Ablation of a left sided accessory
Ablation of a left-sided accessory pathway requires delivery of RF current to the tissue near the mitral valve annular ring. These lesions may potentially cause mitral injury. Sometimes a trapped leaflet or chordae underneath the tip of the catheter may cause the insufficiency [7,8,12–14]. However, approaching the mitral annulus via transseptal puncture from the atrial side or retrograde from the ventricular side does not seem to produce superior results. Studies have failed to show significant difference in these techniques in terms of success or complication rates [3,5]. We speculate that because there is variation in the anatomy of mitral annulus, some pathways may be more closely approached by one or the other method.
The retrograde approach may safely be performed in young children. Our youngest patient was 4 years old with WPW syndrome. The left lateral accessory pathway was successfully ablated in a fairly short procedure time (i.e. 45min). No recurrence or complications were seen during the follow-up.
Cryoablation may be considered a safer alternative to RF ablation, primarily due to the potential for reversible tissue injury with cryomapping and catheter transketolase due to adhesion. Cryoablation was used successfully by Gist et al.  in the treatment of left-sided accessory pathways in pediatric patients. The procedures were performed transseptally, with an observed acute success rate of 97% and recurrence rate of 4.2%. However, by using RF ablation, we refrained from using the stiffer and thicker cryoablation catheter while passing through the aortic valve.
Conflict of interest
Introduction The subcutaneous implantable cardioverter defibrillator (S-ICD) is an emerging alternative to the transvenous ICD (T-ICD) for the prevention of sudden cardiac death. The safety and efficacy of this device have been shown in multiple studies [1–3]. The rate of inappropriate shocks, specifically due to T wave oversensing (TWOS), remains an Achilles heel of this therapy. The original S-ICD studies reported 13–15% yearly rates of inappropriate shocks [4,5], with TWOS accounting for the vast majority of cases (estimated as the cause of 64–85% of all inappropriate shocks [1,3,4]). The addition of a conditional tachycardia detection zone (2 zones vs. 1 zone programming) significantly decreased the rate of inappropriate shocks due to supraventricular rhythms and TWOS . In aggregate, increased operator experience with S-ICD programming and routine use of a conditional zone have resulted in a significant decrease in the rate of inappropriate shocks, which has been reflected in newer studies reporting an annual incidence of 5–7% for inappropriate therapies [2,3]. However, TWOS remains responsible for the majority of these inappropriate shocks. Limited data are available on the clinical predictors of inappropriate shocks [4,7], and therefore, we sought identify clinical and electrocardiographic predictors of TWOS in a cohort of patients undergoing S-ICD implantation at our institution.
Materials and methods The Emory University institutional review board approved the study protocol in 2015 (IRB # 00077019). We retrospectively identified all patients who underwent S-ICD implantation (Cameron health-model number 1010 SQ-RX, with a subcutaneous lead-Cameron health model 3010) at our institution from April 2010 to January 2015. Baseline clinical characteristics and procedural outcomes were ascertained by medical record review. Data on post-implant clinical events and survival were obtained from review of medical records and device-clinic follow-up. Pre-procedure screening for S-ICD candidacy was performed using body-surface electrocardiograms (ECGs) as recommended by the manufacturer; however, the ultimate decision to implant an S-ICD was at the discretion of the implanting physician. Patients were programmed with 2 tachy-arrhythmia zones (200 and 220beats/min). All S-ICD shocks were adjudicated by an electrophysiologist and classified as appropriate or inappropriate and further sub-classified based on cause (i.e., appropriate therapies for ventricular tachycardia/fibrillation or inappropriate therapies for TWOS or supraventricular rhythms).