Impact of Catheter Ablation of the Coronary Sinus on Paroxysmal or Persistent Atrial Fibrillation

Ablation-induced left atrial mechanical dysfunction recovers in weeks after ablation

BACKGROUND

The immediate impact of catheter ablation on left atrial mechanical function and the timeline for its recovery in patients undergoing ablation for atrial fibrillation (AF) remain uncertain. The mechanical function response to catheter ablation in patients with different AF types is poorly understood.

METHODS

A total of 113 AF patients were included in this retrospective study. Each patient had three magnetic resonance imaging (MRI) studies in sinus rhythm: one pre-ablation, one immediate post-ablation (within 2 days after ablation), and one post-ablation follow-up MRI (≤ 3 months). We used feature tracking in the MRI cine images to determine peak longitudinal atrial strain (PLAS). We evaluated the change in strain from pre-ablation, immediately after ablation to post-ablation follow-up in a short-term study (< 50 days) and a 3-month study (3 months after ablation).

RESULTS

The PLAS exhibited a notable reduction immediately after ablation, compared to both pre-ablation levels and those observed in follow-up studies conducted at short-term (11.1 ± 9.0 days) and 3-month (69.6 ± 39.6 days) intervals. However, there was no difference between follow-up and pre-ablation PLAS. The PLAS returned to 95% pre-ablation level within 10 days. Paroxysmal AF patients had significantly higher pre-ablation PLAS than persistent AF patients in pre-ablation MRIs. Both type AF patients had significantly lower immediate post-ablation PLAS compared with pre-ablation and post-ablation PLAS.

CONCLUSION

The present study suggested a significant drop in PLAS immediately after ablation. Left atrial mechanical function recovered within 10 days after ablation. The drop in PLAS did not show a substantial difference between paroxysmal and persistent AF patients.

Coronary Sinus Isolation for High-Burden Atrial Fibrillation: A Randomized Clinical Trial

BACKGROUND

The coronary sinus is an arrhythmogenic structure that can initiate and maintain atrial fibrillation (AF). Coronary sinus ablation has been shown to be effective in prolonging the AF cycle length and terminating AF in patients with both paroxysmal and persistent AF who have persistent AF after pulmonary vein isolation (PVI).

OBJECTIVES

The objective of this study was to undertake a randomized controlled trial to investigate the efficacy of coronary sinus isolation (CSI) as an adjunctive ablation strategy for the treatment of high-burden AF.

METHODS

Consecutive patients presenting with symptomatic long episodes of paroxysmal AF (≥48 h but ≤7 days) or persistent AF (>7 days and ≤12 months) referred for first-time ablation were enrolled. Participants were randomized to either PVI, roofline ablation, and CSI (CSI group) or PVI and roofline ablation only (non-CSI group). Participants were assessed postprocedurally via clinical follow-up and 7-day Holter monitoring at regular intervals. The primary outcome was single-procedure drug-free atrial arrhythmia-free survival at 2 years.

RESULTS

One hundred participants were recruited to the study; 48 were randomized to the CSI group and 52 to the non-CSI group. Acutely successful CSI was achieved in 45 of the 48 patients in the CSI group. At 2 years follow up, 30 of 48 patients (62.5%) in the CSI group and 33 of 52 (63.4%) in the non-CSI group were free from arrhythmia recurrence. Single-procedure drug-free survival at 2 years was no different between groups (P = 0.91). Similarly, multiple procedure drug assisted survival at 5 years was not different between groups (P = 0.80). Complication rates were not significantly different between groups (P = 0.19).

CONCLUSIONS

Adjunctive CSI as part of a de novo ablation strategy does not confer any additional benefit greater than PVI and roofline for the treatment of high-burden AF.

Radiofrequency catheter ablation of atrial fibrillation: A review of techniques

Ablation of atrial fibrillation is a key area of current research. A multitude of techniques have been tested, some of which are poorly evidenced and not recommended in routine clinical practice whilst others are more promising. Additionally, a plethora of issues exist when researching ablation techniques, from control arm ablation strategy to the relevance of outcome measures. In this review article, we discuss these issues in the context of the current evidence base.

Role of non-pulmonary vein triggers in persistent atrial fibrillation

Pulmonary vein isolation is an well-established treatment strategy for atrial fibrillation (AF), and it is especially effective for patients with paroxysmal AF. However, the success rate is limited for patients with persistent AF, because non-pulmonary vein triggers which increase AF recurrence are frequently found in these patients. The major non-pulmonary vein triggers are from the left atrial posterior wall, left atrial appendage, ligament of Marshall, coronary sinus, superior vena cava, and crista terminalis, but other atrial sites can also generate AF triggers. All these sites have been known to contain atrial myocytes with potential arrhythmogenic electrical activity. The prevalence and clinical characteristics of these non-pulmonary vein triggers are well studied; however, the clinical outcome of catheter ablation for persistent AF is still unclear. Here, we reviewed the current ablation strategies for persistent AF and the clinical implications of major non-pulmonary vein triggers.

Feasibility of Linear Irreversible Electroporation Ablation in the Coronary Sinus

INTRODUCTION

Previous studies demonstrated that the coronary sinus (CS) is an important target for ablation in persistent atrial fibrillation. However, radiofrequency ablation in the CS is associated with coronary vessel damage and tamponade. Animal data suggest irreversible electroporation (IRE) ablation can be a safe ablation modality in vicinity of coronary arteries. We investigated the feasibility of IRE in the CS in a porcine model.

METHODS

Ablation and pacing was performed in the CS in six pigs (weight 60-75 kg) using a modified 9-French steerable linear hexapolar Tip-Versatile Ablation Catheter. Pacing maneuvers were performed from distal to proximal segments of the CS to assess atrial capture thresholds before and after IRE application. IRE ablations were performed with 100 J IRE pulses. After 3-week survival animals were euthanized and histological sections from the CS were analyzed.

RESULTS

A total of 27 IRE applications in six animals were performed. Mean peak voltage was 1509 ± 36 V, with a mean peak current of 22.9 ± 1.0 A. No complications occurred during procedure and 3-week survival. At 30 min post ablation 100% isolation was achieved in all animals. At 3 weeks follow-up pacing thresholds were significant higher as compared to baseline. Histological analysis showed transmural ablation lesions in muscular sleeves surrounding the CS.

CONCLUSION

IRE ablation of the musculature along the CS using a multi-electrode catheter is feasible in a porcine model.

Assessing the impact of blocking distal coronary sinus-left atrial muscular connection on inducible rate of atrial fibrillation and follow-up recurrence in persistent atrial fibrillation patients with different fibrotic degrees of left atrial: A retrospective study

Background

The musculature of the coronary sinus (CS), especially its distal connection with the post wall of the left atrial (LA), has been associated with the genesis and maintenance of atrial flutter (AFL) and atrial fibrillation (AF). However, the relative contributions of the distal coronary sinus (CSD)-LA connection to PersAF with various degrees of atrial fibrosis remain unknown.

Objective

This study aimed to explore the different roles of blocking the CSD-LA connection in the induction of acute AF and middle-term follow-up of recurrence among PersAF patients with various degrees of LA fibrosis.

Methods and results

A retrospective cohort of 71 patients with drug-refractory and symptomatic PersAF underwent ablation for the first time were studied. The population was divided into two groups according to disconnection of the CSD-LA or not. All patients enrolled accepted the unified ablation procedure (circumferential pulmonary vein isolation, non-pulmonary vein trigger ablation and ablation of the CSD-LA connection). Group A (n = 47) successfully blocked the CSD-LA electrical connection and Group B (n = 24) failed. Twenty-five patients could be induced into sustained AF in the Group A compared to 20 in the Group B (53.2 vs. 83.3%, p = 0.013). After a mean follow-up of 185 ± 8 days, 24 (33.8%) patients experienced atrial arrhythmia recurrences. The Group A had significantly fewer recurrences (25.5%) compared to Group B (50%). Meanwhile, in Group A, the ROC curve analysis suggested that in the case of blocking CSD-LA, low voltage area (LVA) of LA can act as a predictive factor for acute AF induction (AUC = 0.943, Cut-off = 0.190, P < 0.001) with sensitivity and specificity of 92.3 and 90.5%, and middle-term recurrence (AUC = 0.889, Cut-off = 0.196, P < 0.001) with sensitivity and specificity of 100 and 65.7%.

Conclusion

Disconnection of CSD-LA could reduce the inducible rate of acute AF and the recurrences of atrial arrhythmia during middle-term follow-up. The PersAF patients with CSD-LA muscular connection blocked, experienced a higher acute AF inducible rate with larger proportion of LVA of LA (≥19%) and a higher recurrent rate of atrial arrhythmias with a larger proportion of LA fibrosis (≥19.6%).

The Relevance of Heart Rate Fluctuation When Evaluating Atrial Substrate Electrical Features in Catheter Ablation of Paroxysmal Atrial Fibrillation

Coronary sinus (CS) catheterization is critical during catheter ablation (CA) of atrial fibrillation (AF). However, the association of CS electrical activity with atrial substrate modification has been barely investigated and mostly limited to analyses during AF. In sinus rhythm (SR), atrial substrate modification is principally assessed at a global level through P-wave analysis. Cross-correlating CS electrograms (EGMs) and P-waves’ features could potentiate the understanding of AF mechanisms. Five-minute surface lead II and bipolar CS recordings before, during, and after CA were acquired from 40 paroxysmal AF patients. Features related to duration, amplitude, and heart-rate variability of atrial activations were evaluated. Heart-rate adjustment (HRA) was applied. Correlations between each P-wave and CS local activation wave (LAW) feature were computed with cross-quadratic sample entropy (CQSE), Pearson correlation (PC), and linear regression (LR) with 10-fold cross-validation. The effect of CA between different ablation steps was compared with PC. Linear correlations: poor to mediocre before HRA for analysis at each P-wave/LAW (PC: max. +18.36%, p = 0.0017, LR: max. +5.33%, p = 0.0002) and comparison between two ablation steps (max. +54.07%, p = 0.0205). HRA significantly enhanced these relationships, especially in duration (P-wave/LAW: +43.82% to +69.91%, p < 0.0001 for PC and +18.97% to +47.25%, p < 0.0001 for LR, CA effect: +53.90% to +85.72%, p < 0.0210). CQSE reported negligent correlations (0.6−1.2). Direct analysis of CS features is unreliable to evaluate atrial substrate modification due to CA. HRA substantially solves this problem, potentiating correlation with P-wave features. Hence, its application is highly recommended.

Innovations and paradigm shifts in atrial fibrillation ablation

Treatment of symptomatic atrial fibrillation has seen important changes in the past decades. Advancements have especially been made in the field of non-pharmacological treatment of this disease. Patients in whom a rhythm control strategy is chosen the place of catheter ablation has become more frontline therapy in the past years. The procedure itself has also seen changes in technologies that can be used, either using point-by-point radiofrequency or one of the single-shot techniques. One of the major limitations that remain is that re-do procedures are often necessary due to incomplete pulmonary vein isolation and/or atrial fibrillation being initiated by other mechanisms than pulmonary vein triggers. Therefore, there is further need for developing ablation tools that reproducibly isolate the pulmonary vein transmurally. Furthermore, addressing the underlying conditions before and after catheter ablation has been shown to be of great importance. In this review, we will give an overview of the evolution of catheter ablation, highlight the latest technologies and their future endeavours, and lifestyle modifications are being discussed as part of the catheter ablation strategy.

Efficacy and safety of ethanol infusion into the vein of Marshall for mitral isthmus ablation

INTRODUCTION

Chemical ablation by retrograde infusion of ethanol into the vein of Marshall (VOM-EI) can facilitate the achievement of mitral isthmus block. This study sought to describe the efficacy and safety of this technique.

METHODS AND RESULTS

Twenty-two consecutive patients (14 males, median age 71 years) with attempted VOM-EI for mitral isthmus ablation were included in the study. VOM-EI was successfully performed with a median of 4 ml of 96% ethanol in 19 patients (86%) and the mitral isthmus was successfully blocked in all (100%). Touch up endocardial and/or epicardial ablation after VOM-EI was necessary for 12 patients (63%). Perimitral flutter was present in 12 patients (63%) during VOM-EI and terminated or slowed by VOM-EI in 4 and 3 patients, respectively. The low-voltage area of the mitral isthmus region increased from 3.1 cm² (interquartile range [IQR] 0-7.9) before to 13.2 cm² (IQR: 8.2-15.0) after VOM-EI and correlated significantly with the volume of ethanol injected (p = .03). Median high-sensitive cardiac troponin-T increased significantly from 330 ng/L (IQR: 221-516) the evening of the procedure to 598 ng/L (IQR: 382-769; p = .02) the following morning. A small pericardial effusion occurred in three patients (16%), mild pericarditis in one (5%), and uneventful VOM dissection in two (11%). After a median follow-up of 3.5 months (IQR: 3.0-11.0), 10 of 18 patients (56%) with VOM-EI and available follow-up had arrhythmia recurrence. Repeat ablation was performed in five patients (50%) and peri-mitral flutter diagnosed in three (60%).

CONCLUSION

VOM-EI is feasible, safe, and effective to achieve acute mitral isthmus block.

Approach to recurrence of atrial fibrillation after catheter ablation

Atrial fibrillation (AF) is the most commonly observed sustained rhythm disorder during adult ages. Since it has been shown that the ectopic beat initiating AF is usually caused by pulmonary veins, AF ablation has become the mainstay of therapy worldwide. Cryoballoon and radiofrequency ablation are the most commonly used methods in today's technologies. However, despite technological advances, the success of a single procedure in AF ablation is still limited and multiple procedures may be required for the majority of patients. In cases in which a redo ablation is required, pulmonary vein isolation is still the main target, but non-pulmonary vein targets should also be considered in AF episodes that continue despite multiple ablations. Many issues are still unclear as to which energy to choose in the first procedure, and what ablation strategy will be utilized when a redo ablation is required. The studies on this subject are very limited but, it still seems feasible and a rational approach to utilize a customized treatment strategy in each specific patient subgroup.

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.

PRECAF Randomized Controlled Trial

BACKGROUND

We have previously shown that the presence of dual muscular coronary sinus (CS) to left atrial (LA) connections, coupled with rate-dependent unidirectional block in one limb, is associated with atrial fibrillation (AF) induction. This study sought to examine whether ablation of distal CS to LA connections at a first AF ablation reduces arrhythmia recurrence during follow-up.

METHODS

In this single-center, randomized, controlled trial, 35 consecutive patients with drug-refractory AF undergoing first-time ablation between August 2018 and August 2019, were randomly assigned to (1) standard ablation (pulmonary vein isolation and nonpulmonary vein trigger ablation) versus (2) standard ablation plus elimination of distal CS to LA connections targeting the earliest LA activation during distal CS pacing with a deca-polar catheter placed with its proximal electrode at the ostium. Change of the local CS atrial electrogram and LA activation sequence to early activation of the LA septum or roof during distal CS pacing were the end point for CS-LA connection elimination.

RESULTS

Thirty patients completed 6 months study follow-up (15 patients in each group). Demographic characteristics including age and AF persistence were similar in both groups. After a mean follow-up of 170±22 days, there were 7 atrial arrhythmia recurrences in the standard group and 1 recurrence in the CS-LA connection elimination group (46.7% versus 6.7%, hazard ratio, 0.12, P=0.047).

CONCLUSIONS

Elimination of distal CS to LA connections reduced atrial arrhythmia recurrences compared with standard pulmonary vein isolation and nonpulmonary vein trigger ablation in patients undergoing a first AF ablation procedure in a small randomized study. This strategy warrants further evaluation in a multicenter randomized trial. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT03646643.

Coronary sinus diverticulum: Importance, function, and treatment

The importance of venous structure in the heart is usually overshadowed by that of the arterial system. Coronary sinus (CS) is a part of cardiac venous apparatus and connects left atria to the right atria. Other than having role in physiological contractions of both atria, it contributes substantially to cardiac electrical conduction system. Due to unique placement and connections of the CS, it has become growing interest in clinical cardiology. It is used in cardiac resynchronization therapy with biventricular pacing, left-sided catheter ablation of arrhythmias, and administration of retrograde cardioplegia in cardiac surgery. In some individuals, CS is presented with anatomical variants. CS diverticulum is a congenital outpouching that provides muscular connection between atria and ventricle. This connection provides a suitable substrate for occurrence of arrhythmias, which even results in life-threatening events such as sudden cardiac death. Early diagnosis leads to treatment with ablation techniques, which ultimately eliminates origins of arrhythmias.

Electrophysiologic evidence of epicardial connections between low right atrium and remote right atrial region or coronary sinus musculature: Relevance for catheter ablation of typical atrial flutter

BACKGROUND

The coronary sinus (CS) is surrounded by a myocardial coat with extensive connections to the left and right atria that contributes to the interatrial electrical connection. Whereas epicardial connections between CS musculature and the left atrium have largely been demonstrated, clinically relevant epicardial connections from the CS musculature toward the low right atrium (LRA) and epicardial connections between two regions of the right atrium remain questionable.

METHODS

Five patients underwent electrophysiology (EP) study for typical atrial flutter (AFl) using either conventional multipolar catheters (four patients) or three-dimensional high-density mapping system (one patient).

RESULTS

All five patients had a similar sequence of events during the EP studies. After several cavotricuspid isthmus (CTI) radiofrequency (RF) applications, double potentials were recorded along the ablation line while tachycardia persisted. The right atrial activation pattern strongly suggested the presence of a complete endocardial CTI line of the block. Based on the detailed conventional atrial mapping, RF applications at the middle cardiac vein/CS ostium allowed sinus rhythm restoration in four patients. High-density mapping showed an early breakthrough site at the septal side of the ablation line, close to the CS ostium during counterclockwise AFl, in the fifth patient. RF applications at this site resulted in tachycardia termination.

CONCLUSION

Our observations suggested the existence of epicardial fibers connecting the LRA with either the CS musculature or a remote right atrial region. When AFl ablation fails whereas evidence for the local endocardial block is observed, the operators should integrate this finding in the diagnosis and ablation strategy.

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.

Sustained and self-terminating atrial fibrillation induced immediately after pulmonary vein isolation exhibit differences in coronary sinus electrical activity from onset

INTRODUCTION

Little data exists on the electrophysiological differences between sustained atrial fibrillation (sAF; >5 minutes) vs self-terminating nonsustained AF (nsAF; <5 minutes). We sought to investigate the electrophysiological characteristics of coronary sinus (CS) activity during postpulmonary vein isolation (PVI) sAF vs nsAF.

METHODS AND RESULTS

We studied 142 patients post-PVI for paroxysmal AF (PAF). In a 50-patient subset, CS electrograms in the first 30 seconds of induced AF were analyzed manually. A custom-made algorithm for automated electrogram annotation was derived for validation on the whole patient set. In patients with sAF post-PVI, CS fractionated potentials were ablated. Manual analysis showed that patients with sAF exhibited higher activation pattern variability (2.1 vs 0.5 changes/sec; P < .001); fewer proximal-to-distal wavefronts (25 vs 61%; P < .001); fewer unidirectional wavefronts (60 vs 86%; P < .001); more pivot locations (4.3 vs 2.1; P < .001); shorter cycle lengths (190 vs 220 ms; P < .001); and shorter cumulative isoelectric segments (35 vs 44%; P = .045) compared to nsAF. These observations were confirmed on the whole study population by automated electrogram annotation and sample entropy computation (SampEn: 0.29 ± 0.15 in sAF vs 0.15 ± 0.05 in nsAF; P < .0001). The derived model predicted sAF with 78% sensitivity, 88% specificity; agreement with manual model: 88% (Cohen's kappa= 0.76). CS defragmentation resulted in AF termination or noninducibility in 49% of sAF.

CONCLUSION

In PAF patients post-PVI, induced sAF shows greater activation sequence variability, shorter cycle length, and higher SampEn in the CS compared to nsAF. Automated electrogram annotation confirmed these results and accurately distinguished self-terminating nsAF episodes from sAF based on 30-second recordings at AF onset.

Anomalous coronary sinus communication to the left atrium

This report highlights an unusual anatomical finding with serious implications in clinical cardiac care. We present a case of a fistula or bridging vein originating from the left atrium (LA) and inserting into the coronary sinus (CS) which courses posteriorly to the right atrium and inserts near the superior vena cava, essentially serving as a left to right shunt in a 64-year-old woman presenting with chest pain. The coronary venous system serves as a vital access point in the placement of cardiac pacemakers and defibrillators. Coronary sinus anomalies are rare and often occur in isolation or in association with other vascular anomalies. The described conduit serves as a functional interatrial shunt, though likely with minimal hemodynamic significance given the low pressure state of the left and right atria. This case highlights the importance of understanding the coronary venous anatomy and its variations in terms of anatomic course, valves, diameter, angulation, relationship to coronary arteries. .

Coronary Sinus Ablation Is a Key Player Substrate in Recurrence of Persistent Atrial Fibrillation

Atrial fibrillation (AF) is the most frequent atrial arrhythmia. During the last few decades, owing to numerous advancements in the field of electrophysiology, we reached satisfactory outcomes for paroxysmal AF with the help of ablation procedures. But the most challenging type is still persistent AF. The recurrence rate of AF in patients with persistent AF is very high, which shows the inadequacy of pulmonary vein isolation (PVI). Over the last few decades, we have been trying to gain insight into AF mechanisms, and have come to the conclusion that there must be some triggers and substrates other than pulmonary veins. According to many studies, PVI alone is not enough to deal with persistent AF. The purpose of our review is to summarize updates and to clarify the role of coronary sinus (CS) in AF induction and propagation. This review will provide updated knowledge on developmental, histological, and macroscopic anatomical aspects of CS with its role as arrhythmogenic substrate. This review will also inform readers about application of CS in other electrophysiological procedures.

Coronary venous anatomy and anomalies

Coronary venous anatomy can be divided into the greater cardiac venous system and the lesser cardiac venous system. With protocol optimization, including appropriate contrast bolus timing, coronary veins can be depicted with excellent detail on CT. Knowledge of variant coronary venous anatomy can sometimes play a role in pre-procedural planning. Analysis of the coronary venous anatomy on CT can detect coronary venous anomalies that cause right to left shunts with risk of stroke, left to right shunts, and arrhythmias.

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.

Frequency Gradient Within Coronary Sinus Predicts the Long-Term Outcome of Persistent Atrial Fibrillation Catheter Ablation

Background

The coronary sinus (CS), as a junction of the atria, contributes to atrial fibrillation (AF) by developing unstable reentry, and isolating the atria by ablation at the CS could terminate AF. The present study evaluated whether AF activities at the CS in a subset of patients contributed to AF maintenance and predicted clinical outcome of ablation.

Methods and Results

We studied 122 consecutive patients who had a first‐time radiofrequency ablation for persistent AF. Bipolar electrograms were obtained from multiple regions of the left atrium by a Lasso mapping catheter before ablation. Pulmonary vein isolation terminated AF in 12 patients (9.8%). Sequential stepwise ablation was conducted in pulmonary vein isolation nontermination patients and succeeded in 22 patients (18%). In the stepwise termination group, AF frequency in the proximal CS (CSp) was significantly higher (10.2±2.1 Hz versus 8.3±1.8 Hz, P<0.001), and the ratio of distal CS (CSd) to proximal CS (CSd/CSp ratio, 56.6%±10.11% versus 70.7%±9.8%, P<0.001) was significantly lower than that in the nontermination group. The stepwise logistic regression analysis indicated that the CSd/CSp ratio was an independent predictor with an odds ratio of 1.131 (95%CI 1.053‐1.214; P=0.001). With a cutoff of 67%, the patients with lower CSd/CSp ratios had significantly better index and long‐term outcomes than those with higher ratios during a follow‐up of 46±18 months.

Conclusions

Rapid repetitive activities in the musculature of the proximal CS may contribute to maintenance of AF after pulmonary vein isolation alone in persistent AF. A cutoff at 67%, of the CSd/CSp frequency ratio might be an indicator to stratify the subset of patients who might benefit from CS ablation.

Association of Rate-Dependent Conduction Block Between Eccentric Coronary Sinus to Left Atrial Connections With Inducible Atrial Fibrillation and Flutter

BACKGROUND

We sought to describe the prevalence and variability of coronary sinus (CS) and left atrial (LA) myocardium connections, their susceptibility to rate-dependent conduction block, and association with atrial fibrillation (AF) and flutter induction.

METHODS AND RESULTS

The study cohort included 30 consecutive AF patients (age 63.3±10.5 years, 63% male). Multipolar catheters were positioned in the CS, high right atrium (HRA), and LA parallel to and near the CS. Trains of 10 pacing stimuli were delivered during sinus rhythm from each of the following sites: CS proximal (CSp), CS distal (CSd), LA septum (LAs), lateral LA (LAl), and HRA, at the following cycle lengths: 1000, 500, 400, 300, and 250 ms, while recording from the other catheters. With the CS 9 to 10 bipole just inside the CS ostium, CS-LA connections were observed in 100% at CS 9 to 10, 30% at CS 7 to 8, 23% at CS 5 to 6, 23% at CS 3 to 4, and 97% at CS 1 to 2. Eighteen patients (60%) had AF/atrial flutter induced. Rate-dependent conduction block of a CS-LA connection at cycle length of ≥250 ms was present in 17 (94%) of those with versus none of those without AF/atrial flutter induction (P<0.001).

CONCLUSIONS

Rate-dependent eccentric CS-LA conduction block is associated with AF/atrial flutter induction in patients with drug-refractory AF undergoing ablation. The presence of dual muscular CS-LA connections, coupled with unidirectional block in one limb, seems to serve as a substrate for single or multiple reentry beats, and arrhythmia induction.

Flow velocity is relatively uniform in the coronary sinusal venous tree: structure-function relation

The structure and function of coronary venous vessels are different from those of coronary arteries and are much less understood despite the therapeutic significance of coronary sinus interventions. Here we aimed to perform a hemodynamic analysis in the entire coronary sinusal venous tree, which enhances the understanding of coronary venous circulation. A hemodynamic model was developed in the entire coronary sinusal venous tree reconstructed from casts and histological data of five swine hearts. Various morphometric and hemodynamic parameters were determined in each vessel and analyzed in the diameter-defined Strahler system. The findings demonstrate an area preservation between the branches of the coronary venous system that leads to relatively uniform flow velocity in different orders of the venous tree. Pressure and circumferential and wall shear stresses decreased abruptly from the smallest venules toward vessels of order -5 (80.4 ± 39.1 µm) but showed a more modest change toward the coronary sinus. The results suggest that vessels of order -5 denote a hemodynamic transition from the venular bed to the transmural subnetwork. In contrast with the coronary arterial tree, which obeys the minimum energy hypothesis, the coronary sinusal venous system complies with the area-preserving rule for efficient venous return, i.e., da Vinci's rule. The morphometric and hemodynamic model serves as a physiological reference state to test various therapeutic rationales through the venous route.

NEW & NOTEWORTHY

A hemodynamic model is developed in the entire coronary sinusal venous tree of the swine heart. A key finding is that the coronary sinusal venous system complies with the area preservation rule for efficient venous return while the coronary arterial tree obeys the minimum energy hypothesis. This model can also serve as a physiological reference state to test various therapeutic rationales through the venous route.

Adjunctive Therapies for Catheter Ablation of Non-Paroxysmal Atrial Fibrillation

The success rate of pulmonary vein antral isolation (PVAI) for paroxysmal atrial fibrillation (AF) has not been realized for persistent or long-standing AF, collectively termed nonparoxysmal AF. Many investigators have described adjunctive ablation strategies to improve outcomes for catheter ablation in patients with non-paroxysmal AF. In this focused review we aim to describe these therapies and current evidence pertaining to their utilization. At present, left atrial posterior wall (LAPW) ablation, non-pulmonary vein (non-PV) trigger ablation and rotor ablation appear to improve outcomes for patients with non-paroxysmal AF when performed in conjunction with PVAI. Randomized controlled trials are necessary to further elucidate such claims.

Atrial Fibrillation Ablation Strategy: "Ready Made" or "Tailored"?

Atrial fibrillation (AF) is the most common arrhythmia leading to hospital admissions. Catheter ablation has evolved as an effective treatment strategy; however, ablation strategies continue to evolve due to the complex and multifactorial nature of atrial fibrillation. A standardized and primarily anatomical approach may not be sufficient to eliminate all mechanisms of atrial fibrillation. A tailored ablation strategy can target specific triggers and drivers of atrial fibrillation; however, it is limited by the accuracy and sensitivity of the methods used in identifying specific mechanisms of atrial fibrillation.

Ability of magnetocardiography to detect regional dominant frequencies of atrial fibrillation

BACKGROUND

Lead V1 on electrocardiography (ECG) can detect the dominant frequency (DF) of atrial fibrillation (AF) in the right atrium (RA). Paroxysmal AF is characterized by a frequency gradient from the left atrium (LA) to the right atrium (RA). We examined the ability of magnetocardiography (MCG) to detect regional DFs in both the atria.

METHODS

Study subjects comprised 18 consecutive patients referred for catheter ablation of persistent AF. An MCG system with 64 magnetic sensors was used to perform MCG in the frontal, lateral, and back planes prior to the ablation procedure in each patient. DFMCG and organization index (OIMCG) were calculated using fast Fourier transformation. Intracardiac electrograms (ICEs) in both the atria and the coronary sinus (CS) were mapped at 17 sites. Regional DFsICE were also determined.

RESULTS

Mean LA DFICE was higher than mean RA DFICE (6.40±0.66 versus 6.16±0.80 Hz, P=0.03). DFMCG in the channel having the highest OIMCG was 6.61±0.88 Hz in the frontal plane, 6.52±0.64 Hz in the lateral plane, and 6.42±0.62 Hz in the back plane (P=0.3). In each plane, DFMCG correlated with DFICE at the RA appendage (R=0.95, P<0.0001), the LA appendage (R=0.91, P<0.0001), and the CS (R=0.93, P<0.0001). DFECG in V5 modestly correlated with DFICE at the LA appendage (R=0.82, P<0.0001).

CONCLUSIONS

MCG could more precisely detect the DFs in the LA and the CS than ECG. However, the usefulness of pre-procedural detection of the AF frequency gradient for ablation therapy needs to be evaluated in future prospective studies.

Atresia of the right atrial ostium of the coronary sinus without persistent left superior vena cava

We present a case of atresia of the right atrial ostium of the coronary sinus. Recognizing this anomaly is important during catheter ablation or cardiac surgery, which could be noninvasively evaluated by multidetector CT.

Impact of left atrial appendage ridge ablation on the complex fractionated electrograms in persistent atrial fibrillation

BACKGROUND

The left atrial appendage (LAA) is a possible key contributor to the maintenance of persistent atrial fibrillation (PsAF). The effect of LAA ostial ablation on global left atrial higher-frequency sources remains unclear.

METHODS

Complex fractionated electrograms (CFEs) and dominant frequency (DF) maps acquired with a NavX system in 58 PsAF patients were enrolled and examined before and after LAA posterior ridge ablation, which followed a stepwise linear ablation.

RESULTS

High-density left atrial mapping identified continuous CFE sites in 50 % and high-DFs (≥ 8 Hz) in 53 % of patients at the LAA posterior ridge. In 44 patients in whom AF persisted despite pulmonary vein isolation (PVI) and linear ablation, LAA ablation significantly increased the mean CFE cycle length from 98 ± 29 to 108 ± 30 ms (P<0.0001) and decreased DF from 6.1 ± 0.8 to 5.9 ± 0.8 Hz (P<0.005) within the coronary sinus (CS). A multivariate analysis showed single-procedure failures could be predicted by the left atrial volume index and absence of continuous CFEs at the LAA posterior ridge region. The percent decrease in the global left atrial DF after LAA posterior ridge ablation was significantly lower in the patients with than in those without an enlarged left atrium (LA) (>90 mL/m(2)) (median 0 vs 4.8 %; P<0.01) and significantly lower in the patients with than in those without the absence of continuous CFEs in the LAA posterior ridge region (median 0.6 vs 4.8 %; P<0.05).

CONCLUSION

These findings suggested that an approach incorporating an LAA posterior ridge ablation was effective in modifying higher-frequency sources in the global LA in PsAF patients, but a lesser effect was documented in patients with electroanatomical remodeling of the LA.

Substrate modification by adding ablation of localized complex fractionated electrograms after stepwise linear ablation in persistent atrial fibrillation

PURPOSE

Linear left atrial (LA) ablation in patients with persistent atrial fibrillation (PsAF) resulting in the elimination of most complex fractionated electrogram (CFE) sites has been demonstrated. This study was designed to evaluate the impact of a localized CFE ablation in addition to a representative linear LA ablation in patients with PsAF.

METHODS

A total of 40 consecutive patients with PsAF underwent construction of CFE and dominant frequency (DF) maps using NavX. A stepwise linear ablation including at the PV antra, septum, roof, mitral annulus, and ridge of the appendage was performed followed by additional ablation of localized CFEs detected by an automatic algorithm.

RESULTS

A significant reduction in the continuous CFE burden (<50 ms) after the linear ablation (69 vs. 21 %; P < 0.0001) was confirmed, and localized CFEs (40-120 ms) were observed with a significant predilection for the anterior (30 %), posterior (30 %), and inferior LA (38 %) regions (P < 0.01). Comparing the localized CFEs with higher frequency sources, 45 % (70/156) of the localized CFE sites included continuous CFE regions, and 59 % (92/156) of those sites overlapped with the high-DF sites (>8 Hz). Additional localized CFE-targeted ablation further terminated PsAF in 20 % of the patients and further increased the mean CFE cycle length (110 ± 31 to 125 ± 39 ms; P = 0.0033) and decreased the DF (6.0 ± 0.8 to 5.7 ± 0.7 Hz; P = 0.0013) within the CS.

CONCLUSIONS

The presence of localized CFE sites with a predilection for particular LA regions after a representative linear LA ablation could provide the optimal sites for selective substrate modification of the atrial fibrillation substrate in patients with PsAF.

Coronary sinus to left atrium communication

Coronary sinus anomalies are rare. They can be associated with other vascular anomalies such as persistent left superior vena cava or can occur in isolation. We present a rare case of an isolated coronary sinus communication to the left atrium. This anomaly may be clinically relevant in the setting of significant left-to-right shunting or when shunt reversal results from right-sided heart failure. It may also be significant in cases of persistent atrial fibrillation after attempted pulmonary vein isolation.

A detailed assessment of the human coronary venous system using contrast computed tomography of perfusion-fixed specimens

BACKGROUND

Access to the coronary venous system is required for the delivery of several cardiac therapies including cardiac resynchronization therapy, coronary sinus ablation, and coronary drug delivery. Therefore, characterization of the coronary venous anatomy will provide insights to gain improved access to these vessels and subsequently improved therapies. For example, cardiac resynchronization therapy has a 30% nonresponder rate, partially due to suboptimal lead placement within the coronary veins.

OBJECTIVE

To understand the implications of coronary venous anatomy for the development of devices deployed within these vessels.

METHODS

We cannulated the coronary sinus of 121 perfusion-fixed human hearts with a venogram balloon catheter and injected contrast into the venous system while obtaining computed tomographic images. For each major coronary vein, distance to the coronary sinus, branching angle, arc length, tortuosity, number of branches, and ostial diameter were assessed from the reconstructed anatomy.

RESULTS

Twenty-nine percent (35/121) specimens did not have a venous branch overlying the inferolateral side of the heart large enough to fit a 5F pacing lead. No significant differences in anatomy were found between subgroups with varying cardiac medical histories.

CONCLUSION

The anatomical approach employed in this study has allowed for the development of a unique database of human coronary venous anatomy that can be used for the optimization of design and delivery of cardiac devices.

Triggers and anatomical substrates in the genesis and perpetuation of atrial fibrillation

The definition of atrial fibrillation (AF) as a functional electrical disorder does not reflect the significant underlying structural abnormalities. Atrial and Pulmonary Vein (PV) muscle sleeve microstructural remodeling is present, and establishes a vulnerable substrate for AF maintenance. In spite of an incomplete understanding of the anatomo-functional basis for AF, current evidence demonstrates that this arrhythmia usually requires a trigger for initiation and a vulnerable electrophysiological and/or anatomical substrate for maintenance. It is still unclear whether the trigger mechanisms include focal enhanced automaticity, triggered activity and/or micro re-entry from myocardial tissue. Initiation of AF can be favored by both parasympathetic and sympathetic stimulation, which also seem to play a role in maintaining AF. Finally, evolving clinical evidence demonstrates that inflammation is associated with new-onset and recurrent AF through a mechanism that possibly involves cellular degeneration, apoptosis, and subsequent atrial fibrosis.

Human coronary venous anatomy: implications for interventions

The coronary venous system is a highly variable network of veins that drain the deoxygenated blood from the myocardium. The system is made up of the greater cardiac system, which carries the majority of the deoxygenated blood to the right atrium, and the smaller cardiac system, which drains the blood directly into the heart chambers. The coronary veins are currently being used for several biomedical applications, including but not limited to cardiac resynchronization therapy, ablation therapy, defibrillation, perfusion therapy, and annuloplasty. Knowledge of the details of the coronary venous anatomy is essential for optimal development and delivery of treatments using this vasculature. This article is part of a JCTR special issue on Cardiac Anatomy.

Spatial relationship between high-dominant-frequency sites and the linear ablation line in persistent atrial fibrillation: its impact on complex fractionated electrograms

AIMS

Complex fractionated electrograms (CFEs) and high-dominant-frequency (DF) sites theoretically represent abnormal substrates and targets for atrial fibrillation (AF) ablation. The relationship between the high-DF sites in the left atrium (LA) and commonly used linear ablation line to the distribution of the CFEs in patients with persistent AF is unknown.

METHODS AND RESULTS

This study enrolled 62 persistent AF patients who underwent construction of LA CFE and DF maps (>350 points/map). Circumferential pulmonary vein isolation and linear ablation including that at the septum, roof, mitral-annulus, and ridge of the appendage were performed. Multipolar catheter mapping identified sites with high DFs (≥ 8 Hz) in all patients (9.8 ± 4.6/patient). In 47 patients in whom AF persisted despite ablation, there was a significant reduction in the continuous CFE (<50 ms) burden after the linear ablation (62 vs.11%; P < 0.0001), with a decrease in both the DF within the coronary sinus (6.9 ± 0.9 vs. 5.9 ± 0.8 Hz; P < 0.0001) and CFE surface area (42.8 ± 18.8 vs. 12.6 ± 10.5 cm(2); P < 0.0001). Comparing the high-DF sites with the ablated lesions, 64% of the high-DF sites (324 of 507) were on or adjacent to the ablation lines. Residual CFEs were observed in the infero-posterior regions in 83% of the patients. Almost half of the high-DF sites away from the linear ablation line were identified in the inferior (34%) and posterior (14%) LA regions.

CONCLUSION

Linear ablation resulted in the localization of the continuous CFE regions and reduced the global LA DF in patients with persistent AF. This may be related to the proximity relationship between the linear ablation lines and high-DF sites except for in the infero-posterior regions.

Predictors of atrial fibrillation termination and clinical success of catheter ablation of persistent atrial fibrillation

The termination of persistent atrial fibrillation (AF) during catheter ablation has been associated in some, but not all, studies with reduced arrhythmia during clinical follow-up. We sought to determine the rate of persistent AF termination achievable with a stepwise ablation strategy, the predictors of AF termination, and the clinical outcomes associated with termination and nontermination. A total of 143 consecutive patients (age 62 ± 9 years, AF duration 5.7 ± 5.2 years) with persistent and longstanding persistent AF resistant to antiarrhythmic medication who presented in AF for catheter ablation were studied. Ablation was done with a stepwise approach, including pulmonary vein isolation, followed by complex fractionated atrial electrogram ablation and ablation of resultant atrial tachycardias. Clinical follow-up was then performed after a 2-month blanking period to assess arrhythmia recurrence, defined as AF or atrial tachycardia lasting ≥ 30 seconds. AF termination by ablation was achieved in 95 (66%) of the 143 patients. Multivariate predictors of AF termination included longer baseline AF cycle length (p <0.001) and smaller left atrial size (p = 0.002). AF termination by ablation was associated with both a lower incidence of arrhythmia recurrence after a single procedure without antiarrhythmic drugs (p = 0.01) and overall clinical success (single or multiple procedures, with or without antiarrhythmic drugs; p = 0.005). On multivariate analysis, the predictors of overall clinical success included AF termination by ablation (p = 0.001), a shorter ablation duration (p = 0.002), younger age (p = 0.02), male gender (p = 0.03), and the presence of hypertension (p = 0.03). In conclusion, among patients with persistent AF, termination of AF by ablation can be achieved in most patients and is associated with reduced recurrence of arrhythmia.

Coronary sinus isolation: no myth but reality

Coronary sinus (CS) has muscular connections with atria and is often targeted to complete left atrial ablation for curing atrial fibrillation; however, complete CS isolation is difficult to achieve with hard end points. We present a distinctive case of complete isolation of CS that had an unusual muscular connection.

Complications from catheter ablation of atrial fibrillation: a systematic review

Atrial fibrillation (AF) is the most common arrhythmia requiring treatment that is encountered in clinical practice. Recent advances in the understanding of underlying mechanisms of AF have led to the increased use of catheter ablation (CA) as a treatment modality for paroxysmal, persistent, or long-standing persistent AF in patients with symptomatic AF despite treatment with antiarrhythmic medications. Because of the complexity in technique and anatomic location of the ablation sites, it is not surprising that CA of AF is associated with a greater risk of procedural complications compared with simpler cardiac ablation procedures. Major and minor complications, including life-threatening complications, have been described and quantified. This systematic review describes the potential risks of CA that have been reported over a period and provides insights into the evolving strategies to minimize these complications, thus making CA techniques safer and potentially more efficacious for AF.