Ablation of Ganglionic Plexi During Combined Surgery for Atrial Fibrillation

Neurohumoral Markers of Cardiac Autonomic Denervation after Surgical Ablation of Long-Standing Persistent Atrial Fibrillation

Although the autonomic nervous system has an evident impact on cardiac electrophysiology and radiofrequency ablation (RFA) is the conventional technique for treating persistent atrial fibrillation, the specific effects of RFA have been insufficiently studied to date. Here, we investigated whether RFA affects neurohumoral transmitter levels and myocardial 123I-metaiodobenzylguanidine (123I-MIBG) uptake. To perform this task, we compared two groups of patients with acquired valvular heart disease: patients who had undergone surgical AF ablation and patients with sinus rhythm. The decrease in norepinephrine (NE) level in the coronary sinus had a direct association with the heart-to-mediastinum ratio (p = 0.02) and a negative correlation with 123I-MIBG uptake defects (p = 0.01). The NE level decreased significantly after the main surgery, both in patients with AF (p = 0.0098) and sinus rhythm (p = 0.0039). Furthermore, the intraoperative difference between the norepinephrine levels in the ascending aorta and coronary sinus (ΔNE) of -400 pg/mL was determined as a cut-off value to evaluate RFA efficacy, as denervation failed in all patients with ΔNE < -400 pg/mL. Hence, ΔNE can be utilized to predict the efficacy of the "MAZE-IV" procedure and to assess the risk of AF recurrence after RFA.

Intrinsic Cardiac Neuromodulation in the Management of Atrial Fibrillation- A Potential Missing Link?

Atrial fibrillation (AF) is the most common supraventricular arrhythmia that is linked with higher cardiovascular morbidity and mortality. Recent evidence has demonstrated that catheter-based pulmonary vein isolation (PVI) is not only a viable alternative but may be superior to antiarrhythmic drug therapy for long-term freedom from symptomatic AF episodes, a reduction in the arrhythmia burden, and healthcare resource utilization with a similar risk of adverse events. The intrinsic cardiac autonomic nervous system (ANS) has a significant influence on the structural and electrical milieu, and imbalances in the ANS may contribute to the arrhythmogenesis of AF in some individuals. There is now increasing scientific and clinical interest in various aspects of neuromodulation of intrinsic cardiac ANS, including mapping techniques, ablation methods, and patient selection. In the present review, we aimed to summarize and critically appraise the currently available evidence for the neuromodulation of intrinsic cardiac ANS in AF.

Neuromodulation therapy for atrial fibrillation

Atrial fibrillation has a multifactorial pathophysiology influenced by cardiac autonomic innervation. Both sympathetic and parasympathetic influences are profibrillatory. Innovative therapies targeting the neurocardiac axis include catheter ablation or pharmacologic suppression of ganglionated plexi, renal sympathetic denervation, low-level vagal stimulation, and stellate ganglion blockade. To date, these therapies have variable efficacy. As our understanding of atrial fibrillation and the cardiac nervous system expands, our approach to therapeutic neuromodulation will continue evolving for the benefit of those with AF.

Neuroscientific therapies for atrial fibrillation

The cardiac autonomic nervous system (ANS) plays an integral role in normal cardiac physiology as well as in disease states that cause cardiac arrhythmias. The cardiac ANS, comprised of a complex neural hierarchy in a nested series of interacting feedback loops, regulates atrial electrophysiology and is itself susceptible to remodelling by atrial rhythm. In light of the challenges of treating atrial fibrillation (AF) with conventional pharmacologic and myoablative techniques, increasingly interest has begun to focus on targeting the cardiac neuraxis for AF. Strong evidence from animal models and clinical patients demonstrates that parasympathetic and sympathetic activity within this neuraxis may trigger AF, and the ANS may either induce atrial remodelling or undergo remodelling itself to serve as a substrate for AF. Multiple nexus points within the cardiac neuraxis are therapeutic targets, and neuroablative and neuromodulatory therapies for AF include ganglionated plexus ablation, epicardial botulinum toxin injection, vagal nerve (tragus) stimulation, renal denervation, stellate ganglion block/resection, baroreceptor activation therapy, and spinal cord stimulation. Pre-clinical and clinical studies on these modalities have had promising results and are reviewed here.

Effect of Lidocaine Injection of Ganglionated Plexi in a Canine Model and Patients With Persistent and Long-Standing Persistent Atrial Fibrillation

Background

This study assessed the effect of blockading neural transmission in the ganglionated plexi by injecting lidocaine into fat pads in the vagal nerve stimulation canine model and patients with persistent atrial fibrillation (AF).

Methods and Results

An efficacy test of lidocaine injection was performed in 7 canines. During vagal nerve stimulation, AF was sustained for >5 minutes. The lidocaine was injected into ganglionated plexi during sinus rhythm and reinduction of AF was attempted. Six patients with persistent AF were studied at open heart surgery. Lidocaine was injected into ganglionated plexi. Atrial electrograms were recorded from 96 epicardial electrodes covering Bachmann's bundle and atrial appendages. In the canine vagal nerve stimulation AF model, AF was not inducible in 4 of 7 after lidocaine injection. In patients with persistent AF, during baseline AF, there was a left atrium (LA)‐to‐right atrium (RA) frequency gradient (LA, mean cycle length [CL] 175±17 ms; RA, mean CL 192±17 ms; P<0.01). After lidocaine injection, AF persisted in all patients, and the LA‐to‐RA frequency gradient disappeared (LA, mean CL 186±13 ms; RA, mean CL 199±23 ms; P=0.08). Comparison of mean CLs before and after lidocaine demonstrated prolongation of LA CLs (P<0.05) with no effect on RA CLs.

Conclusions

In the canine vagal nerve stimulation AF model, lidocaine injection decreased inducibility of AF. In patients with persistent AF, atrial electrograms from the LA had shorter CLs than RA, indicating an LA‐to‐RA frequency gradient. Lidocaine injection significantly prolonged only LA CLs, explaining disappearance of the LA‐to‐RA frequency gradient. The mechanism of localized atrial electrogram CL prolongation in patients with persistent AF is uncertain.

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Long-term results of the maze procedure with GP ablation for permanent atrial fibrillation

OBJECTIVES

We investigated the effect of the maze procedure with intensive pulmonary vein isolation (PVI) guided by ganglionated plexus (GP) mapping (the Maze with GP ablation group) on a long-term postoperative maintenance of sinus rhythm in patients with permanent atrial fibrillation (AF) and compared with that in patients undergoing the maze procedure with the conventional PVI (the Maze group).

METHODS AND RESULTS

We investigated 48 patients who underwent the maze procedure with GP ablation for persistent AF and 43 patients who underwent the maze procedure. The Maze procedure was conducted by the endocardial application of bipolar radiofrequency ablation and cryoablation. Conventional PVI was applied three times for the entrance of right and left PVs, respectively. Intensive PVI for GP ablation was repeated six-to-eight times for both sides of PVs to cover the bilateral GP regions identified by GP mapping. The duration of permanent AF, the prevalence of concomitant primary heart diseases, and the postoperative follow-up period were comparable between the two groups. At discharge, 1 year, 5 years after the surgery, sinus rhythm was maintained in 74.4%, 61%, and 40.5% of the Maze group. In contrast, it was maintained in 93.7%, 88.9%, and 75.7% of the Maze with GP ablation group. The cumulative freedom rate from AF at 10 years after surgery was significantly higher in the Maze with GP ablation group.

CONCLUSIONS

More intense PV isolation including adjacent GP may improve long-term results of maze procedure in patients with permanent AF.

Ganglion Plexus Ablation in Advanced Atrial Fibrillation: The AFACT Study

BACKGROUND

Patients with long duration of atrial fibrillation (AF), enlarged atria, or failed catheter ablation have advanced AF and may require more extensive treatment than pulmonary vein isolation.

OBJECTIVES

The aim of this study was to investigate the efficacy and safety of additional ganglion plexus (GP) ablation in patients undergoing thoracoscopic AF surgery.

METHODS

Patients with paroxysmal AF underwent pulmonary vein isolation. Patients with persistent AF also received additional lines (Dallas lesion set). Patients were randomized 1:1 to additional epicardial ablation of the 4 major GPs and Marshall's ligament (GP group) or no extra ablation (control) and followed every 3 months for 1 year. After a 3-month blanking period, all antiarrhythmic drugs were discontinued.

RESULTS

Two hundred forty patients with a mean AF duration of 5.7 ± 5.1 years (59% persistent) were included. Mean procedure times were 185 ± 54 min and 168 ± 54 min (p = 0.015) in the GP (n = 117) and control groups (n = 123), respectively. GP ablation abated 100% of evoked vagal responses; these responses remained in 87% of control subjects. Major bleeding occurred in 9 patients (all in the GP group; p < 0.001); 8 patients were managed thoracoscopically, and 1 underwent sternotomy. Sinus node dysfunction occurred in 12 patients in the GP group and 4 control subjects (p = 0.038), and 6 pacemakers were implanted (all in the GP group; p = 0.013). After 1 year, 4 patients had died (all in the GP group, not procedure related; p = 0.055), and 9 were lost to follow-up. Freedom from AF recurrence in the GP and control groups was not statistically different whether patients had paroxysmal or persistent AF. At 1 year, 82% of patients were not taking antiarrhythmic drugs.

CONCLUSIONS

GP ablation during thoracoscopic surgery for advanced AF has no detectable effect on AF recurrence but causes more major adverse events, major bleeding, sinus node dysfunction, and pacemaker implantation. (Atrial Fibrillation Ablation and Autonomic Modulation via Thoracoscopic Surgery [AFACT]; NCT01091389).

Elimination Of Triggers Without An Additional Substrate Modification Is Not Sufficient In Patients With Persistent Atrial Fibrillation

Atrial fibrillation (AF) is a multifactorial disease with complex pathophysiology. Although restoring sinus rhythm delays the progression of atrial remodeling, non-pharmacologic intervention, such as radiofrequency catheter ablation (RFCA), should be done based on the background pathophysiology of the disease. While circumferential pulmonary vein isolation (CPVI) has been known to be the cornerstone of AF catheter ablation, a clinical recurrence rate after CPVI is high in patients with persistent AF (PeAF). Step-wise linear ablation, complex fractionate atrial electrogram (CFAE)-guided ablation, rotor ablation, ganglionate plexus ablation, and left atrial appendage isolation may improve the ablation success rate after CPVI. But, there are still substantial AF recurrences after such liberal atrial substrate ablation, and current ablation techniques regarding substrate modification still have limitations. Therefore, more understanding about AF pathophysiology and early precise intervention may improve clinical outcome of AF management. Keeping in mind "more touch, more scar," operators should generate most efficient substrate modification to achieve better long-term clinical outcome.

Cardiac Autonomic Denervation for Ablation of Atrial Fibrillation

The influence of the autonomic nervous system (ANS) on triggering and perpetuation of atrial fibrillation (AF) is well established. Ganglionated plexi (GP) ablation achieves autonomic denervation by affecting both the parasympathetic and sympathetic components of the ANS. GP ablation can be accomplished endocardially or epicardially, i.e. during the maze procedure or thoracoscopic approaches. Recent evidence indicates that anatomic GP ablation at relevant atrial sites appears to be safe and improves the results of pulmonary vein isolation in patients with paroxysmal and persistent AF.

Outflow tract premature ventricular depolarizations after atrial fibrillation ablation may reflect autonomic influences

PURPOSE

Autonomic modulation following catheter ablation of atrial fibrillation may promote the development of catecholamine-sensitive arrhythmias, such as outflow tract (OT) ventricular premature depolarizations (VPDs). The purpose of this study was to determine the incidence and prognostic significance of OT VPDs occurring in patients after atrial fibrillation (AF) ablation.

METHODS

We prospectively examined 53 consecutive patients undergoing wide-area circumferential antral pulmonary vein (PV) isolation; no patients had evidence of OT VPDs on 24 h of preprocedural telemetry monitoring. Cases (OT+) had postprocedure telemetry monitoring with >30 continuous beats or >3/min OT VPDs. Clinical follow-up included transtelephonic monitoring at 6 weeks, 6 months, and 1 year.

RESULTS

The incidence of OT VPDs in this population was 11% (6/53). There was no difference in AF recurrence at 1 year between those with or without OT VPDs (17 vs 28%, p = 0.6). There was a strong association with higher immediate postprocedure heart rate (HR) in OT+ compared to OT- patients (86 vs 76, p = 0.03); this difference persisted at 1 year (79 vs 60, p < 0.01). OT VPDs resolved in 5/6 of the OT+ patients over the 1-year follow-up. In a multivariable linear regression model, OT VPDs were associated with higher HR (odds ratio (OR) 1.14 [1.10-1.18], p < 0.001) despite adjustment for medication dose.

CONCLUSIONS

A minority of patients undergoing antral PV isolation develops OT VPDs associated with a sustained increase in mean heart rate; this effect may result from the modulation of adjacent autonomic ganglia.

Heart rate turbulence for predicting new-onset atrial fibrillation in patients undergoing coronary artery bypass grafting

BACKGROUND

Cardiac autonomic dysfunction reportedly contributes to the AF triggering and maintenance. Heart rate turbulence (HRT) is a promising noninvasive measure of cardiac autonomic function. We investigated whether ambulatory ECG-based HRT measurement could predict in-hospital new-onset atrial fibrillation (AF) after coronary artery bypass graft (CABG) surgery.

METHODS

HRT onset (TO) and slope (TO) were prospectively measured from 24-h Holter recording in 113 consecutive patients prior to CABG. Abnormal HRT was defined as at least one abnormal value in TO (> 0%) and TS (< 2.5 ms/RR).

RESULTS

Patients with abnormal HRT (n = 60) showed a significantly higher AF incidence (47% versus 21%, P = 0.005) and AF burden (29 ± 9 versus 7 ± 5 h, P = 0.043) than those with normal HRT (n = 53). Abnormal HRT were identified as independent predictors for the new-onset postoperative AF. During the follow-up period (12.0 ± 10.5 months), the abnormal HRT group showed a worse prognosis versus the normal HRT group regarding the AF recurrence/postoperative stroke (P = 0.018). Additionally, the postoperative AF incidence, in-hospital AF burden, and the rate of AF recurrence/postoperative stroke gradually elevated as the number of abnormal HRT values increased from 0 to 2.

CONCLUSIONS

Preoperative abnormal HRT was significantly associated with worse short-term (in-hospital new-onset AF) and long-term outcomes (post-discharge AF recurrence/postoperative stroke) after CABG surgery. Additional studies incorporating preventive interventions depending on the preoperative HRT results might be worthwhile in this patient group.

Surgical Minimally Invasive Pulmonary Vein Isolation for Lone Atrial Fibrillation

Objective

Minimally invasive surgical pulmonary vein isolation (SMI-PVI) is an emerging therapy for the treatment of symptomatic drug-refractory atrial fibrillation (AF). Nevertheless, the midterm and long-term results of SMI-PVI remain unknown. The aim of this retrospective multicenter study was to report on midterm efficacy and safety of SMI-PVI.

Methods

The study design was retrospective, multicentric, and observational. From July 2005 to November 2011, a total of 86 patients with drug-refractory paroxysmal or persistent AF underwent SMI-PVI in three centers. Patients were eligible for SMI-PVI if they had symptomatic, drug-refractory AF or after failed transcatheter pulmonary vein isolation. Success was defined as absence of AF on 24- or 96-hour Holter monitoring during follow-up, in the absence of antiarrhythmic drugs (AADs).

Results

The mean ± SD age was 54 ± 11 years, and 78% were men. The median AF duration was 30 months (range, 2–203); paroxysmal AF was present in 86% of the patients, persistent in 14%. Fifteen patients (17%) underwent previous transcatheter ablations. After a median follow-up of 24 months (range, 6–78), 72% of all patients were free from atrial arrhythmias without the use of AADs. With AADs, this was 83%. Major perioperative adverse events occurred in 7 patients (8%).

Conclusions

This retrospective multicenter study shows that SMI-PVI is effective at a median follow-up of 24 months for the treatment of mostly paroxysmal drug-refractory AF. Perioperative adverse events do remain a point of caution.

Towards personalized clinical in-silico modeling of atrial anatomy and electrophysiology

Computational atrial models aid the understanding of pathological mechanisms and therapeutic measures in basic research. The use of biophysical models in a clinical environment requires methods to personalize the anatomy and electrophysiology (EP). Strategies for the automation of model generation and for evaluation are needed. In this manuscript, the current efforts of clinical atrial modeling in the euHeart project are summarized within the context of recent publications in this field. Model-based segmentation methods allow for the automatic generation of ready-to-simulate patient-specific anatomical models. EP models can be adapted to patient groups based on a-priori knowledge and to the individual without significant further data acquisition. ECG and intracardiac data build the basis for excitation personalization. Information from late enhancement (LE) MRI can be used to evaluate the success of radio-frequency ablation (RFA) procedures and interactive virtual atria pave the way for RFA planning. Atrial modeling is currently in a transition from the sole use in basic research to future clinical applications. The proposed methods build the framework for model-based diagnosis and therapy evaluation and planning. Complex models allow to understand biophysical mechanisms and enable the development of simplified models for clinical applications.

The intrinsic autonomic nervous system in atrial fibrillation: a review

The procedure of catheter ablation for the treatment of drug resistant atrial fibrillation (AF) has evolved but still relies on lesion sets intended to isolate areas of focal firing, mainly the myocardial sleeves of the pulmonary veins (PVs), from the rest of the atria. However the success rates for this procedure have varied inversely with the type of AF. At best success rates have been 20 to 30% below that of other catheter ablation procedures for Wolff-Parkinson-White syndrome, atrioventricular junctional re-entrant tachycardia and atrial flutter. Basic and clinical evidence has emerged suggesting a critical role of the ganglionated plexi (GP) at the PV-atrial junctions in the initiation and maintenance of the focal form of AF. At present the highest success rates have been obtained with the combination of PV isolation and GP ablation both as catheter ablation or minimally invasive surgical procedures. Various lines of evidence from earlier and more recent reports provide that both neurally based and myocardially based forms of AF can separately dominate or coexist within the context of atrial remodeling. Future studies are focusing on non-pharmacological, non-ablative approaches for the prevention and treatment of AF in order to avoid the substantive complications of both these regimens.

Surgical Treatment of Isolated (Lone) Atrial Fibrillation with Gemini-S Ablation and Left Atrial Appendage Excision (GALAXY Procedure)

Objective

Surgical ablation with radiofrequency is a safe and effective treatment for atrial fibrillation. Recent advances in instrumentation have allowed for the application of bipolar radiofrequency through a minimally invasive approach using small bilateral thoracotomies for pulmonary vein isolation, destruction of autonomic ganglia, and excision of the left atrial appendage (GALAXY procedure).

Methods

Thirty-two patients underwent surgical ablation of atrial fibrillation with the GALAXY procedure over a 43-month period. Data were collected in a prospective manner during hospitalization and at 1-, 3-, 6-, and 12-month intervals for rhythm, medications, and subsequent interventions.

Results

There were no operative mortality, no myocardial infarction, and no stroke. One patient required reexploration for bleeding. Mean follow-up was 28 months (range, 4–43 months). Freedom from atrial fibrillation at 12 and 24 months, respectively, was 90% and 67% for patients with paroxysmal fibrillation and 80% and 63% for patients with persistent atrial fibrillation. Of the patients who were not in sinus rhythm, four reverted to atrial fibrillation and two reverted to atrial flutter.

Conclusions

The GALAXY procedure is a safe and effective, minimally invasive method for treatment of isolated (lone) atrial fibrillation. The operation provides excellent short-term freedom from atrial fibrillation and should be considered in patients with isolated paroxysmal atrial fibrillation.

Complex fractionated electrograms in the right atrial free wall and the superior/posterior wall of the left atrium are affected by activity of the autonomic nervous system

BACKGROUND

Complex fractionated atrial electrograms (CFAEs) are supposed to be related to structural and electrical remodeling. Animal studies suggest a role of the autonomic nervous system (ANS). However, this has never been studied in humans.

OBJECTIVE

The goal of this study was to investigate the influence of ANS on CFAEs in patients with idiopathic atrial fibrillation (AF).

METHODS

Thirty-six patients (28 men, 55 ± 9 years) were included before undergoing catheter ablation. In the 24 hours preceding the procedure, 20 patients were in AF (group 1) and 16 were in sinus rhythm (SR, group 2). With 2 decapolar catheters, 1 in the right atrium (RA) and 1 in the left atrium (LA), 20 unipolar electrograms were simultaneously recorded during a 100-second AF-period (in group 2 after induction of AF). After atropine and metoprolol administration, a second 100-second AF-period was recorded 30 minutes later. Five patients of group 2 served as controls and did not receive atropine and metoprolol prior to the second recording. CFAEs were assessed and the prevalence of CFAEs was expressed as percentage of the recording time.

RESULTS

The prevalence of CFAEs was greater in group 1 than in group 2 in both RA and LA (P = 0.026, P < 0.001, respectively). Atropine and metoprolol significantly reduced CFAEs in group 1 (P < 0.001) and prevented the time-dependent increase of CFAEs in group 2.

CONCLUSION

The prevalence of CFAEs is greater in long-lasting AF episodes. Atropine and metoprolol administration reduces CFAEs in both atria. Thus, CFAEs are at least partly influenced by the ANS.

Non-pharmacological, non-ablative approaches for the treatment of atrial fibrillation: experimental evidence and potential clinical implications

In this review, we initially covered the basic and clinical reports that provided the prevalent concepts underlying the mechanisms for atrial fibrillation (AF). The clinical evolution of catheter ablation and its eventual application to AF has also been detailed. A critique of the results based on a review of the literature has shown that either or both drugs or catheter ablation therapy for preventing AF recurrences have significant limitations and even serious complications. Finally, we have presented recent experimental studies which suggest that an alternative approach to reducing AF inducibility can be achieved with low-level autonomic nerve stimulation. Specifically, electrical stimulation of the vago-sympathetic trunks, at levels well below that which slows the heart rate can significantly increase AF thresholds and suppress AF inducibility. Further studies will determine if this new method can be used as an effective means of treating some forms of clinical AF.

The surgical treatment of atrial fibrillation

Atrial fibrillation is a complex disease affecting a significant portion of the general population. Although medical therapy is the mainstay of treatment, intervention plays an important role in selected patients. The Cox-Maze procedure is the gold standard for the surgical treatment of atrial fibrillation and has more than 90% success in eliminating atrial fibrillation. Ablation technologies have played a key role in simplifying this technically demanding procedure and making it available to more patients. A myriad of new lesion sets and approaches were introduced over the last decade which has made the operative treatment of atrial fibrillation less invasive and more confusing.

The Autonomic Nervous System and Atrial Fibrillation:The Roles of Pulmonary Vein Isolation and Ganglionated Plexi Ablation

After the sequential successes of catheter ablation for the treatment of pre-excitation syndromes (WPW), junctional reentry (AVNRT) atrial flutter (AFL) and ventricular arrhythmias, clinical electrophysiologists have focused on the myocardial basis of atrial fibrillation (AF). Thus, the strategy for ablation of drug and cardioversion refractory AF was to isolate the myocardial connections from the focal firing pulmonary veins (PVs) in addition to altering the atrial substrate maintaining AF. However, the overall success rates have not achieved those of the other types of ablation procedures. In this review we have summarized the favorable aspects and drawbacks of pulmonary vein isolation (PVI). As for the role of the Intrinsic Cardiac Autonomic Nervous System (ICANS), both basic and clinical evidence has shown that ganglionated plexi (GP) stimulation promotes initiation and maintenance of AF, and that GP ablation reduces recurrence of AF following catheter or surgical ablation of these structures. Based on these findings, the GP Hyperactivity Hypothesis has been proposed to explain, at least in part, the mechanistic basis for the focal form of AF. For example, PV isolation may not always be necessary for elimination of AF, as in the early stages of paroxysmal AF. GP ablation alone, in these cases, may suffice for focal AF termination. In the persistent and long standing persistent forms the substrate for AF may be more extensive and therefore require GP ablation plus PV isolation and/or CFAE ablations. Clinical reports, both catheter based as well as minimally invasive surgical procedures, which include PVI plus GP ablation have shown relatively long-term success rates much closer to or equal to those achieved by myocardial ablation procedures in patients with WPW, AVNRT and AFL.