Marshall vein as arrhythmogenic source in patients with atrial fibrillation: correlation between its anatomy and electrophysiological findings

Comparison of the effect of ethanol infusion into the vein of Marshall between with and without collateral veins

BACKGROUND

Despite the potential benefits of ethanol infusion into the vein of Marshall (EIVOM) for atrial fibrillation (AF) ablation, concerns about its reversible and unpredictable effects persist.

OBJECTIVE

To assess the effectiveness of EIVOM in the vein of Marshall (VOM) with collateral veins (CVs) during mitral isthmus and AF ablation.

METHODS

We included 142 AF patients. EIVOM was performed before radiofrequency ablation, and low-voltage areas (<0.5 mV) were measured before, immediately after, and 1 h after EIVOM.

RESULTS

Among the 142 patients, 93 (65%) underwent EIVOM, and among these, 35 (37%) were found to have CVs. In the VOM with CVs group, areas with low voltage measured 0 (0-1.85) cm2 before EIVOM, 6.9 (4.1-11.2) cm2 immediately after EIVOM, and 5.7 (3.5-10.6) cm2 1 h after EIVOM. Conversely, in the group designated as VOM without CVs-from which the nine leakage cases were excluded-the areas measured 0 (0-1.35) cm2 , 5.5 (2.6-11.8) cm2 , and 4.7 (1.8-13.5) cm2 at the respective time points. MI line block was fully achieved in 89% (31/35) of cases in the VOM with CVs group and 88% (44/49) in the VOM without CVs groups (p = .94). There was no significant difference in the outcome of AF ablation between these groups (log-rank p = .73). Additionally, no significant difference was observed between EIVOM (+) and EIVOM (-) groups (log-rank p = .59).

CONCLUSION

EIVOM effectively creates MI line block, and its beneficial effects are sustained for at least 1 h after the procedure despite the low-voltage areas showing a slight reduction in size.

Efficacy and durability of posterior wall isolation with ethanol infusion into the vein of Marshall

INTRODUCTION

Ethanol infusion into the vein of Marshall (EIVOM) is expected to be an adjunctive therapy for mitral isthmus (MI) ablation. Additionally, EIVOM can widely ablate the epicardium via the branches that extend to the left atrial posterior wall (LAPW) and facilitate LAPW isolation. This study aimed to investigate the efficacy and durability of LAPW isolation with EIVOM.

METHODS

Our cohort consisted of 413 patients with atrial fibrillation (AF) who underwent both LAPW and MI ablations. EIVOM was first attempted in 177 (35%) patients with adequate VOMs. The VOM was infused with 5 mL of ethanol with a double coaxial guiding catheter technique. Both ablations were performed only by radiofrequency ablation (the RF group) in the remaining 236 (57%) patients.

RESULTS

EIVOM with 5 mL of ethanol was completely achieved in 106 patients (the EIVOM group). The application duration of LAPW isolation did not differ significantly between the two groups (718 ± 276 vs. 709 ± 288 s; p = .78). LAPW debulking ablation was required in 64/106 (60%) and 176/236 (75%) patients in the EIVOM and RF groups, respectively (p < .05). However, AF- or atrial tachycardia-free survival analyses revealed no significant differences between the two groups (log-rank p = .70). Among the cases of recurrence, 17 and 38 patients underwent subsequent ablation sessions; LAPW was reconnected in 9/17 (53%) and 25/38 (53%) patients (p = .36) in the EIVOM and RF groups, respectively.

CONCLUSION

EIVOM reduced the number of cases that required LAPW debulking ablation but did not improve the durability of LAPW isolation or clinical outcomes.

Optimization of intra-operative electrophysiological localization of the ligament of Marshall

Background

The ligament of Marshall (LOM) may play a role in the pathophysiology of several tachyarrhythmias and accurate electrophysiological localization of this structure is crucial for effective ablation therapy. This study therefore quantifies electrophysiological properties of the LOM, and identifies which electrogram (EGM) recording (uni- or bipolar) and processing technologies [local activation time (LAT) and/or voltage mapping] are most suitable for accurate localization of the LOM.

Methods

The LOM was electrophysiologically identified in 19 patients (mean age 66 ± 14 years; 12 male) undergoing elective cardiac surgery using intra-operative high-density epicardial mapping, to quantify and visualize EGM features during sinus rhythm.

Results

Only a third of LOM potentials that were visualized using unipolar EGMs, were still visible in bipolar activation maps. Unipolar LOM potentials had lower voltages (P50: LOM: 1.51 (0.42–4.29) mV vs. left atrium (LA): 8.34 (1.50–17.91) mV, p < 0.001), less steep slopes (P50: LOM: –0.48 (–1.96 to –0.17) V/s vs. LA: –1.24 (–2.59 to –0.21) V/s, p < 0.001), and prolonged activation duration (LOM: 20 (7.5–30.5) ms vs. LA: 16.5 (6–28) ms, p = 0.008) compared to LA potentials. Likewise, bipolar LOM voltages were also smaller (P50: LOM: 1.54 (0.48–3.28) mV vs. LA: 3.12 (0.50–7.19) mV, p < 0.001).

Conclusion

The LOM was most accurately localized in activation and voltage maps by using unipolar EGMs with annotation of primary deflections in case of single potentials and secondary deflections in case of double or fractionated potentials.

Angiographic Characteristics of the Vein of Marshall in Patients with and without Atrial Fibrillation

Background: Ethanol infusion into the vein of Marshall (Et-VOM) is a novel therapeutic treatment for atrial fibrillation (AF). However, few studies have focused on the difference between AF and non-AF patients (presented other types of arrhythmias) regarding the characteristics of the vein of Marshall (VOM). Objective: This study sought to investigate the incidence, morphology, and angiographic characteristics of the VOM. Methods: Coronary sinus (CS) angiography was performed in all patients. The baseline, angiographic characteristics and measurements of VOM dimensions were compared between the AF and non-AF group. Results: CS angiography was performed in 290 patients. The VOM detection rate was higher in the AF group than in the non-AF group (91.8% vs. 84.1%, p = 0.044). In the right anterior oblique (RAO) projection, AF patients had significant larger VOM ostium, CS ostium, and CS diameter at VOM ostium than non-AF patients (1.9 ± 0.9 vs. 1.7 ± 0.7 mm, p = 0.015; 12.8 ± 4.1 vs. 11.4 ± 3.7 mm, p = 0.016; 9.1 ± 3.1 vs. 8.2 ± 2.9 mm, p = 0.028, respectively). There was a slight linear correlation between the VOM ostium and the CS ostium diameter as well as left atrial volume (LAV). Conclusion: AF patients seem to have a higher incidence of the VOM, larger VOM ostium, CS ostium, and CS lumen in RAO view. Meanwhile, the VOM ostium may correlate with the CS ostium and LAV.

Recurrent Atrial Fibrillation with Isolated Pulmonary Veins: What to Do

When patients have symptomatic recurrent atrial tachyarrhythmias after 2 months following pulmonary vein antral isolation, a repeat ablation should be considered. Patients might present with isolated pulmonary veins posterior wall. In these patients, posterior wall isolation is extended, and non-pulmonary vein triggers are actively sought and ablated. Moreover, in those with non-paroxysmal atrial fibrillation or a known higher prevalence of non-pulmonary vein triggers, empirical isolation of the superior vena cava, coronary sinus, and/or left atrial appendage might be performed. In this review, we will focus on ablation of non-pulmonary vein triggers, summarizing our current approach for their mapping and ablation.

Durability of mitral isthmus ablation with and without ethanol infusion in the vein of Marshall

INTRODUCTION

Ethanol infusion in the vein of Marshall (EIVOM) effectively creates a linear ablation lesion in the mitral isthmus (MI). However, data on the long-term success rates of MI ablation is limited.

METHODS AND RESULTS

Our cohort consisted of 560 patients with nonparoxysmal atrial fibrillation (AF) who underwent an initial MI ablation. Ablations were performed by only radiofrequency (RF) in 384 (RF group) or by RF and EIVOM in 176 (EIVOM/RF group) patients; 5 ml anhydrous ethanol was used to perform EIVOM in advance of RF. Following EIVOM, RF pulses were delivered to the lateral MI line. Bidirectional MI block was fully achieved in 353/384 (92%) (First 318, Re-do 35) patinents in the RF group and 171/176 (97%) (First 128, Re-do 43) patients in the EIVOM/RF group (p = .09 in the first, p = .10 in the re-do ablation cases). In cases with complete MI line block, recurrent AF or atrial tachycardia was observed in 130/353 (37%) patients in the RF group and in 64/171 (37%) patients in the EIVOM/RF group (log-rank p = .12 in the first, and p = .30 in the re-do ablation cases). Of the total 560 patients, 123 proceeded to the subsequent ablation session. Reconduction across MI line block was observed in 39/80 (49%) patients in the RF group and 25/43 (58%) patients in the EIVOM/RF group (p = .32).

CONCLUSION

EIVOM effectively ensures MI line block; however, the reconduction rate was similar between the two groups.

Anatomical targets and expected outcomes of catheter-based ablation of atrial fibrillation in 2020

Anatomical-based approaches, targeting either pulmonary vein isolation (PVI) or additional extra PV regions, represent the most commonly used ablation treatments in symptomatic patients with atrial fibrillation (AF) recurrences despite antiarrhythmic drug therapy. PVI remains the main anatomical target during catheter-based AF ablation, with the aid of new technological advances as contact force monitoring to increase safety and effective radiofrequency (RF) lesions. Nowadays, cryoballoon ablation has also achieved the same level of scientific evidence in patients with paroxysmal AF undergoing PVI. In parallel, electrical isolation of extra PV targets has progressively increased, which is associated with a steady increase in complex cases undergoing ablation. Several atrial regions as the left atrial posterior wall, the vein of Marshall, the left atrial appendage, or the coronary sinus have been described in different series as locations potentially involved in AF initiation and maintenance. Targeting these regions may be challenging using conventional point-by-point RF delivery, which has opened new opportunities for coadjuvant alternatives as balloon ablation or selective ethanol injection. Although more extensive ablation may increase intraprocedural AF termination and freedom from arrhythmias during the follow-up, some of the targets to achieve such outcomes are not exempt of potential severe complications. Here, we review and discuss current anatomical approaches and the main ablation technologies to target atrial regions associated with AF initiation and maintenance.

Beyond Pulmonary Vein Isolation in Nonparoxysmal Atrial Fibrillation: Posterior Wall, Vein of Marshall, Coronary Sinus, Superior Vena Cava, and Left Atrial Appendage

The optimal ablation strategy for non-paroxysmal atrial fibrillation remains controversial. Non-PV triggers have been shown to have a major arrhythmogenic role in these patients. Common sources of non-PV triggers are: posterior wall, left atrial appendage, superior vena cava, coronary sinus, vein of Marshall, interatrial septum, crista terminalis/Eustachian ridge, and mitral and tricuspid valve annuli. These sites are targeted empirically in selected cases or if significant ectopy is noted (with or without a drug challenge), to improve outcomes in patients with non-paroxysmal atrial fibrillation. This article focuses on summarizing the current evidence and the approach to mapping and ablation of these frequent non-PV trigger sites.

Novel concepts and approaches in ablation of atrial fibrillation: the role of non-pulmonary vein triggers

Ablation of non-pulmonary vein (PV) triggers is an important step to improve outcomes in atrial fibrillation ablation. Non-pulmonary vein triggers typically originates from predictable sites (such as the left atrial posterior wall, superior vena cava, coronary sinus, interatrial septum, and crest terminalis), and these areas can be ablated either empirically or after observing significant ectopy (with or without drug challenge). In this review, we will focus on ablation of non-PV triggers, summarizing the existing evidence and our current approach for their mapping and ablation.

Importance of the vein of Marshall involvement in mitral isthmus ablation

BACKGROUND

Epicardiac conduction via the vein of Marshall (VOM) can bypass the mitral isthmus (MI) line, making MI ablation difficult. This study aimed to assess the contribution of the VOM in achieving MI conduction block.

METHODS

This study included 143 consecutive patients with nonparoxysmal atrial fibrillation who underwent initial MI ablation. They were retrospectively classified into two groups, a VOM-guided group (n = 28) and a conventional group (n = 115), according to the use of a 2-Fr electrode catheter inserted in the VOM. The acute success rate of achieving MI block and the ablation data were assessed. When the bidirectional block was verified exclusively in the VOM or coronary sinus (CS) electrodes, we defined it as a pseudo MI block. In the VOM-guided group, we ascertained the complete MI block, verified both in the VOM and CS electrodes.

RESULTS

In the VOM-guided group, the pseudoblock was observed in 33.3% of the patients during MI ablation. With significantly less radiofrequency energy (19 322.6 ± 11 352.8 vs 25 389.3 ± 19 951.9, P = 0.04), we achieved a similar level of success rate in MI ablation in the VOM-guided group (96.4% vs 91.3%, P = 0.36). Notably, after achieving complete MI block, atrial burst pacing induced two perimitral flutters in the VOM-guided group, which were successfully terminated by the additional radiofrequency application.

CONCLUSIONS

Assessment of electrical conduction through the VOM could clarify the existence of a pseudo MI conduction block. However, the existence of a slow conduction through the MI could be detected only after induction of perimitral atrial tachycardia with atrial programmed stimulation.

Individualized ablation strategy guided by live simultaneous global mapping to treat persistent atrial fibrillation

Atrial fibrillation (AF) is the most common clinical arrhythmia encountered. Catheter ablation has become the first-line therapy for symptomatic drug-refractory paroxysmal and persistent AF. Although pulmonary vein electrical isolation is still the cornerstone of the ablation strategy, the clinical outcome particularly in treating persistent AF is suboptimal. Significant efforts have been applied with live global chamber mapping of AF aimed to identify patient-specific drivers and/or maintainers located outside of the pulmonary veins to further improve the outcome of catheter ablation. Within this review, we present an overview of contemporary global chamber AF mapping technologies and characteristics, with a particular focus on global, noncontact, dipole density mapping illustrated with a clinical case of persistent AF ablation using this novel methodology.

The Human Left Atrial Venous Circulation as a Vascular Route for Atrial Pharmacological Therapies: Effects of Ethanol Infusion

OBJECTIVES

This study catalogued the human venous left atrium (LA) circulation system and the ablative effects of ethanol in different branches.

BACKGROUND

Vascular routes to target the LA could have significant therapeutic potential. Beyond the vein of Marshall (VOM), the fluoroscopic LA venous anatomy has not been described.

METHODS

Patients undergoing ethanol infusion in the VOM as adjunctive therapy to atrial fibrillation (AF) catheter ablation were included in this study. Balloon occlusion venograms of the VOM and other LA veins were obtained in 218 patients.

RESULTS

Sequentially from the coronary sinus (CS) ostium, LA veins included: 1) proximal septal vein draining the inferior septum; 2) inferior LA vein in the annular inferior LA; 3) VOM; 4) LA appendage vein; and 4) anterior LA vein. Additionally, venous sinuses not connected to the CS included roof veins and posterior wall veins, which drained into the right and left atria, respectively. Venous connections between LA veins through capillaries and with pulmonary veins were abundant. Extracardiac collateral vessels were present in 38 patients (17.4%). Ethanol infusion in LA veins led to tissue ablation in their corresponding regions.

CONCLUSIONS

The atrial venous anatomy is amenable to selective cannulation. Consistent anatomical patterns are present. Targeting atrial tissues through atrial veins can be used for therapeutic purposes.

Long-term outcome after catheter ablation of paroxysmal atrial fibrillation: Impact of different atrial fibrillation foci

BACKGROUND

We aimed to determine whether differing foci in paroxysmal atrial fibrillation (PAF) affected the long-term outcome of catheter ablation (CA).

METHODS

A total of 865 consecutive PAF patients (age, 61±10years; 670 male) undergoing initial AF ablation were included. After pulmonary vein (PV) isolation, superior vena cava (SVC) isolation was performed for SVC foci; other non-PV foci were focally ablated. Long-term outcomes were compared among patients with SVC foci (Group SVC), other non-PV foci (Group Non-PV), and those without these foci (Group PV).

RESULTS

Groups PV, SVC, and Non-PV contained 740 (85.8%), 57 (6.6%), and 68 (7.6%) patients, respectively. Structural heart disease (P=0.01) and duration of AF history (P=0.04) were significantly associated with Group Non-PV, and female sex (P=0.0002) was significantly associated with Group SVC. AF recurrence-free rates at 5years in Group PV, SVC, and Non-PV were 62.0%, 66.3%, and 49.3%, respectively (P=0.03), after the initial CA, and 84.7%, 83.9%, and 77.0%, respectively (P=0.02), after the final CA. The duration of AF history (HR, 1.04, P<0.0001) and left atrial dimension (HR, 1.37 per 10mm increase, P=0.0003) were significant predictors of AF recurrence after the initial CA. Although Group Non-PV was weakly associated (HR 1.38, P=0.08) with AF recurrence, Group SVC was not associated with AF recurrence.

CONCLUSIONS

Long-term outcome of CA of PAF was significantly worse in patients with non-PV foci other than SVC foci. These foci may affect the outcome not independently but as an aspect of atrial remodeling.

The role of empiric superior vena cava isolation in atrial fibrillation: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

It is not clear whether additional empiric superior vena cava isolation (SVCI) to pulmonary vein isolation (PVI) results in low recurrences of atrial fibrillation. We aimed to perform a systematic review and meta-analysis of all randomized controlled trials (RCTs) that evaluated role of empiric SVCI in atrial fibrillation ablation.

METHODS

We searched PubMed, EMBASE, Cochrane, Scopus, and relevant references for RCTs (inception April 15, 2016 without language restrictions) and performed meta-analysis using random effects model. Recurrence rates of atrial fibrillations, procedural times, fluoroscopic times, and adverse events were the measured outcomes.

RESULTS

Three RCTs with a total population of 526 were analyzed. There was no difference in the recurrence rate between PVI plus SVCI versus PVI alone when comparison was made across all types of AF (39 vs 60; odds ratio 0.68; 95 % CI 0.43-1.07; P = 0.73; I ² = 0 %). When analysis was restricted only to paroxysmal AF, there was a trend towards low recurrence rate in combination group without statistical significance (19 vs 35, OR 0.54; 95 % CI 0.29-1.00; P = 0.05; I ² = 0). Similarly, no difference was noted between two groups in procedural (weighted mean difference [WMD] 10.12; 95 % CI -9.84 to 30.08; P = 0.32; I ² = 85 %) and fluoroscopic time (WMD 4.66; 95 % CI -0.92 to 10.25; P = 0.1; I ² = 94). Adverse events were similar in both groups.

CONCLUSION

Empiric SVCI does not provide additional benefit to PVI alone for atrial fibrillation ablation.

Long-term results of minimally invasive stand-alone bi-atrial surgical ablation with a bipolar ablation device for persistent and longstanding persistent AF: a single-center case series of 91 patients

Background

Minimally invasive surgical treatment of lone atrial fibrillation (AF) is an alternative for AF that is refractory to medical treatment. We present long-term results of standalone surgical ablation of AF using a bipolar ablation device in 91 consecutive patients.

Methods

This was an observational, retrospective study of 91 patients (77 % males; mean age, 53 ± 10 years [range, 23–75 years]) who underwent minimally invasive standalone surgical ablation of persistent and longstanding persistent AF using a bipolar ablation device from 2008 to 2014. Mean follow-up was 60 ± 21 months. The absence of arrhythmia was confirmed at 3, 6, and 12 months, and annually thereafter, with 24-hour Holter monitoring.

Results

The mean duration of preoperative AF was 6.5 ± 5.4 years. Persistent AF was present in 86 % of patients and longstanding persistent AF in 14 %. Mean left atrial diameter was 4.3 ± 0.8 cm. There were two postoperative strokes (2 %) and three conversions to median sternotomy (3 %). Permanent pacemakers were implanted in six (7 %) patients. There were no intra- or postoperative deaths. At 1, 2, 3, 4, and 5 years postoperatively, freedom from AF was 59, 45, 41, 38, and 38 % of patients, respectively. The failure to achieve pulmonary vein isolation was the only independent predictor of long-term recurrence of AF (HR −3 [95 % CI 1,858 to 8,586], p = 0,001). There was a tendency towards higher rates of SR at long term follow up in patients with pulmonary vein isolation if division of ligament of Marshall was performed (HR - 2 [95 % CI 0.987 to 4,202], p = 0,067).

Conclusions

In the present series, the efficacy of epicardial surgical ablation was similar to that reported previously. The rate of arrhythmia recurrence increased over time. Achieving pulmonary vein isolation is essential to AF elimination. The division of ligament of Marshall could contribute to improved rates of SR restoration in patients with persistent or long-standing persistent AF if PVI is achieved.

Surgical Treatment of Atrial Fibrillation

Atrial fibrillation (AF) is the most common chronic arrhythmia in the adult population. Ablation lines have largely replaced the historical and challenging cut and sew techniques. Surgical ablation of AF is commonly performed in cases with other indications for cardiac surgery and less commonly as a stand-alone therapy. Pulmonary vein isolation is the cornerstone of this procedure. Extended left atrial ablation lines may increase efficacy in cases with longstanding persistent or permanent AF. Additional efficacy by adding right atrial ablation is controversial but is often performed in cases undergoing right atrial or atrial septal surgery. Left atrial volume reduction is recommended in cases with large left atria and AF undergoing another cardiac surgery. Arrhythmia recurrence is not uncommon after surgical ablation of AF and varies among studies due to heterogeneity in patient population, lesion set and endpoints. Freedom from AF recurrence was 65-87% at 12 months and 58-70% at 2 years follow-up. Long-term monitoring is recommended due to an increased prevalence of asymptomatic recurrences. The strongest predictors of AF recurrence are longstanding or persistent AF and a large left atrium. The most common mechanisms of recurrence are pulmonary vein reconnection, nonpulmonary vein triggers, and gaps in the ablation lines. About 20% of atrial tachyarrhythmia recurrences are atrial flutter or atrial tachycardia. There are not enough data in the surgical literature to support withdrawal of anticoagulation after surgical AF ablation. Patients selected for stand-alone surgical ablation usually have low risk profiles and low postoperative mortality rates (0.2%).

Residual arrhythmogenic foci predict recurrence in long-standing persistent atrial fibrillation patients after sinus rhythm restoration ablation

BACKGROUND

The mechanism of persistent atrial fibrillation (AF) is multifactorial, and arrhythmogenic foci (AMF) might be involved in the occurrence of persistent AF. In this study, we examined the electrophysiological features of AMF during and immediately after ablation, and evaluated the relationship between the presence and number of residual AMF on the risk of AF recurrence after a vigorous sinus rhythm restoration ablation in patients with long-standing persistent AF.

METHODS

The study consisted of 117 consecutive patients with persistent AF who underwent catheter ablation (CA). We performed direct cardioversion to restore sinus rhythm before the pulmonary vein (PV) isolation and at the end of the CA. Then we evaluated the features of the AMF inducible with isoproterenol and the pacing-based AF inducibility.

RESULTS

After the completion of ablation, AF could still be induced in 37 of 117 patients (31.6%). Spontaneous PV AMF during CA were observed in 104 of 117 patients (91%), and non-PV AMF in 63 of 117 (54%). Residual non-PV AMF were significantly associated with the pacing-based AF inducibility and an enlarged left atrial volume. In the multivariate analysis, the AF duration (1.01 [range, 1.00-1.02] months; P = 0.012), left atrial volume (1.01 [range, 1.01-1.02] mm; P = 0.006), and residual AMF (3.95 [range, 1.32-11.8] yes, no; P = 0.004) were independent risk factors for recurrent AF.

CONCLUSIONS

Residual AMF are associated with an increased long-term AF recurrence after sinus rhythm restoration ablation for long-standing persistent AF.

Ethanol infusion in the vein of Marshall leads to parasympathetic denervation of the human left atrium: implications for atrial fibrillation

OBJECTIVES

This study sought to determine whether ethanol infusion in the vein of Marshall (VOM) can ablate intrinsic cardiac nerves (ICN).

BACKGROUND

ICN cluster around the left atrial epicardium and are implicated in the genesis of atrial fibrillation (AF).

METHODS

Patients undergoing catheter AF ablation underwent adjunctive ethanol injection in the VOM. A multipolar catheter was introduced in the VOM and used for high-frequency stimulation (HFS), either as HFS with P-wave synchronized (SynchHFS), 30 pulses, 100 Hz (n = 8) or as HFS with 3 to 10 s bursts (BurstHFS), 33 Hz (n = 72) at 25 mA for 1-ms duration. Atrioventricular (AV) nodal conduction slowing (asystole >2 s or R-R interval prolongation >50%) and AF inducibility were assessed before and after VOM ethanol infusion. Up to 4 1-ml infusions of 98% ethanol were delivered via an angioplasty balloon in the VOM.

RESULTS

SynchHFS induced AF in 8 of 8 patients. In 4 of 8 AF initiated spontaneously without VOM capture. No parasympathetic responses were elicited by SynchHFS. BurstHFS was performed in 32 patients undergoing de novo AF ablation (Group 1) and 40 patients undergoing repeat ablation (Group 2). Parasympathetic responses were found in all 32 Group 1 patients and in 75% of Group 2 patients. After VOM ethanol infusion, parasympathetic responses were abolished in all patients (both groups). There were no acute complications related to VOM ethanol infusion.

CONCLUSIONS

The VOM contains ICN that connect with the AV node and can trigger AF. Retrograde ethanol infusion in the VOM reliably eliminates local ICN responses. The VOM is a vascular route for ICN-targeting therapies.

The surgical treatment for atrial fibrillation: ablation technology and surgical approaches

The Cox maze procedure developed originally in 1987 by Dr James Cox has evolved from a "cut and sew" surgical procedure, where the maze was applied using multiple surgical cuts, to an extensive use of surgical ablation technology where ablation lesions are placed with alternative energy sources (radiofrequency, cryothermy, microwave, and high-frequency ultrasound). Furthermore, the procedure has changed from a median sternotomy approach only to one that can be performed minimally invasively and robotically. The purpose of this paper is to review the current available technology for the ablation of atrial fibrillation as well as the different procedural approaches for the surgical ablation of atrial fibrillation.

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.

Inducible atrial tachycardias with multiple circuits in a stepwise approach are associated with increased episodes of atrial tachycardias after catheter ablation

BACKGROUND

Atrial tachycardia (AT) is commonly observed during catheter ablation (CA) in patients with atrial fibrillation (AF) undergoing a stepwise extensive CA. In this study, we examined the hypothesis that the presence of multiple inducible ATs (multiple-ATs), which allow for latent multiple reentrant circuits, might increase the potential for following AT episodes after CA.

METHODS AND RESULTS

The study population consisted of 347 consecutive AF patients undergoing CA with a stepwise approach. A total of 366 ATs (tricuspid isthmus dependent, 101; mitral annulus, 62; septal, 26; roof dependent, 22; left atrial anterior wall, 13; upper loop, 8; surrounding the left pulmonary veins, 6; surrounding the right pulmonary veins, 6; left atrial appendage, 4; and Cs ostium, 3) occurring during the CA were found in 216 (62.2%) of 347 patients. Multiple-ATs (≥2) during the CA were observed in 93 (26.8%) of 347 patients. The incidence of AT episodes significantly increased as the number of inducible ATs increased (no AT, 7.8%; single AT, 13.7%; and multiple-ATs, 24.2%; P < .001), and multiple-ATs were an independent risk factor for AT episodes (3.07 [1.39-6.78]; P = .005). The impact of the multiple-ATs on the AT episodes was pronounced especially in the patients with coinducible residual AF (with coresidual AF vs without coresidual AF, 8.1% vs 47.7%; P < .001).

CONCLUSIONS

The presence of an atrial substrate allowing for multiple-ATs was associated with increased AT episodes during follow-up.

Electrical activation of sinus venosus myocardium and expression patterns of RhoA and Isl-1 in the chick embryo

Electrical Activity and RhoA in the Embryo.

INTRODUCTION

Myocardium at the venous pole (sinus venosus) of the heart has gained clinical interest as arrhythmias can be initiated from this area. During development, sinus venosus myocardium is incorporated to the primary heart tube and expresses different markers than primary myocardium. We aimed to elucidate the development of sinus venosus myocardium, including the sinoatrial node (SAN), by studying expression patterns of RhoA in relation to other markers, and by studying electrical activation patterns of the developing sinus venosus myocardium.

METHODS AND RESULTS

Expression of RhoA, myocardial markers cTnI and Nkx2.5, transcription factors Isl-1 and Tbx18, and cation channel HCN4 were examined in sequential stages in chick embryos. Electrical activation patterns were studied using microelectrodes and optical mapping. Embryonic sinus venosus myocardium is cTnI and HCN4 positive, Nkx2.5 negative, complemented by distinct patterns of Isl-1 and Tbx18. During development, initial myocardium-wide expression of RhoA becomes restricted to right-sided sinus venosus myocardium, comprising the SAN. Electrophysiological measurements revealed initial capacity of both atria to show electrical activity that in time shifts to a right-sided dominance, coinciding with persistence of RhoA, Tbx18, and HCN4 and absence of Nkx2.5 expression in the definitive SAN.

CONCLUSION

Results show an initially bilateral electrical potential of sinus venosus myocardium evolving into a right-sided activation pattern during development, and suggest a role for RhoA in conduction system development. We hypothesize an initial sinus venosus-wide capacity to generate pacemaker signals, becoming confined to the definitive SAN. Lack of differentiation toward a chamber phenotype would explain ectopic pacemaker foci.

Echocardiographic identification of the oblique vein of the left atrium: its relationship to the persistent left superior caval vein

Thus far, little has been written concerning echocardiographic identification of the oblique vein of the left atrium, or Marshall's vein. There is much discussion, nonetheless, on the potential significance of the vein, or its ligamentous remnant, as an arrhythmic substrate. We describe here four patients in whom transthoracic echocardiography revealed a venous structure protruding within the cavity of the left atrium. We discuss the possibility that these structures represent Marshall's vein, albeit probably as part of a persistent left superior caval vein.

Correlative anatomy for the electrophysiologist: ablation for atrial fibrillation. Part I: pulmonary vein ostia, superior vena cava, vein of Marshall

Ablation procedures for atrial fibrillation (AF) have become an established and increasingly used option for managing patients with symptomatic arrhythmia. The anatomic structures relevant to the pathogenesis of AF and ablation procedures are varied and include the pulmonary veins (PVs), other thoracic veins, the left atrial myocardium, and autonomic ganglia. Exact regional anatomic knowledge of these structures is essential to allow correlation with fluoroscopy and electrograms, and, importantly, to avoid complications from damage of adjacent structures within the chest. We have presented this information in a 2-part series. In the present article, we examine the general anatomic characteristics of the PVs, superior vena cava, and vein of Marshall. Features of particular relevance for the invasive electrophysiologist are pointed out. In a subsequent article, we discuss the regional anatomy of the left and right atria and anatomic considerations in preventing complications during AF ablation.

Retrograde ethanol infusion in the vein of Marshall: regional left atrial ablation, vagal denervation and feasibility in humans

BACKGROUND

The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation due to its autonomic innervation, its location anterior to the left pulmonary veins and drainage in the coronary sinus.

METHODS AND RESULTS

We studied 17 dogs. A coronary sinus venogram showed a VOM in 13, which was successfully cannulated with an angioplasty wire and balloon. In 5 dogs, electroanatomical maps of the left atrium were performed at baseline and after ethanol infusion in the VOM, which demonstrated a new crescent-shaped scar, extending from the annular left atrium towards the posterior wall and left pulmonary veins. In 4 other dogs, effective refractory periods (ERP) were measured at 3 sites in the left atrium, before and after high-frequency bilateral vagal stimulation. The ERP decreased from 113.6+/-35.0 ms to 82.2+/-25.4 ms (p<0.05) after vagal stimulation. After VOM ethanol infusion, vagally-mediated ERP decrease was eliminated (from 108.6+/-24.1 ms to 96.4 +/-16.9ms, p=NS). The abolition of vagal effects was limited to sites near the VOM (ERP: 104+/-14 ms, vs 98.6+/-12.2 ms post vagal stimulation, p=ns), as opposed to sites remote to VOM (ERP: 107.2+/-14.9 ms, vs 78.6+/-14.7ms post vagal stimulation, p<0.05). To test feasibility in humans, 5 patients undergoing pulmonary vein antral isolation had successful VOM cannulation and ethanol infusion: left atrial voltage maps demonstrated new scar involving the infero-posterior left atrial wall extending towards the left pulmonary veins.

CONCLUSIONS

Ethanol infusion in then VOM achieves significant left atrial tissue ablation, abolishes local vagal responses and is feasible in humans.

Ethanol infusion in the vein of Marshall: Adjunctive effects during ablation of atrial fibrillation

BACKGROUND

The vein of Marshall (VOM) is a left atrial (LA) vein that contains autonomic innervation and triggers of AF. Its location coincides with areas usually ablated during pulmonary vein (PV) antral isolation (PVAI).

OBJECTIVE

This study sought to delineate the safety and ablative effects of ethanol infusion in the VOM during catheter ablation of atrial fibrillation (AF).

METHODS

Patients undergoing PVAI (n = 14) gave consent for adjunctive VOM ethanol infusion. In 10 of 14 patients, the VOM was cannulated with an angioplasty wire and balloon. Echocardiographic contrast was injected in the VOM under echocardiographic monitoring. Two infusions of 100% ethanol (1 ml each) were delivered via the angioplasty balloon in the VOM. LA bipolar voltage maps were created before and after ethanol infusion. Radiofrequency ablation times required to isolate each PV and other procedural data were compared with those of 10 age-, sex-, AF type- and LA size-matched control subjects undergoing conventional PVAI.

RESULTS

The VOM communicated with underlying myocardium, as shown by echocardiographic contrast passage into the LA. There were no acute complications related to VOM ethanol infusion, which led to the creation of a low-voltage area in the LA measuring 10.6 +/- 7.6 cm(2) and isolation of the left inferior PV in 4 of 10 patients. Radiofrequency ablation time required to achieve isolation of the left inferior PV was reduced (2.2 +/- 4 min vs. 11.4 +/- 10.3 min in control subjects, P <.05).

CONCLUSION

VOM ethanol infusion is safe in humans, decreases radiofrequency ablation time in the left inferior PV, and may have a role as an adjunct to PVAI.

Recurrence of atrial fibrillation correlates with the extent of post-procedural late gadolinium enhancement: a pilot study

OBJECTIVES

We sought to evaluate radiofrequency (RF) ablation lesions in atrial fibrillation (AF) patients using cardiac magnetic resonance (CMR), and to correlate the ablation patterns with treatment success.

BACKGROUND

RF ablation procedures for treatment of AF result in localized scar that is detected by late gadolinium enhancement (LGE) CMR. We hypothesized that the extent of scar in the left atrium and pulmonary veins (PV) would correlate with moderate-term procedural success.

METHODS

Thirty-five patients with AF, undergoing their first RF ablation procedure, were studied. The RF ablation procedure was performed to achieve bidirectional conduction block around each PV ostium. AF recurrence was documented using a 7-day event monitor at multiple intervals during the first year. High spatial resolution 3-dimensional LGE CMR was performed 46 +/- 28 days after RF ablation. The extent of scarring around the ostia of each PV was quantitatively (volume of scar) and qualitatively (1: minimal, 3: extensive and circumferential) assessed.

RESULTS

Thirteen (37%) patients had recurrent AF during the 6.7 +/- 3.6-month observation period. Paroxysmal AF was a strong predictor of nonrecurrent AF (15% with recurrence vs. 68% without, p = 0.002). Qualitatively, patients without recurrence had more completely circumferentially scarred veins (55% vs. 35% of veins, p = NS). Patients without recurrence more frequently had scar in the inferior portion of the right inferior pulmonary vein (RIPV) (82% vs. 31%, p = 0.025, Bonferroni corrected). The volume of scar in the RIPV was quantitatively greater in patients without AF recurrence (p < or = 0.05) and was a univariate predictor of recurrence using Cox regression (p = 0.049, Bonferroni corrected).

CONCLUSIONS

Among patients undergoing PV isolation, AF recurrence during the first year is associated with a lesser degree of PV and left atrial scarring on 3-dimensional LGE CMR. This finding was significant for RIPV scar and may have implications for the procedural technique used in PV isolation.

Recurrence of atrial fibrillation correlates with the extent of post-procedural late gadolinium enhancement: a pilot study

OBJECTIVES

We sought to evaluate radiofrequency (RF) ablation lesions in atrial fibrillation (AF) patients using cardiac magnetic resonance (CMR), and to correlate the ablation patterns with treatment success.

BACKGROUND

RF ablation procedures for treatment of AF result in localized scar that is detected by late gadolinium enhancement (LGE) CMR. We hypothesized that the extent of scar in the left atrium and pulmonary veins (PV) would correlate with moderate-term procedural success.

METHODS

Thirty-five patients with AF, undergoing their first RF ablation procedure, were studied. The RF ablation procedure was performed to achieve bidirectional conduction block around each PV ostium. AF recurrence was documented using a 7-day event monitor at multiple intervals during the first year. High spatial resolution 3-dimensional LGE CMR was performed 46 +/- 28 days after RF ablation. The extent of scarring around the ostia of each PV was quantitatively (volume of scar) and qualitatively (1: minimal, 3: extensive and circumferential) assessed.

RESULTS

Thirteen (37%) patients had recurrent AF during the 6.7 +/- 3.6-month observation period. Paroxysmal AF was a strong predictor of nonrecurrent AF (15% with recurrence vs. 68% without, p = 0.002). Qualitatively, patients without recurrence had more completely circumferentially scarred veins (55% vs. 35% of veins, p = NS). Patients without recurrence more frequently had scar in the inferior portion of the right inferior pulmonary vein (RIPV) (82% vs. 31%, p = 0.025, Bonferroni corrected). The volume of scar in the RIPV was quantitatively greater in patients without AF recurrence (p < or = 0.05) and was a univariate predictor of recurrence using Cox regression (p = 0.049, Bonferroni corrected).

CONCLUSIONS

Among patients undergoing PV isolation, AF recurrence during the first year is associated with a lesser degree of PV and left atrial scarring on 3-dimensional LGE CMR. This finding was significant for RIPV scar and may have implications for the procedural technique used in PV isolation.

Clinical significance of complete conduction block of the left lateral isthmus and its relationship with anatomical variation of the vein of Marshall in patients with nonparoxysmal atrial fibrillation

BACKGROUND

The vein of Marshall (VOM), which exists along the left lateral isthmus (LLI), constitutes a muscular connection between the coronary sinus (CS) and the left atrium (LA). We hypothesized that anatomical variation of the VOM affects the bidirectional block of LLI and the clinical outcome in patients with nonparoxysmal atrial fibrillation (NPAF).

METHODS

Among 73 patients with NPAF, 54 patients (47 male, 54.1 +/- 10.4 years old) with a clearly visible VOM (74.0%) were included. After circumferential antral ablation, double linear endocardial ablation of LLI was performed along the VOM. Unless LLI block was achievable by endocardial ablation, the ablation was performed inside the CS.

RESULTS

LLI block was achievable in 35 patients (64.8%; 11.1% by endocardial ablation vs 53.7% by additional inside CS ablation; P < 0.01). In patients with failed LLI block, the VOM was significantly longer (P < 0.05) on the right anterior oblique (RAO) view than in those with successful LLI block. LA volume or LLI length measured by CT image were not different (P = NS). During 11.4 +/- 5.0 months follow-up, early recurrences within 3 months (47.4% vs 28.6%, P = NS) and recurrences after 3 months (10.5% vs 17.7%, P = NS) were not different with or without LLI block.

CONCLUSION

LLI block, which is more difficult to achieve in patients with a longer VOM, was achievable in 65% of patients with NPAF by linear ablation along the VOM and additional inside CS ablation, but did not affect the short-term clinical outcome.

Inducibility of atrial and ventricular arrhythmias along the ligament of marshall: role of autonomic factors

BACKGROUND

The mechanism(s) underlying atrial fibrillation (AF) initiation along the ligament of Marshall (LOM) remains controversial.

OBJECTIVES

We sought to examine the role of the autonomic nervous system in arrhythmogenesis along the LOM.

METHODS

In 31 anesthetized dogs, a left thoracotomy exposed the LOM. During atrial pacing, high-frequency stimulation (HFS: 200 Hz, 0.1 ms pulse width, 40 ms duration, 0.6-12 V) was delivered during atrial refractoriness to different sites of LOM (LOM(CS)= near coronary sinus; LOM(LIPV)= near left inferior pulmonary vein; LOM(LS-LIPV)= between LIPV and left superior pulmonary vein (LSPV); LOM(LSPV)= near LSPV). HFS was repeated after intravenous administration of esmolol (1 mg/kg; n = 9) or atropine (2 mg; n = 12). Norepinephrine (10(-7) M, 0.4 cc) was injected into LOM(LSPV) (n = 5).

RESULTS

The median voltages for HFS to induce AF were 3.2 V, 3.2 V, 8.0 V*(,double dagger), and 12 V*(,double dagger) at LOM(CS), LOM(LIPV), LOM(LS-LIPV), and LOM(LSPV), respectively (*P < 0.01, compared with LOM(CS) and double dagger P < 0.01, compared with LOM(LIPV)). Esmolol or atropine markedly increased the threshold for AF induction. Ventricular tachycardias (VT) and accelerated junctional rhythm were induced in 8 of 12 and 6 of 12 dogs after atropine administration, respectively. Sustained VT occurred within minutes in 5 of 5 dogs receiving norepinephrine injection into the LOM(LSPV.)

CONCLUSION

HFS induced AF along LOM with a gradient of stimulation thresholds from LOM(CS) (lowest) toward LOM(LSPV) (highest). This response was inhibited by esmolol or atropine. These data suggest an autonomic basis for AF initiation in LOM, and both sympathetic and parasympathetic neural elements play an important role in AF initiation. Hyperactivity of the sympathetic neural elements in LOM may be crucial in the initiation of ventricular tachyarrhythmias.