High-Power, Short-Duration Ablation in the Treatment of Atrial Fibrillation Patients

Catheter ablation is the cornerstone of the rhythm control treatment of atrial fibrillation (AF). During this procedure, creating a contiguous and durable lesion set is essential to achieve good long-term results. Radiofrequency lesions are created in two phases: resistive and conductive heating. The ablation catheters and the generators have undergone impressive technical developments to enable homogenous and good-quality lesion creation. Despite recent years’ achievements, the durable isolation of the pulmonary veins remains a challenge. These days, intensive research aims to evaluate the role of high-power radiofrequency applications in the treatment of patients with cardiac arrhythmias. The use of high-power, short-duration applications might result in a uniform, transmural lesion set. It is associated with shorter procedure time, shorter left atrial, and fluoroscopy time than low-power ablation. This technique was also associated with a better clinical outcome, possibly due to the better durability of lesions. Multiple clinical studies have proven the safety and efficacy of high-power, short-duration PVI.

Surgery and Radiosurgery in Autism: A Retrospective Study in 10 Patients

<b><i>Introduction:</i></b> A subgroup of patients with autism spectrum disorder (ASD) show self or heteroaggression, dyscontrol episodes, and others are of obsessive-compulsive disorder (OCD) profile; some of them are resistant to medical and behavioural treatment. We describe the long-term outcome in a group of these patients, treated with radiofrequency brain lesions or combined stereotactic surgery and Gamma Knife (GK) radiosurgery. <b><i>Methods:</i></b> We reviewed the medical records of 10 ASD patients with pathological aggressiveness and OCD, who had undergone radiofrequency lesions and/or radiosurgery with GK in our institution. <b><i>Results:</i></b> The 10 patients had a significant reduction of their symptoms (PCQ 39.9 and 33, OAS 11.8 and 5, CYBOCS-ASD 30.4 and 20), preoperatively and in the last follow-up, respectively; <i>p</i> &#x3c; 0.005 (in all cases), although all but 2 needed more than 1 treatment to maintain this improvement. <b><i>Conclusions:</i></b> We observed a marked improvement in behaviour, quality of life, and relationship with the environment in all our 10 patients after the lesioning treatments, without long-lasting side effects.

Optimized radiofrequency lesions through local impedance guidance for effective cavo-tricuspid isthmus ablation in typical right atrial flutter: data from the CHARISMA registry

Funding Acknowledgements Type of funding sources: None. Background Radiofrequency (RF) catheter ablation of the cavo-tricuspid isthmus (CTI) is an established treatment for typical right atrial flutter (RAFL). However, whether local tissue impedance (LI) is able to predict effective CTI ablation and what LI drop values during ablation should be used to judge a lesion as effective remains to be established. Purpose We aimed to investigate the ability of LI to predict ablation efficacy in patients (pts) with RAFL and to characterize the CTI in terms of LI. Methods Consecutive pts undergoing RAFL ablation from the CHARISMA registry were enrolled at 9 centers. A novel RF ablation catheter with dedicated algorithm (DirectSense - DS -) was used to measure LI at the distal electrode of this catheter. RF applications (RFC) were targeted to a minimum LI drop of 10 Ω within 30 seconds and were stopped when a maximum cutoff LI drop of &lt;40 Ω was observed. Successful single RFC was defined according with a split in two separate potentials (SPL), reduction of voltage (RedV) by at least 50% or changes at unipolar EGM (UPC). Agreement among criteria was evaluated. Ablation endpoint was the creation of bidirectional conduction block (BDB) across the isthmus. Results A total of 279 ablation spot lesions were delivered in 30 pts (mean RFC 9 ± 6 lesions per pt): 106 (38%) at anterior, 115 (41%) at mid and 58 (21%) at posterior portions of the CTI. BDB was obtained in all cases and no complications were observed. The median RFC delivery time was 30 [19–45] seconds per lesion. 132 (47%), 150 (54%) and 86 (31%) ablation spots were effective according with SPL, RedV and UPC, respectively. Complete agreement of all the criteria was reached in 70% of the cases. The mean LI was 104.4 ± 11Ω prior to ablation and 92.1 ± 11Ω after ablation (p &lt; 0.0001, mean absolute LI drop 12.2 ± 7Ω, mean time to LI drop 13 ± 8 seconds). Effective ablation spots showed a higher LI drop compared with ineffective sites at each single criteria (16.6 ± 7Ω vs 8.3 ± 4Ω for SPL, p &lt; 0.0001; 16.1 ± 6Ω vs 7.8 ± 5Ω at for RedV, p &lt; 0.0001; 19 ± 6Ω vs 9.2 ± 4Ω for UPC, p &lt; 0.0001) and LI drop values significantly increase according to the number of criteria satisfied (ranging from 7.5Ω % -no criteria- to 19.1 -all criteria-). A 15Ω cut-off value for LI (AUC 0.91, sensitivity = 67%, specificity = 92%, p &lt; 0.0001) was associated with the achievement of all criteria with an OR of 21.9 (95%CI: 11.1 to 43.5, p &lt; 0.0001) and a positive predictive value of 76%. Starting LI and LI drop seem to be higher at mid-septal areas. Conclusion In our preliminary experience, a LI-guided approach of CTI seems to be safe and effective in RAFL ablation. The magnitude of LI drop was associated with effective lesion formation and conduction block and could be used as a marker of ablation efficacy.

Impact of power and contact force in ablation-index guided radiofrequency lesions in an in vitro model

Funding Acknowledgements Type of funding sources: Public Institution(s). Main funding source(s): Electrophisiology Section of the Spanish Society of Cardiology Introduction. Lesion Size Index (LSI) and Ablation Index (AI) are markers of lesion quality that incorporate power, contact force (CF), and time in a weighted formula to estimate lesion size. Although accurate predicting lesion depth in-vitro, their precision in lesion size estimation has not been well established for certain power and CF settings. Purpose. We conducted an experimental ex-vivo study to analyse the effect of power and CF in size and morphology of ablation lesions in a porcine heart model. Methods. 24 sets of 10 perpendicular epicardial radiofrequency applications were performed with two commercially available catheters (TactiCath, Sensor Enabled; and SmartTouch) on porcine left ventricle submerged in 37ºC saline, combining different power (25, 30, 35, 40, 50 and 60W) and CF (10 and 20g) settings, and aiming at a lower (LSI/AI of 5/400) or higher (LSI/AI of 6/550) index. After each application, lesions were cross-sectioned and measured. Results. 480 lesions were performed. For a given target index and CF, significant differences in lesion volume and depth with different power settings were observed with both catheters. Regarding lesion volume, statistically significant differences were observed with all CF and LSI targets with TactiCath, except for 10 g and LSI 5 (10 g and LSI 5, p = 0.4134; 10 g and LSI 6, p &lt; 0.0001; 20 g and LSI 5, p &lt; 0.0001; 20 g and LSI 6, p &lt; 0.0001). The same occurred for SmartTouch, showing statistically significant differences with all CF and AI targets, except for 20 g and AI 550 (10 g and AI 400, p = 0.0001; 10 g and AI 550, p &lt; 0.0001; 20 g and AI 400, p &lt; 0.0001; 20 g and AI 550, p = 0.001). Similar differences could be found in lesion depth with each catheter. Globally, lesions performed with 50 and 60W were significantly smaller and shallower than those performed with 35 or 40W (figure). Regarding CF, catheters behaved differently: lesions performed with 10g were smaller and shallower than those performed with 20g with Tacticath, while being bigger and deeper with SmartTouch. In a side-by-side comparison, lesions performed with TactiCath were smaller and shallower than those performed with SmartTouch when applying a lower CF of 10g, both when targeting a lower index objective (volume: 41.8 ± 54.3mm3 vs 158.3 ± 33.2mm3, p &lt; 0.0001; depth: 2 ± 1.7mm vs 4.6 ± 0.5mm, p &lt; 0.0001) or a higher index objective (volume: 103.1 ± 56.5mm3 vs 280 ± 54mm3, p &lt; 0.0001; depth: 4 ± 1.1mm vs 5.8 ± 0.5mm, p &lt; 0.0001). However, lesions with TactiCath were bigger and deeper when applying a higher CF of 20g aiming at a lower index objective (volume: 123.8 ± 39.9mm3 vs 89.7 ± 29.4mm3, p &lt; 0.0001; depth: 4 ± 0.8mm3 vs 3.6 ± 0.5mm, p &lt; 0.0001). No statistically significant difference was observed when applying a higher CF of 20g aiming at a higher index objective. Conclusions. Size and morphology of index-guided radiofrequency lesions varied significantly with different power and CF settings, highlighting the importance of achieving a good CF in any ablation procedure. Abstract Figure. Box-plot of lesion volume

Radiofrequency Energy and Electrode Proximity Influences Stereoelectroencephalography-Guided Radiofrequency Thermocoagulation Lesion Size: An In Vitro Study with Clinical Correlation

BACKGROUND Radiofrequency thermocoagulation of epileptogenic foci via stereoelectroencephalography (SEEG) electrodes has been suggested as a treatment for medically intractable epilepsy, but reported outcomes have been suboptimal, possibly because lesions generated using conventional high-energy radiofrequency parameters are relatively small. OBJECTIVE To describe a technique of delivering low energy across separate SEEG electrodes in order to create large confluent radiofrequency lesions. METHODS The size and configuration of radiofrequency lesions using different radiofrequency intensity and interelectrode distance was assessed in egg whites. Magnetic resonance images (MRI) from 3 patients who had undergone radiofrequency lesion creation were evaluated to determine the contribution of lesion intensity and electrode separation on lesion size. Electroencephalography, MRI, and clinical data were assessed before and after lesion creation. RESULTS Both in Vitro and in Vivo analysis revealed that less energy paradoxically produced larger lesions, with the largest possible lesions produced when radiofrequency power was applied for long duration at less than 3 W. Linear separation of electrodes also contributed to lesion size, with largest lesions produced when electrodes were separated by a linear distance of between 5 and 12 mm. Clinical lesions produced using these parameters were large and resulted in improvement in interictal and ictal activity. CONCLUSION Radiofrequency lesions produced using low-energy delivery between SEEG electrodes in close proximity can produce a large lesion. These findings might have advantages for treatment of focal epilepsy.