心房有效不应期离散度与心房颤动

心房颤动是临床最常见的心律失常之一,有较高的致残率及致死率,关于心房颤动的机制有较多的学说,目前研究已经证实心房电重构能够促进心房颤动的发生与维持,心房电重构包括心房有效不应期的缩短,心房有效不应期离散度的增加及局部电传导的减慢,现就心房有效不应期离散度与心房颤动的关系及其影响机制做一综述。     

Maintenance of Sinus Rhythm after Cardioversion of Atrial Fibrillation in Patients with Lone Atrial Fibrillation and Patients with Hypertension

Background: The success rate and prognosis of cardioversion of atrial fibrillation (AF) in patients with organic heart disease is well known. In contrast, little data exist about cardioversion success and maintenance of sinus rhythm (SR) in patients with lone AF and in patients with hypertension as the only underlying cardiovascular disease. Methods: In a prospective cardioversion registry 148 of 181 patients (81.8%) with lone AF (age 58 ± 13 years, duration of AF 7.6 ± 19 weeks) and 120 of 148 patients (81.1%) with hypertension (age 62 ± 10 years, duration of AF 6.6 ± 21 weeks) had successful cardioversion and were followed for 7.7 ± 1.9 months. Results: At follow-up, 120 patients (81.1%) with lone AF were in SR, and 18 of these patients had had repeated cardioversion during follow-up (AF total recurrence rate 31.1%). In stepwise regression analysis, the number of previous cardioversions was predictive of rhythm at follow-up (P = 0.0453). Rhythm at follow-up did not differ between patients who were or were not on antiarrhythmic drugs. At follow-up 96 patients (80%) with hypertension were in SR, and 9 of these had had repeated cardioversion during follow-up (AF total recurrence rate 27.5%). As in lone AF, the recurrence rate of AF did not differ between patients with or without antiarrhythmic drug treatment, and in multivariate regression analysis, the number of previous cardioversions was the only clinical predictor of rhythm at follow-up (P = 0.0284). Conclusions: Even in patients with such benign conditions as lone AF or hypertension as the only underlying disease, the prognosis of cardioversion in terms of maintenance of SR is poor. Future studies of rhythm control versus rate control need to include not only patients with organic heart disease but also patients with lone AF and patients with hypertension, since the long-term benefits of these two strategies remain unclear even in these subsets of patients.     

快速心房电刺激对人心房不应期的影响及卡托普利的干预作用

探讨快速心房电刺激对人心房有效不应期 (AERP)的影响及卡托普利的干预作用。选择本院行射频消融术的 38例成年患者为研究对象 ,随机分为卡托普利组 (14例 )、维拉帕米组 (12例 )及生理盐水对照组 (12例 )。分别在阻断心脏自主神经后 ,观察各组用药前、后及快速心房刺激后AERP的变化及AF诱发情况。结果 :①快速心房刺激可使 5 7.9%成人正常心脏诱发AF ;②诱发AF后AERP明显缩短 ,而未诱发AF者的AERP无明显变化 ;③卡托普利及维拉帕米均能显著延长诱发AF患者的AERP ;④卡托普利能减少AF诱发率 ,并缩短AF持续时间 ;而维拉帕米则使AF诱发率增加、持续时间延长。结论 :①快速心房刺激可使部分患者AERP缩短 ,并诱发这类患者发生AF ;②卡托普利可显著延长诱发AF患者的AERP ,并使AF诱发率降低、持续时间缩短     

孤立性心房颤动的危险因素认识

心房颤动是临床上最常见的快速心律失常之一,而大多数的心房颤动在临床上都有确切的病因。孤立性心房颤动是指患者年龄〈60岁,在排除了心肺疾病及高血压后的心房颤动。通常这种心律失常出现在比较年轻的患者当中,且大量的临床证据证明其预后良好。近年来越来越多的临床研究提供了对孤立性心房颤动危险因素的最新认识。随着这些研究的深入,有助于进一步阐明孤立性心房颤动的确切致病机制。     

Latent Arterial Hypertension in Apparently Lone Atrial Fibrillation

Introduction. Longitudinal studies on lone AF are rare and the incidence of hypertension in this population unknown. This study aimed at investigating the incidence of arterial hypertension in patients with apparently lone atrial fibrillation (AF). Methods and Results. Out of 292 consecutive patients presented with permanent or paroxysmal AF, 32 patients were diagnosed as having lone AF according to strict criteria. Three patients were subjected to ablation of the ligament of Marshall, 14 patients to pulmonary vein isolation, and the remainder were treated with beta blockade. Patients were followed-up for a 1–3 year period. During follow-up, 14 patients were diagnosed as having arterial hypertension. Thirteen of them had recurrent AF despite ligament of Marshall ablation (1 patient), pulmonary vein isolation (4 patients) and beta blockade (8 patients). Cox regression analysis revealed that the only significant predictor of development of hypertension was complete or partial response to antiarrhythmic therapy (beta = 3.82, S.E. = 1.22, exp(b) = 45.63, 95% C.I. = 4.17–499.2, p = 0.001), independent of age (beta = −0.01, p = 0.74), sex (beta = −0.91, p = 0.28), left ventricular ejection fraction (beta = 0.06, p = 0.52), left atrial size (beta = 0.58, p = 0.7) and kind of antiarrhythmic therapy (ablation or drug therapy) (beta = 1.36, p = 0.09). In patients with lone AF that did not respond at all to antiarrhythmic therapy, there was a 45.6 times higher risk of diagnosing hypertension during the next 3 years as compared to responders. Conclusion. Approximately 44% of patients with an initial diagnosis of lone AF may represent occult cases of arterial hypertension. In these patients hypertension may affect AF recurrence and treatment outcomes, regardless of the mode of antiarrhythmic therapy used.     

Effects of simultaneous atrioventricular pacing on atrial refractoriness and atrial fibrillation inducibility: role of atrial mechanoelectrical feedback

INTRODUCTION: The purpose of this study was to evaluate the effects of an acute increase in atrial pressure on refractoriness (mechanoelectrical feedback) and the vulnerability to atrial fibrillation (AF) and to investigate the effects of autonomic blockade and verapamil on mechanoelectrical feedback in humans. METHODS AND RESULTS: Right atrial pressure and effective refractory period (ERP) at the right atrial appendage (RAA) and high right atrial septum were measured during sinus rhythm, and during atrial and simultaneous AV pacing at a cycle length of 300 msec, either in the absence (n = 25) or presence (n = 22) of pharmacologic autonomic blockade. In another 15 patients, the protocol was performed before and after infusion of verapamil 0.15 mg/kg. In the absence of autonomic blockade, AV pacing resulted in a higher mean right atrial pressure (11.7 +/- 3.3 vs 4.3 +/- 3.0 mmHg, P < 0.001) and a shorter atrial RAA ERP (144 +/- 23 msec vs 161 +/- 21 msec; P < 0.001) compared with atrial pacing; AF was induced more often during AV pacing (87%) than during atrial pacing (20%) and was related directly to the right atrial pressure (r = 0.39, P = 0.004) and indirectly to the RAA ERP (r = -0.42, P < 0.001). The susceptibility to sustained AF was greatly enhanced by autonomic blockade. Verapamil markedly attenuated the shortening of ERP and the propensity for AF that occurred during simultaneous AV pacing. CONCLUSION: An acute increase in atrial pressure during tachycardia is associated with shortening of atrial refractoriness and a propensity for AF, i.e., atrial mechanoelectrical feedback, which may be enhanced by autonomic blockade and attenuated by calcium channel blockade.     

Ranolazine Exerts Potent Effects on Atrial Electrical Properties and Abbreviates Atrial Fibrillation Duration in the Intact Porcine Heart

Introduction: In vitro studies and ambulatory ECG recordings from the MERLIN TIMI-36 clinical trial suggest that the novel antianginal agent ranolazine may have the potential to suppress atrial arrhythmias. However, there are no reports of effects of ranolazine on atrial electrophysiologic properties in large intact animals.
Methods and Results: In 12 closed-chest anesthetized pigs, effects of intravenous ranolazine (∼9 μM plasma concentration) on multisite atrial effective refractory period (ERP), conduction time (CT), and duration and inducibility of atrial fibrillation (AF) initiated by intrapericardial acetylcholine were investigated. Ranolazine increased ERP by a median of 45 ms (interquartile range 29–50 ms; P < 0.05, n = 6) in right and left atria compared to control at pacing cycle length (PCL) of 400 ms. However, ERP increased by only 28 (24–34) ms in right ventricle (P < 0.01, n = 6). Ranolazine increased atrial CT from 89 (71–109) ms to 98 (86–121) ms (P = 0.04, n = 6) at PCL of 400 ms. Ranolazine decreased AF duration from 894 (811–1220) seconds to 621 (549–761) seconds (P = 0.03, n = 6). AF was reinducible in 1 of 6 animals after termination with ranolazine compared with all 6 animals during control period (P = 0.07). Dominant frequency (DF) of AF was reduced by ranolazine in left atrium from 11.7 (10.7–20.5) Hz to 7.6 (2.9–8.8) Hz (P = 0.02, n = 6).
Conclusions: Ranolazine, at therapeutic doses, increased atrial ERP to greater extent than ventricular ERP and prolonged atrial CT in a frequency-dependent manner in the porcine heart. AF duration and DF were also reduced by ranolazine. Potential role of ranolazine in AF management merits further investigation.     

持续心房颤动时肺静脉口部有效不应期变化的时间进程及其逆转

为探讨持续心房颤动 (AF)肺静脉有效不应期 (ERP)变化的时间进程及其逆转 ,运用起搏方法建立AF模型 ,在起搏前和起搏后的第 1 ,2 ,3,4 ,5 ,6 ,7d对左上肺静脉口、左下肺静脉口、右上肺静脉口及右下肺静脉口的ERP进行测定。采用S1 S2 程序刺激 ,基础起搏周长 (S1 S1 )分别为 4 0 0 ,35 0 ,30 0 ,2 5 0 ,2 0 0ms,S2 为 2 0 0ms,以 5ms的步长递减。程序刺激结合猝发刺激对上述心房结构进行AF的诱发 ,记录AF的发生频率。上述相同方法对起搏停止后 1 ,2 ,3,4 ,5 ,6 ,2 4h 4个肺静脉口的ERP进行测定。结果 :各个基础起搏周长下 4个肺静脉口的ERP在AF后 1 ,2 ,3,4 ,5 ,6 ,7d逐渐缩短 ,且较AF前明显缩短 ,P <0 .0 5 ;AF终止后 4个肺静脉口的ERP逐渐延长 ,但AF终止后 0 ,1 ,2 ,3,4 ,5 ,6hERP与AF前相比仍有明显缩短 ,P <0 .0 5 ;AF终止后 2 4hERP基本恢复到AF前水平 ,随着AF持续时间的延长 4个肺静脉口AF的诱发率逐渐增高 ,与AF前相比 ,AF后 1 ,2 ,3,4 ,5 ,6 ,7dAF的诱发率明显增高 ,P <0 .0 5。结论 :随着AF持续 ,肺静脉的ERP逐渐缩短 ,AF的诱发率逐渐增高 ,AF终止后缩短的ERP逐渐延长致AF前水平。     

Susceptibility to Atrial Fibrillation:

Propensity for Extrastimulus to Induce AF. Introduction : The development of susceptibility to atrial fibrillation (AF) is a common consequence of many forms of cardiovascular disease, especially heart failure. In this study we used a sheep model of pacing-induced stable early heart failure to describe, quantify, and relate the level of susceptibility to AF to changes in structural and electrophysiologic parameters.
Methods and Results : Epicardial electrodes were implanted on the atria and right ventricles of nine sheep. The AF thresbold, atrial vulnerability period, atrial effective refractory period (ERP), and interatrial conduction time were examined during control and over a 6-week period of ventricular pacing at 190 beats/min. Left atrial (LA) area and left ventricular (LV) fractional shortening were monitored using echocardiography. There were significant increases in LA susceptibility to AF (P < 0.0003), LA area (P < 0.0002), and LA FRP400 (P < 0.0002). Rate of increase in LA area was related positively to AF susceptibility (P = 0.02) and inversely to LA ERP400 (P = 0.002). LV fractional shortening decreased to approximately 50% of control value (P < 0.00001). No changes were observed in right atrial electrophysiology.
Conclusion : In this study, susceptibility (the ability of an extrastimulus to induce AF) was rigorously measured within a predetermined format. Significant relationships were found to exist between susceptibility, certain of the observed changes in atrial electrophysiology and structure.     

Effect of Physical Exercise on Platelet Activity and the von-Willebrand-Factor in Patients with Persistent Lone Atrial Fibrillation

BACKGROUND: The risk of stroke is of great clinical importance in patients with atrial fibrillation (AF). It is not known whether physical exercise influences plasma coagulation and platelet aggregability during AF. The purpose of this study was to assess the effect of physical exercise on platelet activity, thrombin generation, and levels of von-Willebrand-factor in patients with persistent AF. METHODS: Thirteen patients with lone AF (>or=1 year) were compared with 13 matched patients in sinus rhythm. Patients with AF were anticoagulated effectively with coumarin. All patients underwent bicycle ergometry using a respiratory gas exchange technique for 20 min at one-third of the age-adjusted maximal workload. Thereafter, workload was increased until maximal exercise capacity was reached. Platelet factor-4 (PF-4), beta-thromboglobulin (beta-TG; marker for platelet activation), von-Willebrand-factor (vWF; marker for endothelial dysfunction), prothrombin fragment F1 + 2 (F1 + 2; marker for thrombin generation) and fibrinogen levels were determined throughout the study in all patients. RESULTS: Gas exchange variables, hemodynamic parameters and norepinephrine levels were comparable in the groups during moderate (45 +/- 5 W) and heavy exercise (198 +/- 38 W). In contrast to moderate exercise, PF-4 and beta-TG levels increased to 212 +/- 56% ( p < 0.05) and to 145 +/- 24% ( p < 0.05), respectively, in patients with AF during heavy exercise. In contrast, physical exercise had no significant effect on platelet activity in patients with sinus rhythm. Levels of vWF increased by delta24% ( p < 0.05) in all patients during maximal exercise, whereas F1 + 2 levels increased only in patients with sinus rhythm. CONCLUSIONS: Heavy physical activity increases platelet activity and vWF levels during AF, whereas moderate exercise has no procoagulatory effect. Coumarin therapy prevents exercise-induced thrombin generation only. Future studies are needed to prove the hypothesis that heavy physical exercise is a risk factor for thromboembolic events in patients with AF.     

血压变异性与心房颤动相关性研究

［］ 目的 探讨血压变异性(BPV)对心房颤动发生及左心结构的影响。方法 随机选取我科2013年6月至2015年10月就诊患者120例患者,其中永久性房颤40例,持续性房颤40例,阵发性房颤40例,选取同期住院的窦性心律患者40例,测24h动态心电图、动态血压、超声心动图对160例患者检测,比较四组患者血压变异性及左房内径。 结果 心房颤动组的血压变异性、左房内径较正常对照组明显增加,房颤组内比较,永久性房颤组较持续性房颤组、阵发性房颤组血压变异性明显增大。 结论 心房颤动的患者血压变异性明显增加,且心房颤动的严重程度与血压变异性呈正相关。#$NL［关键词］心房颤动;血压变异性;左房内径     

B型利钠肽与孤立性心房颤动

目的:探讨B型利钠肽(BNP)与孤立性心房颤动(AF)的血栓事件发生、复律及再发之间的关系。方法:103例孤立性AF患者行食道超声(经食道超声心动图)、头颅计算机断层摄影术或磁共振(CT／MRI)检查及血BNP测定。探讨BNP在AF血栓事件及其相关因素中的作用。根据血栓事件将患者分为有血栓事件组(n=15)和无血栓事件组(n=88)。对于有复律指征的患者,根据AF复律及再发情况分为复律不成功患者(复律失败或随访期内再发,n=16)和复律成功患者(复律成功并随访期内维持窦性心律,n=7),分别进行对比研究。结果:服药后无血栓事件组BNP降低幅度优于血栓事件组,有显著性显异(P<0．05)。复律成功患者较复律不成功患者BNP水平低[(60±32)ng／L比(178±70)ng／L,P<0．05]、病程短[(3．0±1．9)个月比(7．6±2．5)个月,P< 0．05]和左心房内径小[(42．3±3．4)mm比(48．6±5．1)mm,P<0．05],均有显著性差异。多因素Logistic回归分析: BNP是预测孤立性AF血栓事件的独立因素(P<0．05);BNP、左心房内径和AF病程是预测AF复律及再发的独立因素(P均<0．05)。结论:BNP可作为预测孤立性AF血栓事件和AF复律与再发的临床指标。     

The Spatial Dispersion of Atrial Refractoriness and Atrial Fibrillation Vulnerability

The local dispersion of conduction and refractoriness has been considered essential for induction of atrial arrhythmias. This study sought to determine whether a difference of refractoriness and vulnerability for induction of atrial fibrillation between trabeculated and smooth as well as high and low right atrium may contribute to initiation of atrial fibrillation in dogs.In 14 healthy mongrel dogs weighing 22.4 ± 1 kg, closed-chest endocardial programmed stimulation was performed from four distinct right atrial sites. Atrial refractory periods and vulnerability for induction of atrial fibrillation or premature atrial complexes were determined during a basic cycle length of 400 and 300 ms and an increasing pacing current strength.For a pacing cycle length of 300ms, atrial refractory periods were longer on the smooth, as compared to the trabeculated right atrium (102 ± 25 vs. 97 ± 17ms, p < 0.05), whereas for a pacing cycle length of 400ms, there was no significant difference. The duration of the vulnerability zone for induction of atrial fibrillation was longer on the smooth right atrium, for a cycle length of both 400 ms (40 ± 30 vs. 31 ± 22 ms; p < 0.05) and 300 ms (33 ± 25 vs. 23 ± 21 ms; p < 0.01). When comparing high and low right atrium, refractory periods were longer on the the low right atrium, for a cycle length of both 400 ms (111 ± 23 vs. 94 ± 24ms; p < 0.01) and 300 ms (104 ± 20 vs. 96 ± 23ms; p < 0.01). For a pacing cycle length of 300 ms, the duration of the atrial fibrillation vulnerability zone was longer for the high, as compared to the low right atrium (34 ± 22 vs. 22 ± 22, p < 0.01). Seven dogs with easily inducible episodes of atrial fibrillation demonstrated significantly shorter refractory periods as compared to 7 non-vulnerable dogs, regardless of pacing site and current strength.In conclusion, significant differences in refractoriness and vulnerability for induction of atrial fibrillation can be observed in the area of the crista terminalis in healthy dogs. Thus, local anatomic factors may play a role in the initiation of atrial fibrillation.     

Right Atrial Compartmentalization Using Radiofrequency Catheter Ablation for Management of Patients with Refractory Atrial Fibrillation

INTRODUCTION: Atrial fibrillation (AF) is often refractory to antiarrhythmic drugs, and patients who are intolerant of AF may require the maze operation for cure. As a less invasive alternative, a catheter-based, right atrial compartmentalization procedure was evaluated. METHODS AND RESULTS: Twelve patients with AF refractory to Class I and III antiarrhythmic drugs were studied. Four linear right atrial radiofrequency ablations were performed, from superior to inferior vena cava in the posterior wall and interatrial septum, anteriorly from the superior vena cava to the tricuspid annulus through the appendage, and across the tricuspid valve-inferior vena cava isthmus. The radiofrequency catheter was dragged along each line three to four times, until the atrial electrogram amplitude decreased by 75% and there was bidirectional conduction block in the tricuspid valve-inferior vena cava isthmus. One complication occurred: sinus node dysfunction requiring a pacemaker. Eight patients were discharged from the hospital on no antiarrhythmic drugs, and four were discharged on previously ineffective antiarrhythmic drugs. Total duration of follow-up was 21.3 +/- 11.2 months. Four patients discharged on previously ineffective antiarrhythmic drugs had no recurrence of AF. One patient discharged off antiarrhythmic drugs had no recurrence of AF. Seven patients discharged off antiarrhythmic drugs had recurrent AF by 12.6 +/- 13.0 months (median 6, range 1 to 39); 3 of these 7 responded to previously ineffective antiarrhythmic drugs without further AF and 4 did not. Thus, 8 of 12 patients (67%) had suppression of AF after ablation on previously ineffective medication or no medication. CONCLUSION: Right atrial compartmentalization may alter the substrate for AF, thus improving the efficacy of previously ineffective antiarrhythmic drugs. Because it is relatively safe, it may be a reasonable adjunctive intervention to maintain sinus rhythm in patients with drug-refractory AF.     

丹参酮ⅡA磺酸钠对家兔快速心房起搏时心房动作电位及有效不应期的影响

研究丹参酮ⅡA磺酸钠(TSN)对家兔短期快速心房起搏时在体心房单相动作电位(AMAP)及心房有效不应期(AERP)的影响,探讨其防治心房颤动的可能机制。家兔24只,随机分为对照组与TSN组各12只。将电极经颈内静脉置入右房记录AMAP,观察基础状态下、给药后0.5h及以600次/分心房快速起搏后0.5,8hAMAP及其频率适应性的变化。结果:与起搏前相比对照组在S1S1200ms刺激时测量的AERP(AERP200)在起搏后0.5h缩短21.2ms,起搏后8h缩短21.6ms(P<0.05),且心房肌的频率适应性丧失。TSN在基础状态下对AMAPA、AMAPD无明显影响,但使AERP200由105.9±3.8ms延长至114.7±7.2ms(P<0.05)。起搏后TSN组维持原有的心房肌频率适应性。结论:快速心房起搏使心房肌的频率适应性丧失而致电重构,TSN能减轻短期快速心房起搏所致电重构。     

High‐Resolution Signal‐Averaged Analysis of Atrial Electromagnetic Characteristics in Patients with Paroxysmal Lone Atrial Fibrillation

Background: Abnormalities in the electromagnetic signal of the atria during sinus rhythm could serve as markers of triggering foci or substrate for atrial fibrillation (AF). We examined atrial electrophysiologic properties noninvasively by using magnetocardiographic mapping (MCG) in patients with paroxysmal lone AF to find whether any difference exists between those who have frequent triggers of AF and who don't. Methods: MCG was recorded over anterior chest during sinus rhythm in 80 patients with paroxysmal lone AF (44 ± 12 years, 61 males) and 80 matched controls. Atrial wave duration (Pd) and root mean square amplitudes of the last 40 ms (RMS40) of the averaged filtered atrial complex were determined automatically. Patients expressing atrial arrhythmias triggering AF episodes were classified as focal AF. Results: The Pd was 109 ms in patients and 104 ms in controls (P = 0.007). In focal AF (72%) the Pd was slightly prolonged and its proportion of the PR interval was larger, but RMS40 was normal compared to controls. In other patients, the Pd was close to controls, but the RMS40 was reduced (59 ± 17 vs74 ± 36 fT, P = 0.006). Pd and atrial RMS amplitudes were unrelated to duration of AF history or frequency of recurrences. Conclusion: Clinical subclasses of lone AF seem to possess distinct signal profiles of atrial depolarization. Differences in electrophysiological properties between these subclasses may reflect pathogenetic variation and could have implications on diagnostics and therapy.     

Effect of Atrial Tachyarrhythmia Duration on Percentage of Time with Atrial Pacing in Pacemaker Patients with Paroxysmal Atrial Fibrillation

Atrial pacing can prevent the recurrence of paroxysmal atrial tachyarrhythmia (AT) in pacemaker patients. The aim of the study was to determine in pacemaker patients the effect of AT duration on the percentage of time with atrial pacing by programming the same setting twice. METHODS: In 14 pacemaker patients with paroxysmal AT the dual-chamber pacemaker was programmed to identical parameters for two consecutive follow-up periods. The pacemakers were interrogated after three months to determine the percentage of time with atrial pacing relative to the total time of follow-up periods and the AT duration (atrial rates >150 bpm). The two three-month follow-up periods were compared to each other. The differences between the two follow-up periods were determined for the percentage of time with atrial pacing as well as for the AT duration. To assess the relationship between atrial pacing and AT duration, the differences between the two follow-up periods for atrial pacing and AT duration were correlated to each other. In addition, the percentage of atrial pacing was corrected for AT duration. RESULTS: Median percentage of atrial pacing relative to the complete follow-up period was 73% after the first and 76% after the second period and median AT duration 21% and 18%, respectively (not significantly different). The differences between the first and second study period were 1% for atrial pacing and -2% for AT duration. The percentage of atrial pacing and AT duration were inversely related together with a significant correlation coefficient of r = 0.95 ( p = 0.0001). After atrial pacing was corrected for AT duration, the percentage of atrial pacing relative to the time in sinus rhythm was significantly higher with a median of 93% for the first and second period ( p = 0.005). The correlation coefficient between the percentage of atrial pacing relative to the time in sinus rhythm and AT duration was r = 0.08 (not significant). CONCLUSIONS: The percentage of time with atrial pacing can be underestimated in patients with paroxysmal atrial fibrillation and should be carefully interpreted in relation to AT duration.     

Effects of Amiodarone plus Losartan on Electrical Remodeling in Rapid Atrial Pacing in Rabbits

Objectives To investigate the electrical remodeling and the effects of amiodarone and losartan on electrical remodeling in rapid atrial pacing on rabbit model. Methods 40 normal rabbits were randomly divided into 4 groups ： the saline group （control group）, amiodarone group, losartan group, anti ＋ los group. All rabbits were raised drugs in a week. The atrial effective refractory period （AERP） was measured. Then, take a rapid atrial pacing （600 bpm） and the AERP was measured after 0.5, 1, 2, 4, 6 and 8 hours pacing and 30 minutes after the termination of rapid pacing. Results （1） In control group, after 8 hours rapid pacing, AERP200 and AERP150 were significantly shortened 16. 11% ± 3.1% （ P 〈 0. 01 ） and 9. 99 % ± 4. 2% （ P 〈 0. 01 ）. And the degree of AERP shortening induced by rapid pacing was greater at basic cycle lengths of 200 ms （BCL200） than that at BCL150. The AERP of amiodarone, losartan group and ami ＋ los group were not shortened during rapid pacing. （2） In the control group, after the termination of rapid pacing, the AERP gradually increased. The AERP at all of the BCLS examined recovered to almost the 95.78% and 96. 76% of baseline values within the first 10 minutes and recovered to almost the 99.07% and 99.39% of baseline values within the first 30 minutes. Conclusions Short-term atrial rapid pacing can induce the atrial electrical remodeling. Amiodarone and losartan can prevent the electrical remodeling.