10-year follow-up of interventional electrophysiology: updated German survey during the COVID-19 pandemic.

INTRODUCTION: This study provides an update of survey-based data providing an overview of interventional electrophysiology over the last decade. Overall infrastructure, procedures, and training opportunities in Germany were assessed. METHODS: By analyzing mandatory quality reports, German cardiology centres performing electrophysiological studies were identified to repeat a questionnaire from 2010 and 2015. RESULTS: A complete questionnaire was returned by 192 centers performing about 75% of all ablations in Germany in 2020. In the presence of the COVID-19 pandemic, a total of 76.304 procedures including 68.407 ablations were reported representing a 38% increase compared to 2015. The median number of ablations increased from 180 in 2010 to 377 in 2020. AF was the most common arrhythmia ablated (51 vs. 35% in 2010). PVI with radiofrequency point-by-point ablation (64%) and cryo-balloon ablation (34%) were the preferred strategies. Less than 50 (75) PVI were performed by 31% (36%) of all centres. Only 25 and 24% of participating centres fulfilled EHRA and national requirements for training centre accreditation, respectively. There was a high number of EP centres with no fellows (38%). The proportion of female fellows in EP increased from 26% in 2010 to 33% in 2020. CONCLUSION: Comparing 2020, 2010 and 2015, an increasing number of EP centres and procedures were registered. In 2020, more than every second ablation was for therapy of AF. In the presence of an increasing number of procedures, training opportunities were still limited, and most centres did not fulfill recommended EHRA or national requirements for accreditation.

[MRI-based catheter ablation : Current status and outlook]. / MRT-basierte Katheterablation : Aktueller Stand und Ausblick.

Fluoroscopy-based catheter ablation has established itself as a standard procedure for the treatment of patients with cardiac arrhythmias. However, it is subject to certain limitations with regard to the visualization of arrhythmogenic substrate and ablation lesions and is associated with radiation exposure. Within the framework of studies, initial experience with MRI-based, radiation-free electrophysiological examinations and ablations could be gained. The integration of MRI technology into electrophysiological procedures promises numerous advantages. The ability to operate in a radiation-free environment during MRI-based catheter ablation is significant and promising. Furthermore, MRI provides important procedure-relevant information in terms of visualization of individual arrhythmogenic substrate. In order to further improve immediate and long-term ablation success, especially in the context of complex arrhythmias and structural heart disease, the direct and successful integration of MRI-generated findings into the ablation process is of utmost importance. The future of MRI-based catheter ablation could thus lie in particular in the treatment of more complex cardiac arrhythmias, which require personalized therapy paths. In this respect, however, the data situation is still extremely limited. Further technical developments and larger studies are indispensable in order to gain further important insights into the feasibility, safety and success rate of MRI-based invasive electrophysiological diagnostics and therapy in comparison to conventional ablation methods.

Subjective assessment of complexity and prognosis after pulmonary vein isolation as significant predictor for procedural success.

PURPOSE: Subjective estimation of recurrence after atrial fibrillation ablation is an important tool in clinical use. The aim of this study is to evaluate (1) if the subjective complexity of an atrial fibrillation ablation procedure is correlated with rhythm stability and (2) if the subjective prognosis of the operator has a predictive value. METHODS: We prospectively enrolled patients admitted for ablation of atrial fibrillation. Two scores were given immediately after the procedure by the operator: the complexity and the prognosis scores. With routine follow-ups, we tried to evaluate the correlation between the subjective scores and measured outcome. RESULTS: The study population included 611 patients (63 ± 10 years, 37% females, 61% persistent AF). During follow-up (FU) (median 24, IQR 7-36 months), recurrences occurred in 44% patients. Both scores (prognosis and complexity) correlated significantly with age, persistent AF, LA diameter, procedural characteristics, and recurrences. On multivariable analysis, complexity (OR 1.304, 95%CI 1.016-1.675, p = 0.037) and prognosis (OR 1.443, 95%CI 1.080-1.982, p = 0.013) scores remained significant predictors for arrhythmia recurrences. On ROC analysis, both scores showed significant predictive value for rhythm outcomes after catheter ablation (AUC 0.599 and 0.613, both p < 0.001 for complexity and prognosis scores, respectively). CONCLUSIONS: Complexity and prognosis scores are significant predictors for arrhythmia recurrences after AF catheter ablations and even independent when competing with simple risk factors.

[Treatment of premature ventricular contractions in patients with structural heart disease : Insights from imaging]. / Therapie der ventrikulären Extrasystolen bei strukturellen Herzerkrankungen : Welchen Mehrwert hat die Bildgebung?

The diagnosis of premature ventricular contractions (PVC) is presumptively based on the presence of frequent symptoms. Particularly in patients with a relatively low PVC burden, the relationship between the PVCs and an individual arrhythmia substrate can be challenging to ascertain. Late gadolinium enhancement (LGE) on cardiac magnetic resonance imaging (CMR) has been found to be beneficial in identifying the presence of potential individual arrhythmia substrates even in patients with normal left ventricular function. Consequently, CMR has been useful in risk stratification of patients with PVCs. The authors aimed to demonstrate and discuss the current role and future use of CMR in the diagnostic algorithm to guide PVC ablation.

[Coherent mapping in adults with congenital heart disease : Role of the novel coherent mapping technique for treatment of atrial tachycardia in adults with congenital heart disease]. / Coherent-Mapping bei angeborenen Herzfehlern : Stellenwert des neuen Coherent-Modules zur Behandlung von atrialen Tachykardien bei Erwachsenen mit angeborenen Herzfehlern.

A 31-year-old woman with a surgically corrected double outlet right ventricle and recurrent narrow QRS complex tachycardia was admitted to our hospital. The patient was scheduled for electrophysiology study. Coherent mapping identified the critical isthmus as a slow conduction area within posterolateral intercaval scar tissue. A continuous line of ablation was applied resulting in termination of the atrial tachycardia at the site of the critical isthmus from coherent mapping. Thus, coherent mapping facilitates complex ablation procedures and improves efficacy and efficiency.

Evaluation of the right heart using cardiovascular magnetic resonance imaging in patients with cardiac devices.

BACKGROUND: Patients with cardiac implantable electronic devices (CIED) necessitate comprehensive cardiovascular magnetic resonance (CMR) examinations. The aim of this study was to provide data on CMR image quality and feasibility of functional assessment of the right heart in patients with CIED depending on the device type and imaging sequence used. METHODS: 120 CIED carriers (Insertable cardiac monitoring system, n = 13; implantable loop-recorder, n = 22; pacemaker, n = 30; implantable cardioverter-defibrillator (ICD), n = 43; and cardiac resynchronization therapy defibrillator (CRT-D), n = 12) underwent clinically indicated CMR imaging using a 1.5 T. CMR protocols consisted of cine imaging and myocardial tissue characterization including T1-and T2-weighted blackblood imaging and late gadolinium enhancement (LGE) imaging. Image quality was evaluated with regard to device-related imaging artifacts per right-ventricular (RV) segment. RESULTS: RV segmental evaluability was influenced by the device type and CMR imaging sequence: Cine steady-state-free-precision (SSFP) imaging was found to be non-diagnostic in patients with ICD/CRT-D and implantable loop recorders; a significant improvement of image quality was achieved when using cine turbo-field-echo (TFE) sequences with a further improvement on post-contrast TFE imaging. LGE scans were artifact-free in at least 91% of RV segments with best results in patients with a pacemaker or an insertable cardiac monitoring system. CONCLUSIONS: In patients with CIED, artifact-free CMR imaging of the right ventricle was performed in the majority of patients and resulted in highly reproducible evaluability of RV functional parameters. This finding is of particular importance for the diagnosis and follow-up of right-ventricular diseases.

Intravenous thrombolysis in wake-up stroke: real-world data from the Austrian Stroke Unit Registry.

BACKGROUND AND PURPOSE: Data on real-world experience with intravenous thrombolysis (IV tPA) in wake-up stroke (WUS) are limited. The aim of this study was to examine the efficacy and safety of IV tPA in patients with WUS included in the Austrian Stroke Unit Registry. METHODS: Data from a large nationwide stroke unit registry including initial stroke severity, vascular risk factors, comorbidities, treatment with IV tPA, symptomatic intracerebral haemorrhage (sICH) and functional outcome were extracted and analysed. Patients with WUS were compared with patients with known-onset stroke (KOS) regarding the frequency of IV tPA treatment, neurological improvement (National Institutes of Health Stroke Scale score ≥4), sICH and 3-month functional outcome by modified Rankin Scale score using standard statistical tests. RESULTS: A total of 107 895 stroke patients entered the analysis, including 12 534 with WUS and 91 899 with KOS. Altogether, 904 (7.2%) patients with WUS received IV tPA as compared with 16 694 (18.2%) patients with KOS. Patients with WUS who received IV tPA treatment had twofold higher initial National Institutes of Health Stroke Scale score (median 8 vs. median 4) as compared with patients with KOS. There was no statistical difference in functional outcome by modified Rankin Scale score 0-1 at 3 months between patients with WUS and patients with KOS treated with IV tPA (adjusted odds ratio, 1.08; 95% confidence interval, 0.9-1.31). Also, the rate of sICH did not differ (4.1% vs. 4%, P = 0.852). CONCLUSIONS: In this large non-randomized comparison, the safety and efficacy of IV tPA in patients with WUS in the real-world setting seems to be comparable to patients with KOS.

Structured pain management reduces patient discomfort after catheter ablation and rhythm device surgery.

BACKGROUND: The goal was to test the effectiveness of a structured pain management programme after invasive electrophysiological interventions in cardiology including ablation of atrial fibrillation (AF) or ventricular tachycardia (VT) and implantation, or explantation, of pacemakers or implantable cardioverter defibrillators. METHODS: This was a prospective study with a pre-/post-design where a post-intervention group (116 consecutive patients) was compared to a pre-intervention group (102 consecutive patients) after implementation of a structured pain-management programme using the numeric rating scale (NRS 0-10) and classified as moderate-to-severe if NRS > 3. Measurements were recorded every two hours during the first 24 h post-operatively. The location of the pain and the amount of analgesic used were also recorded. RESULTS: The proportion of patients who experienced moderate-to-severe pain after the procedure decreased after initiation of the pain-management program: 47% versus 61%; p = 0.048. This difference was driven primarily by reduced pain late (8-24 h) after the procedure; 16% versus 39%; p < 0.001. The risk to develop late (8-24 h) post-procedural pain was reduced approximately three-fold after implementation of the pain-management programme (OR = 0.32, 95% CI 0.16-0.64, p = 0.001). Multivariate analysis indicated chronic pain, early pain (0-6 h), and type of intervention were associated with late post-interventional pain. In contrast, age, diabetes mellitus, BMI, gender and procedure time were not related. CONCLUSION: The findings illustrate the potential value of a structured pain-management programme. The proportion of patients who experienced moderate-to-severe pain after these electrophysiological procedures decreased significantly. SIGNIFICANCE: This is the first exploratory study that evaluates the impact of a multidisciplinary pain-management programme after cardiac electrophysiological interventions. It demonstrates that significant quality improvement is achievable following simple rules together with patient and staff education. The programme reduces the proportion of patients with moderate-to-severe pain after electrophysiological procedures significantly.

Relativistic Electron Streaming Instabilities Modulate Proton Beams Accelerated in Laser-Plasma Interactions.

We report experimental evidence that multi-MeV protons accelerated in relativistic laser-plasma interactions are modulated by strong filamentary electromagnetic fields. Modulations are observed when a preplasma is developed on the rear side of a µm-scale solid-density hydrogen target. Under such conditions, electromagnetic fields are amplified by the relativistic electron Weibel instability and are maximized at the critical density region of the target. The analysis of the spatial profile of the protons indicates the generation of B>10 MG and E>0.1 MV/µm fields with a µm-scale wavelength. These results are in good agreement with three-dimensional particle-in-cell simulations and analytical estimates, which further confirm that this process is dominant for different target materials provided that a preplasma is formed on the rear side with scale length ≳0.13λ_{0}sqrt[a_{0}]. These findings impose important constraints on the preplasma levels required for high-quality proton acceleration for multipurpose applications.

Excess of exercise increases the risk of atrial fibrillation.

An interesting and still not well-understood example for old medical wisdom "Sola dosis facit venenum" is the increased prevalence of atrial fibrillation (AF) in athletes. Numerous studies have shown a fourfold to eightfold increased risk of AF in athletes compared to the normal population. Analysis of the existing data suggests a dose-dependent effect of exercise. Moderate exercise seems to have a protective effect and decreases the risk of AF, whereas excessive exercise seems to increase the risk of AF. The described cases illustrate clinical manifestations within the spectrum of AF in elderly athletes, that is, exercise-induced AF, vagal AF, chronic AF, and atrial flutter. As the arrhythmia worsened quality of life and exercise capacity in all patients, recovery of sinus rhythm was desired in all described cases. As the atrial disease was advanced on different levels, different treatment regimes were applied. Lifestyle modification and temporary anti-arrhythmic drug therapy could stabilize sinus rhythm in one patient, whereas others needed radiofrequency ablation to achieve a stable sinus rhythm. The patient with the most advanced atrial disease necessitated anti-arrhythmic drug therapy and another left atrial ablation. All described patients remained in sinus rhythm during the long-term follow-up.

[How to approach the patient with supraventricular tachycardia in the EP lab: A systematic overview]. / Diagnostik bei supraventrikulären Tachykardien : Wie ist das Vorgehen im elektrophysiologischen Labor?

The term supraventricular tachycardia (SVT) summarizes those tachycardias involving the atrial myocardium along with the atrioventricular (AV) node. The prevalence is about 2.25 per 1000 (without atrial fibrillation and atrial flutter) and, therefore, SVT represents one of the most common group of arrhythmias besides atrial fibrillation encountered in the emergency department especially since they tend to recur until definite therapy. The clinical symptoms may include palpitations, anxiety, presyncope, angina, and dyspnea. Pharmacological therapy of these arrhythmias often fails. The present article deals with the differential diagnosis of SVT and also introduces a series of manuscripts that provide detailed insight into the differential diagnosis and treatment of these arrhythmias.

Battery related cobalt and REE flows in WEEE treatment.

In batteries associated with waste electrical and electronic equipment (WEEE), battery systems can be found with a higher content of valuable and critical raw materials like cobalt and rare earth elements (REE) relative to the general mix of portable batteries. Based on a material flow model, this study estimates the flows of REE and cobalt associated to WEEE and the fate of these metals in the end-of-life systems. In 2011, approximately 40 Mg REE and 325 Mg cobalt were disposed of with WEEE-batteries. The end-of-life recycling rate for cobalt was 14%, for REE 0%. The volume of waste batteries can be expected to grow, but variation in the battery composition makes it difficult to forecast the future secondary raw material potential. Nevertheless, product specific treatment strategies ought to be implemented throughout the stages of the value chain.

Rheological behaviour of reconstructed skin.

Reconstructed skins have been developed to replace skin when the integrity of tissue has been compromised following severe injury, and to provide alternative methods validating the innocuousness and effectiveness of dermatological and cosmetic products. However the functional properties of tissue substitutes have not been well characterised, mainly since mechanical measurement devices have not been designed to test cell culture materials in vitro. From the mechanical standpoint, reconstructed skin is a heterogeneous multi-layer viscoelastic material. To characterise the time-dependent behaviour of reconstructed skin, spherical indentation load-relaxation tests were performed with a specific original device adapted to measure small soft tissue samples. Load-relaxation indentation tests were performed on a standard reconstructed skin model and on sub-components of the reconstructed skin (3D-scaffold alone and dermal equivalent). Generalised Maxwell and Kelvin-Voigt rheological models are proposed for analysing the mechanical behaviour of each biological tissue. The results indicated a modification of the rheological behaviour of the samples tested as a function of their biological structure. The 3D-scaffold was modelled using the one-branch Maxwell model, while the dermis equivalent and the reconstructed skin were modeled using a one-branch and a two-branch Kelvin-Voigt model, respectively. Finally, we demonstrated that skin cells contribute to global mechanical behaviour through an increase of the instantaneous relaxation function, while the 3D-scaffold alone influences the mechanical response of long relaxation times.

Insulin-transferrin-selenium as an alternative to foetal serum for epidermal equivalents.

OBJECTIVE: Organotypic skin models are powerful tools for research in development, ageing and diseases. They have become more and more complex with the use of multiple cell types. This requires a culture medium adapted to optimize the development of such in vitro skin. Foetal bovine serum (FBS) is the most complete supplement in existence at the moment, providing at once growth factors, vitamins, hormones and other circulating compounds. However, this cocktail suffers from batch variability and its animal origin is ethically questionable. More importantly, its biological activities may interfere with the study of certain signalling pathways. Here, we present a strategy for constructing an epidermal equivalent using a defined culture medium without serum. METHODS: An epidermal equivalent was constructed with primary human keratinocytes cultured using an insulin-transferrin-selenium (ITS) medium. Determination of steady-state gene expression levels and the immunohistological characterization of keratinocyte markers were performed to compare the ITS medium condition with a reference model, where keratinocytes were co-cultured with fibroblasts in the presence of FBS. RESULTS: The data show that the ITS medium promoted the expression of keratinocyte proliferation and differentiation markers at the protein and transcript levels in a similar way to that of the reference model. CONCLUSION: We show that culture using the ITS medium appears as a viable replacement for FBS in the construction of epidermal equivalents, opening the way to signal transduction studies.

Incidental and ablation-induced findings during upper gastrointestinal endoscopy in patients after ablation of atrial fibrillation: a retrospective study of 425 patients.

BACKGROUND: Although rare, atrioesophageal fistula is a serious and often lethal complication of radiofrequency catheter ablation in patients with atrial fibrillation (AF). Consequently, esophagogastroduodenoscopy after AF catheter ablation has been suggested to detect thermal esophageal lesions. OBJECTIVE: To report the incidence of thermal lesions and other incidental gastrointestinal (GI) abnormalities in patients with AF after radiofrequency catheter ablation. METHODS: Four hundred twenty-five (mean age 59 ± 10 years; 64% men) consecutive patients with symptomatic AF who underwent left atrial radiofrequency catheter ablation were scheduled for upper GI endoscopy 1-3 days after the procedure. Patients were asymptomatic for GI diseases, that is, exhibiting no dysphagia, heart burn, or abdominal pain. RESULTS: Pathological GI findings were observed in 328 (77%) patients and included gastral erosions (22%), esophageal erythema (21%), gastroparesis (17%), hiatal hernia (16%), reflux esophagitis (12%), thermal esophageal lesion (11%), and suspected Barrett's esophagus (5%). Biopsies were performed in 70 (17%) patients, showing gastritis (84%), Helicobacter pylori colonization (17%) and mucosa-associated lymphoid tissue (17%), esophagitis (9%), and Barrett's esophagus (4%). Further diagnostic workup or treatment was initiated in 105 (25%) patients. CONCLUSIONS: Upper GI pathologies are observed frequently in asymptomatic patients. Half of all patients have a requirement for treatment. Among the findings, thermal esophageal lesions and gastroparesis can be attributed to AF catheter ablation. The high incidence of gastroparesis is a novel finding that deserves further investigation.

Non-fluoroscopic catheter visualization using MediGuide™ technology: experience from the first 600 procedures.

A novel cardiovascular navigation system known as MediGuide™ (MG) which allows non-fluoroscopic catheter tracking over a background of pre-recorded cine loops was recently introduced. This system allows significant reduction of fluoroscopy exposure which is one of the potentially harmful aspects of today's electrophysiological procedures such as ablations or device implantations. We provide a summary of recently published studies related to this new technological platform and describe our experience from the first 600 MG procedures at our institution.After reviewing the currently available publications in the field of MG-supported EP procedures, we describe the workflows for (1) ablation of supraventricular tachycardia (SVT), atrial fibrillation (AF), and ventricular tachycardia using MG-enabled diagnostic and ablation catheters, as well as (2) implant of cardiac resynchronization therapy (CRT) devices using sensor-equipped delivery tools including sheaths, sub-selectors, and guidewires.As shown in several studies [5-9], MG procedures resulted in similar efficacy as conventional cases but with a significant reduction in fluoroscopy time and dose. In particular, for SVT ablations, the median fluoroscopy time using the MG technology was 0.5 ± 1.4 min compared to 10.2 ± 9.6 min in conventional fluoroscopic settings. Similar reductions were demonstrated for AF ablation procedures from 25 min in conventional settings with electroanatomical mapping systems and live x-ray to 4.6 min with the addition of the MG technology. Recently, it was demonstrated that the application of MG for CRT device implants could successfully result in a median fluoroscopy time of 2.6 min for LV lead deployment.In summary, the first measurable clinical impact of the MG technology on a daily clinical routine is the reduction of fluoroscopy time and radiation exposure for various EP indications. These beneficial effects were achieved without negative consequences on procedural efficacy, complications, or time in more than 600 EP procedures.

[Therapeutic management of non-valvular atrial fibrillation. Update 2013]. / Therapeutisches Management des nichtvalvulären Vorhofflimmerns. Update 2013.

In western countries one in ten of elderly persons (> 65 years old) will develop atrial fibrillation. The main goal in atrial fibrillation therapy is the prophylaxis of thromboembolic complications through anticoagulation according to the individual risk profile (CHA2DS2-Vasc score) of patients and treatment of cardiovascular comorbidities. Symptoms during atrial fibrillation guide the further therapeutic concept. Doctors can deploy a rate control strategy with a heart rate at rest less than 110/min and/or a rhythm control strategy with cardioversion, antiarrhythmic drugs and catheter ablation to alleviate complaints. To what extent maintaining the sinus rhythm improves the prognosis of atrial fibrillation patients is part of ongoing trials.

In vivo skin biophysical behaviour and surface topography as a function of ageing.

Normal skin ageing is characterised by an alteration of the underlying connective tissue with measurable consequences on global skin biophysical properties. The cutis laxa syndrome, a rare genetic disorder, is considered as an accelerated ageing process since patients appear prematurely aged due to alterations of dermal elastic fibres. In the present study, we compared the topography and the biomechanical parameters of normal aged skin with an 17 year old cutis laxa patient. Skin topography analyses were conducted on normal skin at different ages. The results indicate that the skin relief highly changes as a function of ageing. The cutaneous lines change from a relatively isotropic orientation to a highly anisotropic orientation. This reorganisation of the skin relief during the ageing process might be due to a modification of the skin mechanical properties, and particularly to a modification of the dermis mechanical properties. A specific bio-tribometer, based on the indentationtechnique under light load, has been developed to study the biophysical properties of the human skin in vivo through two main parameters: the physico-chemical properties of the skin surface, by measuring the maximum adhesion force between the skin and the bio-tribometer; and the bulk mechanical properties. Our results show that the pull-off force between the skin and the biotribometer as well as the skin Young's modulus decrease with age. In the case of the young cutis laxa patient, the results obtained were similar to those observed for aged individuals. These results are very interesting and encouraging since they would allow the monitoring of the cutis laxa skin in a standardised and non-invasive way to better characterize either the evolution of the disease or the benefit of a treatment.

[Patient selection for catheter ablation of atrial fibrillation: from paroxysmal to chronic]. / Patientenselektion zur Katheterablation von Vorhofflimmern: von paroxysmal bis lang andauernd.

Atrial fibrillation (AF) is the arrhythmia that causes most arrhythmia-associated hospitalisations in the western world. In Germany it affects approximately 3 million people. The limited success rates of drug treatment stimulated an exploration of interventional treatment options for AF. As our knowledge on initiating triggers and perpetuating substrate of AF expanded, catheter ablation techniques have been developed. In this article we review the patient selection criteria according to the current guidelines, and discuss established and recently found risk factors for recurrences of AF and complications by catheter ablation that may influence current patient selection for catheter ablation of AF.

Electrophysiological Evaluation of Pulmonary Vein Isolation.

Since the pulmonary veins (PVs) were identified as a major source of AF triggers, ablation strategies targeting the PVs have evolved from focal ablation inside the PVs to wide area circumferential PV isolation (PVI) which at this juncture is the standard approach. Despite the widespread popularity of PVI, a universal definition is lacking. While "entrance block" is a generally accepted endpoint for PVI, the role of "exit block" has yet to be determined. Inexcitability of the circular ablation line has been introduced as a promising additional endpoint for PVI and was associated with an improved clinical outcome in a randomized trial. Correct interpretation of PV electrograms during an ablation procedure is critical in terms of efficacy and safety. A variety of electrophysiological techniques help to correctly differentiate components of complex PV electrograms. Resumption of PV conduction after initially successful PVI leading to AF recurrence remains a major problem and confirmation of bi-directional conduction block does not exclude reversible tissue damage along the ablation line. Prolongation of post-PVI monitoring and application of provocative procedures such as the administration of adenosine after initial PVI to unmask dormant PV conduction may improve clinical outcome although there is lack of valid data supporting these strategies. This article aims on clarifying the electrophysiological criteria for complete pulmonary vein isolation and the explain the importance of this cornerstone in almost all atrial fibrillation ablation procedures.