Occam's razor and the unraveling of atrial fibrillation

The search for a mechanism to explain atrial fibrillation (AF) has lasted for over a century and continues. Significant progress in understanding this arrhythmia accelerated with the era of operative treatment of this arrhythmia and intensified with the advent of catheter ablation. Through considerable trial and some error, effective "curative" therapies have evolved for paroxysmal AF and are evolving for persistent AF. It is becoming clear that no single mechanism suffices to explain AF in all its forms and multiple mechanisms are playing a role in the most complicated cases.     

Intra-operative cooled-tip radiofrequency linear atrial ablation to treat permanent atrial fibrillation.

AIMS: To demonstrate the safety and efficacy of saline irrigated cooled-tip atrial linear endocardial radiofrequency ablation (SICTRA) concomitant to open-heart surgical procedures in the treatment of permanent atrial fibrillation (AF). METHODS AND RESULTS: Two hundred and twenty-two patients presenting with permanent AF and the need for cardiac surgery were included. In addition to the cardio-surgical procedure [mitral valve (MV) surgery (n = 94), aortic valve replacement (n = 29), bypass surgery (n = 76 including 24 patients with additional MV surgery), and combined procedures (n = 23)] concomitant SICTRA was performed. In 116 patients, the ablation pattern was restricted to the left atrium alone. During the mean follow-up of 29 months, 174 patients (78%) converted to sinusrhythm (SR). In patients with SICTRA restricted to the left atrium conversion rates were not different compared to a biatrial approach (83 vs. 74%, P = 0.47). Thirty-days mortality was found to be 4% (9/222). Post-mortem evaluation revealed 23% of all lesions to be histologically non-transmural. In the overall group, only 4% of patients developed sustained secondary regular atrial arrhythmia. CONCLUSIONS: SICTRA safely and effectively restores stable SR in 78% of patients with permanent AF undergoing open-heart surgery. Rhythm outcome is not influenced by treatment of the right atrium. Sustained regular atrial arrhythmia with the need for invasive treatment strategies occurs in 4% although intra-operative ablation lesions are often non-transmural.     

Left atrial radiofrequency ablation during cardiac surgery in patients with atrial fibrillation

Introduction: Intraoperative left atrial radiofrequency (RF) ablation recently has been suggested as an effective surgical treatment for atrial fibrillation (AF). The aim of this study was to verify the outcome of this technique in a controlled multicenter trial. Methods and Results: One hundred three consecutive patients (39 men and 65 women; age 62 ± 11 years) affected by AF underwent cardiac surgery and RF ablation in the left atrium (RF group). The control group consisted of 27 patients (6 men and 21 women; age 64 ± 7 years) with AF who underwent cardiac surgery during the same period and refused RF ablation. Mitral valve disease was present in 89 (86%) and 25 (92%) patients, respectively (P = NS). RF endocardial ablation was performed in order to obtain isolation of both right and left pulmonary veins, a lesion connecting the previous lines, and a lesion connecting the line encircling the left veins to the mitral annulus. Upon discharge from the hospital, sinus rhythm was present in 65 patients (63%) versus 5 patients (18%) in the control group (P < 0.0001). Mean time of cardiopulmonary bypass was longer in the RF group (148 ± 50 min vs 117 ± 30 min, P = 0.013). The complication rate was similar in both groups, but RF ablation‐related complications occurred in 4 RF group patients (3.9%). After a mean follow‐up of 12.5 ± 5 months (range 4–24), 83 (81%) of 102 RF group patients were in stable sinus rhythm versus 3 (11%) of 27 in the control group (P < 0.0001). The success rate was similar among the four surgical centers. Atrial contraction was present in 66 (79.5%) of 83 patients in the RF group in sinus rhythm. Conclusion: Endocardial RF left atrial compartmentalization during cardiac surgery is effective in restoring sinus rhythm in many patients. This technique is easy to perform and reproducible. Rare RF ablation‐related complications can occur. During follow‐up, sinus rhythm persistence is good, and biatrial contraction is preserved in most patients. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1289‐1295, December 2003)     

Long-Term Follow-Up of Corridor Operation for Lone Atrial Fibrillation:

Late Results of Surgery for AF. Introduction: Currently, surgery- and catheter-mediated ablation is applied when drug refractoriness of atrial fibrillation is evident, although little is known about the long-term incidence of new atrial arrhythmia and the preservation of sinus node function.
Methods and Results: To address this issue, 30 patients with successful corridor surgery for lone paroxysmal atrial fibrillation and normal preoperative sinus node function were followed in a single outpatient department. Five years after surgery, the actuarial proportion of patients with recurrence of atrial fibrillation arising in the corridor was 8%± 5%, with new atrial arrhythmias consisting of atrial flutter and atrial tachycardia in the corridor 27%± 8%, and with incompetent sinus node requiring pacing therapy 13%± 6%. Right atrial transport was preserved in 69% of the patients without recurrence of atrial fibrillation and normal sinus node function. Stroke was documented in two patients.
Conclusions: Corridor surgery for atrial fibrillation is a transient or palliative treatment instead of a definitive therapy for drug refractory atrial fibrillation. This observation strongly affects patient selection for this intervention and constitutes a word of caution for other, non-pharmacologic interventions for drug refractory atrial fibrillation.     

Hybrid Approach for Minimally-Invasive Operative Therapy of Arrhythmias

The failure of linear radiofrequency lesions to effectively replace operative therapy for atrial fibrillation (AF) is largely related to the inability to produce complete lines of conduction block. While pulmonary vein ablation enjoys success in patients with paroxysmal AF, patients with persistent AF and permanent AF fair less well. As such, a minimally-invasive, preferably off pump robotically-assisted procedure for complex arrhythmias like AF remains highly desirable. The shift to access from a mini-thoracotomy or port access will limit visualization and direct access to the ablation target. For the most part, the tools to overcome these limitations are not yet developed. As these develop, it is critical for the electrophysiologic effects of the delivered lesions to be assessed. With the development of non-fluoroscopic mapping systems and advances in imaging, a hybrid operative, electrophysiology (EP) suite can be equipped to provide full support for the surgeon and electrophysiologist. This will provide the opportunity to assess the efficacy and safety of ablation lesions, ideally with direct feedback to the surgeon. A hybrid approach will provide the opportunity to gain insights into the success and failure of specific ablation tools, approaches and lesions. This step will be crucial in understanding why specific procedures ultimately fail to cure AF and other complex arrhythmias.     

New-onset atrial fibrillation and outcomes following isolated coronary artery bypass surgery: A systematic review and meta-analysis

Prior meta-analyses have shown that new-onset atrial fibrillation (NOAF) occurs in up to 40% of patients following cardiac surgery and is associated with substantial major adverse cardiovascular events. The stroke and mortality implications of NOAF in isolated CABG without concomitant valve surgery is not known. We thought that NOAF would be associated with increased risk of stroke and mortality, even in patients undergoing isolated CABG. A blinded review of studies from MEDLINE, CENTRAL, and Web of Science was done by two independent investigators. Stroke, 30-day/hospital mortality, long-term cardiovascular mortality, and long-term (>1 year) all-cause mortality were analyzed. We used Review Manager Version 5.3 to perform pooled analysis of outcomes. Of 4461 studies identified, 19 studies (n = 129 628) met inclusion criteria. NOAF incidence ranged from 15% to 36%. NOAF was associated with increased risk of stroke (unadjusted OR 2.15 [1.82, 2.53] [P < .00001]; adjusted OR 1.88 [1.02, 3.46] [P = .04]). NOAF was associated with increased 30-day/hospital mortality (OR 2.35 [1.67, 3.32] [P < .00001]) and long-term cardiovascular mortality (OR 2.04 [1.35, 3.09] [P = .0007]) NOAF was associated with increased long-term all-cause mortality (unadjusted OR 1.79 [1.63, 1.96] [P < .00001]; adjusted OR 1.58 [1.24, 2.00] [P = .0002]). We found that the incidence of NOAF following isolated CABG is high and is associated with increased stroke rate and mortality. Early recognition and management of NOAF could improve outcomes.     

A Seven-year Experience for The Surgical Radiofrequency Ablation in Patients With Atrial Fibrillation

Objective A 7-year experience for the treatment strategy using mono- and bi-polar radiofrequency （RF） ablation procedures in a heterogeneous group of patients was reported. Methods Between July 2003 and May 2009, the data of 314 consecutive patients aged 13 -75 （48.70 ± 11.09 ）undergone the radiofrequency ablation procedure for atrial fibrillation （AF） associated with concomitant cardiac surgery were analyzed. Monopolar was used for 91 patients; Medtronic bi-polar RF ablation procedure for 92 patients and Atricure RF ablation procedure for 131 patients. All patients were combined with valve surgery. Regular follow-ups were performed at 3, 6 month after surgery. Results Hospital mortality after combined open heart and surgical RF ablation was 0 %. The success rates for sinus rhythm conversion with monopolar RF were 73.6 % immediately, 74. 7 % at 3 months, 79. 1% at 6 months ; with Medtronic bi- polar RF, the rates were 78.3 % immediately, 82. 8 % at 3 months, 84 % at 6 months ; with Atricure bi-polar RF, the rates were 82. 4 % immediately, 84. 1% at 3 months, 83.9 % at 6 months. Conclusions The use of RF ablation procedures is a safe and efficient option to cure AF during open heart surgery in a selective group of patients.     

Premature atrial beat eliciting atrial fibrillation after coronary artery bypass grafting

Of patients undergoing coronary artery bypass grafting 30% develop atrial fibrillation (AF) or flutter. To determine if AF is initiated from the right or left atrium, atrial electrograms were continuously recorded in patients undergoing this procedure. In addition, to study whether the prematurity index of premature atrial contractions (PACs) eliciting AF differs from PACs not provoking AF, the distribution of prematurity indices was evaluated from R-R interval analysis. The right and left atrial recording electrodes were first activated by the ectopic beat provoking AF in six and eight patients, respectively. The prematurity index of the PAC eliciting AF was located in the middle (in half of the patients) or to the left of the median distribution of prematurity indices. The variability in activation of the atrial electrodes suggests that the PAC provoking AF can have its origin in the right, the septal, or the left region of the atrium. The initiation of AF depends on the prematurity index of the PAC.     

Rhythm outcomes after aortic valve surgery: Treatment and evolution of new‐onset atrial fibrillation

BackgroundThe impact of new‐onset atrial fibrillation (AF) after aortic valve (AV) surgery on mid‐ and long‐term outcomes is under debate. Here, we sought to follow up heart rhythms after AV surgery, and to evaluate the mid‐term prognosis and effectiveness of treatment for patients with new‐onset AF.MethodsThis single‐center cohort study included 978 consecutive patients (median age, 59 years; male, 68.5%) who underwent surgical AV procedures between 2017 and 2018. All patients with postoperative new‐onset AF were treated with Class III antiarrhythmic drugs with or without electrical cardioversion (rhythm control). Status of survival, stroke, and rhythm outcomes were collected and compared between patients with and without new‐onset AF.ResultsNew‐onset AF was detected in 256 (26.2%) patients. For them, postoperative survival was comparable with those without new‐onset AF (1‐year: 96.1% vs. 99.3%; adjusted P = .30), but rate of stroke was significantly higher (1‐year: 4.0% vs. 2.2%; adjusted P = .020). With rhythm control management, the 3‐month and 1‐year rates of paroxysmal or persistent AF between patients with and without new‐onset AF were 5.1% versus 1.3% and 7.5% versus 2.1%, respectively (both P < .001). Multivariate models showed that advanced age, impaired ejection fraction, new‐onset AF and discontinuation of beta‐blockers were predictors of AF at 1 year.ConclusionsIn most cases, new‐onset AF after AV surgery could be effectively converted and suppressed by rhythm control therapy. Nevertheless, new‐onset AF predisposed patients to higher risks of stroke and AF within 1 year, for whom prophylactic procedures and continuous beta‐blockers could be beneficial.     

Early morphologic changes following microwave endocardial ablation for treatment of chronic atrial fibrillation during mitral valve surgery

INTRODUCTION: The aim of this study was to investigate the early qualitative and quantitative structural changes in the left atrial wall after endocardial microwave ablation in patients with chronic atrial fibrillation (AF) undergoing mitral surgery. METHODS AND RESULTS: Seven patients with chronic AF of for at least 6 months underwent surgical microwave energy ablation. Linear isolation of pulmonary veins was performed in all patients by microwave energy applications to the endocardial surface delivered by catheter at 65-W constant power for 45 seconds. Biopsies were obtained from a selected site (below the right lower pulmonary vein) of the left atrial posterior wall before and after the ablation procedure in all patients. Control tissues from the same sites were obtained at autopsy from patients with noncardiac causes of death. Light and electron microscopy was used to examine qualitative and quantitative changes in tissue morphology. Tissues after endocardial ablation procedure showed significantly increased loss of contractile material. Electron microscopy of atrial tissue demonstrated loss of profile of perinuclear and plasma membranes of myocytes, disruption of the endothelial cells of capillary vessels, and presence of macrophages. CONCLUSION: Lesions created by endocardial microwave energy ablation revealed a transmural effect on the left atrial wall without a significant reduction in thickness but a significant increase in the myolytic areas involving the entire cytosol and occlusion of the small intramyocardial vessels within the ablative lesion.     

Atrial fibrillation after cardiac surgery: Prevention and management: The Australasian experience

Background

Atrial fibrillation (AF) after cardiac surgery is a major health problem that is associated with a significant financial burden. This paper aims to highlight this problem and review the current guidelines in the prevention and management of AF after cardiac surgery, providing our experience in the Australasian centers.

Transthoracic and transoesophageal echocardiography in the diagnosis and management of a biatrial myxoma

A 40-year-old female presented with a year's history of atrialfibrillation. Transthoracic echocardiography identified thepresence of a biatrial mass and transoesophageal echocardiographydelineated irs extent. At surgery, a huge myxoma originatingfrom the fossa ovalis and straddling the inter-atrial septumwas removed and the atrial septum repaired. This report highlightsthe role of transthoracic and transoesophageal echocardiographyin the diagnosis and management of this extremely rare cardiacrumour.     

Early Antiarrhythmic Therapy Is No Better than Rate Control Therapy Alone for Suppression of Atrial Fibrillation After Cardiac Surgery

Background: Despite recent advances in therapy for atrial fibrillation (AF) following cardiac surgery, the potential superiority of antiarrhythmics over rate control therapy for suppression of AF has not been convincingly demonstrated. We sought to determine whether early treatment of AF following cardiac surgery with antiarrhythmics improves clinical outcome, as measured by recurrence rate, length of stay, and adverse events. Methods: Out of 1100 consecutive patients undergoing cardiovascular surgery from July 1997 to June 1998, AF was identified in 425 (38.6%) prior to discharge. Patients with a history of chronic AF prior to cardiovascular surgery and patients who died within 48 hours of cardiovascular surgery were excluded from the analysis; 365 patients were studied. Group I patients received rate control alone; Group II received antiarrhythmic drugs within 24 hours of the first onset of AF. Results: With the exception of frequency of pulmonary disease (4 vs 17, P = 0.009), CABG rate (35 vs 45%, P = 0.045), and rate of valve surgery (24 vs 15%, P = 0.028), there were no significant differences in clinical characteristics between the two groups. The rate of return to sinus rhythm within 24 hours (80 vs 82%), and the percentage of patients leaving the hospital in sinus rhythm (90 vs 92%) were similar between the two groups, as were total length of stay (10.6 ± 6.0 vs. 11.4 ± 5.8, P = 0.159) and postoperative length of stay (8.4 ± 15.0 vs. 9.4 ± 5.3, P = 0.061). Embolic event rates were similar in both groups (eight in Group I and three in Group II). Proarrhythmia occurred in two patients receiving early antiarrhythmic therapy. Conclusion: Traditional use of early antiarrhythmic therapy appears to provide no clear advantage to rate control after cardiovascular surgery in terms of length of stay, freedom from AF at discharge, and other common clinical outcomes. Routine use of antiarrhythmics for suppression of AF should be carefully reconsidered. A.N.E. 2000;5(4):365–372     

微创外科消融治疗心房颤动的进展

心房颤动是临床中最常见的心律失常之一,外科治疗心房颤动已有近30年的历史。近10年来,微创外科消融手术作为一种创伤小的、治愈率高的治疗手段在治疗心房颤动方面取得了长足的进展。心房线性消融和自主神经节消融的具体手术策略因尚无统一的标准术式而倍受关注;微创外科用于治疗心房颤动,在应用中也暴露了其自身的缺点和不足,也正因如此,近年来一些新的技术方法和创新理念被融入微创外科消融手术中来,并日渐加以改进和完善。相信伴随着手术方式的改良、手术设备的改进以及理念的创新,微创消融手术治疗心房颤动会不断拓展其手术适应证并会被更多的人接受。     

Surgical approaches to atrial fibrillation

Atrial fibrillation (AF) remains an unsurmounted hurdle toward the cure of supraventricular arrhythmias. Despite its high prevalence, a definitive treatment approach has not been established. AF is triggered in most cases by early premature atrial beats and is maintained by anomalies of the substrate. Elimination or modification of either one or both may be effective in the cure of AF.Surgical ablation, which originated with the favorable results of the Maze procedure developed by Cox, has an important role in the cure of AF associated with heart diseases that require cardiac surgery. This is due to the high success rate and to the simplification of the procedure now used which has resulted in reduction of the procedural time and complications.Various techniques have been proposed, however, it is noteworthy that the posterior part of the left atrium and the ostia of pulmonary veins are involved in all approaches despite the different energy sources used (radiofrequency or cryo energy) and the different design of the intended lesion. These results imply that the posterior part of the left atrium is crucial in the genesis and maintenance of atrial fibrillation. On the other hand, it is not clear if the results of the ablation are due to the linear lesions that modify the substrate or to the electrical isolation that eliminate the triggers. A thorough electrophysiological evaluation post ablation has been performed only in few cases. Greater understanding of the mechanism of success of surgical ablation may advance the development and success of other approaches.Considering that surgical ablation is usually performed in patients with permanent AF, linear lesions modifying the substrate together with pulmonary vein isolation have shown better results than the elimination of the triggers with a pure electrical isolation of the pulmonary veins.Prevention of AF recurrences has been relatively good, however some severe complications (atrioesophagus fistula, coronary artery damage, etc.) have been reported. Considering the relatively benignity of AF in absence of associated cardiopathy, the risk of complications should discourage widespread application of surgical ablation in patients with lone AF. On the contrary it should be routinely proposed in most patients with permanent or paroxysmal AF undergoing cardiac surgery.     

小剂量口服胺碘酮在心脏瓣膜疾病合并心房颤动患者围术期的应用

目的 评估围术期口服胺碘酮对心脏瓣膜疾病合并心房颤动患者术后心房颤动心律的转复和窦性心律维持,以及术后并发症的影响.方法 78例心房颤动且择期行心脏瓣膜手术的患者被分为试验组（38例）和对照组（38例）.试验组开始口服胺碘酮每天2次,每次200 mg至术后第3天,术后第4天至出院前胺碘酮剂量改为每天1次,每次200 mg.对照组以安慰剂代替胺碘酮,服药时间、剂量和方法同实验组.比较两组术后窦性心律的转复和维持、有无低心排血量综合征、心律失常发生及类型、重症监护病房停留时间、住院时间、出院时心房颤动患者的心律和心室率,及术前、术后患者肝功能、甲状腺功能的变化,有无发生肺纤维化.结果 术后两组比较,试验组窦性心律患者比例在手术复跳时（39.4％ vs.10.5％,P＜0.01）、出院前（46.7％ vs.2.6％,P＜0.01）及术后1个月（36.8％ vs.2.6％,P＜0.01）均高于对照组,差异有统计学意义.试验组与对照组比较,术后快速性心房颤动（15.8％ vs.31.6％,P＜0.05）、发作时心室率[（136.5±25.2）次/min vs.（158.6±30.9）次/min,P＜0.05]及室性心律失常（7.9％ vs.18.4％,P＜0.05）低于对照组,差异有统计学意义.试验组重症监护病房停留时间[（40.9±11.2）hvs.（58.5±13.8）h,P＜0.05）]、心房颤动患者出院时心室率[（74.2±8.4）次/min vs.（91.7±10.2）次/min,P＜0.05]均小于对照组,差异有统计学意义.两组患者术后无死亡,无肝功能及甲状腺功能异常及无肺纤维化.结论 行心脏瓣膜置换或整形手术的心房颤动患者围术期口服胺碘酮可明显提高患者术后窦性心律转复率、维持窦性心律时间、降低快速心房颤动及室性心律失常发生率,对心室率的控制满意,减少重症监护病房入住时间,无明显不良反应.     

双极射频消融心房颤动同时手术治疗器质性心脏病的临床效果

目的：探讨双极射频消融钳治疗心房颤动同期行开胸手术治疗器质性心脏病的手术方法和临床结果,提高对此类疾病的治疗水平。方法：回顾分析2009年8月～2012年5月对58例器质性心脏病并发心房颤动用双极射频消融钳治疗房颤的临床资料。结果：本组患者手术均顺利完成。射频时间16～38（24±4） min,主动脉阻断时间64～200（126±36） min,体外循环时间91～238（150±37） min;手术结束及出院时窦性心率分别为46（79%）,45（78%）例,随访3个月,6个月和12个月,窦性心率分别为41（71%）,40（69%）和42（72%）例。全组病例无手术死亡和射频相关并发症。所有患者均无需安装永久起搏器。双心房消融与单独左房消融比较无显著差异。结论：此方法可行,效果满意,但要注意把握适应证。