The impact of abnormal conduction zone on outcomes after catheter ablation for atrial fibrillation

Background The abnormal conduction zone (ACZ) in the left atrium (LA) has attracted attention as an arrhythmia substrate in atrial fibrillation (AF). Purpose We investigated whether the ACZ affects outcomes after catheter ablation (CA) for AF. Methods We studied 78 patients (42 Non-paroxysmal AF, 49 males, and 68±10 years) who received CA for AF. High-density LA mapping during high right atrial pacing was constructed gaining than 2000 points (average 4377±846 points). Isochronal activation maps created at 5-ms interval setting. ACZ was identified by locating a site with isochronal crowding of ≥3 isochrones, and ≥8 isochrones were defined as the conduction block zone (CBZ) in a 4-mm diameter tag (conduction velocity were calculated as ≤27 cm/s and≤10 cm/s, respectively). Result Recurrent AF was detected in 25/78 patients (32%) during the follow-up period (9.2±3.0 month). ACZ and CBZ were distributed linearly, and ACZ was observed in 73 of 78 patients and 8 of these 73 patients had the CBZ. Univariate analysis revealed that elevated body mass index (26.2±3.8 vs. 24.3±3.3 kg/m2, P=0.0303), the higher prevalence of non-paroxysmal AF (72% vs. 45%, P=0.0272), larger LA diameter (47.6±6.6 vs. 42.1±6.9 mm, P=0.0014), and longer length of ACZ (79.7±45.1 vs. 52.9±35.7 mm, P=0.0058) were associated with recurrent AF after CA. On multivariate analysis, longer ACZ was independently associated with recurrent AF. Moreover, patients with longer ACZ (cutoff value: 84 mm) had a higher risk of recurrent AF than shorter ACZ (12/22; 55% vs 13/56; 23%, log-rank P=0.0024). Conclusion The length of ACZ was associated with recurrent AF after CA. FUNDunding Acknowledgement Type of funding sources: None.

Investigation into the Distribution of Erosion-Corrosion in the Furnace Tubes of Oil Refineries

Crude oil is one of the most important sources of energy in the world. To extract its multiple components, we need oil refineries. Refineries consist of multiple parts, including heat exchangers, furnaces, and others. It is known that one of the initial operations in the refineries is the process of gradually raising the temperature of crude oil to 370 degrees centigrade or higher. Hence, in this investigation the focus is on the furnaces and the corrosion in their tubes. The investigation was accomplished by reading the thickness of the tubes for the period from 2008 to 2020 with a test in every two year, had passed from their introduction into the work. Where the thickness of more than one point was measured on each tube in the same row and the corrosion rate was extracted for three furnaces, starting from the area of ​​heat transfer by radiation to the heat transfer area of ​​the convection in three different operating units. It was found that the highest percentage corrosion value between the standard tube thickness and the thickness of conduction position was 37% with the conduction zone, and 31% with radiation zone. There, the tubes specification was tested. Five percent Cr-0.5 Moly and the temperature of radiation zone was 578 °C to 613 °C and the stack temperature was 410 °C to 450 °C. So, the results show that the maximum erosion occur at the convection zone.

A new approach to atrial flutter ablation using functional substrate mapping with wavefront discontinuity during sinus rhythm

Funding Acknowledgements Type of funding sources: None. Background Ultra high-density (UHD) mapping allows accurate identification of local abnormal electrograms and low voltage within a small area range, allowing precise identification of reentry circuits. Areas with high isochronal density in a small area known as deceleration zones (DZ) are responsible for reentry. Purpose Identify the DZ and areas of low voltage in sinus rhythm (SR) and evaluate the feasibility of performing atrial flutter (AFL) ablation by targeting those zones. Methods We prospectively enrolled patients in SR referred for AFL ablation (either typical or atypical). An isochronal late activation mapping (ILAM) during SR with UHD catheter was performed, annotating latest deflection of local electrograms. DZ were defined as areas with >3 isochrones within 1cm radius, prioritizing zones with maximal density. Atrial flutter was then induced and ILAM during flutter was performed for comparison. Voltage mapping was also assessed (0.1-0.5mV). Ablation targeted DZ in SR that displayed the higher voltage. DZ in SR were compared to DZ in AFL. Number of radiofrequency (RF) applications needed to terminate AFL were assessed. After AFL termination, complete line of the slow conduction zone was completed, and pulmonary vein isolation (PVI) was done in case of left AFL. Categorical variables are presented in absolute and relative values and median and interquartile range were used for numerical variables, as well t-student test for correlation of numerical variables. Results We studied 6 AFL (4 atypical, 66.7%) in 5 patients, 2 male (40%), median age 70 (64- 72). UHD ILAM in SR with 2195 points (1212-2865) and 2197 points (1356-3102) in AFL (p = 0.62). The UHD ILAM identified a median of (QR) DZ in SR, that colocalized with AFL isthmus and DZ in AFL in 100%. DZ were not always located in low voltage areas. Aiming at the higher voltage in the DZ terminated the AFL in all cases, with a median RF time of 38 (25-58) seconds and AFL was no longer inducible. However, according to protocol, the complete line of slow conduction zone was done, with a median RF time of 1049.5 (274-1194) seconds (p = 0,009). Conclusions Isochronal mapping in sinus rhythm with UHD catheters can display the functional substrate for reentry in AFL, allowing a substrate guided ablation in case of non-inducible AFL. Targeting the areas of high isochronal density, is effective in terminating AFL, obviating the need for extensive ablation. Abstract Figure.

Characterization of temporal electrical activity patterns for detection of critical isthmus regions of recurrent atypical atrial flutter

Introduction Identifying the critical isthmus region (CIR) of complex atrial tachycardias (AT) is challenging. The Lumipoint® (LP) software, developed for the Rhythmia® mapping system, aims to facilitate successful termination of ATs by identifying the CIR. Objective Objective of this study was to evaluate specificity and sensitivity of LP regarding arrhythmia-relevant CIR detection in patients with atypical-atrial-flutter (AAF). Methods In this retrospective analysis we analyzed 57 AAF-forms. Electrical activity (EA) was mapped over tachycardia cycle length resulting in 2-dimensional EA pattern. The hypothesis was that an EA minimum suggests a potential CIR with slow-conduction-zone. Results A total of n=33 patients were included. LP-algorithm identified a mean of 2.4 EA minima and 4.4 suggested CIRs per AAF-form. Overall, we observed a low specificity with 12.3% but a high sensitivity of 98.2%. Detailed EA analysis revealed that depth (≤20%) and width (>50ms) of EA minima were the best predictors of relevant CIRs. Wide minima occurred rarely (17.5%), while low minima were more frequently present (75.4%). Minima with a depth of EA≤20% showed the best sensitivity and specificity overall (95% and 60%, respectively). Analysis in recurrent ablations in 5 patients presenting de-novo AAF revealed that the CIR of de-novo AAF was already detected by LP during the index procedure. Conclusion The LP algorithm provides an excellent sensitivity (98.2%), but poor specificity (12.3%) to detect the CIR in AAF. Specificity improved by preselection of the lowest and widest EA minima. In addition, there might be role of initial bystander CIRs becoming relevant for future AAFs

Study on Deformation Characteristics and Mechanism of Q3 Loess Microstructrue Before and After Wetting

Microstructure characteristics of loess is an effective way to study the physical and mechanical characteristics of soil under different conditions. Water content in sample of Q3 loess is about 25% ,which was first subjected to X-Ray test to determine the main chemical components in loess and calculated the proportion in the sample. Test analysis shows the particle structure of the loess belonged to the granular structure type. CT scanning tests were performed on the sample before and after wetting. The changes of total number of pores, the maximum pore volume and the position of the centroid of pore of the sample were analyzed before and after wetting. The results shows that the soluble salts of loess have been dissolved after wetting.The volume of the pores of loess have been changed. Some increased, some decreased and others closed in volume. The change of the number of pores indicates that the sample formed obvious saturated zone, transition zone, conduction zone and humid zones after wetting. These results reveals the deformation characteristics and mechanism of Q3 loess microstructure.

Abstract 13669: Slow Conduction Zone of Left Atrium is a Precursor to Low Voltage Area in Patients With Atrial Fibrillation

Introduction: The slow conduction zone (SCZ) in the left atrium (LA) has attracted attention as an arrhythmia substrate of atrial fibrillation (AF). However, the occurrence mechanism of SCZ remains unclear. Hypothesis: The SCZ is related to the low voltage area (LVA) or the LA anatomical contact areas (CoAs) with other organs in patients with AF. Methods: We studied 100 patients (49 non-paroxysmal AF, 66 males, 67.9 ± 9.9 years) who received catheter ablation for AF. High-density LA mapping during right atrial appendage pacing at a rate of 100 bpm after pulmonary vein isolation were constructed. Isochronal activation maps were created at 5-ms interval setting, and the SCZ was identified on the activation map by finding a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s (Figure). The LVA was defined as the following; mild (<1.3 mV), moderate (<1.0 mV), and severe LVA (<0.5 mV). The CoAs (ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using computed tomography. Results: The SCZ was distributed linearly (Figure), and observed in 95 of 100 patients (95%). The SCZ was most frequently observed in the anterior wall region (77%). A longer SCZ was significantly associated with a larger LA size and a prevalence of non-PAF. The 51.2±36.2% of SCZ overlapped with mild LVA, 32.9±32.8% of SCZ with moderate LVA, and 14.6±22.0% of SCZ with severe LVA. In contrast, only 25.6±28.0 % of SCZ matched with the CoAs. Conclusion: The slow conduction zone reflects LA electrical remodeling and may be a precursor finding of the low voltage zone, not LA contact areas in patients with atrial fibrillation.

Slow conduction zone as an early electrical remodeling change in patients with atrial fibrillation

Background The slow conduction zone (SCZ) in the left atrium (LA) detected using 3-D mapping and high-resolution imaging system has attracted attention as an arrhythmia substrate of atrial fibrillation (AF). However, the occurrence mechanism of SCZ remains unclear. Purpose This aim of this study is to clarify whether SCZ is related to the low voltage zone (LVZ) or the LA anatomical contact areas with other organs such as aorta or thoracic spine in patients with AF. Methods We studied 36 patients (21 males, 68±10 years, 14 paroxysmal AF; PAF, 17 persistent AF; PeAF, 5 long-standing persistent AF; LS-PeAF) who received catheter ablation for AF. High-density LA mapping during sinus rhythm or right atrial pacing after pulmonary vein isolation were constructed by acquiring more than 2000 endocardial points in each patient. Isochronal activation maps were created at 5-ms interval setting, and the SCZ was identified on the activation map by finding a site with isochronal crowding of ≥3 isochrones, which are calculated as ≤27 cm/s (figure). The LVZ was defined as the following; mild (&lt;1.5 mV), moderate (&lt;1.0 mV), and severe LA-LVZ (&lt;0.5 mV). The LA contact areas (CoAs; ascending aorta-anterior LA, descending aorta-posterior LA, and vertebrae-posterior LA) were assessed using computed tomography. Results The SCZ was distributed linearly (figure), and observed in 35 of 36 patients (97.2%). The SCZ was often found in the anterior (89%), roof (64%), and septal wall (47%) of LA, and longest in patients with LS-PeAF (PAF: 56±34 mm, PeAF; 79±41 mm, LS-PeAF; 107±34mm, P=0.0351). The prevalence rate of SCZ (97.2%) was higher than LVZ (figure, mild LA-LVZ; 91.7%, moderate LA-LVZ: 66.7%, severe LA-LVZ; 25%). The 55.8% of SCZ overlapped with mild LA-LVZ, 37.6% of SCZ with moderate LA-LVZ, and 19.1% of SCZ with severe LA-LVZ. The LA CoAs were found in all patients. A total of 72 CoAs (average surface area, 7.0±4.0 cm2) were identified. A CoA was found in each of the three representative regions, ascending aorta-anterior LA (4.1±2.0 cm2, 36 of 36 patients, 100%), descending aorta-posterior LA (2.3±1.2 cm2, 12 of 36 patients, 33%), and vertebrae-posterior LA (3.4±2.1 cm2, 24 of 36 patients, 67%). However, only 22% of SCZ matched with the LA anatomical contact areas. Conclusion The slow conduction zone reflects LA electrical remodeling and may be a precursor finding of the low voltage zone, not LA contact areas in patients with atrial fibrillation. Funding Acknowledgement Type of funding source: None