Cardiac Radiofrequency Ablation Research Articles

Review of methods for detecting electrode-tissue contact status during atrial fibrillation ablation

Atrial fibrillation is a common cardiac arrhythmia with an annually increasing global prevalence. Ablation of atrial fibrillation is a minimally invasive procedure that treats atrial fibrillation by using a catheter to deliver radiofrequency energy to heart tissues generating abnormal electrical potentials. The success of this procedure relies significantly on the adhesion between the catheter and the heart tissue, presenting a challenge in accurately assessing the contact force (CF) during surgery. To improve the safety and success rate of surgery, researchers are committed to developing various methods to evaluate or detect catheter-tissue CF. Among these, some studies integrated optical fibers or magnetic elements into the catheter tip to create CF sensing catheters that monitor CF in real time; other studies used impedance measurement, electrical coupling index, local impedance and other methods to evaluate the CF between the catheter and the tissue by measuring changes in electrical signals. These methods have achieved certain success in clinical practice, offering new ways to improve the effectiveness and safety of cardiac radiofrequency ablation surgery.

Signaling Pathways (TNF-α-NF-κB, TLR2-TLR4 as well as ROS-MDA) and Cardiac Damages during Cardiac Surgeries (Coronary stenting, Permanent Pacemaker Implantations, Radiofrequency Ablations).

The mutual activations of multiple signaling pathways are the key factors in the development and progression of myocardial cell injuries. This research aimed to compare the different degrees of myocardial injury after coronary stenting, permanent pacemaker implantations, or cardiac radiofrequency ablation and to investigate the effects of the mutual activation of TNF-α/NF-κB, TLR2/TLR4, and ROS/MDA signaling pathways on myocardial injury in elderly patients after coronary stents or permanent pacemakers or radiofrequency ablation. We determined reactive oxygen species (ROS), malondialdehyde (MDA), toll-like receptor 2 (TLR2), toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB), tumor necrosis factor- α (TNF-α) and high-sensitive cardiac troponin T (hs-cTnT) as a marker of myocardial injury in patients. The levels of ROS, MDA, TLR2, TLR4, NF-κB, TNF-α, and hs-cTnT were increased in patients with permanent pacemaker implantations when compared to patients with cardiac radiofrequency ablation (P < 0.01) at 6 months and were further increased in patients with coronary stenting compared to patients with cardiac radiofrequency ablation and permanent pacemaker implantations at 6 months, respectively (P < 0.01). This research confirmed that ROS, MDA, TLR2, TLR4, NF-κB, and TNF-α predicted myocardial injury severity. Oxidative stress (ROS/MDA signaling pathway) may be linked to immune response (TLR2/TLR4 signaling pathway) and pro-inflammatory response (TNF-α/NF-κB signaling pathway) in myocardial injury, and ROS/MDA signaling may play a dominant role.

In vivo assessment of cardiac radiofrequency ablation in a large-animal model using photoacoustic-ultrasound imaging.

One of the fundamental unmet clinical needs within cardiac electrophysiology is intraoperative assessment of catheter ablation, which can lead to recurrent arrhythmias and subsequent complications if ineffective. This work demonstrates photoacoustic imaging (PAI) of radiofrequency ablation (RFA) lesions in an in vivo swine model (n=3). Spectral unmixing of PAI data provides local myocardial characterization (e.g., oxygen saturation & tissue ablation) by overlaying unmixed PAI images with B-mode ultrasound imaging (PAI/US), with the latter providing anatomical context. Based on stained gross pathology, areas of central tissue necrosis coincided with increases in unmixed ablated regions of the myocardium. An average contrast-to-noise ratio of 2.8±0.2 confirmed lesion detectability, while the lesion dimensions quantified from PAI and pathology did not present significant differences. In vivo PAI of RFA lesions to determine ablation characteristics could lead to a paradigm shift in catheter ablation assessment and improve clinical outcomes.

One-year freedom from arrhythmia following radiofrequency ablation using proactive oesophageal cooling

Abstract Background Proactive esophageal cooling is increasingly being utilized, and is now FDA cleared, to reduce the likelihood of ablation-related esophageal injury resulting from radiofrequency (RF) cardiac ablation of atrial fibrillation (AF). One-year follow-up from the largest randomized controlled study, the IMPACT trial, showed a trend towards improvement in long-term efficacy versus luminal esophageal temperature (LET) monitoring. With larger data sets now available for analysis, we sought to determine 1-year freedom from atrial arrhythmia associated with the use of proactive esophageal cooling. Methods Data from 2 trials comparing freedom from atrial arrhythmia after RF ablation using proactive esophageal cooling to LET monitoring were combined. Data were analyzed using a stratified Cox proportional hazards model to compare arrhythmia recurrence rates, with R statistical analysis software. Results Data from 631 patients across two studies comparing arrhythmia outcomes for proactive oesophageal cooling versus LET monitoring were analysed. Mean patient age was 66.4±9.8 years, and 37.4% were female. Arrhythmias were 56.3% paroxysmal AF and 43.7% persistent or long-standing persistent AF. Freedom from atrial arrhythmia at one year was 77.2% for patients receiving proactive oesophageal cooling and 64.4% for patients receiving LET monitoring (Figure 1), with a hazard ratio for cooling of 0.65 (95% CI 0.43 to 0.99, P = 0.044). Conclusions Proactive oesophageal cooling was associated with significantly greater freedom from atrial arrhythmia at one year when compared to LET monitoring during RF ablation.

Acute and one-year procedural effects with proactive esophageal cooling during radiofrequency ablation with proactive esophageal cooling - comparison of paroxysmal and persistent atrial fibrillation

Abstract Background/Introduction Proactive esophageal cooling is FDA cleared to reduce the likelihood of ablation-related esophageal injury from radiofrequency (RF) cardiac ablation, and is becoming more prevalent as an alternative to luminal esophageal temperature (LET) monitoring. Data also suggest shorter procedure times and improved freedom from arrhythmia with esophageal cooling due to the lower continuity index achieved with esophageal cooling. Purpose To determine acute and long-term procedural outcomes of PVI for paroxysmal and persistent atrial fibrillation (AF) using active esophageal cooling. Methods Procedure times and one-year follow-up rhythm status of all patients treated with PVI for paroxysmal and persistent AF by a single operator were reviewed. Patients were treated over the time span February 2020 through July 2022. Procedure times and freedom from atrial arrhythmia were then compared between paroxysmal and persistent AF. Results A total of 317 patients with paroxysmal or persistent atrial fibrillation were treated over the course of the study timeframe. Of these patients, 167 (52.7%) had paroxysmal atrial fibrillation, and 150 had persistent AF. Mean age was 70.6±11.0 years (paroxysmal AF: 68.2±10.4 years and 43% female, persistent AF: 73.4±11.0 years and 37% female), with 40% female overall. Mean procedure time was 68.8±28.1 minutes (61.4 minutes for paroxysmal, 77.3 minutes for persistent). Most patients (224, or 71%) received no fluoroscopy, while the remainder received 1.28±4.0 minutes of fluoroscopy use. The KM estimate for freedom from atrial arrhythmia at one-year for paroxysmal patients was 81.4±3.9%. For persistent patients, the KM estimate for freedom from atrial arrhythmia at one-year was 70.4±4.4% (Figure 1). Conclusions Proactive esophageal cooling is associated with a high rate of long-term freedom from arrhythmia for both paroxysmal and persistent AF patients, as well as short procedure times, and the ability to achieve low or zero fluoroscopy use.Figure 1

Determination of Continuity Index Values in Atrial Fibrillation Ablation with Proactive Esophageal Cooling.

Radiofrequency (RF) ablation to perform pulmonary vein isolation (PVI) for the treatment of atrial fibrillation involves some risk to collateral structures, including the esophagus. Proactive esophageal cooling using a dedicated device has been granted marketing authorization by the Food and Drug Administration (FDA) to reduce the risk of ablation-related esophageal injury due to RF cardiac ablation procedures, and more recent data also suggest that esophageal cooling may contribute to improved long-term efficacy of treatment. A mechanistic underpinning explaining these findings exists through the quantification of lesion placement contiguity defined as the Continuity Index (CI). Kautzner et al. quantified the CI by the order of lesion placement, such that whenever a lesion is placed non-adjacent to the prior lesion, the CI is incremented by the number of segments the catheter tip has moved over. To facilitate real-time calculation of the CI and encourage further adoption of this instrument, we propose a modification in which the placement of non-adjacent lesions increments the CI by only one unit, avoiding the need to count potentially nebulous markers of atrial segmentation. The objective of this protocol is to describe the methods of calculating the CI both prospectively during real-time PVI cases and retrospectively using recorded case data. A comparison of the results obtained between cases that utilized proactive esophageal cooling and cases that used luminal esophageal temperature (LET) monitoring is then provided.

Association between proactive esophageal cooling and increased lab throughput.

Proactive esophageal cooling has been FDA cleared to reduce the likelihood of ablation-related esophageal injury resulting from radiofrequency (RF) cardiac ablation procedures. Data suggest that procedure times for RF pulmonary vein isolation (PVI) also decrease when proactive esophageal cooling is employed instead of luminal esophageal temperature (LET) monitoring. Reduced procedure times may allow increased electrophysiology (EP) lab throughput. We aimed to quantify the change in EP lab throughput of PVI cases after the introduction of proactive esophageal cooling. EP lab throughput data were obtained from threeEPgroups. We then compared EP lab throughput over equal time frames at each site before (pre-adoption) and after (post-adoption) the adoption of proactive esophageal cooling. Over the time frame of the study, a total of 2498 PVIs were performed over a combined 74 months, with cooling adopted in September 2021, November 2021, and March 2022 at each respective site. In the pre-adoption time frame, 1026 PVIs were performed using a combination of LET monitoring with the addition of esophageal deviation when deemed necessary by the operator. In the post-adoption time frame, 1472 PVIs were performed using exclusively proactive esophageal cooling, representing a mean 43% increase in throughput (p < .0001), despite the loss of two operators during the post-adoption time frame. Adoption of proactive esophageal cooling during PVI ablation procedures is associated with a significant increase in EP lab throughput, even after a reduction in total number of operating physicians in the post-adoption group.

Cardiac Radiofrequency Ablation Exacerbates Myocardial Injury through Pro-Inflammatory Response and Pro-Oxidative Stress in Elderly Patients with Persistent Atrial Fibrillation.

There is a need to assess myocardial damage after radiofrequency ablation of the pulmonary veins (PV) for persistent atrial fibrillation (PAF) in elderly patients. To evaluate oxidative stress, inflammatory response and myocardial damage in elderly patients with PAF after radiofrequency ablation of the PV. High-sensitivity troponin T (hsTnT), malondialdehyde-modified low-density lipoprotein (MDA-LDL), acrolein (ACR), lipid hydroperoxide (LHP), toll-like receptor 4 (TLR4), soluble growth stimulation expressed gene 2 (sST2), angiotensin II (Ang II) and myocardial blood flow (MBF) were determined before ablation and at 1, 3 and 5 months after radiofrequency ablation. The levels of hsTnT, MDA-LDL, ACR, LHP, TLR4, sST2 and Ang II were increased 3 months after ablations compared with before ablation and 1 month after ablation, respectively (P<0.001); they were further increased at 5 months after ablation compared with the 1- and 3-month groups, respectively (P<0.001). MBF was decreased in the 3 months group after ablations compared with before ablation and 1-month after ablation, respectively (P<0.001), and was further decreased in 5-months after ablations compared with 1-month and 3-month groups, respectively (P<0.001). Patients with epicardial monopolar radiofrequency ablation had higher levels of hsTnT, MDA-LDL, ACR, LHP, TLR4, sST2, Ang II and lower MBF than patients with endocardial monopolar and bipolar radiofrequency ablations, respectively (P<0.001). Monopolar radiofrequency ablation method could result in more myocardial injury than bipolar radiofrequency ablation. Oxidative stress and inflammatory response may be involved in cardiac radiofrequency ablation-induced myocardial injury, resulting in myocardial ischemia in elderly patients with PAF.

Quality of life among patients with supraventricular tachycardia post radiofrequency cardiac ablation in Jordan.

Supraventricular tachycardia (SVT) is a common arrhythmia with associated symptoms such as palpitation, dizziness, and fatigue. It significantly affects patients' quality of life (QoL). Radiofrequency cardiac ablation (RFCA) is a highly effective treatment to eliminate arrhythmia and improve patients' QoL. The purpose of this study was to assess the level of QoL among patients with SVT and examine the difference in QoL before and after RFCA. One group pre-posttest design with a convenience sample of 112 patients was used. QoL was assessed by 36-Item Short Form (SF-36). Data were collected at admission through face-to-face interviews and 1-month post-discharge through phone interviews. There was a significant difference between QoL before (33.7±17.0) and 1 month after (62.5±18.5) the RFCA. Post-RFCA patients diagnosed with atrioventricular nodal reentrant tachycardia had higher QoL than other types of SVT. Moreover, there were significant negative relationships between QoL and the number and duration of episodes pre- and post-RFCA. There were no significant differences in QoL based on: age, sex, working status, marital status, smoking, coronary artery disease, diabetes mellitus, and hypertension. After RFCA, the QoL of patients with ST improved for both physical and mental component subscales.

Tissue poromechanical deformation effects on steam pop likelihood in 3-D radiofrequency cardiac ablation

Radiofrequency Cardiac Ablation (RFCA) is a common procedure that heats cardiac tissue to destroy abnormal signal pathways to eliminate arrhythmias. The complex multiphysics phenomena during this procedure need to be better understood to improve both procedure and device design. A deformable poromechanical model of cardiac tissue was developed that coupled joule heating from the electrode, heat transfer, and blood flow from normal perfusion and thermally driven natural convection, which mimics the real tissue structure more closely and provides more realistic results compared to previous models. The expansion of tissue from temperature rise reduces blood velocity, leading to increased tissue temperature, thus affecting steam pop occurrence. Detailed temperature velocity, and thermal expansion of the tissue provided a comprehensive picture of the process. Poromechanical expansion of the tissue from temperature rise reduces blood velocity, increasing tissue temperature. Tissue properties influence temperatures, with lower porosity increasing the temperatures slightly, due to lower velocities. Deeper electrode insertion raises temperature due to increased current flow. The results demonstrate that a 5% increase in porosity leads to a considerable 10% increase in maximum tissue temperature. These insights should greatly help in avoiding undesirable heating effects that can lead to steam pop and in designing improved electrodes.

A Case of Cardioneuroablation Treating Ictal Bradyarrhythmia and Expanding Seizure Therapy Options (P12-1.005)

<h3>Objective:</h3> By attenuating the vagal inputs to the heart, cardioneuroablation can expand therapy options in seizure management, particularly where cardiac inhibition is of concern. <h3>Background:</h3> Radiofrequency cardiac ablation, well-established since the 1990’s, is routinely used to treat various tachyarrhythmias. Cardioneuroablation (CNA), which uses the same technology, can be used to treat disorders mediated by high vagal tone, such as cardioinhibitory syncope. We present a case where this modality was used to expand therapy options in a patient with ictal bradycardia and atrioventricular block. The patient is a 12-year-old female with a history of focal seizures since infancy who presented to the Epilepsy Monitoring Unit for increasing seizure burden despite escalation of anti-seizure medications. She was therefore being considered for vagal nerve stimulator (VNS) therapy, known to sometimes result in the implantation of cardiac pacemakers due to profound bradycardia and asystole. During seizures, bedside monitoring showed multiple runs of ictal heart block (ventricular rates in the 20’s) and two episodes of high-grade block, resulting in 7–10 seconds of asystole. To attenuate her cardiac vagal response and allow for more therapy options, she underwent cardioneuroablation therapy. During the procedure, she had easily induced asystole, greater than 10 seconds, with vagal stimulation. Two areas of vagal input to the heart were successfully ablated. Post ablation, vagal stimulation resulted in only mild sinus slowing (90 bpm down to 80 bpm). The longest inducible pause was one second. She was observed overnight in the epilepsy unit and discharged home the following day. VNS therapy could now be considered in her with less concern for profound bradycardia and cardiac asystole from such therapy. <h3>Design/Methods:</h3> NA <h3>Results:</h3> NA <h3>Conclusions:</h3> Cardioneuroablation is currently primary used to treat difficult to manage cardio-inhibitory syncope. It can be used to treat ictal bradyarrhythmias and expand seizure management options. <b>Disclosure:</b> Dr. Manu has nothing to disclose. Dr. Nwankwo has nothing to disclose. Dr. Clark has nothing to disclose.

Disturbing Effect of Intra-Tissue Temperature Sensors in Pre-Clinical Experimental Studies of Radiofrequency Cardiac Ablation: A Computer-Based Modeling Study

Background: Preclinical studies on radiofrequency (RF) cardiac ablation (RFCA) use very small temperature sensors in specific positions in the tissue subjected to RF heating. Despite the sensors’ small size, the proximity to the ablation electrode and the extremely high thermal gradient around the electrode means that the presence of the temperature sensors could distort the temperatures recorded. Our objective was to assess the thermal impact of intra-tissue temperature sensors during RFCA. Methods: 3D RFCA models were built including different temperature sensors based on fiber optics and T-type thermocouples. Constant power ablation was simulated for 10 s. Results: The results showed that the disturbance caused by the presence of the T-type thermocouples was considerably greater (one order of magnitude) than that caused by the optical fibers. The closer the sensor was to the ablation electrode, the greater the greater the disturbance was and the more it increased with time in sensors more than 3 mm deep. The fiber optic measurements always slightly underestimated (&lt;0.2 °C) the tissue temperature that would exist without the sensors, while the disturbance caused by the T-type thermocouples did not always result in underestimation but depended on the depth of the sensors parallel to the catheter. Conclusions: The presence of thermocouples inserted into the tissue close to the RF ablation electrode involves a disturbance that could affect the measured temperature value, although it does not substantially alter the shape and size of the thermal lesion. Optical fibers cause much less disturbance, possibly due to the absence of internal metal parts that favor heat conduction.

Automated analysis framework for in vivo cardiac ablation therapy monitoring with optical coherence tomography.

Radiofrequency ablation (RFA) is a minimally invasive procedure that is commonly used for the treatment of atrial fibrillation. However, it is associated with a significant risk of arrhythmia recurrence and complications owing to the lack of direct visualization of cardiac substrates and real-time feedback on ablation lesion transmurality. Within this manuscript, we present an automated deep learning framework for in vivo intracardiac optical coherence tomography (OCT) analysis of swine left atria. Our model can accurately identify cardiac substrates, monitor catheter-tissue contact stability, and assess lesion transmurality on both OCT intensity and polarization-sensitive OCT data. To the best of our knowledge, we have developed the first automatic framework for in vivo cardiac OCT analysis, which holds promise for real-time monitoring and guidance of cardiac RFA therapy..

Effects of Pulsed Radiofrequency Source on Cardiac Ablation.

Heart arrhythmia is caused by abnormal electrical conduction through the myocardium, which in some cases, can be treated with heat. One of the challenges is to reduce temperature peaks-by still guaranteeing an efficient treatment where desired-to avoid any healthy tissue damage or any electrical issues within the device employed. A solution might be employing pulsed heat, in which thermal dose is given to the tissue with a variation in time. In this work, pulsed heat is used to modulate induced temperature fields during radiofrequency cardiac ablation. A three-dimensional model of the myocardium, catheter and blood flow is developed. Porous media, heat conduction and Navier-Stokes equations are, respectively, employed for each of the investigated domains. For the electric field, solved via Laplace equation, it is assumed that the electrode is at a fixed voltage. Pulsed heating effects are considered with a cosine time-variable pulsed function for the fixed voltage by constraining the product between this variable and time. Different dimensionless frequencies are considered and applied for different blood flow velocity and sustained voltages. Results are presented for different pulsed conditions to establish if a reasonable ablation zone, known from the obtained temperature profiles, can be obtained without any undesired temperature peaks.

Natural convection effects on heat transfer in a porous tissue in 3-D radiofrequency cardiac ablation

Radiofrequency Cardiac Ablation (RFCA) is a non-surgical procedure to destroy abnormal pathways causing cardiac arrhythmias within the cardiac chamber. RF energy from electrodes contacting the cardiac tissue generates heat, raising tissue temperature and ablating it. Success of the procedure, as in avoiding complications like steam pops, requires its comprehensive mechanistic understanding. Using a 3-D porous media-based model of the cardiac tissue and surrounding chamber blood, with coupled fluid flow, heat transfer (including evaporation and thermally driven natural convection), and resistive heating, provided a more complete picture of the thermal ablation process. Circulation of blood due to buoyancy-driven natural convection reduces the non-uniformity of temperatures, by reducing temperatures initially in the target region but increasing them in the later stages, compared to when natural convection effects are not included. Thus, natural convection affects possible steam pop occurrence differently over the time for the procedure. The more complete picture of the RFCA procedure provided here by the detailed physics-based model can benefit with increased accuracy and thus reduced re-ablation (thus higher success rates), and reduced costs for catheter design and development.

Canine model of electrical conduction recurrence after radiofrequency catheter ablation constructed by CARTO3 and preliminary application evaluation of DOX-L.

Radiofrequency catheter ablation (RFCA) is widely used to treat arrhythmias. However, for atrial fibrillation, the recurrence rate after RFCA is still high. The development of an animal model that mimics the recurrence of electrical conduction after ablation is essential before we can explore the mechanisms involved or develop new therapeutic strategies. Eighteen beagles aged 12 to 24months were randomly assigned to this study. RFCA ablation of the right atrial free wall was performed. Then, electrical block and conduction recovery in the ablation area were evaluated using voltage mapping and pacing tests assisted by CARTO3 system. Finally, liposome doxorubicin (DOX-L) was intravenously injected after ablation to investigate the effect of DOX-L on this animal model. The conduction block (CB) rates at 5min after ablation were 16.7%, 83.3%, and 100%, corresponding to 30w, 35w, and 40w power, respectively. However, after 20min, the rate of CB was 0%, 33.3%, and 75%; thus, the combined success rate of CB and conduction recurrence was 16.7%, 50%, and 25%, respectively. The optimal ablation parameter is 35W for 20s, based on the CB rate, REC rate. After 10days of ablation, the residual conduction recurrence rate was as high as 83.3% in the RFCA alone group, whereas there was no recurrence with RFCA combined with DOX-L treatment. The novel model accurately simulated the electrical conduction recurrence after cardiac radiofrequency ablation. RFCA combined with DOX-L treatment dramatically reduces the recurrence rate of electrical conduction after ablation.

Impact of electrode tip shape on catheter performance in cardiac radiofrequency ablation.

The role of catheter tip shape on the safety and efficacy of radiofrequency (RF) ablation has been overlooked, although differences have been observed in clinical and research fields. The purpose of this study was to analyze the role of electrode tip shape in RF ablation using a computational model. We simulated 108 RF ablations through a realistic 3-dimensional computational model considering 2 clinically used, open-irrigated catheters (spherical and cylindrical tip), varying contact force (CF), blood flow, and irrigation. Lesions are defined by the 50°C isotherm contour and evaluated by means of width, depth, depth at maximum width, and volume. Ablations are deemed as safe, critical (tissue temperature >90°C), and pop (tissue temperature >100°C). Tissue-electrode contact is less for the spherical tip at low CF but the relationship is inverted at high CF. At low CF, the cylindrical tip generates deeper and wider lesions and a 4-fold larger volume. With increasing CF, the lesions generated by the spherical tip become comparable to those generated by the cylindrical tip. The 2 tips feature different safety profiles: CF and power are the main determinants of pops for the spherical tip; power is the main factor for the cylindrical tip; and CF has a marginal effect. The cylindrical tip is more prone to pop generation at higher powers. Saline irrigation and blood flow effect do not depend on tip shape. Tip shape determines the performance of ablation catheters and has a major impact on their safety profile. The cylindrical tip shows more predictable behavior in a wide range of CF values.

First-in-man application of Liwen RF™ ablation system in the treatment of drug-resistant hypertrophic obstructive cardiomyopathy.

This study sought to evaluate the clinical applicability of the Liwen Liu RF™ ablation system for percutaneous intramyocardial septal radiofrequency ablation (PIMSRA). Data on new cardiac radiofrequency ablation devices for the treatment of hypertrophic obstructive cardiomyopathy (HOCM) are limited. From July 2019 to July 2020, a total of 68 patients with drug-resistant HOCM, who underwent PIMSRA with the Liwen RF™ ablation system, which has an ablation electrode of stepless adjustable length, were prospectively enrolled. Safety endpoints included, amongst others, the occurrence of pericardial effusion and/or hemorrhage, cardiac arrhythmias, device failure and procedural death. The reduction in left ventricular outflow tract (LVOT) gradients at 12 months follow-up were used as a surrogate marker for device efficacy. All procedures were technically successful. The total energy output time of the system was 75.8 (IQR: 30.0) min, and the average power was 43.61 ± 13.34 watts. No ablation system error occurred. The incidence of pericardial effusion or hemorrhage, transient arrhythmia and resuscitation was 8.8, 39.7, and 1.5% during procedure, respectively. None of the patients died. During 30-day follow-up, there were no complications with the exception of a pericardial effusion in one patient (1.5%). No further complications were reported after 30 days. The patients' resting [baseline: 75 (IQR: 48) vs. 12-months: 12 (IQR: 19) mmHg, p < 0.001] and provoked [baseline: 122 (IQR: 53) vs. 12-months: 41 (IQR: 59) mmHg, p < 0.001] LVOT gradients decreased significantly during follow-up. In this study, we demonstrate the safety and feasibility of the Liwen RF™ ablation system to treat HOCM. The system allows for significant and sustainable LVOT gradient reduction during 12-months of follow-up. Hence, the Liwen RF™ ablation system is a promising new device that has the potential to become an alternative to existing septal reduction concepts in HOCM patients.

Proactive esophageal cooling protects against thermal insults during high-power short-duration radiofrequency cardiac ablation

Background Proactive cooling with a novel cooling device has been shown to reduce endoscopically identified thermal injury during radiofrequency (RF) ablation for the treatment of atrial fibrillation using medium power settings. We aimed to evaluate the effects of proactive cooling during high-power short-duration (HPSD) ablation. Methods A computer model accounting for the left atrium (1.5 mm thickness) and esophagus including the active cooling device was created. We used the Arrhenius equation to estimate the esophageal thermal damage during 50 W/ 10 s and 90 W/ 4 s RF ablations. Results With proactive esophageal cooling in place, temperatures in the esophageal tissue were significantly reduced from control conditions without cooling, and the resulting percentage of damage to the esophageal wall was reduced around 50%, restricting damage to the epi-esophageal region and consequently sparing the remainder of the esophageal tissue, including the mucosal surface. Lesions in the atrial wall remained transmural despite cooling, and maximum width barely changed (<0.8 mm). Conclusions Proactive esophageal cooling significantly reduces temperatures and the resulting fraction of damage in the esophagus during HPSD ablation. These findings offer a mechanistic rationale explaining the high degree of safety encountered to date using proactive esophageal cooling, and further underscore the fact that temperature monitoring is inadequate to avoid thermal damage to the esophagus.

MRI-Guided Cardiac RF Ablation for Comparing MRI Characteristics of Acute Lesions and Associated Electrophysiologic Voltage Reductions.

Radiofrequency (RF) energy delivered to cardiac tissue produces a core ablation lesion with surrounding edema, the latter of which has been implicated in acute procedural failure of Ventricular Tachycardia (VT) ablation and late arrhythmia recurrence. This study sought to investigate the electrophysiological characteristics of acute RF lesions in the left ventricle (LV) visualized with native-contrast Magnetic Resonance Imaging (MRI). An MR-guided electrophysiology system was used to deliver RF ablation in the LV of 8 swine (9 RF lesions in total), then perform MRI and electroanatomic mapping. The permanent RF lesions and transient edema were delineated via native-contrast MRI segmentation of T1-weighted images and T2 maps respectively. Bipolar voltage measurements were matched with image characteristics of pixels adjacent to the catheter tip. Native-contrast MR visualization was verified with 3D late gadolinium enhanced MRI and histology. The T2-derived edema was significantly larger than the T1-derived RF lesion (2.1 ±1.5 mL compared to 0.58 ±0.34 mL; p=0.01). Bipolar voltage was significantly reduced in the presence of RF lesion core (p 0.05) and edema (p 0.05), with similar trends suggesting that both the permanent lesion and transient edema contributed to the region of reduced voltage. While bipolar voltage was significantly decreased where RF lesions are present (p 0.05), voltage did not change significantly with lesion transmurality (p 0.05). Permanent RF lesions and transient edema are distinct in native-contrast MR images, but not differentiable using bipolar voltage. Intraprocedural native-contrast MRI may provide valuable lesion assessment in MR-guided ablation, whose clinical application is now feasible.