Transmural Lesions Research Articles

Revolutionizing Atrial Fibrillation Treatment: The Robotic Convergent Plus Procedure.

Atrial fibrillation (AF) is widely accepted to be the most common sustained arrhythmia, with an increasing incidence over time. This is thought to be due to the aging population across the world. AF occurs when abnormal electrical foci result in disorganization of atrial depolarization, though the exact pathophysiology leading to these abnormal foci is not well understood. A range of interventions exist for AF - pharmacological therapies (anti-arrhythmic or negative chronotropic medications), cardioversion, or ablations to interrupt the abnormal conduction pathways. Ablation may be via a catheter-based approach, via a surgical approach using the "Maze" procedure (Cox-Maze IV), or more recently, via a hybrid approach. This first involves a surgical epicardial ablation, with catheter-based endocardial ablation following a few weeks later to ensure durable transmural lesion sets via the "Convergent" procedure. We describe the use of the Da Vinci Xi™ robotic platform to improve the procedure, allowing continuous and improved visualization of the anatomy without the need for potentially harmful retraction of the atrial appendage or the back of the left atrium, as well as increased precision with our mapping tools and more complete ablation. Here, we highlight the advantages over a non-robotic (subxiphoid) Convergent procedure, while outlining the key operative steps in undertaking the "Robotic Convergent Plus" procedure using the Da Vinci Xi™ robotic surgical system.

Proactive esophageal cooling during laser cardiac ablation: A computer modeling study.

Laser ablation is increasingly used to treat atrial fibrillation (AF). However, atrioesophageal injury remains a potentially serious complication. While proactive esophageal cooling (PEC) reduces esophageal injury during radiofrequency ablation, the effects of PEC during laser ablation have not previously been determined. We aimed to evaluate the protective effects of PEC during laser ablation of AF by means of a theoretical study based on computer modeling. Three-dimensional mathematical models were built for 20 different cases including a fragment of atrial wall (myocardium), epicardial fat (adipose tissue), connective tissue, and esophageal wall. The esophagus was considered with and without PEC. Laser-tissue interaction was modeled using Beer-Lambert's law, Pennes' Bioheat equation was used to compute the resultant heating, and the Arrhenius equation was used to estimate the fraction of tissue damage (FOD), assuming a threshold of 63% to assess induced necrosis. We modeled laser irradiation power of 8.5 W over 20 s. Thermal simulations extended up to 250 s to account for thermal latency. PEC significantly altered the temperature distribution around the cooling device, resulting in lower temperatures (around 22°C less in the esophagus and 9°C in the atrial wall) compared to the case without PEC. This thermal reduction translated into the absence of transmural lesions in the esophagus. The esophagus was thermally damaged only in the cases without PEC and with a distance equal to or shorter than 3.5 mm between the esophagus and endocardium (inner boundary of the atrial wall). Furthermore, PEC demonstrated minimal impact on the lesion created across the atrial wall, either in terms of maximum temperature or FOD. PEC reduces the potential for esophageal injury without degrading the intended cardiac lesions for a variety of different tissue thicknesses. Thermal latency may influence lesion formation during laser ablation and may play a part in any collateral damage.

Durable pulmonary vein isolationwith optimized high-power and very high-power short-duration temperature-controlled ablation: A step-by-step guide.

Through systematic scientific rigor, the CLOSE guided workflow was developed and has been shown to improve pulmonary vein isolation durability. However, this technique was developed at a time when using power-controlled ablation catheters with conventional power ranges was the norm. There has been increased adoption of a high-power and very high-power short-duration ablation practice propelled by the availability of the temperature-controlled radiofrequency QDOT MICRO catheter. There are fundamental differences in biophysics between very high-powered temperature guided ablation and conventional ablation strategy that may impact patient outcomes. The catheter's design and ablation modes offer flexibility in technique while accommodating the individual operator's clinical discretion and preference to deliver a durable, transmural, and contiguous lesion set. Here, we provide recommendations for 3 different workflows using the QDOT MICRO catheter in a step-by-step manner for pulmonary vein isolation based on our cumulative experience as early adopters of the technology and the data available in the scientific literature. With standardization, temperature-controlled ablation with the QDOT MICRO catheter provides operators the flexibility of implementing different ablation strategies to ensure durable contiguous pulmonary vein isolation depending on patient characteristics.

Surgical options for atrial fibrillation treatment during concomitant cardiac procedures.

Current guidelines recommend concomitant surgical ablation (SA) of atrial fibrillation (AF) in the context of mitral valve disease. A variety of energy sources have been tested for SA to perform effective transmural lesions reliably. To date, only radiofrequency and cryothermy energies are considered viable options. The gold standard for SA is the Cox-Maze ablation set, especially for non-paroxysmal AF (nPAF), with the aim of interrupting macro-reentrant drivers perpetuating AF, without hampering the sinus node activation of both atria, and to maintain the atrioventricular synchrony. Although the efficacy of SA in terms of early and late sinus rhythm restoration has been clearly demonstrated over the years, concomitant AF ablation is still underperformed in patients with AF undergoing cardiac surgery. From a surgical standpoint, concerns have been raised about whether a single (left) or double atriotomy would be justified in AF patients undergoing a "non-atriotomy" surgical procedure, such as aortic valve or revascularization surgery. Thus, an array of simplified lesion sets have been described in the last decade, which have unavoidably hampered procedural efficacy, somewhat jeopardizing the standardization process of ablation surgery. As a matter of fact, the term "Maze" has improperly become a generic term for SA. Surgical interventions that do not align with the principles of forming conduction-blocking lesions according to the Maze pattern, cannot be classified as Maze procedures. In this complex scenario, a tailored approach according to the different AF patterns has been proposed: for patients with concomitant nPAF, a biatrial Cox-Maze ablation is recommended. Conversely, it might be reasonable to limit lesions to the left atrium or the pulmonary veins in patients with paroxysmal AF (PAF) in some clinical scenarios. The aim of this review is to provide an overview of the current ablation strategies for patients with AF undergoing concomitant cardiac surgery.

Evaluation of a New Cystoscopic Cryocatheter and Method for the In Situ Destruction of Bladder Cancer: Preliminary In Vivo Study.

Purpose: To assess the ability to deliver full-thickness bladder wall cryoablation through a cystoscopic approach using a new closed-loop 6F cryocatheter and thermal dose-controlled protocol. Materials and Methods: Evaluations were conducted using a chronic porcine model wherein 10 lesions/animal were created throughout the bladder (bladder wall, trigone region, ureteral orifice, and distal ureter). A 6F cryocatheter was passed through the working channel of a flexible cystoscope. Single 1- and 1.5-minute freeze protocols in a saline environment were evaluated and resultant lesion size was determined. A laparoscopic approach was utilized to observe the transmural extension of the ice propagation. Results: Studies demonstrated the generation of transmural lesions characterized by full-thickness histologic necrosis after freezing for 1.5 minutes regardless of tissue thickness (range 2-12 mm). All animals were found to have good overall health (maintained weight, appetite, mobility, and energy levels) throughout the recovery period. No significant deviations were noted in complete blood count and serum chemistry bloodwork except for elevated creatine kinase levels. Importantly, no fistulas or perforations were noted. Conclusions: The cryocatheter was able to rapidly and effectively freeze the bladder wall through a cystoscopic approach. The results showed the ability to consistently ablate an ∼1 cm diameter and up to 1.2 cm deep using a single 1.5-minute freeze protocol. Analysis of the ablation efficacy revealed ∼80% destruction within the frozen mass. Although further testing and refinement are needed, these studies demonstrate the potential of this new approach to provide a next-generation strategy for the treatment of bladder cancer.

Pulsed Field Ablation Index-Guided Ablation for Lesion Formation: Impact of Contact Force and Number of Applications in the Ventricular Model.

The effect of contact force (CF) on lesion formation is not clear during pulsed field ablation (PFA). The aim of this study was to evaluate the impact of CF, PFA, and their interplay through the PFA index (PF index) formula on the ventricular lesion size in swine. PFA was delivered through the CF-sensing OMNYPULSE catheter. Predefined PFA applications (×3, ×6, ×9, and ×12) were delivered maintaining low (5-25 g), high (26-50 g), and very high (51-80 g) CFs. First, PFA lesions were evaluated on necropsy in 11 swine to investigate the impact of CF/PFA-and their integration in the PF index equation-on lesion size (study characterization). Then, 3 different PF index thresholds-300, 450, and 600-were tested in 6 swine to appraise the PF index accuracy to predict the ventricular lesion depth (study validation). In the study characterization data set, 111 PFA lesions were analyzed. CF was 32±17 g. The average lesion depth and width were 3.5±1.2 and 12.0±3.5 mm, respectively. More than CF and PFA dose alone, it was their combined effect to impact lesion depth through an asymptotically increasing relationship. Likewise, not only was the PF index related to lesion depth in the study validation data set (r2=0.66; P<0.001) but it also provided a prediction accuracy of the observed depth of ±2 mm in 69/73 lesions (95%). CF and PFA applications play a key role in lesion formation during PFA. Further studies are required to evaluate the best PFA ablation settings to achieve transmural lesions.

Catheter-tissue contact optimizes pulsed electric field ablation with a large area focal catheter.

Pulsed electric field (PEF) ablation relies on the intersection of a critical voltage gradient with tissue to cause cell death. Field-based lesion formation with PEF technologies may still depend on catheter-tissue contact (CTC). The purpose of this study was to assess the impact of CTC on PEF lesion formation with an investigational large area focal (LAF) catheter in a preclinical model. PEF ablation via a 10-spline LAF catheter was used to create discrete right ventricle (RV)lesions and atrial lesion sets in 10 swine (eight acute, two chronic). Local impedance (LI) was used to assess CTC. Lesions were assigned to three cohorts using LI above baseline: no tissue contact (NTC: ≤∆10 Ω, close proximity to tissue), low tissue contact (LTC: ∆11-29 Ω), and high tissue contact (HTC: ≥∆30 Ω). Acute animals were infused with triphenyl tetrazolium chloride (TTC) and killed ≥2 hpost-treatment. Chronic animals were remapped 30 days post-index procedure and stained with infused TTC. Mean (± SD) RV treatment sizes between LTC (n = 14) and HTC (n = 17) lesions were not significantly different (depth: 5.65 ± 1.96vs. 5.68 ± 2.05 mm, p = .999; width: 15.68 ± 5.22vs. 16.98 ± 4.45 mm, p = .737), while mean treatment size for NTC lesions (n = 6) was significantly smaller (1.67 ± 1.16 mm depth, 5.97 ± 4.48 mm width, p < .05). For atrial lesion sets, acute and chronic conduction block were achieved with both LTC (N = 7) and HTC (N = 6), and NTC resulted in gaps. PEF ablation with a specialized LAF catheter in a swine model is dependent on CTC. LI as an indicator of CTC may aid in the creation of consistent transmural lesions in PEF ablation.

P168 Specialized pro-resolving lipid mediator Resolvin D1 and omega 6 dihomo-γ-linolenic acid are unable to solve inflammation in the creeping fat of patients with severe postoperative recurrence in Crohn's disease

Abstract Background The ω3 derivate resolvin D1 (RvD1), and the ω6 dihomo-γ-linolenic acid (DGLA) prevent collateral damage by overcoming inflammation and enhancing microbial clearance. In Crohn's disease, the mesenteric adipose tissue becomes inflamed and hyperplasies due to transmural lesions and bacterial translocation, developing the so-called creeping fat. This tissue is unable to clear inflammation and has been linked to severer intestinal inflammation and post-operative recurrence (POR). Recently, we have described the presence of DGLA and the increase in the ω6/ω3 ratio together with pro-inflammatory mediators in the creeping fat at surgery. Our aims were study the mechanisms within the inflammatory resolution related to polyunsaturated fatty acids depending on POR severity. Methods Creeping fat samples were obtained in the intestinal resection of Crohn's disease patients and endoscopic POR was evaluated according to the Rutgeerts score: non recurrence (i0+i1; n=18), mild recurrence (i2; n=14) and severe recurrence (i3+i4; n=10). Mesenteric adipose tissue was also collected from patients with colorectal cancer (n=10) and severe obesity (n=11) as reference groups. RvD1 was evaluated by C18/ELISA, lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) activity by radioassay, and the free fatty acid receptor 1 (FFAR1) expression by qRT-PCR. Results RvD1 was increased in the creeping fat in comparison to the mesenteric adipose tissues of the reference groups (Graphical abstract A) and correlated antagonistically with pro-inflammatory mediators in non-recurrence versus severe recurrence (B). Specifically, factors such as TNF-α, CD14 or IL-18 showed significant positive correlations with RvD1 in severe recurrence while negative in non recurrence. The LPL/HSL ratio indicated greater storage of fatty acids in severe recurrence creeping fats (C), and only in these patients, DGLA negatively correlated with HSL (D) and FFAR1 (E), a receptor that was only detected in Crohn's disease (F). At the same time, this receptor antagonistically correlated with pro-inflammatory mediators such as IL-8 in the creeping fat, positively in non-recurrence and negatively in severe recurrence (G). Conclusion The RvD1 increase suggests a greater production of this factor from ω3, but that would be insufficient to resolve inflammation in severe recurrent creeping fat at surgery time. In this phenotype, HSL activity is linked to a lower presence of DGLA, the only anti-inflammatory ω6. In contrast, the presence of this ligand in severe recurrents seems to reduce the expression of the FFAR1, which acts on the neutrophil function. Thus, immune-inflammation derived from lipid metabolism is antagonistic among the most disparate cases of POR in the creeping fat at surgery.

P022 Development of a novel experimental model for studying creeping fat in Crohn's Disease

Abstract Background A characteristic feature of Crohn's disease (CD) is the transformation of mesenteric adipose tissue into creeping fat (CrF), which becomes inflamed and surrounds the transmural lesion. The occurrence of this condition has been associated with the severity of inflammation and post-surgical recurrence. In this study, we present a promising model of CD induced by 2,4,6-trinitro-benzene sulfonic acid (TNBS) that exhibits experimental CrF. This model provides an innovative tool for the development of surgical techniques as well as the implementation of new therapeutic strategies, as it more accurately depicts the nature of the pathology. Methods Acute colitis was induced by intrarectal instillation of TNBS under conventional conditions. Five days after the administration, acute colitis developed (Fig. A). The variation in the percentage of weight compared to the initial weight was analyzed. Clinical activity was assessed through colonoscopy on the third and fifth days based on parameters such as hyperemia, the extension of ulcers, and presence of stenosis. Further, the weight-to-length ratio of the colon, as well as the area of the lesions, was also collected. All obtained data were analyzed in order to identify any possible differences between the sexes or between the groups that presented CrF or not. Results The frequency of CrF occurrence was approximately 50% in both sexes. Even though, females had smaller volume of CrF and a greater presence of fistulas. As compared to controls, the weight of the animals with CrF decreased (Fig. B) and their clinical activity index increased (Fig. C). Moreover, the area of the lesion was significantly increased in the group with CrF as compared with the group without CrF (Fig. D). The CrF group also demonstrated a significant increase in the weight-to-length ratio of the colon. There were no significant differences between the sexes in the aspects mentioned above. Conclusion The group presenting CrF showed a significant increase in all parameters of disease severity analyzed. We would like to emphasize that animals exhibiting severe symptoms by the fifth day were precisely those that manifested the development of CrF. Importantly, it is noteworthy that monitoring the disease through colonoscopy avoids the necessity for the sacrifice of animals, thereby facilitating a reduction in sample size.

Acute epicardial pulmonary vein reconnection: Nondurable transmural lesion or late manifestation of conduction through intercaval bundle.

Acute pulmonary vein reconnection (PVR) via epicardial fibers can be found during observation period after PV isolation, the characteristics and related factors have not been fully studied. We aimed to investigate the prevalence, locations, electrogram characteristics, and ablation parameters related to acute epicardial pulmonary vein reconnection (AEPVR). Acute PVR was monitored during observation period after PV isolation. AEPVRs were mapped and distinguished from endocardial conduction gaps. The clinical, electrophysiological characteristics and lesion set parameters were compared between patients with and without PVR. They were also compared among AEPVR, gap-related reconnection, and epicardial PVR in repeat procedures. A total of 56.1% acute PVR were AEPVR, which required a longer waiting period (p < .001) than endocardial gap. The majority of AEPVR were connections from the posterior PV carina to the left atrial posterior wall, followed by late manifestation of intercaval bundle conduction from the right anterior carina to right atrium. AEPVR was similar to epicardial PVR in redo procedures in distribution and electrogram characteristics. Smaller atrium (p < .001), lower impedance drop (p = .039), and ablation index (p = .028) on the posterior wall were independently associated with presence of AEPVR, while lower interlesion distance (p = .043) was the only predictor for AEPVR in acute PVR. An integrated model containing multiple lesion set parameters had the highest predictive ability for AEPVR in receiver operating characteristics analysis. Epicardial reconduction accounted for the majority of acute PVR. AEPVR was associated with anatomic characteristics and multiple ablation-related parameters, which could be explained by nondurable transmural lesion or late manifestation of conduction through intercaval bundle.

Catheter Ablation of Persistent AF-Where are We Now?

Persistent atrial fibrillation (AF) is a diverse condition that includes various subtypes and underlying causes of arrhythmia. Progress made in catheter ablation technology in recent years has significantly enhanced the durability of ablation. Despite these advances however, the effectiveness of ablation in treating persistent AF is still relatively modest. Studies exploring the mechanisms behind persistent AF have identified substrate-driven focal and re-entrant sources within the atrial body as crucial in sustaining AF among individuals with persistent AF. Furthermore, the widespread adoption of atrial late gadolinium enhancement cardiac magnetic resonance (CMR) imaging and the ongoing refinement of invasive voltage mapping techniques have allowed for detailed assessment of fibrotic remodelling prior to or at the time of procedure. Translation into clinical practice, however, has yielded overall disappointing results. The clinical application of AF mapping in ablation procedures has not shown any substantial advantages beyond the use of pulmonary vein isolation (PVI) alone and adjunct ablation of fibrotic areas has yielded conflicting results in recent randomized trials. The emergence of pulsed field ablation represents a welcome development in the field and several studies have demonstrated an enhanced safety profile and increased procedural efficiency with this non-thermal energy modality. Pulsed field ablation also holds promise for safe and efficient substrate ablation beyond the pulmonary veins, but further trials are needed to assess its impact on longer term success rates. Continued advancements in our comprehension of AF mechanisms, alongside ongoing developments in catheter technology aimed at safe formation of transmural lesions, are essential for achieving better clinical outcomes for patients with persistent AF.

Abstract 13783: Tissue Thickness is an Essential Factor of Higher Risk of Steam Pop During Bipolar Ablation - Ex-Vivo Assessment

Introduction/Backgrounds: For ventricular arrhythmias originating deep within the myocardium, bipolar ablation can be employed. However, there is currently no standardized strategy for bipolar ablation settings such as energy and ablation time. Hypothesis and Aims: We intended to test a hypothesis that the target tissue thickness may determine the optimal bipolar ablation settings of power and duration. Methods: Using porcine cardiac tissues ex-vivo ablation experiments were conducted. Each radiofrequency (RF) ablation catheter was placed on both sides of the myocardial slice at an angle of 45 degrees and 10g contact. We investigated the depth of ablation lesions and the occurrence of steam-pop under the multiple settings of myocardial tissue thickness, energy and ablation duration. Results: We analyzed in total 194 bipolar RF applications. For myocardial slices of 10-, 15- and 20-mm thickness, we performed 60-second RF ablation of 20, 30, 40 and 50W energy settings. No transmural lesion creation was noted on the 20-mm thickness tissues even by 50W RF energy ( Figure 1 ). Transmural lesion was observed with RF energy of 30W or more on the most of the 10-mm thickness tissues. Prolonged duration of 180 seconds with 30W or more accomplished the transmural lesion on the 15-mm thickness tissues. We observed steam-pop in 11 out of 194 applications (5.7%). Steam-pops were exclusively observed on the 10mm tissue with 30W or more. Conclusion: Our data showed that (1) transmural lesion creation for 10-mm tissue is feasible under 30W or more and 60 seconds bipolar ablation, (2) for thicker tissue even 50W application of 60 seconds may not generate transmural lesion, (3) prolonged RF duration enables transmural lesion for thicker tissues, (4) steam-pop can occur on thinner tissues under higher wattage. These results suggest that we should adapt the bipolar RF settings, particularly the power and duration depending on the target tissue thickness.

Abstract 19121: Averaged Impedance Drop Workflow for Pulmonary Vein Isolation

Background: Previous studies demonstrate that averaged impedance drop (AID) is the most accurate predictor of focal atrial RF ablation lesion transmurality when using the TactiFlex™ SE Ablation Catheter in combination with AutoMark in EnSite™ X EP System version 3.0, however data demonstrating successful incorporation of AID into a pulmonary vein isolation workflow is lacking. Objective: We explored use of AID in conjunction with the AutoMark Distance (AMD) tool to create sets of contiguous, transmural atrial lesions in a chronic swine model and to compare results with inter-lesion gap rates from a historical study of a previous generation catheter (TactiCath) using LSI™ guidance. Methods: RSPV isolation and SVC-IVC and RSPV-CIPV lines were performed in swine (n=9) via point-by-point ablation (target contact force 10g). AID targets of 11, 13, and 15% were selected and minimum-maximum duration bounds were employed (30W/15-50s, 40W/8-20s and 50W/5-10s). Inter-lesion distances of 4mm and 5mm were chosen (balanced across RF powers and anatomical targets). After 12±3 days survival, lesion sets were examined using gross pathology and histology. Results: Histological analysis showed gap incidence rates of 4/223 (1.8%) and 9/215 (4.2%) in the right and left atria, respectively. Per-condition results are shown in Figure 1. The target AID was achieved in 339/487 (69.6%) of ablations, with the target AID reached prior to the minimum duration in 89/487 (18.3%) of trials. Collateral effects were observed, including pulmonary artery thrombosis and inflammation/necrosis extending to trachea/bronchus (N=1). Further characterization of these adverse events could potentially guide upper bounds for AID targets. Conclusions: AID guided ablation resulted in a low rate of inter-lesion gaps, overall comparable to historical data. However, safety and efficacy varied by delivery condition and these results may be useful for guiding clinical use.

Nanosecond Pulsed Electric Field Ablation With a Bipolar Clamp Creates Durable Transmural Lesions in Cardiac Tissue.

Nanosecond Pulsed Electric Field Ablation With a Bipolar Clamp Creates Durable Transmural Lesions in Cardiac Tissue.

Transcatheter occlusion of the coronary sinus increases radiofrequency ablation lesion size in the left ventricular myocardium: a new approach to improve the efficiency of ventricular tachyarrhythmia substrate destruction

The aim. The results of ventricular tachyarrhythmia catheter ablation in patients with structural heart diseases remains to be improved. Both evolution of the arrhythmia substrate and its deep location are the main reasons for standard endocardial ablation limitations. Theoretically, the reduction of myocardial perfusion rate may improve convective heating of the myocardium during radiofrequency (RF) ablation, expanding the volume of damage. The purpose of this study was to assess the effect of coronary sinus (CS) occlusion in order to reduce myocardial perfusion during RF ablation on the volume of myocardial damage.Methods. The study was performed on 13 pigs. Following vascular access accomplishment, a balloon catheter was inserted into the lumen of the CS. A 3.5-mm open-irrigated RF ablation catheter was inserted into the cavity of the left ventricle. RF applications were applied in an alternate order, with and without CS occlusion (power 30 and 40W, application time 40 and 30 s, respectively). Each ablation point was marked on a three-dimensional electroanatomic map. After euthanasia, myocardial lesions were analyzed.Results. The analysis of 50 RF applications was performed (22 with CS occlusion and 28 without CS occlusion). At the same time, 28 applications (13 with occlusion and 15 without occlusion) were performed at a power of 40W, and 22 applications (9 with occlusion and 13 without occlusion) at a power of 30 watts. There was a trend toward the increase in lesion sizes created during CS occlusion. Significantly larger lesions were detected with 40W applications during CS occlusion when compared with open CS applications: depth 11.6±3.9 vs. 8.8±3.8 mm (p=0.04), diameter 11.7±4.6 vs. 8.5±3.9 mm (p=0.03), volume 504.2±499.5 vs. 183.0±157.5 mm3 (p=0.01). Transmural myocardial lesions were more often encountered during applications with CS occlusion with both power settings, 30 and 40W: 68.2% of transmural lesions versus 39.3%; p=0.046.Conclusion. RF applications with a power of 40W and CS occlusion are characterized by greater depth, diameter, and volume of damage, as well as a greater frequency of transmural necrosis. Temporary transcatheter occlusion of CS can be proposed for ablation of ventricular arrhythmia with extended and deep substrate.

Characteristics of tissue temperature during ablation with THERMOCOOL SMARTTOUCH SF versus TactiCath versus QDOT MICRO catheters (Qmode and Qmode+): An in vivo porcine study.

High-power short-duration (HPSD) ablation at 50 W, guided by ablation index (AI) or lesion size index (LSI), and a 90 W/4 s very HSPD (vHPSD) setting are available for atrial fibrillation (AF) treatment. Yet, tissue temperatures during ablation with different catheters around venoatrial junction and collateral tissues remain unclear. In this porcine study, we surgically implanted thermocouples on the epicardium near the superior vena cava (SVC), right pulmonary vein, and esophagus close to the inferior vena cava. We then compared tissue temperatures during 50W-HPSD guided by AI 400 or LSI 5.0, and 90 W/4 s-vHPSD ablation using THERMOCOOL SMARTTOUCH SF (STSF), TactiCath ablation catheter, sensor enabled (TacthCath), and QDOT MICRO (Qmode and Qmode+ settings) catheters. STSF produced the highest maximum tissue temperature (Tmax ), followed by TactiCath, and QDOT MICRO in Qmode and Qmode+ (62.7 ± 12.5°C, 58.0 ± 10.1°C, 50.0 ± 12.1°C, and 49.2 ± 8.4°C, respectively; p = .005), achieving effective transmural lesions. Time to lethal tissue temperature ≥50°C (t-T ≥ 50°C) was fastest in Qmode+, followed by TacthCath, STSF, and Qmode (4.3 ± 2.5, 6.4 ± 1.9, 7.1 ± 2.8, and 7.7 ± 3.1 s, respectively; p < .001). The catheter tip-to-thermocouple distance for lethal temperature (indicating lesion depth) from receiver operating characteristic curve analysis was deepest in STSF at 5.2 mm, followed by Qmode at 4.3 mm, Qmode+ at 3.1 mm, and TactiCath at 2.8 mm. Ablation at the SVC near the phrenic nerve led to sudden injury at t-T ≥ 50°C in all four settings. The esophageal adventitia injury was least deep with Qmode+ ablation (0.4 ± 0.1 vs. 0.8 ± 0.4 mm for Qmode, 0.9 ± 0.3 mm for TactiCath, and 1.1 ± 0.5 mm for STSF, respectively; p = .005), correlating with Tmax . This study revealed distinct tissue temperature patterns during HSPD and vHPSD ablations with the three catheters, affecting lesion effectiveness and collateral damage based on Tmax and/or t-T ≥ 50°C. These findings provide key insights into the safety and efficacy of AF ablation with these four settings.

How to ablate the septo-pulmonary bundle: a case-based review of percutaneous ablation strategies to achieve roof line block.

Electrical conduction through cardiac muscle fibres separated from the main myocardial wall by layers of interposed adipose tissue are notoriously difficult to target by endocardial ablation alone. They are a recognised important cause for procedural failure due to the difficulties of delivering sufficient energy via the endocardial radiofrequency catheter to reach the outer epicardial layer without risking adverse events of the otherwise thin walled atria. Left atrial ablations for atrial fibrillation (AF) and tachycardia are commonly affected by the presence of several epicardial structures, with the septo-pulmonary bundle (SPB), Bachmann's bundle, and the ligament of Marshall all posing substantial challenges for endocardial procedures. Delivery of a transmural lesion set is essential for sustained pulmonary vein isolation and for conduction block across linear atrial lines which in turn has been described to translate into a reduced AF/atrial tachycardia recurrence rate. To overcome the limitations of endocardial-only approaches, surgical ablation techniques for epicardial or combined hybrid endo-epicardial ablations have been described to successfully target these connections. Yet, these techniques confer an increase in procedure complexity, duration, cost, and morbidity. Alternatively, coronary venous system ethanol ablation has been successfully employed by sub-selecting the vein of Marshall to facilitate mitral isthmus line block, although this approach is naturally limited to this area by the coronary venous anatomy. Increased awareness of the pathophysiological relevance of these epicardial structures and their intracardiac conduction patterns in the era of high-resolution 3D electro-anatomical mapping technology has allowed greater understanding of their contribution to the persistence of AF as well as failure to achieve transmural block by traditional ablation approaches. This might translate into novel catheter ablation strategies with procedural success rates comparable to surgical 'cut-and-sew' techniques. This review aims to give an overview of percutaneous catheter ablation strategies to target the SPB, an important cause of failed block across the roof line and isolation of the left atrial posterior wall and/or the pulmonary veins. Existing and investigational technologies will be discussed and an outlook of future approaches provided.

Pulmonary endarterectomy in patients with occlusive isolated pulmonary vasculitis

BackgroundIsolated pulmonary vasculitis (IPV) is a rare, insidious, and localized inflammatory disease affecting the pulmonary arteries, often leading to severe luminal obstruction. The prognosis for patients with occlusive IPV is poor, and there is currently a lack of effective treatments. The objective of this study was to evaluate the performance of pulmonary endarterectomy (PEA) as a treatment for occlusive IPV.MethodsThis single-center retrospective analysis included patients who received PEA for occlusive IPV between January 2018 and June 2022. Clinical characteristics and hemodynamic parameters were evaluated at baseline and follow-up.ResultsAmong 114 consecutive patients who underwent PEA, occlusive IPV was identified in 7 patients. Two patients underwent bilateral PEA for the involvement of both pulmonary arteries. Patch angioplasty was performed to treat four severe constrictions. One patient died from residual pulmonary hypertension after limited PEA of a transmural vascular lesion. In addition, no obvious surgical complications were observed. Three months after PEA, a substantial relief in symptoms was achieved. Also, there is a decrease in the mean pulmonary artery pressure (median 33 [20–48] mmHg before versus median 21 [16–26] mmHg after; P < 0.018) and pulmonary arterial resistance (median 234 [131–843] dyn.s.cm−5 versus median 180 [150–372] dyn.s.cm−5; P = 0.310). Three patients experienced a relapse of restenosis of the treated arteries within a 6-month follow-up period, despite daily oral prednisolone administration. They were treated with balloon pulmonary angioplasty of both the main pulmonary arteries and branches.ConclusionsPEA is a valuable choice for treating occlusive IPV, with notable hemodynamic and clinical advantages. To increase long-term vascular patency, complete management should be optimized.

Dielectric response as a novel marker for ablation lesion quality: Relation to conventional ablation parameters.

The tissue response viewer (TRV) is a novel marker for ablation lesion quality that aims to classify lesions into transmural or nontransmural lesions (high or low dielectric response, HDR or LDR) using dielectric-based tissue assessment. The objective of this study was to gain insight in the TRV by relating its outcomes to conventional ablation parameters. Patients that had repeat ablation for atrial fibrillation with a dielectric imaging-based mapping system were enrolled. All ablation data were downloaded from the mapping system and analyzed to explore associations between TRV outcomes and other ablation parameters. The cohort included 24 patients, in which 58 pulmonary veins and 8 superior vena cavas were targeted. A total of 388 energy applications were applied, resulting in 639 ablation points. The system classified 36% of ablation points as HDR and 44% as LDR. The system did not provide a dielectric response in 20%. The system's ability to provide a dielectric response was related to longer ablation duration and absence of dragging ablation. HDR (versus LDR) was multivariably associated with longer energy applications, higher mean ablation power, and lower wall thickness. Greater impedance drop was univariably associated with HDR. Outcomes of the TRV are associated with conventional ablation parameters (e.g., duration and power) but also local wall thickness. Catheter stability seems important for successful lesion assessment with the TRV. Further reduction of missing outcomes and validation of the tool are warranted before widespread use.

Linear epicardial cryoablation effects in a porcine model: Lesion characteristics and vascular risk.

Cryoablation in open-chest surgical interventions for ventricular arrhythmias has been reported with reasonable procedural outcomes. However, the characteristics of cryoablation lesions on the ventricular myocardium are not well defined. The purpose of the present study was to determine the tissue and vascular effects of a linear epicardial cryoablation probe in a porcine animal model. Five adult Yorkshire swine underwent median sternotomy and application of linear cryoablation lesions using a malleable aluminum linear cryoablation probe of varying duration (2, 3, 4, and 5 min), including one lesion placed intentionally over the left anterior descending coronary (LAD) artery. Histological analysis was performed. Maximum lesion depth was approximately 1.0 cm with 3 min freezes, with no significant increase in depth achieved with longer lesions. No transmural lesions were achieved. No large vessel epicardial coronary artery injuries were seen to the LAD; however, surprisingly, remote isolated interventricular septal injury was seen in all animals, suggestive of possible compromise of smaller coronary arterial vessels. Single application freezes with an aluminum linear cryoablation probe can create homogeneous ablative lesions over the ventricular myocardium with a maximum depth of approximately 1.0 cm. No large vessel injury occurred with direct lesion application of the LAD; however, small coronary vessels may be at risk.