of 2 to 21 years' duration. All patients were refractory to all antiarrhythmic medications and each patient failed an average of 5.2 drugs preoperatively. There were no operative deaths and all perioperative morbidity resolved. All 22 patients have been cured of atrial fibrillation with surgery alone. One late isolated episode of atrial flutter occurred in a patient who is now receiving encainide. Preservation of atrial transport function has been documented in all of the patients postoperatively and all have experienced marked clinical improvement.