Radiofrequency Lesions Research Articles

The shape of the left lateral ridge as a predictor of long-term outcome of catheter ablation for atrial fibrillation based on clinical and experimental data

BackgroundThe left lateral ridge (LLR) is an important structure for ablation of atrial fibrillation (AF). This study assessed how the LLR shape is associated with the long-term outcomes of AF ablation and investigated the relationship with radiofrequency (RF) lesion formation. Methods and resultsClinical study - we assessed multi-detector computed tomography (MDCT) images in 247 patients who underwent AF ablation. Patients were classified into two groups according to the shape of the LLR: Narrow LLR group (n = 116; 47%) and Wide LLR group (n = 131; 53%). After a follow-up period 475 ± 245 days, the AF-free rate was significantly higher in the wide LLR than Narrow LLR group (83.2% vs. 62.9%, p = 0.0004). A multivariate analysis showed that the shape of the LLR was an independent predictor of AF recurrence after ablation (hazard ratio 2.58; 95% confidential interval = 1.48–4.51, p = 0.001).Experimental study - Two types of the ridge models were made with porcine atrial tissues: “Narrow ridge(4.2 ± 0.9 mm)” and “Wide ridge(9.7 ± 1.8 mm)” RF ablation was performed on each ridge model using a contact force (CF)-sensing catheter. The mean CF and the RF lesion volume of the narrow ridge were significantly less than those of the wide ridge model (5.42 ± 3.13 g vs. 10.37 ± 3.98 g, p = 0.001; 19.8 ± 9.9 mm3 vs. 44.2 ± 13.6 mm3, p < 0.001, respectively). ConclusionsAF recurrence after ablation was more frequent in patients with a narrow LLR. LLR shape as assessed using MDCT is associated with long-term outcomes after AF ablation. CF and lesion formation data using the porcine atrial tissue model support our clinical results.

Impact of Catheter Contact Angle on Lesion Formation and Durability of Pulmonary Vein Isolation

Objectives: This study aimed to evaluate the impact of catheter contact angle on lesion formation and durability of pulmonary vein isolation (PVI). Background: Little is known on the effect of catheter contact angle on lesion formation and durability of PVI. Methods: Both in vitro experiment and retrospective observational study were conducted. For in vitro experiment, radiofrequency lesions were created on explanted swine hearts in three different catheter contact angles (0{degree sign}, 45{degree sign}, and 90{degree sign}). In the retrospective observational study, we assessed patients who had undergone repeat catheter ablation due to atrial fibrillation recurrence after initial PVI. When pulmonary vein (PV) reconnection was observed, we analyzed the previous ablation points within and without the gap area. The gap areas were where ablation had changed the PV activation sequence or eliminated the PV potential in the repeat session. Results: In the in vitro experiment, lesion width was the smallest (5.3 {plus minus} 0.4 mm) in perpendicular contact compared to 0{degree sign} (vs 5.8 {plus minus} 0.5 mm, p=0.040) and 45{degree sign} (vs 6.4 {plus minus} 0.4 mm, p<0.001). In the retrospective observational study, we assessed 666 tags of 16 patients with PV reconnections, and 60 tags were in the gap area. Tags in the gap area had longer interlesion distance (odds ratio [OR] 1.49, p < 0.001), greater contact force variability (OR 1.03, p = 0.008), and higher rate of perpendicular contact (OR 3.26, p < 0.001) on multivariate analysis. Conclusion:Perpendicular contact was associated with a smaller lesion and higher rate of PV reconnection

Prospective Randomized Evaluation of High Power During CLOSE-Guided Pulmonary Vein Isolation: The POWER-AF Study.

CLOSE-guided atrial fibrillation (AF) ablation is based on contiguous (intertag distance ≤6 mm), optimized (Ablation Index >550 anteriorly and >400 posteriorly) point-by-point radiofrequency lesions. The optimal radiofrequency power remains unknown. The POWER-AF study is a prospective, randomized controlled monocentric study including patients with paroxysmal AF, planned for first CLOSE-guided pulmonary vein isolation using a contact force radiofrequency catheter (Thermocool SmartTouch, Biosense Webster, Inc, Irvine, CA). A total of 100 patients were randomized into 2 groups (1:1). The control group received AF ablation using the standard CLOSE protocol (35 W), whereas in the experimental group, pulmonary vein isolation was performed using high power (45 W). Endoscopic evaluation was performed in patients with intraesophageal temperature rise >38.5 °C. The resulting sample size was 96 (48+48) patients. In the high power group, shorter procedure time (80 versus 102 minutes, P<0.001), shorter total radiofrequency application time (16 versus 26 minutes, P<0.001), and radiofrequency time per application (26 versus 37 s anteriorly, P<0.001 and 13 versus 17 s posteriorly, P<0.001) were observed. Endoscopic evaluation (performed in 19/48 versus 25/48 patients respectively, P=0.31) showed an ulcerative perforation in a high power group patient (treated by endoscopic stenting and normalization after ≈4 months) and a superficial ulcerative lesion in a control group patient (conservative treatment). Both occurred following excessive Ablation Index applications (up to 460 and 480, respectively) with excessive contact force (30 g on average, with peaks up to 50 g). Six-months AF recurrence was not significantly different (10% in high power versus 8% in control, P=0.74). This randomized controlled study shows that a 45 W radiofrequency power CLOSE protocol in patients with paroxysmal AF significantly increases the global procedural efficiency with similar midterm efficacy. However, our study showed a narrower safety margin and a limited increased efficiency at the posterior wall using high power. This advocates against the use of high power in the region neighboring the esophagus.

Abstract 15612: Force, Power, and Temperature Settings in Slow Pathway Modification Utilizing an Irrigated Force Sensing Ablation Catheter

Introduction: Atrioventricular node reentry tachycardia (AVNRT) ablation is typically performed with solid tip catheters set to temperature control (TC) mode. Radiofrequency (RF) output, tip temperature (T), and junctional rhythm response (JRR) during RF application have been well defined. JRR in an intermittent burst, sinus-junction-junction, or sinus-junction-sinus pattern is associated with successful modification of the AV nodal slow pathway (SP). Irrigated force-sensing catheters (IFSC) are often utilized for mapping and ablation of the SP. Despite this, parameters for IFSC used in TC mode resulting in JRR have not been well described. Hypothesis: Parameters predicting JRR and successful SP modification with IFSC include power (P), force (F), impedance drop (I), and target temperature (T). Methods: Consecutive patients that underwent electrophysiologic study and successful ablation of typical AVNRT with an IFSC were studied. Lesion parameters including P, T, F, time and I change were analyzed. Lesions producing JRR were considered efficacious. Independent T-Test and ANOVA were used to determine significance between the two groups (efficacious and non-efficacious lesions). Results: 296 lesions in 39 patients (age 52+/-14) were analyzed. All patients had successful SP modification without complication. Average F producing JRR was 8g, average T producing JRR was 41 o C, average I drop producing JRR was 9 Ohms, and average P producing JRR was 28W. Only RF lesion time was a significant predictor of JRR (p=0.009). (Table 1). Conclusions: Successful SP modification with IFSC was accomplished with catheter contact force as low as 2g. Lower average tip T, and lower average P settings compared to parameters typically used with solid tip catheters were observed. Parameters including P, F, T, and I change were not predictive of JRR. Additional studies controlling for catheter location while varying parameters are indicated.

Ablation catheter orientation: In vitro effects on lesion size and in vivo analysis during PVI for atrial fibrillation.

Catheter-delivered radiofrequency (RF) lesion formation is a complex phenomenon, and few studies have explored the effect of catheter orientation on lesion size and catheter orientation behavior during pulmonary vein isolation (PVI) procedures. We evaluated the influence of catheter orientation on lesion dimensions in an in vitro experimental setting and investigated the catheter orientation behavior during PVI. 72 lesions were created in vitro on a porcine heart using a contact force catheter in a parallel, oblique, and perpendicular tip to tissue orientation. The superficial lesion length (SLL) increased shifting the catheter from perpendicular to parallel orientation. The intratissue absolute maximal lesion length (AML) was greater with an oblique catheter orientation. The lesion depth (LD) and the superficial lesion width (SLW) resulted similar with any orientation. Data from 21 PVI procedures in patients with paroxysmal atrial fibrillation using the "wide antral circumferential RF ablation" (WACA) technique were retrospectively analyzed. The mean contact angle among 1130 RF lesions was 28 ± 20°. A prevalent parallel orientation was noted in the anterior WACA segments, whereas it resulted more perpendicular in the posterior segments. Significant differences in catheter orientation between the three operators were found only in few WACA segments. In an in vitro setting, catheter orientation affects SLL and AML, but not LD and SLW. During PVI procedures, catheter orientation resulted mostly parallel to the endocardium. Catheter orientation varied among different WACA segments, but only small differences were found between three operators when considering similar WACA segments.

Risk Factors for Early Recurrence Following Ablation for Accessory Pathways: The Role of Consolidation Lesions.

Atrioventricular reentrant tachycardia is common in children. Catheter ablation is increasingly used as a first-line therapy with a high acute success rate, but recurrence during follow-up remains a concern. The aim of this study was to identify risk factors for recurrence after accessory pathway (AP) ablation. Retrospective cohort study including patients who underwent AP ablation between 2013 and 2018. Cox proportional hazards model was used to examine the association between patient and procedural characteristics and recurrence during follow-up. From 558 AP ablation procedure, 542 (97%) were acutely successful. During a median follow-up of 0.4 (interquartile range, 0.1-1.4) years, there were 42 (8%) patients with documented recurrence. On univariate analysis, early recurrence was associated with younger age, congenital heart disease, multiple AP, AP location (right sided and posteroseptal versus left sided), cryoablation (versus radiofrequency), empirical ablation, the lack of full power radiofrequency lesions (<50 W), radiofrequency consolidation time <90 seconds and the use of fluoroscopy without a 3-dimensional electroanatomic mapping system. On multivariable analysis, only multiple AP (hazard ratio, 2.78 [95% CI, 1.063-4.74]) and radiofrequency consolidation time < 90 seconds (hazard ratio, 4.38 [95% CI, 1.92-9.51]) remained significantly associated with early recurrence; this association remained true when analyzed in subgroups by pathway location for right and left free wall AP. In our institutional experience, radiofrequency consolidation time <90 seconds after ablation of AP was associated with an increased risk of early recurrence.

Long-Term Improvement of Parkinson Disease Motor Symptoms Derived From Lesions of Prelemniscal Fiber Tract Components

Prelemniscal radiations (Raprl) are composed of different fiber tracts, connecting the brain stem and cerebellum with basal ganglia and cerebral cortex. In Parkinson disease (PD), lesions in Raprl induce improvement of tremor, rigidity, and bradykinesia in some patients, while others show improvement of only 1 or 2 symptoms, suggesting different fiber tracts mediate different symptoms. To search for correlations between improvements of specific symptoms with surgical lesions of specific fiber tract components of Raprl in patients with PD. A total of 10 patients were treated with unilateral radiofrequency lesions directed to Raprl. The improvement for tremor, rigidity, bradykinesia, posture, and gait was evaluated at 24 to 33 mo after operation through the Unified Parkinson's Disease Rating Scale (UPDRS) score, and the precise location and extension of lesions through structural magnetic resonance imaging and probabilistic tractography at 6 to 8 mo postsurgery. Correlation between percentage of fiber tract involvement and percentage of UPDRS-III score improvement was evaluated through Spearman's correlation coefficient. Group average improvement was 86% for tremor, 62% for rigidity, 56% for bradykinesia, and 45% for gait and posture. Improvement in global UPDRS score correlated with extent of lesions in fibers connecting with contralateral cerebellar cortex and improvement of posture and gait with fibers connecting with contralateral deep cerebellar nuclei. Lesion of fibers connecting the globus pallidum with pedunculopontine nucleus induced improvement of gait and posture over other symptoms. Partial lesion of Raprl fibers resulted in symptom improvement at 2-yr follow-up. Lesions of selective fiber components may result in selective improvement of specific symptoms.

Abstract P203: Insights To Lesion Formation For Percutaneous Renal Denervation: Human And Porcine Histological Analyses

Background: The safety and efficacy of radiofrequency (RF) renal denervation (RDN) have been demonstrated in multiple randomized trials. We performed histological analyses in a swine model and human cadavers to investigate RF lesion geometry, morphology and location in the context of local anatomic structures and describe their impact on procedural outcomes. Methods: The Symplicity Spyral catheter was used to perform RDN in 164 renal arteries from healthy swine terminated at 7 days post-treatment. Lesion characteristics were determined by semi-quantitative histology. Renal nerve functionality was measured by quantitative immunohistochemistry and correlated to renal norepinephrine. In addition, we investigated the retroperitoneal space in 10 human cadavers to determine the relative location of extravascular tissues. Results: In the swine model, RF lesions developed exclusively in the perivascular adipose tissue which contains the renal nerves. Lesions were irregularly shaped due to inherent sparing of surrounding perfused structures, such as veins and lymph nodes. Maximum depth of the irregularly shaped RF lesions was 6.8±2.5 mm, and mean depth was 3.9±2.4 mm. Renal norepinephrine levels were lowest when &gt;80% of renal nerves were ablated ( Figure ). Reendothelialization of the lesion area was &gt;99% within 7 days. In humans, only 0.3% of renal nerves were localized on the opposite side of the renal veins. Conclusion: Patterns of RF RDN are uniquely influenced by electrical and thermal conduction properties of tissues surrounding the renal arteries. Maximal reduction of renal norepinephrine content requires ablation of at least 80% of the renal nerves.

Efficacy of high-power and short-duration ablation in patients with atrial fibrillation: a prospective randomized controlled trial.

The formation of radiofrequency lesions depends on the power and duration of ablation, and the contact force (CF). Although high power (HP) creates continuous and transmural lesions, most centres still use 25-30 W for 30-40 s for safety reasons. We evaluated the clinical efficacy and safety of a HP and short-duration (HPSD) strategy for atrial fibrillation (AF) ablation. One hundred and fifty patients [58.2 ± 10.0 years, 48% with paroxysmal AF (PAF)] scheduled for index AF ablation using a CF-sensing catheter were randomly assigned to three groups [30 W, 40 W, and 50 W at ablation sites of anterior, roof, and inferior segments of pulmonary vein (PV) antra and roof line between each upper PV]. In 25-30 W for ≤20 s was applied at posterior wall ablation site in all subjects. Compared with the 30 W and 40 W groups, procedure (P < 0.001) and ablation times (P < 0.001) were shorter and ablation number for PV isolation (P < 0.001) was smaller in the 50 W group. There were no significant differences in the CF and ablation index (AI) among the three groups. There were no significant differences in the procedure-related complication rates. During the 12-month follow-up, AF recurred in 24 (16%) patients with no significant difference among the groups (P = 0.769). In the multivariate analysis, non-PAF [hazard ratio (HR) 2.836, P = 0.045] and AI (HR 0.983, P = 0.001) were independent risk factors for AF recurrence. Radiofrequency ablation with HPSD is a safe and effective strategy with reduced ablation number and shortened procedure time compared to conventional ablation.

Impedance, power, and current in radiofrequency ablation: Insights from technical, ex vivo, and clinical studies.

Radiofrequency (RF) power is routinely considered during RF application. In contrast, impedance has been relatively poorly studied, despite also influencing RF lesion creation. The aim of this study was to examine the influence of electric impedance on RF lesion characteristics and on clinical RF ablation parameters. In the first part of the study, power and impedance were systematically varied and the resulting current was calculated using custom-made software. In the second part of the study, ablation lesions (n = 40) were analyzed in a porcine ex vivo model. RF applications were delivered in cardiac muscle preparations with systematically varied values of electric impedance using a contact force ablation catheter. In the third part of the study, n = 3378 clinical RF applications were analyzed, power, impedance, and current data were exported and correlated with clinical patient data. 20 ± 3 W/80 Ω, 30 ± 3 W/120 Ω, 40 ± 3 W/160 Ω, and 50 ± 3 W/200 Ω RF applications resulted in 498 ± 40, 499 ± 26, 500 ± 20, and 500 ± 16 mA RF current, which were not significantly different (p = .32). Ablation lesions were significantly different in depth and diameter when applied with the same power but different impedances (p < .01); lesion sizes decreased when increasing impedance. In clinical data, a large range of delivered current (e.g., 39-40 W: 530-754 mA) was measured, due to variations in impedance. RF lesion creation is determined by current rather than by power. During clinical RF ablation procedures, impedance significantly influences current delivery and varies considerably between patients. Impedance and current are clinically relevant parameters that should be considered during RF ablation.

Update on high-power short-duration ablation for pulmonary vein isolation.

Pulmonary vein isolation (PVI) is the cornerstone of atrial fibrillation (AF) ablation. However, this procedure remains complex and time-consuming, and the recurrence of AF after PVI is still unsatisfactory. Current technologies have improved our knowledge of the association between radiofrequency lesion creation and ablation parameters (power and duration), which triggered the development of high-power short-duration (HPSD). During the past decade, several preclinical and clinical studies have been conducted to confirm the feasibility, safety, and outcome of PVI ablation with HPSD or very high-power short-duration (vHPSD) settings, which increased electrophysiologists' interests in the utility of HPSD strategies. This paper describes the theoretical basis and recent research findings of HPSD or vHPSD ablation and summarizes the state-of-the-art evidence behind the role of this strategy in PVI.

Comparison of Atrial Remodeling Caused by Sustained Atrial Flutter Versus Atrial Fibrillation

BackgroundAtrial flutter (AFL) and atrial fibrillation (AF) are associated with AF-promoting atrial remodeling, but no experimental studies have addressed remodeling with sustained AFL. ObjectivesThis study aimed to define the atrial remodeling caused by sustained atrial flutter (AFL) and/or atrial fibrillation (AF). MethodsIntercaval radiofrequency lesions created a substrate for sustained isthmus-dependent AFL, confirmed by endocavity mapping. Four groups (6 dogs per group) were followed for 3 weeks: sustained AFL; sustained AF (600 beats/min atrial tachypacing); AF superimposed on an AFL substrate (AF+AFLs); sinus rhythm (SR) with an AFL substrate (SR+AFLs; control group). All dogs had atrioventricular-node ablation and ventricular pacemakers at 80 beats/min to control ventricular rate. ResultsMonitoring confirmed spontaneous AFL maintenance >99% of the time in dogs with AFL. At terminal open-chest study, left-atrial (LA) effective refractory period was reduced similarly with AFL, AF+AFLs and AF, while AF vulnerability to extrastimuli increased in parallel. Induced AF duration increased significantly in AF+AFLs and AF, but not AFL. Dogs with AF+AFLs had shorter cycle lengths and substantial irregularity versus dogs with AFL. LA volume increased in AF+AFLs and AF, but not dogs with AFL, versus SR+AFLs. Optical mapping showed significant conduction slowing in AF+AFLs and AF but not AFL, paralleling atrial fibrosis and collagen-gene upregulation. Left-ventricular function did not change in any group. Transcriptomic analysis revealed substantial dysregulation of inflammatory and extracellular matrix-signaling pathways with AF and AF+ALs but not AFL. ConclusionsSustained AFL causes atrial repolarization changes like those in AF but, unlike AF or AF+AFLs, does not induce structural remodeling. These results provide novel insights into AFL-induced remodeling and suggest that early intervention may be important to prevent irreversible fibrosis when AF intervenes in a patient with AFL.

Atrial tachycardia circuits include low voltage area from index atrial fibrillation ablation relationship between RF ablation lesion and AT.

No study to date has used high-density mapping to investigate the relationship between prior radiofrequency (RF) lesions for persistent atrial fibrillation (PsAF) ablation and subsequent atrial tachycardias (ATs). From 41 consecutive patients who underwent AT ablation at a second procedure using an ultrahigh-density mapping system, 22 patients (38 ATs) were included as they also had complete maps with a multipolar catheter and three-dimensional (3D) mapping system at the time of the first PsAF ablation procedure. We, therefore, compared voltage maps from the first AF ablation procedure to those from the subsequent AT ablation procedure, as well as the lesion sets used for AF ablation vs the activation patterns in AT during the second procedure. In the 38 ATs, 211 of 285 analyzed atrial areas displayed low voltage area (LVA) (74%). Eighteen percent (38/211) existed before the index ablation for AF while 82% (173/211) were newly identified as LVA during the second procedure. Ninety-nine percent (172/173) of the newly developed LVA colocalized with RF lesions delivered for PsAF. Of the 38 ATs, 89.5% (34/38) AT circuits were associated with newly developed LVA due to RF lesions whilst 10.5% (4/38) AT circuits were associated with pre-existing LVA observed at the index procedure. No AT circuit was completely independent from index RF lesions in this series. Analysis of detailed 3D electroanatomical mapping demonstrates that most ATs after PsAF ablation are involving LVAs due to index RF lesions.

Magnetic Resonance-Based Radiomic Analysis of Radiofrequency Lesion Predicts Outcomes After Percutaneous Cordotomy: A Feasibility Study.

To date, there is limited data on evaluation of the cordotomy lesion and predicting clinical outcome. To evaluate the utility of magnetic resonance (MR)-based radiomic analysis to quantify microstructural changes created by the cordotomy lesion and predict outcome in patients undergoing percutaneous cordotomy for medically refractory cancer pain. This is a retrospective interpretation of prospectively acquired data in 10 patients (5 males, age range 43-76 yr) who underwent percutaneous computed tomography-guided high cervical cordotomy for medically refractory cancer pain between 2015 and 2016. All patients underwent magnetic resonance imaging (MRI) of the cordotomy lesion on postoperative day 1. After segmentation of T2-weighted images, 310 radiomic features were extracted. Pain outcomes were recorded on postoperative day 1 and day 7 using the visual analog scale. R software was used to build statistical models based on MRI radiomic features for prediction of pain outcomes. A total of 20 relevant radiomic features were identified using the maximum relevance minimum redundanc method. Radiomics predicted postoperative day 1 pain scores with an accuracy of 90% (P=.046), 100% sensitivity, 75% specificity, 85.7% positive predictive value, and 100% negative predictive value. The radiomics model also predicted if the postoperative day 1 pain score was sustained on postoperative day 7 with an accuracy of 100% (P=.028), 100% sensitivity, 100% specificity, and 100% positive and negative predictive value. MR-based radiomic analysis of the cordotomy lesion was predictive of pain outcomes at 1 wk after percutaneous cordotomy for intractable cancer pain.

652The effect of varying irrigation flow rate during irrigated radiofrequency ablation on optimising lesion shape

Abstract Funding Acknowledgements Investigator Sponsored Research grant from Boston Scientific Introduction Irrigated catheters are the standard tool for radiofrequency (RF) ablation in the left atrium and ventricles. However, pathological studies of irrigated RF lesions show a "tear-drop" shape, with the widest diameter some depth below the endocardial surface and relative endocardial sparing. This requires overlap of lesions to achieve contiguity at the endocardial surface. There has been little investigation into the effect of altering irrigation rate on lesion shape and volume. Purpose To test the hypothesis that varying the irrigation flow rate would optimise lesion shape by minimising endocardial sparing while maintaining lesion depth. Methods In an ex vivo animal heart model, irrigated ablation lesions were performed in porcine ventricular tissue at 30W using an Intellatip MiFi OI catheter with 5 different irrigation protocols: A. fixed rate (30ml/min); B. continuous reduction (30 to 2ml/min over 30s); C. continuous increase (2 to 30ml/min over 30s); D. stepwise reduction (30ml/min (10s) to 16ml/min (10s) to 2ml/min (10s)); E. stepwise increase (2ml/min (10s) to 16ml/min (10s) to 30ml/min (10s). Contact force (10g) and ablation duration (30s) were constant. Steam pops during ablation were recorded. Tissue sections were stained with triphenyltetrazolium chloride (TTC) after ablation to allow accurate measurement of lesion boundaries. Surface diameter, lesion depth, maximum diameter, and depth at maximum diameter were measured using Vernier Calipers to calculate lesion volume. Pictures of lesions were analysed further by ImageJ software to measure the degree of endocardial sparing. The optimal protocol was further tested against fixed-rate irrigation at 20W – 40W. Results 10-20 lesions were performed for each irrigation protocol. Of the 4 experimental protocols, continuous reduction (protocol B) resulted in the most optimal lesion shape (Figure). With this protocol, endocardial sparing area was significantly reduced compared to fixed-rate irrigation (1.61 vs. 2.64mm2, P &amp;lt; 0.0001), with a trend towards an increase in surface diameter (9.25 vs. 8.46mm, P = 0.08). There was no significant difference in lesion depth (5.35 vs. 4.77mm), lesion volume (374 vs. 332mm3) or maximum diameter (10.3 vs. 10.8mm). Steam pop occurred in 1 of 20 (5%) lesions in each of protocols A and B. Significantly reduced endocardial sparing with preserved volume/depth was consistent for continuous reduction when compared to fixed-rate irrigation across power settings of 20W (17ml/min), 30 W (17ml/min or 30ml/min) and 40W (30ml/min) (P &amp;lt; 0.0001). Conclusions Continuous reduction in irrigation flow rate from 30 to 2ml/min during irrigated RF ablation results in reduced endocardial sparing with preserved lesion depth and volume when compared to fixed-rate irrigation across power settings of 20 – 40W. This may allow for greater lesion spacing while maintaining endocardial contiguity and merits further investigation to improve irrigated RF ablation efficiency. Abstract Figure

Focal Pulsed Field Ablation for Pulmonary Vein Isolation and Linear Atrial Lesions: A Preclinical Assessment of Safety and Durability.

A novel ablation and mapping system can toggle between delivering biphasic pulsed field (PF) and radiofrequency energy from a 9-mm lattice-tip catheter. We assessed the preclinical feasibility and safety of (1) focal PF-based thoracic vein isolation and linear ablation, (2) combined PF and radiofrequency focal ablation, and (3) PF delivered directly atop the esophagus. Two cohorts of 6 swine were treated with pulsed fields at low dose (PFLD) and high dose (PFHD) and followed for 4 and 2 weeks, respectively, to isolate 25 thoracic veins and create 5 right atrial (PFLD), 6 mitral (PFHD), and 6 roof lines (radiofrequency+PFHD). Baseline and follow-up voltage mapping, venous potentials, ostial diameters, and phrenic nerve viability were assessed. PFHD and radiofrequency lesions were delivered in 4 and 1 swine from the inferior vena cava onto a forcefully deviated esophagus. All tissues were submitted for histopathology. Hundred percent of thoracic veins (25 of 25) were successfully isolated with 12.4±3.6 applications/vein with mean PF times of <90 seconds/vein. Durable isolation improved from 61.5% PFLD to 100% with PFHD (P=0.04), and all linear lesions were successfully completed without incurring venous stenoses or phrenic injury. PFHD sections had higher transmurality rates than PFLD (98.3% versus 88.1%; P=0.03) despite greater mean thickness (2.5 versus 1.3 mm; P<0.001). PF lesions demonstrated homogenous fibrosis without epicardial fat, nerve, or vessel involvement. In comparison, radiofrequency+PFHD sections revealed similar transmurality but expectedly more necrosis, inflammation, and epicardial fat, nerve, and vessel involvement. Significant ablation-related esophageal necrosis, inflammation, and fibrosis were seen in all radiofrequency sections, as compared with no PF sections. The lattice-tip catheter can deliver focal PF to durably isolate veins and create linear lesions with excellent transmurality and without complications. The PF lesions did not damage the phrenic nerve, vessels, and the esophagus.

Radiofrequency Ablation of Prelemniscal Radiations for the Treatment of Non-Parkinsonian Tremor

Objective: Previous reports proposed prelemniscal radiations (Raprl) as a target to treat motor symptoms of Parkinson’s disease, and this was found particularly effective to control rest and postural tremor. However, tremor of other etiologies has been seldom treated with deep brain stimulation or ablation in this target. We present a series of such cases successfully treated by Raprl radiofrequency (RF) lesions. Material and Methods: Six patients with predominant unilateral tremor on the right arm: 4 intention, 1 cerebellar and 1 rubral tremor, incapacitating in spite of at least 2 regimes of medical treatment at maximal tolerated doses, were operated under local anesthesia. RF lesions were performed in Raprl contralateral to most prominent symptoms. Patients had monthly evaluation of tremor severity through the Fahn-Tolosa-Marin Tremor Rating Scale and disability through the Tremor Disability Scale along a 1-year follow-up. Results: In 4/6 patients tremor was stopped by the simple insertion of an RF electrode in Raprl; in the other 2 cases, stimulation through the RF electrode at 100 Hz, with 100 µs and 1.0–1.5 V, stopped the tremor without side effects. Tremor disappeared in all cases immediately after surgery and partially reappeared in 2 cases with an amplitude about 20% of the preoperative condition. RF lesions in postoperative MRI ranked from 1.8 to 2.6 mm in diameter. Conclusions: RF lesioning in Raprl is a simple, highly effective, inexpensive way to treat tremor of different etiologies.

Comparisons of Monopolar Lesion Volumes with Hypertonic Saline Solution in Radiofrequency Ablation: A Randomized, Double-Blind, Ex Vivo Study

Chronic degeneration of the zygapophyseal joints in the cervical or lumbar spine are common causes of axial back pain. Radiofrequency (RF) ablation is a treatment modality in the denervation of facet joint-related pain. Although multiple factors have been theorized to contribute to the size of the optimal RF lesion, the addition of hypertonic saline solution has been posited to create larger RF lesion sizes. This study compares lesion of 20-gauge RF monopolar probe using 2% lidocaine, 0.9% normal saline solution, and 3% saline solution administered through the RF needle prior to ablation, with subsequent lesion sizes recorded. Randomized, double-blinded, ex vivo study using clinically relevant conditions. Procedural laboratory in an academic institution. RF ablation lesions were reproduced in room temperature (21°C ± 2°C) chicken breast specimens with 20-gauge monopolar RF probes inserted. RF was applied for 90 seconds at 80°C after injection of 1 mL of either 2% lidocaine, 2% lidocaine and 0.9% normal saline solution in a 1:1 ratio, or 2% lidocaine and 3% saline solution in a 1:1 ratio. Tissues were dissected, measured, and ellipsoid volumes of burn calculated. Homogeneity of variances was assessed via the Bartlett's test, and heteroskedasticity with the studentized Breusch-Pagan test. One-way analysis of variance (ANOVA) (alpha of 0.05) was used to evaluate statistical significance between volume means across groups. When the null hypothesis of no difference in burn volume between samples could not be rejected, a predefined equivalence volume of ± 0.05 cm3 was used with Welch's 2 one-sided t-tests (TOST) with a Bonferroni adjusted alpha of 0.0167 to evaluate for null acceptance. The mean lesion volume for monopolar RF with 1 mL 2% lidocaine was 0.16 cm3. Monopolar RF with 1 mL 2% lidocaine + 0.9% normal saline solution had a mean lesion volume of 0.15 cm3, and treatment with 1 mL 2% lidocaine + 3% saline solution measured 0.17 cm3. ANOVA failed to reject the null, and TOST accepted as equivalent all 3 comparisons. In vivo anatomy and physiology of a human organism was not used for this study. Samples were not warmed to physiologic temperature. Randomization resulted in slightly unequal sample sizes, although all groups were of sufficient size that the central limit theorem should apply. Three commonly used solutions were found to have equivalent lesion sizes from monopolar probe RF ablation. Radiofrequency, ablation, lesion shape, lesion size, monopolar RF, hypertonic saline solution.

The force stability of tissue contact and lesion size index during radiofrequency ablation: An ex-vivo study.

Radiofrequency (RF) ablation is a commonly used tool in the invasive electrophysiology laboratory to treat a variety of rhythm disorders. Reliable creation of transmural ablation lesions is crucial for long-term success. Lesion size index (LSI) is a multiparametric index that incorporates time, power, contact force (CF), and impedance data recorded during RF ablation in a weighted formula and has been shown to predict the extent of myocardial tissue lesions. Whether the force stability of contact influences lesion size in LSI-guided ablations is unknown. The aim of this study was to analyze the influence of the force stability of contact on lesion size during LSI-guided ablations in an ex-vivo model. A total of 267 RF lesions (n=6 hearts) were created on porcine myocardial slabs by using an open-tip irrigated ablation catheter with the following settings: 35 W with either intermittent (varied between 0 and up to 20g), variable (10 to 20g), or constant tissue contact (15g) in a perpendicular or parallel fashion (applied manually) up to a target LSI of either 5 or 6. Subsequently, lesion width and depth were determined. Lesion width was mainly influenced by catheter tip orientation and LSI, whereas lesion depth was mainly influenced by LSI alone. The force stability of catheter contact had no relevant impact on lesion width or depth. The force stability of catheter contact has only little effect on lesion depth or width in LSI-guided catheter ablation while the catheter orientation primarily affects lesion width.

Evaluation of ECG Imaging to Map Hemodynamically Stable and Unstable Ventricular Arrhythmias.

ECG imaging (ECGI) has been used to guide treatment of ventricular ectopy and arrhythmias. However, the accuracy of ECGI in localizing the origin of arrhythmias during catheter ablation of ventricular tachycardia (VT) in structurally abnormal hearts remains to be fully validated. During catheter ablation of VT, simultaneous mapping was performed using electroanatomical mapping (CARTO, Biosense-Webster) and ECGI (CardioInsight, Medtronic) in 18 patients. Sites of entrainment, pace-mapping, and termination during ablation were used to define the VT site of origin (SoO). Distance between SoO and the site of earliest activation on ECGI were measured using co-registered geometries from both systems. The accuracy of ECGI versus a 12-lead surface ECG algorithm was compared. A total of 29 VTs were available for comparison. Distance between SoO and sites of earliest activation in ECGI was 22.6, 13.9 to 36.2 mm (median, first to third quartile). ECGI mapped VT sites of origin onto the correct AHA segment with higher accuracy than a validated 12-lead ECG algorithm (83.3% versus 38.9%; P=0.015). This simultaneous assessment demonstrates that CardioInsight localizes VT circuits with sufficient accuracy to provide a region of interest for targeting mapping for ablation. Resolution is not sufficient to guide discrete radiofrequency lesion delivery via catheter ablation without concomitant use of an electroanatomical mapping system but may be sufficient for segmental ablation with radiotherapy.