Open-irrigated Ablation Catheter Research Articles

Local impedance drop as a predictor of sucessful pulmonary vein isolation

Abstract 1. Introduction Pulmonary vein isolation (PVI) is the cornerstone of AF treatment. An accurate estimation of the lesion size and a optimal evaluation of the catheter-myocardium coupling is crucial for achieving an effective and safe radiofrequency (RF) ablation. A few studies have suggested that local impedance (LI) drop is a better predictor than general impedance drop in terms of lesion size, electrical coupling and therefore acute PVI success. An open-irrigated ablation catheter designed to measure contact force (CF) and LI drop while applying RF has been recently developed. 2. Purpose The aim of this study is to evaluate if conduction GAPS are located in certain areas and if LI drop can predict the presence of conduction gaps in each of these segments. 3. Methods Observational prospective study including 55 consecutive patients who underwent PVI. The RF lesions were delivered with 30 W (posterior wall) or 35 W (anterior wall) for a maximum of 30 seg with a CF > 5 g. The applications were stopped if a LI of 35 Ohm was reached on the posterior wall or 40 Ohm on the anterior wall. PVs were divided into seven segments and ablation tags were assigned to a segment according to their anatomical position (figure 1) We categorized the tags included in each segment as successful or not according to the presence of conduction gaps detected with an Ultrahigh density mapping catheter once the WACA was completed. At the same time lesion by lesion were studied regardless of the segment where it was located. 4. Results We analyzed 4002 lesion tags of 55 patients who underwent PVI. 53 Gaps were found in 19/55 (34.5%) left WACA and 16/54 (29,6%) right WACA and were localized predominantly in three PVI segments (L1, L6 and R3) 34(54.85%) vs 19 (35,8%) (L2-L5, L7, R1-R2, R4-R7) (p<0.001) (figure 1). They were mainly circumscribed to anterior segments in left PVs and posterior-superior segment in right PVs (figure1). When examining lesions independently of their location we found a significant difference in LI drop among successful and unsuccessful lesions (24.22±8.31 vs 15.67±7.85) Ohm, p<0.001). In the same line when studying lesions in those segments with > 10% of GAPS (L1, L6 R1 and R3) LI drop was greater in successful lesion tags: L1 25.2 ± 5.35 vs 16.8 ± 5.17 (p<0.001), L6 25.2±5.7 vs 16±5.48 (p<0.001), R1 27.9±4.78 vs 17.1±5.73 (p=0.03) and R3 18.5±5.4 vs 10.7±2.49 (p<0.001). 5. Conclusions Gaps were located predominantly in anterior segments in left PVs and posterior-superior segment in right PVs. A low LI drop was an excellent predictor of conduction gaps, and it performs well regardless of the segment where it was analyzedFig. 1

Comparative study of lesions obtained with radiofrequency between irrigated ablation catheter with flexible tip and non-irrigated catheter in ex vivo porcine heart slices

Abstract Background Lesion formation through radiofrequency (RF) is related to various parameters, including power, contact force, duration of energy delivery and temperature. Notably, the characteristics of the lesions differ when comparing irrigated to non-irrigated catheters. Non-irrigated catheter lesions present a larger surface area and shallower depth, while irrigated catheters induce deeper lesions with higher volumes. Particularly, flexible-tip open-irrigated catheter exhibit unique irrigation characteristics and the resulting lesions may show a reduced surface area but extend deeper into the tissue. Main drawbacks of using non-irrigated catheter are the risk of clot formation and of steam pops, both possibly avoidable with an irrigated catheter. Purpose The aim of the study was to demonstrate that flexible-tip open-irrigated catheter generate lesions with a smaller surface area and deeper extension when compared to non-irrigated catheter. Methods An ex vivo model consisting of porcine heart slices in a warmed saline chamber was used. A flexible-tip open-irrigated ablation catheter and a non-irrigated catheter were positioned with a stable tissue contact weight ranging from 10 to 20 g of force in perpendicular position. RF was delivered at powers of 20, 30 and 40 Watt for 60s. Lesion dimensions were analyzed. The occurrence of steam pop was registered. Results The ablations were conducted using flexible-tip open-irrigated (n=55) and non-irrigated (n=39) catheters in a power-control mode. Superficial length and width of lesions were greater with the non-irrigated catheter than with the irrigated catheter, irrespective of the power delivered (superficial length: p=0,0001 at 20W, p=0,002 at 30 W and p=0,0001 at 40 W; superficial width: p=0,001 at 20 W, p=0,019 at 30 W and p=0,003 at 40 W). When computing superficial areas, lesions performed with the non-irrigated catheter were significantly wider, regardless of the power delivered (p=0,001 at 20 W, p=0,005 at 30 W and p=0,001 at 40 W). The irrigated catheter determined significantly greater values of lesion maximum depth at high power delivery (40 W, p=0.007). No steam pop was observed using the irrigated ablation catheter, while 12 steam pops occurred with the non-irrigated catheter. Conclusions This study highlights that RF ablation using flexible-tip open-irrigated catheter has the potential to generate smaller lesion areas when compared to a non-irrigated tip. Furthermore, it may contribute to decrease steam pops, even with escalating power output. This irrigated catheter might be a preferable choice when precision is crucial, particularly in determining superficial area of lesions. Specifically, it might be advantageous for procedure as atrioventricular nodal reentry tachycardia (AVNRT) ablation, minimizing the risk of iatrogenic conduction disturbance related to RF delivery in the region of the compact AV node, located superficially at a millimeter distance from the ablation site.Experiment setting, lesion measurementsLesion superficial area

Safe and effective delivery of high-power, short-duration radiofrequency ablation lesions with a flexible-tip ablation catheter.

High-power, short-duration (HPSD) radiofrequency ablation (RFA) may reduce ablation time. Concerns that catheter-mounted thermocouples (TCs) can underestimate tissue temperature, resulting in elevated risk of steam pop formation, potentially limit widespread adoption of HPSD ablation. The purpose of this study was to compare the safety and efficacy of HPSD and low-power, long-duration (LPLD) RFA in the context of pulmonary vein isolation (PVI). An open-irrigated ablation catheter with a contact force sensor and a flexible-tip electrode containing a TC at its distal end (TactiFlexTM Ablation Catheter, Sensor EnabledTM, Abbott) was used to isolate the left pulmonary veins (PVs) in 12 canines with HPSD RFA (50 W for 10 seconds) and LPLD RFA (30 W for a maximum of 60 seconds). PVI was assessed at 30 minutes and 28 ± 3 days postablation. Computed tomographic scans were performed to assess PV stenosis after RFA. Lesions were evaluated with histopathology. A total of 545 ablations were delivered: 252 with LPLD (0 steam pops) and 293 with HPSD RFA (2 steam pops) (P = .501). Ablation time required to achieve PVI was >3-fold shorter for HPSD than for LPLD RFA (P = .001). All 24 PVs were isolated 30 minutes after ablation, with 12/12 LPLD-ablated and 11/12 HPSD-ablated PVs still isolated at follow-up. Histopathology revealed transmural ablations for HPSD and LPLD RFA. No major adverse events occurred. An investigational ablation catheter effectively delivered RFA lesions. Ablation time required to achieve PVI with HPSD with this catheter was >3-fold shorter than with LPLD RFA.

161 ABLATION OF EPICARDIAL VENTRICULAR TACHYCARDIA ORIGINATING IN THE AREA OF PERICARDIAL ADHESIONS INDUCED BY STEREOTACTIC RADIOABLATION IN A PATIENT WITH ISCHEMIC CARDIOMYOPATHY

Abstract This is the case of a 64-year-old male patient with prior inferior wall myocardial infarction, wearing a cardiac resynchronization therapy defibrillator and suffering from recurrent ventricular tachycardia (VT). The patient had undergone a transitory successful endocardial radiofrequency catheter ablation (RFCA) in 2013 and a stereotactic ablative body radiotherapy (SABR) in 2021, targeting the VT originating in the inferior wall myocardial scar. The patient was referred to our institution due to recurrent highly symptomatic slow-VT. A coronary angiography ruled out coronary artery disease (CAD) progression and a RFCA was rescheduled. Given the suspected epicardial origin of VT based on a 12-lead ECG, the decision was made to perform a combined epi-endocardial ablation. SABR-induced pericardial adhesions prevented posterior pericardial access, thus requiring an anterior access approach (Figure 1, Panel A, yellow star). Following epicardial and endocardial electroanatomic mapping (EAM), VT ablation relied on a substrate-based approach. Local abnormal ventricular activities (LAVAs), detected both in the accessible epicardial inferior wall of the left ventricle and at the opposite endocardial site, were eliminated by radiofrequency (RF) current. Upon completion of endocardial ablation, ventricular pacing induced hemodynamically unstable VT, exiting from the epicardial region corresponding to the SABR-induced pericardial adhesions. Mechanical adhesiolysis, using the elbow of the open-irrigated ablation catheter, was performed to disrupt SABR-induced pericardial adhesions in the inferior wall. The epicardial EAM performed with the open-irrigated catheter recorded LAVAs in the infero-posterior wall of the left ventricle, corresponding to the SABR-disrupted pericardial adhesions. A RF current was delivered, targeting LAVAs at this site (Figure 1, Panel B: the central green dot corresponds to the area of disrupted pericardial adhesions). At the end of the procedure, no sustained VT was induced by programmed ventricular stimulation. Conclusion SABR constitutes a novel and promising non-invasive radioablative treatment of VT, potentially associated with cardiac toxicity. To our knowledge, this is the first reported case of combined epicardial and endocardial RFCA of recurrent VT after SABR. Based on the first RFCA report and exclusion of CAD progression, we hypothesized that SABR might have favoured progression of the inferior low voltage area. With this case report, we would like to demonstrate that even if pericardial adhesions could be a consequence of SABR, gentle catheter-driven manoeuvres can be enough to disrupt the adhesions and to achieve full EAM. Further research is mandatory to shed light on SABR's long-term arrhythmogenic role.

Needle-Tipped Catheter Ablation of Papillary Muscle Results in Deeper and Larger Ablation Lesions.

Ventricular tachycardia associated with papillary muscle (PM) is often refractory to standard radiofrequency ablation (RFA). The needle-tipped ablation catheter (NT-AC) has been used to treat deep intramyocardial substrates, but its use for PM has not been characterized. Using an ex vivo experimental platform, both 3mm and 6mm NT-AC created larger ablation lesion volumes and depths than open-irrigated ablation catheter did (OI-AC; e.g., 57.12 ± 9.70mm3 and 2.42 ± 0.22mm, respectively; p < 0.01 for all comparisons). Longer NT-AC extension (6mm) resulted in greater ablation lesion volumes and maximum depths (e.g., 333.14 ± 29.13mm3 and 6.46 ± 0.29mm, respectively, compared to the shorter 3mm NT-AC extension, 143.33 ± 12.77mm3, and 4.46 ± 0.14mm; both p < 0.001). There were no steam pops. In conclusion, for PM ablation, the NT-AC was able to achieve ablation lesions that were larger and deeper than with conventional OI-AC. Ablation of PM may be another application for needle-tip ablation. Further studies are warranted to establish long-term safety and efficacy in human studies.

Comparison of ablation index versus time-guided radiofrequency energy dosing using normal and half-normal saline irrigation in a porcine left ventricular model.

Ablation Index (AI) is a multiparametric quality marker to assess the durability of radiofrequency (RF) lesions. The comparative effectiveness and safety of AI versus time-based energy dosing for ablation of ventricular arrhythmias are unknown. We compared AI and time-based RF dosing strategies in the left ventricles (LVs) of freshly harvested porcine hearts. Ablation was performed in vitro with an open-irrigated ablation catheter (Thermocool ST/SF), 40 W, contact force 10-15 g. Tissue samples were stained in triphenyltetrazolium chloride for the measurement of lesion dimensions. A total of 560 lesions were performed (AI-group: [n = 360]; time-group: [n = 200]). Using normal saline (NS) (n = 280), growth in lesion depth slowed after 30 s and AI > 550 in comparison to width, volume, and magnitude of impedance drops which continued to increase with longer RF duration. Risk of steam pop (SP) was higher for RF > 30 s (RF < 30 s:1 SP [2.5%] vs. RF > 30 s: 15 SP [25%];p = .002) or AI targets >550 (AI: 350-550: 2 SP [2%] vs. AI 600-750: 15 SP [19%];p = .001). Using half-normal saline (HNS) (n = 280), lesion dimension and impedance drops were larger and growth in lesion depth slowed earlier (AI: 500). Risk of SPs was higher above AI 550 (AI: 350-550: 7 [7%] SPs vs. AI 600-750: 28 [35%] SPs; p < .00001). While codependent variables, correlation between AI and time was modest-to-strong but decreased with longer RF duration. In this ex vivo study, AI was a better predictor of lesion dimensions than ablation time and magnitude of impedance drop in the LV using NS and HNS irrigation. AI targets above 550 led to a higher risk of SPs. Future trials are required to verify these findings.

Catheter ablation for ventricular arrhythmias using remote magnetic navigation in patients with reduced ejection fraction

Objective. Radiofrequency catheter ablation is an effective treatment option for cardiac arrhythmias including complex and ventricular arrhythmias. Remote magnetic catheter navigation (RMN) has been developed as a novel way of approach aiming to improve outcome and reduce complication rate, and reduce radiation exposure for both operator and patient. Our aim was to compare success and complication rate in patients with or without severely reduced left ventricular ejection fraction (LVEF). Methods. We retrospectively analyzed all the patients (n = 98) which have undergone RMN in our center between 2015-2021. No selection criteria for RMN procedure have been applied. All clinical and paraclinical, as well as procedural data were collected. Patients were divided into two groups, with or without severely reduced LVEF ≤ 35%. CARTO system was used for 3D electroanatomic mapping. RMN was done using Niobe ES system and an open-irrigated magnetic ablation catheter. Success rate was defi ned by complete elimination of clinical arrhythmia. Non-inducibility following ablation was assessed in all patients presenting with any type of ventricular arrhythmia other than premature ventricular contractions. Testing for inducibility was done by ventricular programmed pacing with up to four extra-stimuli. The statistical analysis was performed using SPSS software. P-value &lt; 0.05 was considered signifi cant. Results. Successful ablation with complete elimination of the clinical arrhythmia was achieved in 92.3% of the patients with severely reduced LVEF and in 88.1% of patients with LVEF &gt; 35% (p = 0.73). Overall minor complication rate was 2.04% with spontaneous resolution. No major complications were reported. Non-inducibility was achieved in 56.4% of the patients with LVEF ≤ 35% and in 79.2% of the patients with LVEF &gt;35% (p = 0.023). Conclusion. Radiofrequency catheter ablation using RMN is effective and safe regardless of the presence or not of a severely reduced LVEF.

B-PO03-130 COMPARISON BETWEEN TIME AND ABLATION INDEX-BASED RADIOFREQUENCY ENERGY DOSING DURING ABLATION IN LEFT VENTRICULAR PORCINE MODEL

Ablation Index (AI) is a quality marker combining contact force (CF), time, and power to assess durability of radiofrequency (RF) lesions. However, the risk-benefit of AI for ablation of ventricular arrhythmias is currently unknown. We compared AI and time-based RF dosing strategies in left ventricles of freshly harvested porcine hearts. Ablation was performed in vitro using an open-irrigated ablation catheter (Thermocool ST/SF), power of 40 Watts and CF of 10-15 grams. After ablation, tissue samples were cross-sectioned and stained in triphenyltetrazolium chloride for measurement of lesion dimensions. In total, 560 lesions were performed. Using NS (n=280), growth in lesion depth slowed substantially after 30 seconds and after reaching an AI of 550, although size of impedance drops continued to increase with longer ablation time and higher AI cut offs. Risk of steam pop (SP) was higher after 30 seconds of ablation (RF < 30 sec: 1 SP (2.5%) vs. RF > 30 sec: 15 SP (25%);p=0.002) and AI >550 (AI 350-550: 2 SP (2%) vs AI 600-750: 15 SP (19%);p=0.001). Using HNS (n=280), impedance drops were larger but growth in lesion depth slowed after reaching AI of 500. Risk of SPs was higher above AI 550 (AI 350-550: 7 (7%) SPs vs. AI 600-750: 28 (35%)SP; p<0.00001). While co-dependent variables, correlation between AI and time was modest despite similar power and CF parameters. Long durations of RF may result in excessive tissue heating and risk of SPs without necessarily achieving substantial increase in lesion depth desired. An AI-guided protocol including variables beyond time, may improve procedure time, safety and efficacy during ventricular ablation.

Use of infrared thermography to delineate temperature gradients and critical isotherms during catheter ablation with normal and half normal saline: Implications for safety and efficacy.

Radiofrequency (RF) ablation with half-normal saline (HNS) has shown promise as a bail-out strategy following failed ventricular tachycardia ablation using standard approaches. To use a novel infrared thermal imaging (ITI) model to evaluate biophysical and lesion characteristics during RF ablation using normal saline (NS) and HNS irrigation. Left ventricular strips of myocardium were excised from fresh porcine hearts. RF ablation was performed using an open-irrigated ablation catheter (Thermocool ST/SF) with NS (n = 75) and HNS (n = 75) irrigation using different power settings (40/50 W), RF durations (30/60 s), contact force of 10-15 g, and flow rate of 15 ml/min. RF lesions were recorded using an infrared thermal camera and border zone, lethal, 100° isotherms were matched with necrotic borders after 2% triphenyltetrazolium chloride staining. Lesion dimensions and isotherms (mm2 ) were measured. In total, 150 lesions were delivered. HNS lesions were deeper (6.4 ± 1.1 vs. 5.7 ±0.8 mm;p = .03), and larger in volume (633 ± 153 vs. 468 ± 107 mm3 ; p = .007) than NS lesions. Steam pops (SPs) occurred during 19/75 lesions (25%) in the NS group and 32/75 lesions (43%) in the HNS group (p = .34). Lethal (57.8 ± 6.5 vs. 36.0 ± 3.9 mm2 ;p = .001) and 100°C isotherm areas (16.9 ± 6.9 vs. 3.8 ± 4.2 mm2 ; p = .003) areas were larger and were reached earlier in the HNS group. RFA using HNS created larger lesions than NS irrigation but led to more frequent SPs. The presence of earlier lethal isotherms and temperature rises above 100°C on ITI suggest a potentially narrower therapeutic-safety window with HNS.

Half‐normal saline versus normal saline for irrigation of open‐irrigated radiofrequency catheters in atrial fibrillation ablation

The creation of effective and permanent lesions is a crucial factor in determining the success rate of atrial fibrillation (AF) ablation. By increasing the efficacy of radiofrequency (RF) energy-mediated lesion formation, half-normal saline (HNS) as an irrigant for open-irrigated ablation catheters has the potential to reduce procedural times and improve acute and long-term outcomes. This is a double-blindrandomized clinical trial of 99 patients undergoing first-time RF catheter ablation for AF. Patients enrolled were randomly assigned in a 1:1 fashion to perform ablation using HNS or normal saline (NS) as an irrigant for the ablation catheter. The use of HNS is associated with shorter RF times (26 vs. 33 min; p = .02) with comparable procedure times (104 vs. 104 min). The rate of acute pulmonary vein reconnections (16% vs. 18%) was comparable, with a median of 1 vein reconnection in the HNS arm versus 2 in the NS arm. There was no difference in procedure-related complications, including the incidence of postprocedural hyponatremia when using HNS. Over the 1-year follow-up, there is no significant difference between the HNS and NS with respect to the recurrence of any atrial arrhythmia (off antiarrhythmic drugs[AAD]: 47% vs. 52%; hazard ratio [HR]: 1.17, 95% confidence interval [CI]: 0.66-2.06; off/on AAD: 66% vs. 66%, HR: 1.06, 95% CI: 0.53-2.12), with a potential benefit of using HNS when considering the paroxysmal AF cohort (on/off AAD 73% vs. 62%, HR: 0.72, 95% CI: 0.19-2.70). In a mixed cohort of patients undergoing first-time AF ablation, irrigation of open-irrigated RF ablation catheters with HNS is associated with shorter RF times, with a comparably low rate of procedure-related complications. In the long term, there is no significant difference with respect to the recurrence of any atrial arrhythmia. Larger studies with a more homogeneous population are necessary to determine whether HNS improves clinical outcomes.

Incidence of ablation-induced esophageal injury associated with high-power short duration temperature-controlled pulmonary vein isolation using a specialized open-irrigated ablation catheter: A retrospective single-center study.

To evaluate short-term efficacy and incidence of ablation-induced endoscopically detected esophageal injury in patients undergoing high-power, short-duration (HPSD) pulmonary vein isolation using a novel irrigated radiofrequency ablation catheter and ablation generator setup. Atrial fibrillation (AF) patients, who underwent AF ablation using an irrigated radiofrequency ablation catheter specifically designed for a HPSD ablation approach (50 W, with a target Ablation Index of 350 at posterior wall), received postablation esophageal endoscopy after ablation. In total 45 consecutive patients (67 ± 10 years; 58% male; 42% paroxysmal AF) undergoing AF ablation using a specialized ablation catheter (QDOT) were included in the study. Thirty-one of 45 patients (69%) underwent a first-time pulmonary vein isolation (Group 1, 67 ± 11 years; 55% male; 48% paroxysmal AF). Fourteen patients (31%) underwent a redo AF procedure (Group 2, 66 ± 8 years; 64% male; 29% paroxysmal AF). Patients undergoing first-time pulmonary vein isolation were included in the final analysis. In these patients an endoscopically detected esophageal lesion (EDEL) was detected in 5 of 31 (16%) patients (erosion n = 2, ulcer n = 3). Mean contact force at posterior wall ablation sites was significantly lower in patients with postprocedural EDEL compared with patients without EDEL (11.9 ± 0.8 g vs. 15.6 ± 4.7 g). PVI using a specialized high-power ablation catheter in conjunction with a HPSD ablation approach results in a 16% incidence of EDEL in first AF ablation candidates. Future studies evaluating high-power short duration ablation strategies should include esophageal endoscopy to estimate the risk of clinically relevant esophageal complications.

The use of half normal saline during catheter ablation of typical atrial flutter has no impact on the time to achieve bidirectional block

Abstract Background Achieving bidirectional block (BB) is generally considered to be the endpoint in the ablation of typical atrial flutter (AFL), however acute reconnection is common. Recent data suggest that deeper ablation lesions may be created by decreasing the irrigant ionic concentration using half normal saline (HNS) delivered through an open irrigated ablation catheter compared with normal saline (NS). We sought to assess whether the use of HNS was associated with a more rapid achievement of BB and less reconnections compared with NS. Methods Patients were randomly allocated to catheter ablation with either NS or HNS using a 4-mm irrigated catheter at a power setting of 30 W. Ablation approach employing either a maximum voltage guided (MVG) or empiric cavo-tricuspid isthmus (CTI) line was performed aiming for BB that was confirmed by double potentials separated by an isoelectric line measuring ≥110 ms and evidence of conduction block using differential pacing. Study was powered to an endpoint of acute reconnection within 30 mins. Results A total of 60 patients underwent catheter ablation for typical AFL with either HNS (n=30) or NS (n=30). There were no significant differences between the two groups in terms of patient age (68±7 yrs HNS vs. 68±10 yrs NS) and BMI (31±7 HNS vs 31±5 NS). BB was achieved in all patients. The MVG approach was employed in 28/60 patients. Acute reconnection was observed in 11 patients (18%); 4 in HNS vs 7 in NS group (ns). The mean RF time to achieve BB was 386±262 seconds in HNS vs 456±270 seconds in NS (p=0.21). The approach to CTI ablation showed a significant difference in time to BB: Time to block in MVG cases was 264±143 seconds vs 567±273 in empiric CTI line cases. Figure 1 demonstrates the time to block in both approaches with the choice of irrigant not appearing to impact the time to BB. There were 4 steam pops in the HNS arm and 0 steam pops observed in the NS arm. There were no significant complications in either arm. Conclusion Irrigation with HNS resulted in no statistically significant reduction in duration of RF time or improvement in acute outcomes over NS in the atrial flutter population. Reduction in duration of RF time was driven by MVG approach. However, acute reconnections were higher in NS group, all 4 steam pops occurred in HNS arm. Figure 1 Funding Acknowledgement Type of funding source: None

Utility of novel Omnipolar activation mapping for the detection of ventricular premature contraction origin

Abstract Background Bipolar electrograms are significantly influenced by direction of the propagating wavefront in relation to the recording bipole. Omnipolar voltage mapping may be superior to standard bipolar mapping since it obtains maximum voltage of all possible bipolar electrode orientations without the need for catheter rotation. Therefore, omnipolar maps can provide voltage maps with larger voltages as well as better defined boundaries. Purpose Whether omnipolar activation maps also describe better activation maps versus traditional bipolar maps during ventricular premature contraction (VPC) catheter ablation is unclear. Methods A high-density mapping catheter was advanced to the ventricular outflow tract and a high-resolution activation map was created. Each electrode along and across the splines of the catheter are 4mm apart. Bipoles were calculated along (MAP 2), across (MAP 3) and bidirectional (MAP 4) the splines while omnipoles (MAP 1) were derived from a right triangle clique. Within a square area, four omnipolar and two bipolar values along, across and bidirectional values were defined. Results Though the earliest activation site was vague by along and across maps (arrow), white color became evident by bidirectional map, and the VPC origin became distinct with omnipolar mapping. RF lesions were given via an open-irrigated ablation catheter targeting a lesion size index 5.0. The VPC was eliminated by radiofrequency ablation. Conclusion Omnipolar activation mapping may be more accurate than traditional bipolar mapping during ventricular premature contraction (VPC) catheter ablation. Figure 1 Funding Acknowledgement Type of funding source: None

133Bipolar ablation of refractory ventricular arrhythmias originating from the close proximity of His bundle

Abstract Introduction Biophysics of bipolar radiofrequency catheter ablation (Bi-RFCA) suggest more condensed and selective lesion formation when compared to conventional-unipolar approach. Whether more selective Bi-RFCA can result in safe and effective ablation of arrhythmic substrates in close proximity of His bundle has not been investigated so far. Purpose To determine feasibility and effectiveness of Bi-RFCA in His bundle area. Methods Consecutive patients after failed unipolar ablation for symptomatic premature ventricular complexes (PVC) or ventricular tachycardia (VT) originating from the vincity of His bundle underwent Bi-RFCA. Results We ultimately enrolled 8 patients (2 females, age 60 ± 15 years) to undergo Bi-RFCA of PVC/VT. Previous pharmacological treatment consisting of at least one antiarrhythmic drug and conventional catheter ablation failed in all. Bi-RFCA using open-irrigated and non-irrigated ablation catheters (AC) was delivered from two earliest PVC/VT activation sites located in the vincity of His bundle (Figure, panels A-B). A total number of 93 bipolar applications were delivered (mean bipolar RF time 508 ± 565s, mean power 35 ± 13W, mean impedance 163 ± 18Ω). Transient conduction disturbances occurred in 2 patients and were associated with mechanical compression of conduction system. No persistent conduction disturbances occurred. Bipolar RFCA led to acute elimination of PVC/VT in 6 (75%) patients. Follow up lasted 11 ± 5 months: two patients underwent repeat procedure using dual-irrigated Bi-RFCA, there was no VT recurrence and 72% PVC burden reduction was achieved (16200 ± 11600 pre-ablation vs 4500 ± 6200 post-ablation PVC/day, p = 0,035) (Figure, panel C). Conclusion Bi-RFCA performed in proximity of His bundle can be safe and effective in majority of patients. Abstract Figure. Bipolar ablation of parahisian PVC/VT

Evaluation of Radiofrequency AblationIrrigation Type: InVivo Comparison of Normal Versus Half-Normal SalineLesionCharacteristics.

This study investigated the impact of the type of catheter irrigant used during delivery of radiofrequency ablation. The use of half-normal saline (HNS) as an irrigant has been suggested as a method for increasing ablation lesion size but has not been rigorously studied in the beating heart or the use of a low-flow irrigation catheter. Sixteen swine underwent left ventricular mapping and ablation using either normal saline (NS) (group 1: n=9) or half-normal saline (HNS) (group 2: n=7). All lesions were delivered using identical parameters (40W with 10-second ramp, 30-second duration, 15ml/min flow, and 8- to14-g target contact force). An occurrence of steam pop, catheter char, or thrombus was assessed using intracardiac echocardiography and catheter inspection following each application. Lesion depth, width, and area were measured using electronic calibers. A total of 109 lesions were delivered in group 1 and 77 in group 2. There were significantly more steam pops in group 2 (32 of 77 [42%] vs. 24 of 109 [22%], respectively). The frequencies of catheter tip char were similar (group 1: 9 of 109 [8%] vs. group 2: 10 of 77 [13%]; p=0.29). Lesion depths, widths, and areas also were similar in both groups. The use of an HNS irrigant using a low-flow open irrigated ablation catheter platform results in more tissue heating due to higher radiofrequency current delivery directed to tissue, but this can lead to higher rate of steam pops. In this invivo porcine beating-heart model, the use of HNS does not appear to significantly increase lesion size innormal myocardium despite evidence of increased radiofrequency heating.

Contact-Force-Sensing-Based Radiofrequency Catheter Ablation in Paroxysmal Supraventricular Tachycardias (COBRA-PATH): a randomized controlled trial

BackgroundMultiple studies have demonstrated the importance of adequate catheter–tissue contact in the creation of effective lesions during radiofrequency catheter ablation. The development of contact force (CF)-sensing catheters has contributed significantly to improve clinical outcomes in atrial fibrillation. However, CF-sensing technology is not used in the ablation of paroxysmal supraventricular tachycardia (PSVT). The possible reason for this is that PSVT ablation with the conventional approach (i.e. nonirrigated, non-CF-sensing catheters) is considered a relatively low-risk procedure with fairly high success rates (short and long term). The aim of this study is to determine whether CF sensing can further improve the outcomes of PSVT ablation.Methods/designThe COBRA-PATH study is a single-center, two-armed, randomized controlled trial. Patients without structural heart disease being referred for electrophysiology study, because of PSVT and potential treatment with radiofrequency (RF) catheter ablation, will be randomly assigned to either manual ablation with standard nonirrigated ablation catheters or manual ablation with an open-irrigated ablation catheter equipped with CF sensing (used in a virtual nonirrigated modus). The primary study endpoint is the difference in the number of RF applications during the ablation of atrioventricular nodal re-entry tachycardia, and that of Wolff–Parkinson–White syndrome and atrioventricular re-entrant tachycardia. Secondary outcome parameters include acute and long-term procedural success rates, overall duration of RF applications, procedure/fluoroscopy durations and safety parameters.DiscussionWe expect to see a reduced number/duration of RF applications required to achieve effective lesion creation, and consequently a decrease in total procedure/fluoroscopy times. Although a significant improvement in procedural success rates (acute/long term) might not be feasible to demonstrate (given the relatively high success rate of the standard ablation method), the possible decrease in procedure duration and the consequential reduction of radiation exposure has important clinical implications for both operators and patients undergoing the procedure.Trial registrationClinicalTrials, NCT04078685. Retrospectively registered on 2 September 2019.

2019 APHRS expert consensus statement on three-dimensional mapping systems for tachycardia developed in collaboration with HRS, EHRA, and LAHRS.

2019 APHRS expert consensus statement on three-dimensional mapping systems for tachycardia developed in collaboration with HRS, EHRA, and LAHRS.

High-Power and Short-Duration Ablation for Pulmonary Vein Isolation: BiophysicalCharacterization.

This study sought to examine the biophysical properties of high-power and short-duration (HP-SD) radiofrequency ablation for pulmonary vein isolation. Pulmonary vein isolation is the cornerstone of atrial fibrillation ablation. However, pulmonary vein reconnection is frequent and is often the result of catheter instability, tissue edema, and a reversible nontransmural injury. We postulated that HP-SD ablation increases lesion-to-lesion uniformity and transmurality. This study included 20 swine and a novel open-irrigated ablation catheter with a thermocouple system able to record temperature at the catheter-tissue interface (QDOT Micro Catheter). Step 1 compared 3 HP-SD ablation settings:90 W/4 s, 90 W/6 s, and 70 W/8 s in a thigh muscle preparation. Ablation at 90 W/4 s was identified as the best compromise between lesion size and safety parameters, with no steam-pop or char. In step 2, a total of 174 single ablation applications were performed in the beating heart and resulted in 3 (1.7%) steam-pops, all occurring at catheter-tissue interface temperature≥85°C. Additional 233 applications at 90 W/4 s and temperature limit of 65°C were applied without steam-pop. Step 3 compared the presence of gaps and lesion transmurality in atrial lines and pulmonary vein isolation between HP-SD (90 W/4 s, T≤65°C) and standard (25 W/20 s) ablation. HP-SD ablation resulted in 100% contiguous lines with all transmural lesions, whereas standard ablation had linear gaps in 25% and partial thickness lesions in 29%. Ablation with HP-SD produced wider lesions (6.02 ± 0.2 mm vs. 4.43 ± 1.0 mm; p= 0.003) at similar depth (3.58 ± 0.3 mm vs. 3.53 ± 0.6 mm; p= 0.81) and improved lesion-to-lesion uniformity with comparable safety end points. In a preclinical model, HP-SD ablation (90 W/4 s, T≤65°C) produced an improved lesion-to-lesionuniformity, linear contiguity, and transmurality at a similar safety profile of conventional ablation.

Efficacy and safety comparison between different types of novel design enhanced open-irrigated ablation catheters in creating cavo-tricuspid isthmus block

BackgroundClinical utility of irrigation-tip ablation catheters for cavo-tricuspid isthmus (CTI) ablation is established. Recently, new-generation enhanced-cooling irrigation-tip catheters were introduced into clinical use. This study compared the performance of different types of novel irrigation-tip catheters in CTI ablation. MethodsOne hundred patients undergoing CTI ablation with novel irrigated-tip catheters were included. Ablation was performed with a power output of 30–35W using either 4-mm flexible tip catheters [FlexAbility (FAs) St. Jude Medical, St. Paul, MN, USA] or 3.5-mm enhanced-cooling ring-tip catheters without [ThermoCool SurroundFlow (SFs), Biosense Webster, Diamond Bar, CA, USA] and with contact force sensing [ThermoCool SmartTouch SurroundFlow (STSFs), Biosense Webster] in 32, 34, and 34 patients, respectively. ResultsThe successful CTI block creation rate was significantly higher for FAs than SFs/STSFs [32/32 (100%), 30/34 (88.2%), and 27/34 (79.4%), p=0.006]. In all 11 failed procedures, block was created by additional 5 (2–7) applications with 8-mm tip catheters. The radiofrequency (RF) application number (p=0.001) and energy (p=0.021) were significantly lower, and total RF time (p=0.005) and procedure time (p=0.036) significantly shorter in the FA than SF/STSF groups. The FA catheter was associated with significantly higher tip temperature readings (34.9°C vs. 32.0/33.0°C, p<0.001) and lower initial impedances than SF/STSF catheters (both p<0.001). The tip temperature reached the maximum temperature setting in 15/295 (5.1%) FA catheter applications among 11 (34.3%) patients, 0/521 (0%) ST applications, and 0/448 (0%) STSF applications. The mean RF power achieved during RF applications was significantly lower for FA than SF/STSF catheters (28.6W vs. 30.4/30.8W, p<0.001). Audible steam pops were detected in 1/448 applications in only the STSF group. ConclusionsIn human CTI ablation, flexible irrigation-tip catheters showed a significantly better performance than rigid enhanced-cooling irrigation-tip catheters.

P857Comparison of pulmonary vein isolation using a laser balloon and using an open irrigated mapping and ablation catheter (nMARQ)

P857Comparison of pulmonary vein isolation using a laser balloon and using an open irrigated mapping and ablation catheter (nMARQ)