Catheter ablation techniques for selective cardiac autonomic denervation to treat patients with paroxysmal atrial fibrillation

The Role of the Atrial Neural Network In Atrial Fibrillation: The Metastatic Progression Hypothesis

With the advent of catheter ablation of atrial fibrillation (AF) there has been acceleration in our understanding of the mechanisms underlying the etiology of this common clinical arrhythmia. In this regard, the role of the intrinsic cardiac autonomic nervous system in the initiation and maintenance of AF began to receive attention in numerous experimental and clinical investigations. Up to now, the focus has been on the large ganglionated plexi (GP) which are located in the posterior left atrium mainly at the pulmonary vein-atrial junctions. As long term outcomes have been reported and single procedures have indicated diminished success rates particularly for persistent/long standing persistent AF, emphasis has begun to shift away from the pulmonary vein isolation (PVI) alone as well as GP ablation with or without PVI. An understanding of the atrial substrate represented by the extensions of the intrinsic cardiac autonomic system constituting the atrial neural network is beginning to evolve. In this review, the contribution of the intrinsic cardiac autonomic nervous system to the etiology of AF is addressed, particularly in regard to the greater prevalence of AF in the elderly. In addition, we emphasize the involvement of the atrial neural network in the "metastatic" progression of paroxysmal to persistent and long standing persistent forms of AF.

Decreased postoperative atrial fibrillation following cardiac transplantation: the significance of autonomic denervation

BACKGROUND

Endocardial ablation approaches targeting the retroatrial cardiac ganglia to treat atrial fibrillation (AF) have been proposed. However, the potential value using this approach is unknown. Disruption of the autonomic inputs with orthotropic heart transplant (OHT) provides a unique opportunity to study the effects of autonomic innervation on AF genesis and maintenance. We hypothesized that due to denervation, the risk of postoperative AF would be lower following OHT compared to surgical maze even though both groups get isolation of the pulmonary veins.

METHODS AND RESULTS

We reviewed 155 OHTs (mean age 52 ± 11 years, 72% males) and used 1:1 age-, sex-, and date-of-surgery-matched two control groups from patients undergoing surgical maze or only coronary artery bypass grafting (CABG). Using conditional logistic regression we compared the odds of AF within 2 weeks following OHT versus controls. Postoperative AF occurred in 10/155 (6.5%) OHT patients. The conditional odds of postoperative AF were lower for OHT as compared to controls (vs maze: odds ratio [OR] 0.27 [95% confidence interval (CI) 0.13-0.57], vs CABG: OR 0.38 [0.17-0.81], P = 0.003; and on additional adjustment for left atrial enlargement, vs maze: OR 0.28 [0.13-0.60], vs CABG: OR 0.14 [0.04-0.47], P = 0.0009).

CONCLUSIONS

Risk of postoperative AF is significantly lower with OHT as in comparison to surgical maze. As both surgeries entail isolation of the pulmonary veins but only OHT causes disruption of autonomic innervation, this observation supports a mechanistic role of autonomic nervous system in AF. The benefit of targeting the cardiac autonomic system to treat AF needs further investigation.

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.

Catheter Ablation of Right Atrial Ganglionated Plexi in Patients With Vagal Paroxysmal Atrial Fibrillation

Background—

Catheter ablation of ganglionated plexi (GP) in the left atrium has been proposed in different subgroup of patients with atrial fibrillation (AF). Anatomic studies found a high prevalence of GP in the posterior surface of the right atrium (RA). Experimental data suggested the potential role of right atrial GP in the AF initiation and maintenance. The aim of our study was to assess the efficacy of GP ablation in RA in patients with vagal AF.

Methods and Results—

Thirty-four patients without structural heart diseases were randomly assigned for a selective ablation procedure targeted on the elimination of vagal reflex evoked by high frequency stimulation or an extensive approach at anatomic sites of GP. All patients underwent Holter ECG and heart rate variability evaluation at baseline and at 3, 6, 12, and 18 months of follow-up. At a mean follow-up of 19.7±5.2 months, AF recurred in 5 of 17 patients with anatomic ablation and in 13 of 17 patients with a selective approach ( P =0.01). No patient had major complications. After ablation, heart rate variability parameters showed a significant parasympathetic (and sympathetic) denervation in the first 6 months, which was more prominent in patients with anatomic GP ablation and in those without AF recurrence.

Conclusions—

This study demonstrates that in a selected population of vagal paroxysmal AF, the anatomic ablation of GPs in the RA is effective in about 70% of patients. These results confirm that atrial vagal denervation can abolish AF, as suggested by experimental and clinical data.