Central Ablation Research Articles

Genome-wide association study of patients with atrioventricular nodal reentry tachycardia

Abstract Background Supraventricular tachycardias (SVTs) originate from the atria or the area close to the AV node. AV nodal reentry tachycardia (AVNRT) is one of the tachyarrhytmias comprising the group of SVTs. The typical patient is female, young at disease onset, with a structurally normal heart. At present we do not know the etiology of AVNRT. We therefore hypothesized that AVNRT might be caused by changes in the DNA. Methods DNA from purified blood was obtained from patients with AVNRT verified by an invasive electrophysiological study. Patients were recruited from five ablation centers in Denmark and individuals from the general population of Denmark (the BEFUS cohort) served as controls. DNA was subjected to chip genotyping, imputation and analyses in a genome-wide association study (GWAS) setup. Results A GWAS on 1,143 AVNRT patients and 3,004 controls revealed one locus close to the gene MYH6 to reach genome-wide significance for association with AVNRT (P=4.8x10–8). MYH6 encodes the α-isoform of the protein myosin heavy chain important for the contractile units of the heart, the sarcomeres. The gene is predominantly expressed in the atria. Additional subthreshold loci located close to other plausible arrhythmia genes were identified. Conclusion We report the first genetic locus to be associated with AVNRT close to the sarcomere gene MYH6. This is, to our knowledge, the first gene ever associated with AVNRT. Manhattan plot Funding Acknowledgement Type of funding source: Public hospital(s). Main funding source(s): Rigshospitalets Forskningspulje - 3 years PhD salary

Low mortality rate after atrial fibrillation ablation: results from the Netherlands Heart Registration

Abstract Background Ablation therapy is widely used as a treatment of atrial fibrillation (AF) and is associated with 3.6% minor and major complications in the Netherlands. Mortality following AF ablation is rare, but has been reported 0.46% in the United States in recent literature. We hypothesize that in the Netherlands, where AF ablation is performed in high volume centres only, 30-day mortality rate is low. Purpose To describe 30-day mortality in the Netherlands after AF ablation. Methods In the Netherlands Heart Registration, all 16 Dutch ablation centres participate and 14 out of 16 centres reported AF ablation outcomes using predefined variables for quality purposes. The number of reported procedures per centre was on average 236/year [range, 33–593], where 87.5% of the centres perform >150 AF ablations per year. All patients who underwent AF ablation were eligible for this analysis irrespective of ablation method used, or whether it was the first or a redo AF ablation. 30-day mortality was derived from, the municipal death registration, and individually checked by each participating ablation centre. No further analysis was available on the cause of death. Results In total, 20,230 patients who underwent AF ablation between 01-01-2013 and 31-12-2018 were included. The majority of patients were male (68%), mean age was 60.9±9.8 years, mean body mass index was 27.3±4.2kg/m2, and the average CHA2DS2VASc score was 1.6±1.3. Reduced left ventricular (LV) ejection fraction (<50%) was present in 13.2% of the patients. Paroxysmal AF was present in 72.7% of patients, persistent AF in 24.9% and longstanding persistent in 2.3%. The index procedure was a redo-ablation in 22.7%. Mortality outcomes were available for 18,413 (91.0%) procedures, as some centres had a backlog of patients that needed death certificate checking [range, 0% - 19.4%], this factor was considered random. In total 12 patients (0.07%) died within 30-days after an AF ablation procedure. These patients were 68.5 years old [range, 55–76 years], 91.7% had a history of paroxysmal AF and 8.3% persistent AF, LV ejection fraction was <50% in 8.3% and 25% of the patients had a previous AF ablation (p=0.02 for age, others p=NS). Conclusion Patients undergoing AF ablation in the Netherlands mainly presented with paroxysmal AF. In a setting where AF ablation is performed in high volume centres only, such as the Netherlands, 30-day mortality is very low after AF ablation. Funding Acknowledgement Type of funding source: None

Impact of procedural volume on complication and recurrence rate after atrial fibrillation ablation in European centers. An ESC EORP Registry: Atrial Fibrillation Long-Term

Abstract Background Catheter ablation has emerged as an effective therapy in patients with atrial fibrillation (AF). Despite high success rates of the method, there is still heterogeneity of outcomes and complications across Europe. A center's volume of AF ablations performed per year might also play an important role in the success rate of the procedure as compared to other confounding factors which may be different among centers (such as type of AF ablated, patient selection criteria, referral bias and/or ablation strategy). Purpose Aim of the study was to investigate differences in clinical outcomes and complication rates among European AF ablation centers related to the volume of ablations performed annually. Methods Data for this analysis were extracted from the European AF Ablation Long-Term Study, a prospective registry designed to describe the clinical epidemiology of patients undergoing AF ablation. Based on 33th and 67th percentiles of number of AF ablations performed, the participating centers were classified into high volume (HV) (≥180 procedures/year), medium volume (MV) (<180 and ≥74/year) and low volume (LV) (<74/year). One-year success was defined as patient survival free from any atrial arrhythmia, from the end of the 3-month blanking period to 12 months following the ablation procedure. Results A total of 91 centers in 26 European countries enrolled 3368 patients. There was a significantly higher reporting of cardiovascular complications in LV centers (5.2%), especially pericarditis and cardiac perforation, while the HV and MV centers reported cardiovascular complications in 3.0 and 4.3% of cases, respectively (p=0.039). Additionally, stroke incidence after ablation was significantly higher in LV centers (0.5% of cases vs 0% in HV and MV centers, p=0.008). One-year success after AF ablation ranged from 77.8% in HV vs 70.5% in LV vs 77.3% in MV centers (p<0.001). Despite these unadjusted differences, Kaplan-Meier survival analysis based on adjusted data demonstrated, however, that there were not significant differences in complication and recurrence rates according to volume's center (p=0.328 and p=0.476 accordingly, Figure A). This result was mainly driven by a proportional increase in severity/risk of cases ablated (as evidenced by CHA2DS2-VASc score and AF type) in relation to a center's procedural volume (Figure B). Conclusions Low volume centers present slightly higher cardiovascular complications' and stroke incidence and a lower unadjusted success rate after AF ablation. On the other hand, adjusted overall complication and recurrence rates are non-significantly different among different volume centers, a fact reflecting inhomogeneity of patient and procedural profiles and a counterbalance between expertise and risk level among participating centers. Funding Acknowledgement Type of funding source: None

Real life experience with atrial fibrillation cryoballoon ablation: results from a nationwide registry

Abstract Cryoballoon ablation (CBA) is an effective strategy for AF management. The Russian Cryoballoon Atrial Fibrillation Ablation Registry (NCT03040037) is a prospective observational multicenter national registry that aims to provide real-world efficacy, safety and outcomes of this technology. Purpose To evaluate the CBA efficacy, types of adverse events following CBA based on a multicenter nationwide registry. Materials and methods A web-based registry platform was developed for prospective data entry. The platform consisted of 8 sections: AF ablation experience, patient and CBA characteristics, periprocedural management, 12-month FU, redo procedures, early and late procedure-related complications. Inclusion criteria were the following: indications for AF catheter ablation, planned CBA, a signed informed consent. 32 ablation centers and 1118 patients (572 males, a mean age 68.3±11.4) were included into the registry. Paroxysmal AF was presented in 722 pts, persistent AF – 350 pts, long standing persistent AF – 46 pts. The main underlying diseases were hypertension, coronary artery disease, chronic heart failure; less commonly - hypertrophic cardiomyopathy and dilated cardiomyopathy. The mean LA diameter was 44.7±11.1 mm, LVEF was 62.6±10.8%. The mean BMI was 32.3±3.5 kg/m2. Cardioversion prior to CBA was performed in 32.8%. There were different strategies of AF recurrence documentation: ECG, 24-hour ECG monitor, ECG loop recorder implantation. Results The mean temperature of cryoablation was −45.7±17.4 C. The mean fluoroscopy time was 23.98 mins. The mean patient procedure duration was 108.46 mins [min 30; max 266]. The combination of RFA and CBA was reported in 9 cases. Periprocedural anticoagulant therapy included: uninterrupted NOACs (535 pts), bridge anticoagulation (365 pts), uninterrupted warfarin (67 pts), anticoagulation initiated only after CBA (151 pts). Transesophageal echo-guided CBA was performed in 126 cases, intracardiac echocardiography-guided CBA was performed in 474 cases. Esophageal temperature was controlled in 16 cases. A 12-months follow-up was completed in 906 pts (81.0%). Arrhythmia recurrence was documented in 238 cases (21.3%), mainly AF. Elective cardioversions were performed in 39 pts. Redo ablation procedures were performed in 122 cases. There were a wide range of antithrombotic therapy, as well as pts without anticoagulants despite the fact of AF recurrence. There were 35 (3.1%) CBA-related major adverse events. Esophageal damage was found in 3 cases. There were registered 3 deaths (1 – oncology, and 2 due to unknown cause), 1 MI, 3 persistent phrenic nerve dysfunctions, 3 valve dysfunctions. Conclusion This nationwide registry represents contemporary safety and efficacy of CBA for AF. A high success rate of the procedure has been shown during 12 months post procedure. Although a total low number of procedure-related complications has been noted, the occurrence of life-threatening adverse events calls for a caution. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): Government of the Russian Federation

Catheter ablation in atrial fibrillation: comorbidities and mortality from high-volume centers

Abstract Background Catheter ablation (CA), has gained wider acceptance as an attractive option for treating symptomatic AF. Although traditionally seen as a safe procedure, there is limited and conflicting data on procedure-related early morbimortality, with new evidence suggesting early mortality may be as high as 0.5%-1%. Purpose We aimed to assess the rates of early and late morbimortality of post-atrial fibrillation (AF) ablation in high-volume centers. Methods Prospective registry of 2 high-volume ablation centers, comprising 3722 consecutive patients (mean age 61.1±11.2, 66.4% male, n=2471), who underwent AF ablation from 2005 to 2019. Early mortality was defined as death during initial admission or during the first 45 days after ablation. Median follow-up time was 5.4 years. Results Most patients were treated with radiofrequency (97%) while 3% were treated with cryoablation. Early mortality was 0.08% (n=3), with a median time from ablation to death of 22 days. Cumulative mortality at 3, 6 and 12 months was 0.08%, 0.16% and 0.19%, respectively. At 3 and 5 years, mortality remained low at 0.48% and 0.73%, respectively. Early mortality was higher among patients who had suffered procedural complications (fistula and stroke, p<0.001). Among the latter, pericardial effusion and tamponade were the most frequently found (0.6%, n=24), only 1 of which required emergent surgical drainage and myocardial repair. Early ischemic stroke occurred in 2 patients (0.1%). Other less frequent complications were atrio-esophageal fistula (0.1%, n=2), phrenic nerve palsy (0.1%, n=2), anoxic encephalopathy following cardiac arrest (0.03%, n=1) and pulmonary vein stenosis (0.03%, n=1). Conclusion Early mortality following ablation is very low (<0.1%), when performed by an experienced high-volume team. Severe complications are rare (<1%) and mostly amenable to treatment. Our findings reaffirm the overall safety of AF ablation. AF catheter ablation morbimort Funding Acknowledgement Type of funding source: None

Gender-specific risk of complications in catheter ablation for atrial fibrillation

Abstract Background Catheter ablation is an established treatment modality for atrial fibrillation (AF). The risk of procedural complications is not negligible. Some studies suggested that female patients have a higher risk of complications. Purpose To identify gender-specific predictors of major complications (MCs) in patients undergoing catheter ablation for AF in a tertiary ablation centre. Methods A total of 4733 catheter ablations for AF (65% paroxysmal, 26% repeated procedures) were performed at our centre between January 2006 and August 2018. Patients (71% males) aged 60±10 years and had body mass index of 29±4 kg/m2 at the time of the procedure. Radiofrequency point-by-point ablation was employed in 96.3% procedures with the use of 3D navigation systems and facilitated by intracardiac echocardiography. Pulmonary vein isolation was mandatory; cavotricuspid isthmus and left atrial substrate ablation were performed in 22% and 38% procedures, respectively. MCs were defined as those that resulted in permanent injury, required intervention or prolonged hospitalization. Variables were assessed by uni- and multivariate analysis, two-sided α<0.05 was considered significant. Results A total of 160 (3.4%) MCs were detected - 60 (4.4%) in females and 100 (2.9%) in males (P=0.012). Both lower body height and the presence of bundle branch block (BBB) were associated with MCs only in females; for left bundle branch block (LBBB), the effect size was higher. On the contrary, higher left ventricular end-diastolic diameter (LVEDd) and persistent AF were associated with MCs in males (Table). Conclusion Females have a higher risk of MCs during catheter ablation for AF. Body height, AF type, BBB, and LVEDd may belong among gender-specific risk factors for MCs in AF ablation procedures. Whether BBB and LVEDd represent true risk factors warrants a validation in further studies. Funding Acknowledgement Type of funding source: None

Epicardial adipose tissue and atrial fibrillation: guilty as charged or guilty by association?

Abstract Background Epicardial adipose tissue (EAT) has been linked to the presence and burden of atrial fibrillation (AF). However, it is still unclear whether this relationship is causal or simply a surrogate marker of other risk factors commonly associated with AF. Purpose The purpose of this study was to assess the relationship between these factors and EAT, and to compare their performance in predicting AF recurrence after an ablation procedure. Methods We assessed 575 consecutive patients (mean age 61±11 years, 62% male) undergoing AF ablation preceded by cardiac CT in a high-volume ablation center. EAT was measured on cardiac CT using a modified simplified method. Patients were divided into 2 groups (above vs. below the median EAT volume). Cox regression was used to assess the relationship between epicardial fat, risk factors, and AF relapse. Results Patients with above-median EAT volume were older (p<0.001), more often male (OR 1.7, p=0.002), had higher body mass index, and higher prevalence of smoking, hypertension, diabetes and dyslipidemia (p<0.05). Non-paroxysmal AF was also more common in those with above-median EAT volume. During a median follow-up of 18 months, 232 patients (40.3%) suffered AF recurrence. After adjustment for BMI and other univariate predictors of relapse, three variables emerged independently associated with time to AF recurrence: non-paroxysmal AF (HR 2.1, 95% CI: 1.5–2.7, p<0.001), indexed left atrial (LA) volume (HR 1.006 per mL/m2, 95% CI: 1.002–1.011, p<0.001), and indexed epicardial fat volume (HR 1.87 per mL/m2, 95% CI: 1.66–2.1, p<0.001). None of the classic cardiovascular risk factors were an independent predictor of AF recurrence (all p>0.10). Conclusion Classic cardiovascular risk factors are more prevalent in patients with higher amounts of epicardial fat. However, unlike these risk factors, EAT is a powerful predictor of AF recurrence after ablation. These findings suggest that EAT is not merely a surrogate marker, but an important participant in the pathophysiology of AF. EAT, cvrf and AF burden Funding Acknowledgement Type of funding source: None

Improved ablation resistance of 3D-Cf/SiBCN composites with (PyC/SiC)3 multi-layers as interphase

Ablation behavior of 3D-Cf/SiBCN composites with (PyC/SiC)3 multi-layers as interphase was investigated in plasma ablation flame at a heat flux of 4.02 MW m−2. During ablation, amorphous SiBCN matrix is firstly oxidized and forms a borosilicate glass, in which B2O3 is volatilized as the ablation going on. At the ablation center with higher temperature, SiC and Si3N4 grains are precipitated from the amorphous SiBCN matrix. And then, these SiC and Si3N4 grains are oxidized, forming a certain viscous silica rich protective coating on the sample surface. Moreover, it is revealed that the SiC layers in (PyC/SiC)3 multi-layers interphase can protect the carbon fibers from ablation damage effectively. Compared with the Cf/(PyC)SiBCN composites, much improved ablation resistance is achieved for the Cf/(PyC/SiC)3SiBCN composites. The linear and mass recession rates of the Cf/(PyC/SiC)3SiBCN composites are as low as 1.7 ± 0.4 μm s−1 and 0.0427 ± 0.0053 mg mm−2s−1, which are ∼43 % and ∼21 % lower than those of Cf/(PyC)SiBCN.

Cool enough? Lessons learned from cryoballoon-guided catheter ablation for atrial fibrillation in young adults.

Cryoballoon (CB)-guided ablation of atrial fibrillation (AF) is established in symptomatic AF patients. This study sought to determine the safety and efficacy of CB pulmonary vein isolation (PVI) in young adults. A total of 93 consecutive patients aged <45 years referred to our center for AF ablation were included in this observational study. All patients received CB-guided PVI according to a standardized institutional protocol. Follow-up was performed in our outpatient clinic using 72-h Holter monitoring and periodic telephone interview. Recurrence was defined as any AF/atrial tachycardia (AT) episode >30 s following a 3-month blanking period. A propensity matched control group consisting of patients older than 45 years were used for further evaluation. Mean age was 35 ± 7 years, 22% suffered from persistent AF, 85% were male. Mean follow-up was 2.6 ± 2 years. At the end of the observational period, 83% of patients were free of any AF/AT episodes. There was an excellent overall 12-month success rate of 92%. In comparison to a matched group the overall recurrence rate was noticeably lower in the young group (15% vs. 27%). Increasing age was associated with a hazard ratio of 1.16 for recurrence. In a multivariate analysis model, left atrial diameter remained as significant predictor of AF/AT recurrence. The complication rate was low, no permanent phrenic nerve palsy was observed. CB-guided PVI in young adults is safe and effective with favorable long-term results. It may be considered as first-line therapy in this relatively healthy population.

Long-term incidence and predictive factors of thromboembolic events after a cryoballoon ablation for atrial fibrillation

BackgroundLong-term outcomes in terms of thromboembolic events (TEs) are poorly described after cryoballoon pulmonary vein isolation (cryo-PVI) for atrial fibrillation (AF). We evaluated the long-term incidence and predictive factors of TE after cryo-PVI. MethodsAll consecutive patients who underwent cryo-PVI for paroxysmal or persistent AF between November 2012 and October 2017 were included. They were prospectively followed for at least 12 months in the ablation center and then by their cardiologist. Data on all ischemic events (stroke, transient ischemic attack (TIA), systemic embolism) were collected. ResultsIn total, 450 patients (78% men, median age 61 years) were included. The mean CHA2DS2-VASc score was 1.6 ± 1.3 and 26 patients (6%) had a history of stroke/TIA before the procedure. OAT was discontinued for 75 patients (17%) after the procedure, among whom 50 (67%) had no indication for long-term anticoagulation. Six patients experienced an ischemic event, all considered as a TE: three strokes, two TIAs, and one acute lower-limb ischemia. The mean follow up was 30 months. Thus, the incidence of TE was 0.53%/year. Three of the six patients who experienced a TE had no recurrence of atrial arrhythmia documented before, at the time, or after the event. All patients who experienced a TE had a class I or class IIa indication for long-term anticoagulation. After multivariate analysis, the CHA2DS2-VASc Score (p = .0005) was a predictor of TEs. ConclusionThe long-term incidence of TEs after cryo-PVI was 0.53%/year. The CHA2DS2-VASc Score was the only independent predictor of TEs.

Predictors of hospital expenses and hospital stay among patients undergoing total laryngectomy: Cost effectiveness analysis.

To determine the predictive factors of postoperative hospital stay and total hospital medical cost among patients who underwent total laryngectomy. A total of 213 patients who underwent total laryngectomy in a tertiary referral center for tumor ablation were enrolled retrospectively between January 2009 and May 2018. Statistical analyses including Pearson's chi-squared test were used to determine whether there was a significant difference between each selected clinical factors and outcomes. The outcomes of interest including postoperative length of hospital stay and inpatient total medical cost. Logistic regression analyses were performed to reveal the relationship between clinical factors and postoperative length of hospital stay or total inpatient medical cost. Preoperative radiotherapy (p = 0.007), method of wound closure (p < 0.001), postoperative serum albumin level (p = 0.025), and postoperative serum hemoglobin level (p = 0.04) were significantly associated with postoperative hospital stay in univariate analysis. Postoperative hypoalbuminemia (odds ratio [OR]: 2.477; 95% confidence interval [CI]: 1.189-5.163; p = 0.015) and previous radiotherapy history (OR 2.194; 95% CI: 1.228-3.917; p = 0.008) are independent predictors of a longer postoperative hospital stay in multiple regression analysis. With respect to total inpatient medical cost, method of wound closure (p < 0.001), preoperative serum albumin level (p = 0.04), postoperative serum albumin level (p < 0.001), and history of liver cirrhosis (p = 0.037) were significantly associated with total inpatient medical cost in univariate analysis. Postoperative hypoalbuminemia (OR: 6.671; 95% CI: 1.927-23.093; p = 0.003) and microvascular free flap reconstruction (OR: 5.011; 95% CI: 1.657-15.156; p = 0.004) were independent predictors of a higher total inpatient medical cost in multiple regression analysis. Postoperative albumin status is a significant factor in predicting prolonged postoperative hospital stay and higher inpatient medical cost among patients who undergo total laryngectomy. In this cohort, the inpatient medical cost was 48% higher and length of stay after surgery was 35% longer among hypoalbuminemia patients.

Subregion Radiomics Analysis to Display Necrosis After Hepatic Microwave Ablation-A Proof of Concept Study.

The aim of this study was to improve the visualization of coagulation necrosis after computed tomography (CT)-guided microwave ablation (MWA) in routine postablational imaging. Ten MWAs were performed in 8 pigs under CT guidance. After each ablation, we obtained contrast-enhanced CT scans in venous phase. Ablations were then resected as a whole, and histologic slices were obtained orthogonally through the ablation center. Subsequently, a vital stain was applied to the sections for visualization of coagulation necrosis. Computed tomography images were reformatted to match the histologic slices. Afterwards, quantitative imaging features were extracted from the subregions of all images, and binary classifiers were used to predict the presence of coagulation necrosis for each subregion. From this, heatmaps could be created, which visually represented the extent of necrosis in each CT image. Two independent observers evaluated the extent of coagulative necrosis between the heat maps and histological sections. We applied 4 different classifiers, including a generalized linear mixed model (GLMM), a stochastic gradient boosting classifier, a random forest classifier, and a k-nearest neighbor classifier, out of which the GLMM showed the best performance to display coagulation necrosis. The GLMM resulted in an area under the curve of 0.84 and a Jaccard index of 0.6 between the generated heat map and the histologic reference standard as well as a good interobserver agreement with a Jaccard index of 0.9. Subregion radiomics analysis may improve visualization of coagulation necrosis after hepatic MWA in an in vivo porcine model.

Periportal fields cause stronger cooling effects than veins in hepatic microwave ablation: an in vivo porcine study.

Vascular cooling effects are a well-known source for tumor recurrence in thermal in situ ablation techniques for hepatic malignancies. Microwave ablation (MWA) is an ablation technique to be considered in the treatment of malignant liver tumors. The impact of vascular cooling in MWA is still controversial. To evaluate the influence of different intrahepatic vessel types, vessel sizes, and vessel-to-antenna-distances on MWA geometry in vivo. Five MWAs (902-928 MHz) were performed with an energy input of 24.0 kJ in three porcine livers in vivo. MWA lesions were cut into 2-mm slices. The minimum and maximum radius of the ablation area was measured for each slice. Distances were measured from ablation center toward all adjacent hepatic vessels with a diameter of ≥1 mm and within a perimeter of 20 mm around the antenna. The respective vascular cooling effect relative to the maximum ablation radius was calculated. In total, 707 vessels (489 veins, 218 portal fields) were detected; 370 (76%) hepatic veins and 185 (85%) portal fields caused a cooling effect. Portal fields resulted in higher cooling effects (37%) than hepatic veins (26%, P < 0.01). No cooling effect could be observed in close proximity of vessels within the central ablation zone. Hepatic vessels influenced MWA zones and caused a distinct cooling effect. Portal fields resulted in more pronounced cooling effect than hepatic veins. No cooling effect was observed around vessels situated within the central white zone.

P955Non-invasive mapping: what is the minimal number of electrodes needed to obtain a good spatial resolution of the activation map?

Abstract Introduction and aims The 12-lead ECG is highly inaccurate for localization of the site of origin of supraventricular and ventricular arrhythmias. Non-invasive mapping systems (ECGI) based on a high number of electrodes recording the electrical activity on the surface of the torso have already proven good accuracy for mapping different arrhythmic substrates. The aim of this study was to assess what is the minimal number of leads needed to obtain a precise mapping with the ECGI. Methods This study enrolled 14 patients (9 male, median age 50 (44-58) years) referred to our center for catheter ablation of premature ventricular contractions (PVC). Patients underwent pre-procedural ECGI using the epicardial and endocardial mapping system . This system uses the DICOM images from contrast computed tomography of the heart and up to 28 adhesive electrodes with 8 leads each, adding up to 224 body-surface leads. All patients underwent invasive electroanatomical mapping and ablation with the magnetic navigation system. We analysed the number of recording leads used to construct the non-invasive activation map of the PVCs and the accuracy and the spatial resolution of the map when comparing to the invasive map. We then reprocessed the exam, using progressively less leads until we only left the leads placed in the standard 12 lead ECG positions and evaluated the concordance with the invasive map as well as the spatial resolution. We considered an earliest activation site (EAS) area of 1 cm2 a good spatial resolution and using a ROC curve we calculated the minimal number of leads necessary to obtain a good spatial resolution. Results The median number of electrodes used for the initial map was 170 (138-177). Concordance between non-invasive and invasive site of origin occurred in 11 out of 14 patients. The results are presented in the Table. The minimal number of electrodes to have a good spatial resolution was 100. The area of EAS was significantly lower when using more than 100 leads, respectively 0.65 (0.5-1) cm2 versus 3 (1.6-5) cm2, p &amp;lt; 0.001. Conclusions The minimal number of leads to achieve a good spatial resolution was high. Reducing the number of leads resulted in a significant decrease in spatial resolution and a lower concordance rate. ECGI data Number of adhesive electrodes Median number of leads Amycard/Carto concordance Median area of EAS in the ECGI (cm2) Maximal nº electrodes 170 (138-177) 11/14 0.64 (0.5-0.9) 12 electrodes 76 (61-80) 11/14 1.6 (1.4-2.6) 6 electrodes (2 Ant, 2 Lat ,2 Post) 38 (32-44) 9/14 4.3 (3.2-5.4) 12 leads 12 0/14 - Ant anterior; Lat: lateral; Post: posterior; EAS: early activation site. Abstract Figure. Area of EAS according to the N of leads

Microstructure and properties of a novel designed interpenetrating network structure silicide/HfxZr1−xC multi-phase outer layer

In this paper, a novel interpenetrating network structure was designed for the outer layer of Zr-Hf-Si-C multi-layer and multi-phase coating for carbon matrix to improve the ablation resistance and anti-particle scour. The proposed interpenetrating network structure is prepared via a one-step method of embedding infiltration/thermal evaporation. The microstructural, micro-mechanical, and ablation resistance properties of the coating were studied. Results show that the silicide and HfxZr1−xC(0.50 < x < 0.71) penetrate each other in the outer layer. The mechanical properties have increased by 27.7% in the outer layer owing to the interpenetrating network structure. The multi-phase outer layer with silicide showed a significant improvement in the ablation resistance as compared to that of the multi-phase outer layer without silicide and could protect carbon matrix for >60 s at 2800 ± 70 °C. Under the action of the interpenetrating network structure silicide, the ablation centre and the corresponding transition region form a dense Zr(Hf)O2 layer and Zr(Hf)CxOy region, respectively.

Intelligent cooling structure design of "Z-pins like" silicon rods to enhance the ablation resistance of C/C-ZrC-SiC composites above 2500 °C

In order to improve the ablation resistance of C/C-ZrC-SiC composites by reducing the damage of the protective oxide layer, novel "Z-pins like" silicon rods, which were designed and fabricated by liquid phase sintering, were utilised as a dissipative agent. The microstructure evolution and thermal dissipation behaviour were investigated after ablating above 2500 °C for 300 s. After the "Z-pins like" silicon rods were implanted, the anti-ablative property of the C/C-ZrC-SiC composites was drastically improved by the dissipative thermal protection mechanism. The linear ablation rate of the "Z-pins like" silicon rod-reinforced C/C-ZrC-SiC composite was -0.28 μm/s, which is 112.72% lower than the unmodified composite. Additionally, the actual ablative temperature dropped approximately 357 °C, which enabled abundant SiO2 to remain in the ablation centre. Furthermore, a dense SiO2-rich oxide layer with a low oxygen diffusion coefficient is formed that covers the entire ablative surface.

A Systematic Review of the Spectrum of Cardiac Arrhythmias in Sub-Saharan Africa.

Major structural cardiovascular diseases are associated with cardiac arrhythmias, but their full spectrum remains unknown in sub-Saharan Africa (SSA), which we addressed in this systematic review. Atrial fibrillation/atrial flutter (AF/AFL) prevalence is 16–22% in heart failure, 10–28% in rheumatic heart disease, 3–7% in cardiology admissions, but <1% in the general population. Use of oral anticoagulation is heterogenous (9–79%) across SSA. The epidemiology of sudden cardiac arrest/death is less characterized in SSA. Cardiopulmonary resuscitation is challenging, owing to low awareness and lack of equipment for life-support. About 18% of SSA countries have no cardiac implantable electronic devices services, leaving hundreds of millions of people without any access to treatment for advanced bradyarrhythmias, and implant rates are more than 200-fold lower than in the western world. Management of tachyarrhythmias is largely non-invasive (about 80% AF/AFL via rate-controlled strategy only), as electrophysiological study and catheter ablation centers are almost non-existent in most countries.Highlights:- Atrial fibrillation/flutter prevalence is 16–22% in heart failure, 10–28% in rheumatic heart disease, 3–7% in cardiology admissions, and <1% in the general population in sub-Saharan Africa (SSA).- Rates of oral anticoagulation use for CHA2DS2VASC score ≥2 are very diverse (9–79%) across SSA countries.- Data on sudden cardiac arrest are scant in SSA with low cardiopulmonary resuscitation awareness.- Low rates of cardiac implantable electronic devices insertions and rarity of invasive arrhythmia treatment centers are seen in SSA, relative to the high-income countries.

The effect of YB4 addition in ZrB2-SiC composites on the mechanical properties and oxidation performance tested up to 2000 °C

The influence of YB4 and Y2O3 on densification, mechanical properties and oxidation performance of ZrB2-SiC (ZS) composite was studied. The oxidation tests were performed in static air up to temperature of 1650 °C for 1 h as well as under dynamic conditions of oxyacetylene torch at 2000 °C. Static oxidation of ZS led to the formation of protective silica-based glass on the surface. However, ablation tests showed absence of silica in ablation centre. Only dense zirconia layer was left on the top of ZS. Composites with Y-containing additives exhibited significantly inferior oxidation performance in static conditions, since severe spallation and deeper degradation of the material were observed. On the contrary, the depth of material degradation after ablation was comparable with ZS. Samples were covered by solid solution of zirconia and yttria. Due to very low vapor pressure, yttria-based oxidation products are of interest considering even higher application temperatures exceeding 2000 °C.

Ablation resistance and mechanism of SiC–LaB6 and SiC–LaB6–ZrB2 ceramics under plasma flame

In this study, silicon carbide-lanthanum hexaboride (SiC–LaB6) and silicon carbide–lanthanum hexaboride–zirconium boride (SiC–LaB6–ZrB2) ceramics were fabricated by spark plasma sintering at 1900 °C, and their ablation resistance was tested under plasma flames over 2300 °C. The results indicate that the SiC–LaB6–ZrB2 ceramic exhibits better ablation resistance than the SiC–LaB6 ceramic. After ablation under the plasma flame for 60 s, the mass and linear ablation rates of the SiC–LaB6 ceramic were 15.83 μg/s and 1.08 μm/s, respectively, while those of SiC–LaB6–ZrB2 were -8.42 μg/s and -0.27 μm/s. With the addition of ZrB2, SiC–LaB6–ZrB2 ceramic attained a high density and fewer inner oxygen diffusion channels. Moreover, the ZrO2–La2O3–SiO2 oxide scale with good self-healing ability and excellent stability was formed in the ablation centre, which can retard the further oxidation during ablation.

Radiofrequency-Assisted Transseptal Access for Atrial Fibrillation Ablation Viaa SuperiorApproach.

This study describes the technique and outcomes of atrial fibrillation (AF) ablation via a superior approach in patients with interrupted or absent inferior vena cavas (IVCs). In patients with interrupted or absent IVCs, transseptal access cannot be obtained via standard femoral venous access. In these patients, alternative strategies are necessary to permit catheter ablation in the left atrium (LA). This study reports on the outcomes of AF ablation from a superior venous access with a radiofrequency (RF)-assisted transseptal puncture (TSP) technique. This study identified patients with interrupted or absent IVCs who underwent AF ablation via a superior approach at 2 ablation centers from 2010 to2019. Fifteen patients (mean age: 50.8 ± 11.2 years; 10 men; 10 with paroxysmal AF) with interrupted or absent IVCs underwent AF ablation with transseptal access via a superior approach. Successful TSP was performed either with a manually bent RF transseptal needle (early cases: n=4) or using a RF wire (late cases: n=11); this approach permitted LA mapping and ablation in all patients. Mean time required to perform single (n=8) or double (n=7) TSP was 16.1 ± 4.8min, and mean total procedure time was 227.9 ± 120.7min (fluoroscopy time: 57.0 ± 28.5min). LA mapping and ablation were successfully performed in all patients. In patients with AF undergoing catheter ablation and who had a standard transseptal approach via femoral venous approach is impossible due to anatomic constraints, RF-assisted transseptal access via a superior approach can be an effective alternative strategy to permit LA mapping and ablation.