An important advantage of echocardiographic guidance

An important advantage of echocardiographic guidance during TP is the possibility of initiating anticoagulation safely before TP. This appears to be a very important benefit, especially in patients with AF, in whom the risk of thrombus formation is high, despite anticoagulation to ACT >250s. In one study, the incidence of thrombosis was significantly lower when heparin was given before the first or second TP compared with heparin administration after the TP (3.1% vs. 9%, p<0.001). A thrombus was observed on a mapping or ablation catheter in 16 of 29 patients, and in the remaining 13, it was detected in the left atrium or appendage. Additionally, a thrombus aspiration was safely performed through the sheath in 21 of 29 cases [12]. In our study, we also aimed to evaluate the advantages of echocardiographic guidance during TP by initiating anticoagulation safely before TP, but only one patient in the fluoroscopy-guided group experienced a thromboembolic event, which was not statistically different from the TEE-guided group. Although in our study the TEE probe was removed after successful TP, there are many other possible advantages of continuous TEE usage during the cryoablation of AF. Siklódy et al. [13] studied 124 PVs in 30 patients. Under continuous TEE assessment, a cryoballoon was placed in the antrum of each PV aiming for complete PV occlusion as documented by color Doppler. They reported that, compared to their previously published data [14], times with the cryoballoon were shorter (including both ablation time and mapping time after ablation), similar to previously published cryoballoon data [15]. Fluoroscopy times were not longer and tended to be shorter at the end of the study, as they had advanced in their learning curve. They also noted that TEE allowed them to observe some undescribed phenomena, as well as to resolve them during the procedure. Whenever PV occlusion cannot be achieved, particularly by complex anatomies such as extremely oval PV or supplementary right-sided PVs, echocardiography precisely localized the site of leakage and permitted the development of alternative strategies. In the last cases of their series, oval PVs were successfully ablated by freezing the balloon at the cranial part of the PV antrum, and then pulling it gently back after approximately 45s under attentive TEE supervision, aiming to close the gap by slightly pulling the frozen PV balloon toward the caudal aspect of the antrum. This maneuver could only be echocardiographically documented, as apigenin fluid could not be injected through the balloon once the temperature fell below 0°C. Whenever this last “pull-back” strategy was not feasible, the PV antrum was ablated in 2 stages, sequentially aiming at the cranial and the caudal aspects of the PV antrum. Supplementary right-sided PVs were specifically targeted by selecting them with the guidewire: this approach permitted the creation of more complete overlapping lesions around the septal PVs, as cotyledon includes LA tissue located between the superior and the inferior septal PV. Additionally, they reported that TEE also avoided inflating the balloon across the interatrial septum while attempting to isolate a right inferior PV. In the study of Siklody et al., all patients underwent a computed tomography scan, 3D anatomical models of the LA were reconstructed, and if all PVs presented a diameter <18mm, the PV isolation was performed using a 23-mm diameter cryoballoon. If any PV was >18mm, they chose a 28-mm balloon (Arctic Front, Cryocath, Montreal, Quebec, Canada, 11-Fr shaft size) in order to create wider lesions including part of the LA surrounding the PV. The main observed complication was a transient phrenic nerve paralysis. The ratio between the vein size and the balloon size seems to play a crucial role in the appearance of this complication [15,16]. TEE has been reported as strongly correlated to magnetic resonance (MR) angiography in assessing PV anatomy [17], and Peyrol et al. [18] suggested that TEE was an easily available and effective tool to select the cryoballoon size for PVI according to evaluated PV diameters and anatomy. Instead of using MR angiography for evaluating the PV diameter and selecting the cryoballoon size, we think that it is reasonable to use TEE. This way, continuous TEE usage can enable us to evaluate the size of right-sided PVs before choosing the balloon size and a large balloon can be preferred. Although cryoballoon positioning at the PV antrum may be influenced not only by the TP site but also by the anatomical findings of both the left atrium and the PV antrum in each case, TEE-guided TP can shorten fluoroscopy, total cryoablation, and total procedural times. Importantly, it can also facilitate cryoablation of inferior pulmonary veins.
Conclusions
Conflict of interest
Introduction Radiofrequency (RF) catheter ablation is an established method of therapy for symptomatic supraventricular tachycardia (SVT). It has gained widespread acceptance for the treatment of accessory pathways in pediatric SVTs [1]. Accessory pathways are distributed unevenly along the right and left atrioventricular valve annuli. The left-sided accessory pathways are most common and may be accessed by using the transseptal approach or the retrograde aortic approach, or less commonly, from within the coronary sinus. Each approach has proven to be successful, but has a unique set of risks [2].