Contemporary approach to ablation of paroxysmal atrial fibrillation

Pulmonary veins have been shown to play an important role in the initiation and maintenance of paroxysmal atrial fibrillation. Seg-mental ostial isolation of the pulmonary veins results in cure in about 2/3 of the patients. This approach does not address non-pulmonary venous triggers of atrial fibrillation or the importance of the left atrium itself. Left atrial circumferential ablation has also been shown to be efficacious in patients with paroxysmal atrial fibrillation. This approach seems to address not only the various triggers of atrial fibrillation but also the left atrial substrate. Recently, a randomized study compared the 2 strategies and showed that left atrial ablation is superior to segmental ostial isolation. This review will highlight the anatomy and electrophysiology of the pulmonary veins, and the possible mechanisms by which they initiate and maintain paroxysms of atrial fibrillation. Segmental ostial isolation of the pulmonary veins and left atrial ablation will be compared as well.     

Catheter ablation of focal triggers and drivers of atrial fibrillation

It has been demonstrated that most paroxysmal atrial fibrillation (AF) is triggered by ectopic beats originating from the pulmonary veins (PVs). It has been recently reported that some AF episodes are maintained by focal drivers and AF substrates in the PVs and atrium. Left atrial ablation combined with PV isolation targeting AF triggers and drivers may be effective for eliminating atrial arrhythmias. However, multiple AF drivers in the PVs and atrium and acute conduction recovery after the PV isolation may sometimes render that technique less reliable. In this article, we describe the current status of the catheter ablation of focal triggers and drivers of AF in the PVs and atrium, illustrating with case presentations.     

Katheterablation bei Vorhofflimmern

In recent years there have been substantial developments in the diagnostics and treatment of atrial fibrillation (AF) which in particular increase the value of interventional treatment. Based on the knowledge that focal triggers from the pulmonary veins (PV) represent the predominant site for paroxysmal atrial fibrillation (PAF), catheter ablation in the form of an electrophysiological disconnection of the PV has become increasingly established. The principle of this treatment is elimination of the trigger (e.g. atrial extrasystole) responsible for initiation of AF, and in particular, PAF. According to the recommendations of international societies the indication for isolation of pulmonary veins is fulfilled if patients with symptomatic PAF fail at least one anti-arrhythmic therapy. The aim of ablation is to permanently isolate the trigger activity by electrical disconnection of the PV in the area of the transition to the left atrium. Pulmonary vein isolation is now the generally accepted primary aim and will, in 60–80% of cases with PAF, lead to successful treatment after the first attempt. The success rate of repeated catheter ablation is ≥80%. In patients with long-lasting, chronic atrial fibrillation (CAF) it is very rare that PVs are the only substrate for initiating and maintaining AF, so in the majority of these patients isolation of pulmonary veins alone is not sufficient. This can be pathophysiologically explained in long-lasting AF by advanced atrial remodeling at electrical and structural levels. In recent years it could be shown that patients with CAF benefit from additional substrate modification. Subsequently, pulmonary vein isolation, followed by defragmentation and possibly linear lesions were combined in a step-wise ablation approach with the aim of terminating AF through ablation. Under these circumstances approximately half of the patients need several procedures which require treatment of the subsequently occurring atrial tachycardia. Because treatment is time-consuming, the lack of transferability of these very complex procedures with lacking long-term results and the possible complications, catheter ablation is not yet clinically established for CAF patients and should only be carried out in experienced centers with great expertise. In summary the invasive treatment of symptomatic medical therapy refractive AF has become increasingly more established in recent years. Current meta-analyses in randomized studies comparing the success rates of radio frequency ablation with medical anti-arrhythmic therapy indicate that catheter ablation is advantageous with respect to freedom from recurrence. Studies with prognostically relevant endpoints, such as mortality or frequency of stroke are ongoing.     

Canadian Cardiovascular Society atrial fibrillation guidelines 2010: catheter ablation for atrial fibrillation/atrial flutter

Catheter ablation of atrial fibrillation (AF) offers a promising treatment for the maintenance of sinus rhythm in patients for whom a rhythm control strategy is desired. While the precise mechanisms of AF are incompletely understood, there is substantial evidence that in many cases (particularly for paroxysmal AF), ectopic activity most commonly located in and around the pulmonary veins of the left atrium plays a central role in triggering and/or maintaining arrhythmic episodes. Catheter ablation involves electrically disconnecting the pulmonary veins from the rest of the left atrium to prevent AF from being triggered. Further substrate modification may be required in patients with more persistent AF. Successful ablation of AF has never been shown to alter mortality or obviate the need for oral anticoagulation; thus, the primary indication for this procedure should be improvement of symptoms caused by AF. The success rate of catheter ablation for AF is superior to the efficacy of antiarrhythmic drugs, but success is still in the range of 75%-90% after 2 procedures. Ablation is also associated with a complication rate of 2%-3%. Thus, ablation should primarily be used as a second-line therapy after failure of antiarrhythmic drugs. In contrast to AF, catheter ablation of atrial flutter has a higher success rate with a smaller incidence of complications. Thus, catheter ablation for atrial flutter may be considered a first-line alternative to antiarrhythmic drugs.     

Substrate Ablation in Treatment of Atrial Fibrillation

From the time catheter ablation of atrial fibrillation (AF) was first reported, of the two dominant approaches for AF ablation, only pulmonary vein (PV) isolation has been modified, while circumferential pulmonary vein ablation (CPVA) as performed by our group in Milan has remained substantially unmodified. In fact, PV isolation as initially performed by Haissaguerre et al. has undergone rapid evolution toward substrate modification with significantly higher success rates without major complications. Modification of such technique was due to modification of the substrate. It is now evident that substrate modification is indeed crucial for curing AF particularly in patients with long-lasting or permanent AF. Indeed, to achieve good outcomes, any ablation technique should simultaneously include elimination of all triggers associated with modification of both anatomic and autonomic substrate, as we started to do many years ago by performing CPVA.     

Ablation of atrial fibrillation

Associated with significant morbidity and mortality, atrial fibrillation is one of the most common cardiac rhythm disorders. Cure of this arrhythmia has been elusive over the years, despite development of different antiarrhythmic drugs and advances in the understanding of its pathophysiology. Initial experience with catheter ablation procedures based on the creation of linear lesions in both atria has been disappointing, but has led to the key observation that focal triggers localized in the pulmonary veins are responsible for initiation of atrial fibrillation, and thus are suitable targets for catheter ablation. With advances in technology and larger experience, it has become clear that electrical isolation of all four pulmonary veins from the left atrium provides the higher cure rates. However, the procedure is still operator dependent and is associated with a small but significant risk of pulmonary vein stenosis. Further simplification of the isolation techniques and refinement in the catheter design will allow more widespread use of this procedure and higher success rate.     

Canadian Cardiovascular Society atrial fibrillation guidelines 2010: surgical therapy

Surgery for atrial fibrillation (AF) has been demonstrated as an effective treatment to restore and maintain sinus rhythm in patients for whom a rhythm control strategy is desired. It is usually offered to patients undergoing other types of cardiac surgery (eg, mitral valve repair or replacement, coronary artery bypass grafting, aortic valve surgery, intracardiac defects, ascending aortic surgery). It is also feasible as a stand-alone procedure, bearing a high success rate. In the past few years, less-invasive procedures have been described. AF is a triggered arrhythmia, resulting from ectopic activity most commonly located in and around the pulmonary veins of the left atrium. Therefore, electrical isolation of the pulmonary veins from the rest of the left atrium in order to prevent AF from being triggered is the rationale common to all surgical techniques. Further substrate modification may be required in patients with more persistent AF. This is done by adding ablation of the posterior left atrium with connecting lines of block between pulmonary veins, to the mitral valve annulus, as well as in specific sites in the right atrium. The left atrial appendage is resected or occluded at the same time. Despite patients' high rate of freedom from AF after surgery (70%-85% at 1 year), surgical ablation of AF has never been clearly shown to alter long-term mortality. The available literature supports the recommendation to stop oral anticoagulation therapy 6 months after surgery when sinus rhythm can be documented, because a very low rate of thromboembolic events is reported. However, there is no evidence-based data to support the safety of omitting long-term oral anticoagulation. Thus, surgery should be used primarily as a concomitant procedure during cardiac surgery for other diseased states or as a stand-alone procedure after failure of prior attempts of catheter ablation and antiarrhythmic drugs.     

Curative treatment of atrial fibrillation 2000: percutaneous catheter ablation techniques and intraoperative ablation with minimally invasive techniques

Summary Experimental and clinical mapping studies have indicated that the initiation of atrial fibrillation has to be differentiated from the perpetuation. Curative treatment of atrial fibrillation is one of the main challenges of today's electrophysiology, and the trigger as well as the substrate have recently been targeted. The arrhythmogenic foci which have been identified as being critical for the initiation of paroxysmal atrial fibrillation have been found in the vast majority of patients in the area of the proximal pulmonary veins. In a subset of patients with paroxysmal atrial fibrillation, these firing foci may be the only electrophysiologic abnormality. In other patients, different atrial arrhythmia types may be driven by pulmonary vein foci. Haissaguerre et al. have introduced mapping strategies to identify active foci within the pulmonary veins. The success rate of percutaneous pulmonary vein focus ablation strongly depends on the number of active foci. In contrast to elimination of the initiating triggers in patients with paroxysmal atrial fibrillation, modification of the maintaining substrate of atrial fibrillation is the alternative target for ablation in patients with chronic atrial fibrillation or in patients with prolonged episodes of paroxysmal atrial fibrillation. Different linear lesion line concepts within the right and/or left atrium have been followed within the last few years with moderate success rates. The lesion geometries that have been applied percutaneously so far seem to be empirical, and no successful lesion geometry concept for percutaneous application has been validated. A surgical curative treatment concept for patients with chronic atrial fibrillation is the maze procedure introduced by Cox et.al. which, however, is an extensive and time consuming surgical technique. Within the last few years, several attempts have been made to develop alternative surgical treatment strategies that should be safe, effective, and easy to apply. One of the promising new concepts is the intraoperative radiofrequency ablation of atrial fibrillation by elemination of anatomically determined so-called anchor reentrant circuits involving the pulmonary vein orifices and the mitral annulus. In this review, data on percutaneous ablation of pulmonary vein foci, percutaneous placement of linear right and/or left atrial lesion lines and, finally, intraoperative radiofrequency (RF) ablation using minimally invasive techniques are summarized.     

Carto系统指导下环肺静脉线性消融治疗心房颤动的临床应用

目的 报道50例在Carto标测指导下环肺静脉线性消融治疗心房颤动(房颤)的结果和体会.方法 46例阵发性和4例持续性房颤患者采用Carto标测构建左心房三维电解剖图,行肺静脉造影了解其形态,围绕左侧和右侧肺静脉口线性消融,对肺静脉进行隔离.结果 50例患者均完成预定的线性消融.4例阵发性房颤患者术后1～2 d有房颤复发,l例自行转复,3例静脉用胺碘酮转复.术后1例患者出现少量心包积液,1例出现顽固性呃逆,3例出现颈部血肿.随访6～12(8.5 ±3.8)个月,37例患者未发生有症状的房颤,13例患者术后出现复发,1例患者发生肺静脉狭窄.结论 环肺静脉线性电隔离治疗房颤有较好的治疗效果,但也存在一定的并发症和复发可能性,仍需积累更多病例和做更长时间的观察.     

Is pulmonary vein isolation enough for persistent atrial fibrillation?

Pulmonary vein isolation (PVI) is a well‐established treatment for atrial fibrillation (AF); however, studies report suboptimal outcomes in persistent AF. Adjuvant ablation targeting the substrate outside the pulmonary veins has been proposed to improve the success rates of the procedure. In this review, we summarize the current evidence regarding additional ablation over PVI in persistent AF. We describe the different approaches for adjuvant ablation, outcomes, and future perspectives.     

The place of ablation in the treatment of atrial fibrillation: where are we and where are we going?

Atrial fibrillation, the most common arrhythmia, is frequently disabling and drug resistant and is associated with significant complications, especially thromboembolic events. Non-pharmacological approaches including surgery and catheter-based ablation have been developed for the most symptomatic patients. These new treatment strategies have dramatically increased our knowledge of the pathophysiology of this arrhythmia but most importantly have demonstrated that atrial fibrillation is curable. Since 1994, 2 different concepts have been used, aiming to modify the substrate responsible for AF maintenance using linear lesions, or to ablate the triggers located from within the pulmonary veins (PV) in about 90% of cases. The vast majority of the laboratories in the world are now using approaches centred on isolation of the PV. These approaches are far from being perfect but good enough to be offered in routine practice to selected patients in experienced centres. The importance of PVs in the initiation of AF has been clearly demonstrated and they also have a possible role in the maintenance of AF. However, the existence of non venous foci or a prominent substrate for AF maintenance limits the success rate to about 70%. As a consequence, a combination of PV isolation and linear lesions is commonly used. This more complex procedure carries a significantly higher success rate however with an increased risk of tamponade. As a consequence, we need to identify which patients will require linear lesions in addition to PV isolation. At the present time, AF ablation is restricted to symptomatic patients who have failed at least 1-2 antiarrhythmic drugs but future technical improvements based on presently applied concepts are likely to widen the indications for ablation therapy of AF.     

肺静脉和左房内嵴形态与心房颤动射频消融术后早期心律失常的关系

目的探讨肺静脉开口大小和心房内嵴宽度与心房颤动(简称房颤)射频消融术后早期心律失常的关系。方法38例房颤患者应用GE LightSpeed VCT进行CT扫描,采用多平面重组和仿真内窥镜测量四个肺静脉开口内径和心房内嵴的宽度,接受Carto-Merge技术指导的环肺静脉电隔离术,门诊随访3个月。结果术后3个月内,有19例出现房性心律失常,包括16例房性早搏(简称房早),8例短阵房性心动过速(简称房速),7例心房扑动,14例房颤。3个月内出现与未出现各种房性心律失常患者的肺静脉开口面积均无明显差别(P>0.05)。术后早期有短阵房速或房颤的患者左右两侧肺静脉间嵴的宽度都明显大于无短阵房速或房颤的患者(P<0.05)。术后有房早的患者的左心耳与左侧肺静脉间嵴的宽度明显大于无房早者(P<0.05)。结论Carto-Merge技术指导房颤环肺静脉电隔离手术后3个月的各种房性心律失常,与肺静脉开口基本无关,而左心耳与左侧肺静脉间嵴的宽度与术后早期房早有关,左右两侧肺静脉间嵴的宽度与术后早期短阵房速和房颤有关。     

Catheter Ablation for Long-Standing Persistent Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia worldwide and represents a major burden to health care systems. Atrial fibrillation is associated with a 4- to 5-fold increased risk of thromboembolic stroke. The pulmonary veins have been identified as major sources of atrial triggers for AF. This is particularly true in patients with paroxysmal AF but not always the case for those with long-standing persistent AF (LSPAF), in which other locations for ectopic beats have been well recognized. Structures with foci triggering AF include the coronary sinus, the left atrial appendage (LAA), the superior vena cava, the crista terminalis, and the ligament of Marshall. More than 30 studies reporting results on radiofrequency ablation of LSPAF have been published to date. Most of these are observational studies with very different methodologies using different strategies. As a result, there has been remarkable variation in short- and long-term success, which suggests that the optimal ablation technique for LSPAF is still to be elucidated. In this review we discuss the different approaches to LSPAF catheter ablation, starting with pulmonary vein isolation (PVI) through ablation lines in different left atrial locations, the role of complex fractionated atrial electrograms, focal impulses and rotor modulation, autonomic modulation (ganglionated plexi), alcohol ablation, and the future of epicardial mapping and ablation for this arrhythmia. A stepwise ablation approach requires several key ablation techniques, such as meticulous PVI, linear ablation at the roof and mitral isthmus, electrogram-targeted ablation with particular attention to triggers in the coronary sinus and LAA, and discretionary right atrial ablation (superior vena cava, intercaval, or cavotricuspid isthmus lines).     

Persistent Atrial Fibrillation Ablation: Where Do We Go From Here?

Catheter ablation is being used increasingly for the treatment of atrial fibrillation (AF). Pulmonary vein antral isolation is considered the "cornerstone" for the ablation of AF. This approach has demonstrated consistent rates of success for paroxysmal AF, but the rates of success for persistent AF are lower. There has long been a hypothesis that additional ablation beyond pulmonary vein isolation is required to achieve better outcomes in the population with persistent AF. However, large clinical trials have demonstrated recently that such approaches as empiric linear ablation and/or ablation of complex fractionated electrograms may add no benefit over pulmonary vein isolation alone in persistent AF. Furthermore, new technologies are improving the durability and outcome of pulmonary vein isolation alone. These observations have endorsed a search for new potential targets for adjuvant ablation, which currently include ablation of dynamic phenomena during AF such as rotational and focal activations, ablation of scar regions in the atria, isolation of the left atrial posterior wall, and ablation of nonpulmonary vein triggers. Whether any of these additional approaches will add to the success of ablation for persistent AF is unknown. Smaller study results are mixed. Only the performance of large-scale randomized trials will definitively answer whether additional ablation over pulmonary vein isolation alone with improve outcomes for persistent AF.     

肺静脉电隔离术联合碎裂电位消融治疗持续性房颤疗效观察

目的：观察肺静脉电隔离术（ pulmonary vein isolation , PVI ）联合碎裂电位（ complex fractionated atrial electrograms , CFAE）消融对持续性房颤的疗效。方法对比观察23名于本院行房颤射频消融术的持续性房颤患者,所有患者均行PVI及左房顶部线性消融,其中12例联合CFAE消融,术后随访1年;观察两组手术时间、X线曝光时间、消融时间、手术并发症、左房大小、左房血栓、一次手术成功率等指标。结果联合CFAE消融组总手术时间（252±35） min、X线曝光时间（42±9．1）min、消融时间（94±11）min,单纯行PVI 组分别为（176±22）min、（34±7．6）min、（63±8）min,联合CFAE消融组手术各时间均明显延长（P＜0．01）;两组手术并发症、对左房大小及左房血栓的影响比较差异均无统计学意义;联合CFAE消融组一次手术成功率（75％）明显高于单纯行PVI组（64％）（ P＜0．05）。结论 PVI联合CFAE消融治疗持续性房颤虽增加手术、消融及X线曝光时间,但并不会提高并发症发生率,可提高房颤消融的一次手术成功率。     

Pulmonary edema after extensive radiofrequency ablation for atrial fibrillation

Background: More extensive ablation strategies for the treatment of atrial fibrillation (AF) have increased success rates but are associated with new and sometimes serious complications. We describe a new complication after extensive radiofrequency (RF) ablation in the left atrium (LA) for persistent AF.
Methods and Results: Electroanatomic guided circumferential ablation around both ipsilateral pulmonary veins (PV) was performed with the endpoint of complete conduction block. When necessary, supplementary RF applications were added, including ablation of complex fractionated potentials and/or isolation of other thoracic veins and/or linear left atrial lesions. RF energy was delivered via an irrigated tip catheter with a maximum power of 30–35 W. Four out of 120 patients undergoing extensive RF ablation for persistent AF (including two patients with additional LA substrate modification) developed dyspnea, bilateral pulmonary edema, and signs of a systemic inflammatory response syndrome (SIRS) (rise in body temperature, leukocyte count, and C-reactive protein (CRP levels) 18–48 hours after the procedure. There were no signs of PV stenosis, focal lung injury, left ventricular dysfunction, circulatory failure, or infection. All patients had complete recovery with supportive therapy within 3–4 days after the onset of symptoms.
Conclusions: Extensive LA radiofrequency ablation bears the risk of a severe pulmonary edema. Although the precise mechanism is elusive, clinical features point toward a systemic inflammatory response.     

Atrial Anatomy and Imaging in Atrial Fibrillation Ablation

Catheter ablation of atrial fibrillation (AF) can be a technically challenging procedure, requiring detailed knowledge of the anatomy of the atria and thoracic veins to achieve successful cure of AF with a low complication rate. In this article, we review the anatomy relevant to AF ablation: the intraatrial septum, the pulmonary veins and left atrial antral region, the left atrial vestibule, the right atrium and related veins, and the esophagus. We focus on normal variations of anatomy and the role of the available imaging modalities in facilitating safe and effective ablation of this common and complex arrhythmia.     

Atrial Fibrillation Ablation Using Vein of Marshall Ethanol Infusion

Catheter ablation has become a cornerstone treatment for atrial fibrillation (AF). Pulmonary vein isolation is the accepted approach for paroxysmal AF ablation, but it is less effective for persistent AF. The vein of Marshall (VOM) is located in the epicardial left atrium and can be a source of AF triggers as well as a tract for autonomic nerves. It directly communicates with the underlying myocardium, including the left atrial ridge and the posterior mitral isthmus. This review discusses the latest evidence regarding the mechanisms, procedural aspects, and outcomes of VOM ethanol infusion when used as an adjunct to pulmonary vein isolation in patients with persistent AF.     

Katheterablation bei persistierendem Vorhofflimmern

The invasive treatment of persistent atrial fibrillation (AF) is one of the biggest challenges in modern electrophysiology. Treatment strategies are diverse and include pulmonary vein isolation (PVI) alone, left atrial ablation lines, local electrogram-based ablation of complex fractionated electrograms (CFAE) or various combinations of these techniques. New approaches comprise fibrosis-guided ablation or the localisation and ablation of AF sustaining rotors. Different ablation techniques reflect a different understanding of what the most important pathophysiological mechanism of persistent AF might be. Multiple wavelets, repetitive focal discharges (mostly from the pulmonary veins), instable micro-reentries, anatomically fixed slow conduction zones close to atrial scarring or (relatively stable) rotors have been proposed as AF sustaining factors. It has become evident that conventional ablation strategies often involve more than one ablation procedure to reach acceptable success rates, whereas new methods of fibrosis-guided ablation and rotor ablation are still under evaluation.     

Current Hot Potatoes in Atrial Fibrillation Ablation

Atrial fibrillation (AF) ablation has evolved to the treatment of choice for patients with drug-resistant and symptomatic AF. Pulmonary vein isolation at the ostial or antral level usually is sufficient for treatment of true paroxysmal AF. For persistent AF ablation, drivers and perpetuators outside of the pulmonary veins are responsible for AF maintenance and have to be targeted to achieve satisfying arrhythmia-free success rate. Both complex fractionated atrial electrogram (CFAE) ablation and linear ablation are added to pulmonary vein isolation for persistent AF ablation. Nevertheless, ablation failure and necessity of repeat ablations are still frequent, especially after persistent AF ablation. Pulmonary vein reconduction is the main reason for arrhythmia recurrence after paroxysmal and to a lesser extent after persistent AF ablation. Failure of persistent AF ablation mostly is a consequence of inadequate trigger ablation, substrate modification or incompletely ablated or reconducting linear lesions. In this review we will discuss these points responsible for AF recurrence after ablation and review current possibilities on how to overcome these limitations.