Irrigated Ablation Research Articles

Gastric slow-wave modulation via power-controlled, irrigated radio-frequency ablation.

Recently, radio-frequency ablation has been used to modulate slow-wave activity in the porcine stomach. Gastric ablation is, however, still in its infancy compared to its history in the cardiac field, and electrophysiological studies have been restricted to temperature-controlled, non-irrigated ablation. Power-controlled, irrigated ablation may improve lesion formation at lower catheter-tip temperatures that produce the desired localized conduction block. Power-controlled, irrigated radio-frequency ablation was performed on the gastric serosal surface of female weaner pigs (n = 5) invivo. Three combinations of power (10-15 W) and irrigation settings (2-5 mL min-1) were investigated. A total of 12 linear lesions were created (n = 4 for each combination). Slow waves were recorded before and after ablation using high-resolution electrical mapping. Irrigation maintained catheter-tip temperature below 50°C. Ablation induced a complete conduction block in 8/12 cases (4/4 for 10 W at 2 mL min-1, 1/4 for 10 W at 5 mL min-1, 3/4 for 15 W at 5 mL min-1). Blocks were characterized by a decrease in signal amplitude at the lesion site, along with changes in slow-wave propagation patterns, where slow waves terminated at and/or rotated around the edge of the lesion. Power-controlled, irrigated ablation can successfully modulate gastric slow-wave activity at a reduced catheter-tip temperature compared to temperature-controlled, non-irrigated ablation. Reducing the irrigation rate is more effective than increasing power for blocking slow-wave activity. These benefits suggest that irrigated ablation is a suitable option for further translation into a clinical intervention for gastric electrophysiology disorders.

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

High-density mapping-guided ventricular tachycardia ablation in patients with ischemic cardiomyopathy: outcomes from a tertiary center cohort in Switzerland

Abstract Background Substrate-based ablation has emerged as a successful technique for VT ablation, especially in patients with ischemic cardiomyopathy with markedly reduced left ventricular function. High-density mapping catheters provide high-resolution electroanatomical maps and better discrimination of abnormal substrates and local activation in the heart chambers, making them a valuable and safe resource in the electrophysiology laboratory. Purpose The purpose of this study was to investigate differences in procedural characteristics and clinical outcomes of VT ablation with ischemic cardiomyopathy. VT ablations were guided by two mapping strategies: high-density mapping using a high-density mapping catheter and conventional mapping using an ablation catheter. Methods Patients with ischemic cardiomyopathy receiving VT ablation at our center between January 2018 and June 2023 were retrospectively included. Procedural characteristics and clinical outcomes were compared between patients receiving high-density mapping with a multielectrode-mapping catheter vs conventional mapping with a single-tip irrigated ablation catheter. Results Eighty-four patients with ischemic cardiomyopathy who underwent VT ablation were consecutively included (mean age 67 ± 12 years, mean LVEF 32 ± 11 %, 79 (94%) males). Fifty-seven (68 %) procedures were performed using high-density mapping, and 27 (32 %) conventional mapping. In the high-density mapping and conventional mapping group, the total procedure time was 256 ± 77 min vs. 232 ± 61 min (P < 0.05) and the total fluoroscopic dose was 1643 ± 204 μGy.m2 vs. 948 ± 105 μGy.m2 (P < 0.05), respectively,. However, there was no difference between the two groups in terms of acute success (84% vs 80%, P > 0.05) or major complications (5% vs 4%, P > 0.05). The mean duration of follow-up was 2.6 years (4 - 51 months). The 1-year mortality rates were 4% vs 7% in the high-density mapping and conventional mapping groups, respectively (P < 0.05). The 3-month and 1-year single-procedural sustained VT/VF-free rates were 77% vs 59% and 74% vs 63%, respectively (P < 0.05). The 1-year incidence of sustained VT/VF recurrence was 7.0 per 100 person-years in high-density mapping group, compared with 7.4 per 100 person-years in the conventional group. Conclusions VT ablation in patients with ischemic cardiomyopathy using high-density mapping appears to be superior to conventional mapping in terms of reducing postprocedural VT/VF recurrence and a subsequent reduction of overall mortality.Figure 1Figure 2

Catheter-related and clinical complications associated with contact force–sensing irrigated ablation catheter

Catheter-related and clinical complications associated with contact force–sensing irrigated ablation catheter

Comparative Study of Lesions Obtained through Radiofrequency between the Irrigated Ablation Catheter with a Flexible Tip and the Non-Irrigated Catheter in Ex Vivo Porcine Hearts.

At the same conditions of delivered power and contact force, open-irrigated radiofrequency ablation catheters are believed to create deeper lesions, while non-irrigated ones produce shallower lesions. This ex vivo study aims to directly compare the lesion dimensions and characteristics of an irrigated ablation catheter with a flexible tip and a non-irrigated solid-tip catheter. Radiofrequency lesions were induced on porcine myocardial slabs using both open-tip irrigated and non-irrigated standard 4 mm catheters at three power settings (20 W, 30 W, and 40 W), maintaining a fixed contact force of 10 gr. A lesion assessment was conducted including the lesion depth, depth at the maximum diameter, and lesion surface diameters, with the subsequent calculation of the lesion volume and area being undertaken. Irrigated catheters produced lesions with significantly higher superficial widths at all power levels (3.8 vs. 4.4 mm at 20 W; 3.9 mm vs. 4.4 mm at 30 W; 3.8 mm vs. 4.5 mm at 40 W; p = 0.001, p = 0.019, p = 0.003, respectively). Non-irrigated catheters resulted in significantly higher superficial areas at all power levels (23 mm2 vs. 18 mm2 at 20 W; 25 mm2 vs. 19 mm2 at 30 W; 26 mm2 vs. 19 mm2 at 40 W; p = 0.001, p = 0.005, p = 0.001, respectively). Irrigated catheters showed significantly higher values of lesion maximum depth at 40 W (4.6 mm vs. 5.5 mm; p = 0.007), while non-irrigated catheters had a significantly higher calculated volume at 20 W (202 µL vs. 134 µL; p = 0.002). Radiofrequency ablation using an irrigated catheter with a flexible tip has the potential to generate smaller superficial lesion areas compared with those obtained using a non-irrigated catheter.

Association between different catheter designs for the characterization of the left atrial substrate

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): The study was supported by an investigator sponsored grant (Boston Scientific). Background Bipolar voltage electrograms (BVE) for left atrial (LA) substrate characterization strongly depend on the catheter design and electrode configuration. Purpose The aim of the study was to compare bipolar voltage electrograms (BVE) obtained from the left atrium using four different established mapping catheters and to deduce the individual catheter-specific cut-offs for scar and healthy myocardial tissue. Methods We prospectively included 25 consecutive patients referred for catheter ablation for atrial fibrillation recurrence after index PVI. The pipeline of the analysis leading to the individual cut-off for every catheter based on a reference catheter value is shown in the figure. In detail, consecutive high-resolution electroanatomic mapping was performed using a multipolar catheter (Orion), a duo-decapolar variable circular mapping catheter (Lasso), an irrigated ablation catheter with micro electrodes (MIFI) and a 4.5 mm tip-size irrigated ablation catheter (Nav). BVEs for the four catheters were compared in voxels with a size of 3x3x3mm^3 (Figure, top left). Total least squares regression was performed for every patient to investigate the logarithmic relationship between the BVE measured by two different catheter types (Figure, top right). The mean equivalent BVE cut-off over all patients for every catheter was calculated for the reference cut-offs of 0.1 mV, 0.2 mV, 0.5 mV, 1.0 mV, and 1.5 mV (Figure, bottom left). Results Correlation between the four different BVE maps for the 25 patients showed a slight individual variation between the patients. Compared to the BVE cut-offs from the standard Nav catheter with a 4.5 mm tip, the scar cut-off using the Orion catheter must be lowered to 0.034 mV for a 0.1 mV cut-off, to 0.09 mV for a 0.2 mV cut-off, and to 0.35 mV for the 0.5 mV cut-off (Figure). Similar values hold true for a Lasso map as comparator (Figure). For healthy tissue above 1 mV, similar cut-offs to the reference values might be advisable. Conclusion In contrast to the established Nav or Lasso catheter, the scar voltage cut-off for the Orion catheter needs to be lowered to 0.1 mV instead of the 0.2 mV cut-off and approx. 0.35 mV for a 0.5 mV cut-off. At lower voltages the difference between the catheters increases. The presented connective table enables to transfer the studies of left atrial substrate characterizations using different catheter types.

PO-01-084 HIDING IN PLAIN SIGHT

Substrate based scar modification requires accurate detection and characterization of myocardial scar in sinus rhythm or using different wavefronts of activation. Mapping during ventricular tachycardia can be performed only in about 30% to 40% cases. We describe a challenging case of scar VT with discrepancy in the delineation of scar between voltage mapping and cardiac MRI and the role of Decremental Evoked Potential Mapping as a guide to a more focussed ablation in such circumstances. N/A N/A 56 year diabetic female status post Coronary artery bypass grafting in 2016 and moderate left ventricular dysfunction with recurrent episodes of hemodynamically unstable ventricular tachycardia and patient's refusal for ICD was evaluated and cardiac MRI revealed subendocardial scar in the anterior wall and patent grafts on coronary angiogram. Patient was taken up for 3D mapping and ablation using 3.5 mm tip non force sensing unidirectional irrigation ablation catheter.In view of hemodynamically unstable VT, activation mapping was not possible, hence substrate mapping was planned. Endocardial bipolar voltage mapping didnot delineate any scar in sinus rhythm and after changing the wavefront of activation to right ventricular paced rhythm. Unipolar voltage map didnot show any scar. While mapping the anterior wall , abnormal local electrograms were seen superimposed into the far field electrograms. To do a foccussed ablation we applied the concept of Decremental Evoked Potential Mapping and identified the slow conduction zone - the most critical component of the scar for initiation and maintainence of re-entry. We identified and ablated only the points with abnormal local electrograms with absolute value of decrement more than 10 ms as part of slow conduction zone. Post ablation, VT was not inducible despite induction protocol using triple extrastimuli from two different sites. Activation mapping is not possible in hemodynamically unstable VT. Substrate based mapping needs accurate delineation of myocardial scar. As the 3D mapping system is an automated system and annotates only the largest amplitude signals for color coded voltage mapping, in cases without dense scar, voltage mapping doesnot reliably identify and delineate the scar when compared to cardiac MRI, particularly with a larger tip diameter ablation catheter. Novel mapping techniques like Decremental Evoked Potential Mapping enable limited ablation in such cases.

PO-03-037 FEASIBILITY OF UNIPOLAR SIGNAL GUIDED ABLATION IN CREATING CONTIGUOUS LINES OF CONDUCTION BLOCK: A PROOF-OF-CONCEPT STUDY

Contemporary ablation is guided by non-physiological surrogates such as Ablation indexTM (ABi). Dynamic changes in local atrial unipolar electrogram (Uni-EGM) with loss of the negative S component or “R-pattern” change during radiofrequency ablation (RFA) predicts a transmural lesion. To investigate the feasibility of generating contiguous, transmural lesions that result in conduction block, using ablation guided by Uni-EGM modification. This method was compared with ablation guided by standard ABi parameters. In a beating heart Yorkshire swine model, linear transcaval RFA was performed using an irrigated ablation catheter (Thermocool® SmartTouch Surround-Flow, Biosense Webster, Irwindale, CA) with power of 30W. RF delivery was turned off 3 seconds after a stable R-pattern change was seen on the unipolar EGM (Uni t+3). Inter-lesion spacing was directed by a 2nd operator, blinded to the electroanatomical map, and guided solely by Uni EGM morphology characteristic of viable myocardium as well as current of injury marking the contiguous location with ablated tissue (Figure 1A). Uni EGM signals were processed by the PureEP System (BioSig Technologies). Bidirectional block was demonstrated with standard EP maneuvers and histopathology. Uni EGM guided transcaval lines were compared to a historical cohort of ABi=400 guided transcaval lines. In 5 swine, transcaval ablation lines, guided by Uni EGM were performed. Bidirectional block was demonstrated in 4 of 5 lines (80%) and supported by postmortem histopathology (Figure 1B). Compared with transcaval lines with RFA guided by ABi, there was no difference in initial impedance, impendence drop, or mean length of the ablation line (Table). The Uni-t+3 lines were narrower (5.3±1.5mm vs 11.7±4.8mm, <0.001) and comprised of more closely spaced lesions (2.65±1.3mm vs. 3.4±0.5mm, p=0.001). RFA delivery time per lesion, guided by Uni-EGM modification, was substantially shorter (13.7±5.2sec vs. 21.9±5sec, p<0.001). While total RF delivery time did not differ between the groups [695sec (615-697) vs. 639sec (619-693), p=1). Monitoring changes in the local Uni EGM during ablation offers a real-time physiologic endpoint for titration of RF energy delivery. This study demonstrates that it is feasible to create a transmural line with bidirectional block using ablation that is guided by unipolar signals.Tabled 1Unipolar guided ablation lines Vs ABi linesParameterUt+3 LinesN=5Abi lines (control)N=4PImpedance (ohm)139±7.8131±8.50.3Impedance drop (ohm)14±6.816.1±5.10.1Ablation index333 (296-390)400<0.001Ablation time per lesion (sec)13.7±5.221.9±5<0.001Total RF time (sec)695 (615-697)639 (619-693)1Lesions per line49 (40-50)27 (26-31)0.01Inter-lesion distance (mm)2.65±1.33.4±0.50.001Line length (mm)70 (67-70)67 (66-75)0.62Line width (mm)5.3±1.5411.7±4.8<0.001Transmural80%100% Open table in a new tab

AB-452674-4 SHORT AND SWEET: EXPLORING HIGH POWER, SHORT DURATION RADIOFREQUENCY ABLATION STRATEGIES FOR OPTIMAL LESION FORMATION

High power, short duration (HPSD) radiofrequency (RF) ablation allows for wider, more uniform ablation lesion formation as compared to moderate power, moderate duration ablation. Ablation with HPSD capitalizes on the resistive heating phase providing immediate heating to the target tissue while preventing the consequences of conductive heating. Understanding the threshold where resistive heating transitions to conductive heating may allow for optimization of parameters to favor resistive heating. Additionally, HPSD lesion application has been associated with a lower risk of complications, including cardiac perforation and atrioesophageal fistulas. To assess lesion formation with variations in RF duration and contact force utilizing a HPSD strategy in an ex vivo model. This study utilized recently harvested swine heart tissue ablated using a contact force sensing irrigation ablation catheter submerged in a saline bath with a target temperature of 36 °C and an impedance of 140 Ω. Step 1 compared various RF durations (1-5, 8, and 10 seconds(s)) with 50 Watts (W) and an average of 10g of force applied to the epicardial surface of the left ventricle. Six lesions were applied for each time duration. For step two of the procedure, we assessed the impact of contact force (1g, 5g, 10g, 20g) on lesion size and depth using 50 W and 5s RF duration. Five lesions were applied for each amount of contact force. The tissue was stained in a 2,3,5-Triphenyltetrazolium chloride bath prior to measurements. Of the 42 lesions created utilizing HPSD with variable durations of RF duration, application of >3s resulted in the creation of visual lesions within the tissue. There was an increase in lesion volume with longer duration ablation application (50W/10g), with 5, 8 and 10s durations generating lesion volumes of 16.8mm3, 26.8mm3 and 40.6mm3, respectively. All 20 lesion applications with varying degrees of contact force (50W/5s) resulted in visual lesions. There was an increase in lesion volume with higher contact force plateauing at 10 g, compared to 20g (28.9mm3 vs 31.9mm3, respectively). In an animal model, a HPSD ablation strategy focused on short duration lesion application with lower contact forces (50W/5s/10g) created lesions of similar volume to 20g of force application. In the initial 10s of lesion formation, a force >10g may have a lesser role and may potentially represent a transition point between resistive and conductive heating.

PO-04-230 IMPROVED VISUALIZATION OF LOW AMPLITUDE LATE POTENTIALS WITH VT SUBSTRATE MAPPING USING A NOVEL EP RECORDING SYSTEM

Accurate identification of low-voltage electrograms (EGMs) suffer from artifacts that often interfere with physiological signals in the <0.1-0.5mV range. For substrate based ablation of ventricular tachycardia (VT), dense scar is defined as regions of myocardium with EGM amplitudes below 0.5 mV. Within these regions, current EP recording systems can fail at identifying low-voltage late potentials that are effective targets of ablation therapy. More recently, new EP amplifiers designed specifically to reduce the impact of interference on the fidelity of signals have been introduced. This study used a novel EP recording system (ECGenius System, CathVision, Copenhagen, DK) to identify low amplitude (<0.5mV) late potentials in regions of scar, and quantify their characteristics in a head-head comparison to a standard recording system (LabSystem Pro, Boston Scientific, MA). We collected recordings in parallel from four patients (30-250 Hz bipolar recording bandwidth) referred to our center for an EP study and ablation for VT. We performed substrate mapping during sinus rhythm with a standard 4mm irrigated ablation catheter (SmartTouch, Biosense Webster, Diamond Bar, CA) and a multi-spline mapping catheter (PentaRay, Biosense Webster). In regions of dense scar (< 0.5 mV, delineated with 3-D electroanatomical mapping) we identified late potentials that were above the baseline noise level of the CathVision system that were otherwise not clearly visible with the LabSystem Pro system. In four patients we identified fourteen sites with late potentials (110 beats) that were only identified with the CathVision System (see figure). The average amplitude of the late signals was 0.079 +/- 0.063 mV, which was above the baseline mean noise of 0.008 mV (range 0.006 to 0.015 mV). In contrast, the baseline mean noise of the LabSystem Pro was 0.060 mV (range 0.040 to 0.090 mV). The mean delay of the late potentials (after the start of the surface ECG QRS) was 377ms (range 198 to 470ms). Improved visualization of low voltage EGMs and late potentials can improve upon substrate-based ablation of ischemic VT. With a novel, and state-of-the art recording amplifier, we demonstrate an improved ability to detect clinically relevant sites for ablation that were not visible with a standard recording system. This technology could improve upon current ablation strategies, and may be particularly useful in the current era of micro-electrodes and relatively smaller recording voltages.

Novel use of an irrigated ablation catheter to monitor real-time hemodynamics during ablation.

Hemodynamic decompensation during catheter ablation occurs due to prolonged procedure time and irrigant delivery directly into the cardiac chambers. Real-time hemodynamic monitoring of patients undergoing catheter ablation procedures may identify patients at risk of decompensation; we set out to assess the feasibility of a novel, real-time, intracardiac pressure monitoring system using a standard irrigated ablation catheter. We studied 13 consecutive who underwent pressure measurement of the left atrium (LA) and left ventricle (LV) via transeptal access with a Swan Ganz (SG) catheter followed by two commercially available irrigated ablation catheters. Pressure waveform data was extracted to compare LA peak pressure, LV peak systolic pressure, LV end-diastolic pressure, and waveform analysis. Comparison between the SG and ablation catheters (AblA; AblB) demonstrated that LV systolic pressure (0.61-16.8 mmHg; 1.32-18.2 mmHg), and LV end-diastolic pressure (-3.4 to 2.8 mmHg; -3.0 to 3.35 mmHg) were well correlated and had accepted repeatability. Ablation waveforms demonstrated an 89.9 ± 6.4% correlation compared to SG waveforms. Pressure measurements derived from an irrigated ablation catheter are accurate and reliable when compared to an SG catheter. Further studies are needed to determine how real-time pressure monitoring can improve outcomes during ablation procedures.

First clinical experience using the DiamondTemp catheter and a novel omnipolar high-resolution mapping system for atrial fibrillation ablation.

The DiamondTemp (DT) radiofrequency ablation (RFA) catheter has been introduced as a new tool for atrial fibrillation (AF) ablation. The new technology allows for temperature-controlled irrigated ablation and real-time lesion assessment. Recently, the EnSite X mapping system became commercially available allowing for omnipolar and ultra-high-resolution mapping. We aimed to assess the feasibility of the new DT RFA catheter in performing AF ablation procedures in conjunction with the novel EnSite X system under routine clinical conditions. We analyzed data from 10 consecutive patients who underwent AF ablation using the DT RFA catheter guided by EnSite X. Procedural data and short-term follow-up were assessed as well as potential technical issues. Nine out of 10 patients underwent de-novo pulmonary vein isolation (PVI), and 1 patient underwent repeat ablation. First-pass isolation was observed in 7/10 patients. Total procedure duration (skin-to-skin) was 88.9 ± 30.1 min, and left atrium dwell time was 70 ± 22.3 min. The mean number of RF applications needed for PVI and additional ablation was 70.52 ± 26.70. The HD Grid SE mapping catheter was utilized in 8 patients and the Advisor SE in 2 patients. Bidirectional block of the applied lines was achieved in all patients. No steam pops were observed, and no intraprocedural complications occurred. This first clinical series demonstrated that temperature-controlled irrigated ablation in combination with the novel omnipolar and high-resolution mapping system resulted in rapid, efficient, and durable lesion formation under routine clinical conditions. Randomized controlled trials are needed to elucidate the impact on lesion formation, long-term outcomes, and reproducibility of our initial findings.

In Silico Modelling to Assess the Electrical and Thermal Disturbance Provoked by a Metal Intracoronary Stent during Epicardial Pulsed Electric Field Ablation.

Background: Pulsed Electric Field (PEF) ablation has been recently proposed to ablate cardiac ganglionic plexi (GP) aimed to treat atrial fibrillation. The effect of metal intracoronary stents in the vicinity of the ablation electrode has not been yet assessed. Methods: A 2D numerical model was developed accounting for the different tissues involved in PEF ablation with an irrigated ablation device. A coronary artery (with and without a metal intracoronary stent) was considered near the ablation source (0.25 and 1 mm separation). The 1000 V/cm threshold was used to estimate the ‘PEF-zone’. Results: The presence of the coronary artery (with or without stent) distorts the E-field distribution, creating hot spots (higher E-field values) in the front and rear of the artery, and cold spots (lower E-field values) on the sides of the artery. The value of the E-field inside the coronary artery is very low (~200 V/cm), and almost zero with a metal stent. Despite this distortion, the PEF-zone contour is almost identical with and without artery/stent, remaining almost completely confined within the fat layer in any case. The mentioned hot spots of E-field translate into a moderate temperature increase (<48 °C) in the area between the artery and electrode. These thermal side effects are similar for pulse intervals of 10 and 100 μs. Conclusions: The presence of a metal intracoronary stent near the ablation device during PEF ablation simply ‘amplifies’ the E-field distortion already caused by the presence of the vessel. This distortion may involve moderate heating (<48 °C) in the tissue between the artery and ablation electrode without associated thermal damage.

Abstract 12331: Prospective Evaluation of Risks Ventricular Arrhythmia Ablation With Half Normal Saline Irrigation

Background: Failure of radiofrequency ablation (RFA) of ventricular arrhythmias (VA) is often due to inadequate lesion size. RFA with half-normal saline (HNS) irrigation has the potential to increase lesion size, but can increase steam pops, which could increase risks of perforation and emboli. Optimal energy titration is not defined. Objective: To assess peri-procedural complications of ventricular arrhythmia (VA) ablation with HNS RFA guided by impedance monitoring and intracardiac ultrasound (ICE). Methods: All patients undergoing endocardial RFA only for VA from October 2018 to September 2021 were prospectively assessed for complications in hospital and at 30 days by clinic visit or phone call. Of 862 procedures 616 patients undergoing 663 endocardial RFA were included. HNS or normal saline (NS) RF irrigation and were selected at the discretion of the physician. RFA power was titrated to a &lt; 15 Ohm impedance fall with intracardiac ultrasound monitoring for tissue whitening and increasing bubble formation in most cases. Results: Of 663 procedures HNS was used in 552 (83%) and NS in 111 (17%). The HNS group was older, with more heart disease, ventricular tachycardia, LV ablation sites, and RFA time. There were 59 complications (8.9%) in 53 procedures, including 11 pericardial effusions (1.6%) (2 requiring surgical repair), and 2 strokes (0.3%). There was no significant difference between HNS and HS in complications or mortality (table). Conclusion: HNS irrigation ablation with power guided by impedance fall and ICE is associated with a low incidence of serious complications. A small difference can not be excluded, but would require a very large trial and seems unlikely to be clinically relevant.

Comparison of traditional radiofrequency ablation and high-power short-duration ablation in the treatment of atrial tachyarrhythmias

Atrial tachyarrhythmias are becoming more common in the population. The prevalence increases with age. Often, these arrhythmias lead to disability and reduced life expectancy (indirectly through strokes). Drug therapy of atrial tachyarrhythmias reduces symptoms but does not completely resolve issue of treatment. In this regard, surgical treatment (catheter ablation) is preferable. One of the methods of catheter ablation is ablation using radio frequency energy. The key parameters of radiofrequency catheter ablation are the energy delivered to the endocardium and the time of this energy delivery. According to the traditional method, it is customary to use energy of 30 Watts for 30 s at one point. This technique has a disadvantage – in 30 s the electrode can be displaced, and the application of energy has to be repeated. A new strategy was proposed – reducing the application time by increasing the energy to respond to the challenge of high probability of electrode displacement. The aim of this work was to determine the effectiveness of the рhigh-power short-duration protocol. Materials and methods. To carry out this work, we analyzed the surgical treatment of atrial fibrillation with the help of radiofrequency catheter ablation – isolation of the pulmonary veins. In patient group 1, ablation was performed using an irrigated ablation electrode with an energy of 30 Watts and an application time of 30 s, in group 2 – using the irrigated electrode with the energy of 70 Watts and the application time of 5 s. Ablations were performed under the control of radiography and electroanatomical mapping system. Full electrical isolation of the four pulmonary veins with confirmation of the entrance and exit block were considered as the criteria of efficiency. Results. When comparing the groups by the number of required application cycles during the procedure needed to achieve the clinical effect and time to the first recurrence in all positions of the electrode, group 2 showed a lower number of applications and shorter time to the first recurrence. Reducing the time to pulmonary vein isolation, the number of relapses and restarting the control time, as well as shortening the time spent on the need to rebuild the electroanatomical map have resulted in a significant decrease in the duration of the radiofrequency ablation procedure. Conclusions. The work has shown that the use of the new protocol is more effective and allows to achieve the criteria of success faster than the traditional technique; the number of the procedure complications was not higher compared to traditional methods. When using the ablation protocol with higher energy, a lower incidence of atrial fibrillation recurrence was recorded.

PO-682-05 USE OF DRY SUCTION WATER SEAL DRAINAGE FOR PERICARDIAL FLUID MANAGEMENT DURING EPICARDIAL VT ABLATION

Epicardial ablation is less common but often critical approach for suppression of ventricular arrhythmias (VA), particularly in patients with arrhythmogenic cardiomyopathies. The use of irrigated ablation catheters in this space requires manual aspiration of fluid to prevent tamponade, creating frequent interruptions that prolong procedure time.

Radiofrequency ablation using a novel insulated-tip ablation catheter can create uniform lesions comparable in size toconventional irrigated ablation catheters while using a fraction of the energy and irrigation.

IntroductionDuring radiofrequency ablation (RFA) using conventional RFA catheters (RFC), ~90% of the energy dissipates into the bloodstream/surrounding tissue. We hypothesized that a novel insulated‐tip ablation catheter (SMT) capable of blocking the radiofrequency path may focus most of the energy into the targeted tissue while utilizing reduced power and irrigation.MethodsThis study evaluated the outcomes of RFA using SMT versus an RFC in silico, ex vivo, and in vivo. Radiofrequency applications were delivered over porcine myocardium (ex vivo) and porcine thigh muscle preparations superfused with heparinized blood (in vivo). Altogether, 274 radiofrequency applications were delivered using SMT (4–15 W, 2 or 20 ml/min) and 74 applications using RFC (30 W, 30 ml/min).ResultsRFA using SMT proved capable of directing 66.8% of the radiofrequency energy into the targeted tissue. Accordingly, low power–low irrigation RFA using SMT (8–12 W, 2 ml/min) yielded lesion sizes comparable with RFC, whereas high power–high irrigation (15 W, 20 ml/min) RFA with SMT yielded lesions larger than RFC (p < .05). Although SMT was associated with greater impedance drops ex vivo and in vivo, ablation using RFC was associated with increased charring/steam pop/tissue cavitation (p < .05). Lastly, lesions created with SMT were more homogeneous than RFC (p < .001).ConclusionLow power–low irrigation (8–12 W, 2 ml/min) RFA using the novel SMT ablation catheter can create more uniform, but comparable‐sized lesions as RFC with reduced charring/steam pop/tissue cavitation. High power–high irrigation (15 W, 20 ml/min) RFA with SMT yields lesions larger than RFC.

Perpendicular catheter orientation during papillary muscle ablation results in larger, deeper lesions.

Ablation of papillary muscles (PMs) for refractory ventricular arrhythmias can often be challenging. The catheter approach and orientation during ablation may affect optimal radiofrequency (RF) delivery. Yet, no previous study investigated the association between catheter orientation and PM lesion size. We evaluated ablation lesion characteristics with various catheter orientations relative to the PM tissue during open irrigated ablation, using a standardized, experimental setting. Viable bovine PM was positioned on a load cell in a circulating saline bath. RF ablation was performed over PM tissue at 50 W, with the open irrigated catheter positioned either perpendicular or parallel to the PM surface. Applied force was 10 g. Ablation lesions were sectioned and underwent quantitative morphometric analysis. A catheter position oriented directly perpendicular to the PM tissue resulted in the largest ablation lesion volumes and depths compared with ablation with the catheter parallel to PM tissue (75.26 ± 8.40 mm3 vs. 34.04 ± 2.91 mm3 , p < .001) and (3.33 ± 0.18 mm vs. 2.24 ± 0.10 mm, p < .001), respectively. There were no significant differences in initial impedance, peak voltage, peak current, or overall decrease in impedance among groups. Parallel catheter orientation resulted in higher peak temperature (41.33 ± 0.28°C vs. 40.28 ± 0.24°C, p = .003), yet, there were no steam pops in either group. For PM ablation, catheter orientation perpendicular to the PM tissue achieves more effective and larger ablation lesions, with greater lesion depth. This may have implications for the chosen ventricular access approach, the type of catheter used, consideration for remote navigation, and steerable sheaths.

High-sensitivity cardiac troponin and C-reactive protein dynamics after cardiac electrophysiological procedures

The catheter ablation of cardiac arrhythmias causes myocardial destruction and increase of the cardiac troponin and C-reactive protein (CRP). Data regarding dynamics of high-sensitivity troponin during irrigated ablation are scarce, and for diagnostic electrophysiological studies (EPS) are lacking. We aimed to study the periprocedural dynamics of high-sensitivity cardiac troponin I (hscTn I) and CRP, as well as their relation to different procedural parameters during EPS and ablation of various arrhythmias. Material and methods: Consecutive patients with EPS or ablation performed were studied prospectively. Clinical and procedural characteristics, and pre- and postprocedural values of hscTn I and CRP are presented at days 1, 2 and 3. Six indices were chosen as procedural markers of induced myocardial injury. P-value &amp;#60; 0.05 was accepted as statistically signifi cant for all tests performed. Results: Eight EPS and 98 ablations were performed in 103 patients (58 males, 56.3%). For ablations the baseline values of hscTn I at day 1 were 3.2 ng/L (1.7-4.93), while postprocedural values at days 2 and 3 were 500 ng/L (269-1044) and 404 ng/L (179-1017), р &amp;#60; 0.05 for all days. Postprocedural hscTn I values were moderately to strongly correlated to radiofrequency (RF) energy, time and number of RF applications. Postprocedural increase of CRP was also significant, but its magnitude was much smaller. Its correlation to procedural indices was weak. For EPS the baseline values of hscTn I were 5.95 ± 5.34 ng/L (0.6-15.9), while for the next 2 days these were 53.2 ± 43.1 ng/L (13.3-144) и 16.7 ± 9.65 ng/L (3.3-30.9), р &amp;#60; 0.05 for all days. Conclusion: Signifi cant postprocedural increase of hscTn I was detected in all electrophysiology procedures – EPS and ablations. This increase was more pronounced and prolonged to at least the next day after ablation. It was clearly correlated to the cumulative RF energy, RF time and number of RF applications. Early increase of CRP was also signifi cant, but to a lesser magnitude and in weak correlation to the procedural parameters.

Impedance fluctuation and steam pop occurrence during radiofrequency current ablation: An experimental in vitro model.

The radiofrequency impedance measurement is one of the basic parameters monitored during ablation procedures. An abrupt rise in impedance is often observed corresponding to a steam pop. The exact correlation between the occurrence of steam pop and subsequent rise in impedance has not been experimentally described so far. To evaluate the relationship between steam pop occurrence and impedance fluctuations observed during radiofrequency ablation (RFA). Porcine heart tissue specimens were appropriately prepared and placed in an experimental setup connected to electrophysiological equipment with 3D anatomical mapping facilities. The RFA lesions were performed in standardized conditions with the use of contact force measurement-enabled open irrigation ablation catheter (ThermoCool SmartTouch™, 3.5 mm tip, F-J curvature; Biosense Webster, Irvine, USA) in the power-control mode. The RFA delivery was stopped when the steam pop occurred. Time taken for the steam pop to occur and to the subsequent abrupt impedance rise was recorded, along with the impedance fluctuations during an application. In total, 25 experimental radiofrequency (RF) current deliveries ended up with steam pops, which occurred after 30-60 s. The time recorded from the beginning of the application up to the steam pop was shorter if increased power was applied (35 W compared to 30 W: 41.5 ±9.9 s compared to 49.9 ±8.2 s; p = 0.046). During all RF applications, impedance significantly but gradually decreased from 122.9 ±7.9 Ω to 87.5 ±3.6 Ω (p < 0.001) with a mean drop rate of 0.8 ±0.2 Ω/s. During all experiments, the abrupt and significant impedance increase (8.2 ±2.0 Ω, p < 0.001) was observed always after steam pop occurrence (207.4 ±155.9 ms). During RF current delivery which ended up with steam pop, an abrupt impedance increase was always registered after the occurrence of this phenomenon. Therefore, the impedance rise observed during steam popping cannot be used for its prediction. The time to steam pop was shorter for applications with increased power but not with greater contact force.