*Recent Advances in Catheter Ablation for Atrial Fibrillation and Non-pharmacological Stroke… DOI: http://dx.doi.org/10.5772/intechopen.106319*

the radiofrequency group (124 vs. 141 min, *P* < 0.001), as was the left atrial dwell time (the length of time the catheter was present in the left atrium during the procedure). The mean total fluoroscopy time was shorter in the radiofrequency group than in the cryoballoon group (17 vs. 22 min, *P* < 0.001) due to navigational capabilities utilizing 3D electroanatomic mapping system with RF ablation. Though both methods (RF vs. Cryo) had similar outcomes in terms of safety, Incidence of Phrenic nerve Injury was slightly

#### **Figure 5.**

*Cryoballoon ablation system. There is an integrated circular mapping catheter. Balloon is inflated in the pulmonary vein and single shot application of subzero temperature is delivered to the pulmonary vein antrum. Bottom figure shows an RF ablation catheter which delivers heat energy with a point by point application around the pulmonary vein antrum. Picture courtesy FIRE AND ICE trial investigators [43].*

higher in Cryoablation group, but this was substantially lower compared to reported incidence of Phrenic nerve injury in STOP AF trial group (**Figure 5**).

#### **3.6 Cardio-neural alablation**

Role of Autonomic nervous system in initiation and maintenance of AF has been a great area of interest to understand the pathophysiology of AF. Intrinsic autonomic nervous system [44] is believed to comprise of primarily 5 major ganglionated plexi (GP) located in the epicardial fat pads- superior left GP, Inferior Left GP, Anterior Right GP, Inferior right GP and Ligament of Marshal). GPs predominantly contain parasympathetic neurons but also sympathetic neurons (**Figure 6**).

It is challenging to localize GP with endocardial mapping and hence ablation effectiveness has remained controversial. One technique described to localize major GP is to elicit AV block with High frequency stimulation (HFS) [46, 47]. GPs are consistently located in areas of Left atrial fractionated atrial potential (LA FAP) [44, 46–52] commonly seen around coumadin ridge LAA-Left PV region, ligament of marshall, superior left FAP area, inferoposterior FAP, anterior right FAP. HFS at Cycle length 50 ms, 12–15 V, 10 ms

**Figure 6.** *Schematic diagram of major ganglionate Plexi (shown in yellow) and axons. Picture adopted from [45].*

#### *Recent Advances in Catheter Ablation for Atrial Fibrillation and Non-pharmacological Stroke… DOI: http://dx.doi.org/10.5772/intechopen.106319*

pulse width is delivered to [47, 52] and if AV block is seen (increase in R-R interval >50% during AF) and RF ablation is performed at each site exhibiting a positive HFS response. Ablation of each of the five GP areas usually requires 2–12 (median 6) RF applications. 124,582. HFS is not very sensitive to identify GP. There are other markers such as onset of PV fire from PV other than adjacent GP. There is also significant interplay between GP. AV block is mediated by inferior right GP, hence HFS of other GPs activate Inferior Right GP which innervates the AV node. If a GP is ablated along the course to Inferior Right GP, HFS may not elicited AV block. So it is usually advisable to ablate GP in the order starting with Marshal tract, superior Left, anterior right, inferior left and finally inferior right.

Pokushalov et al. showed regional ablation at the anatomic sites of the left atrial GP can be safely performed and enables maintenance of sinus rhythm in 71% of patients with paroxysmal AF for a 12-month period [53]*.* Katritsis et al. [54] randomized 242 patients with Paroxysmal AF into PVI alone with circumferential antral lesions, GP ablation alone, and combination of PVI with GP ablation. Freedom from AF or AT was achieved in 44 (56%), 39 (48%), and 61 (74%) patients in the PVI, GP, and PVI + GP groups, respectively (*P* = 0.004 by log-rank test). Study concluded that addition of GP ablation to PVI confers a significantly higher success rate compared with either PVI or GP alone in patients with PAF. Pokushalov et al. [55] conducted an RCT in persistent/ long standing persistent AF patients including 264 patients randomized into two ars: PVI + Linear Line (LL) (*n* = 132) and PVI + GP (*n* = 132) to see whether GP or LL ablation can be a better adjunct to PVI. Sinus rhythm at 12 months (47% vs. 54%) and 3 years (34% vs. 49%) were found to be higher in the PVI + GP group. On the other hand, PVI + LL ablation group had higher incidence of Left Atrial Flutter.

Driessen et al. in AFACT [56] study compared surgical epicardial GP ablation in addition to PVI and found no improvement in outcome.

Current HRS/EHRA expert consensus states that usefulness of ablation of autonomic ganglia as an initial or repeat ablation strategy for paroxysmal, persistent, and long-standing persistent AF is not well established (Class IIb, LOE B-NR).
