Exploiting the Close-to-Dirac Point Shift of the Fermi Level in the Sb2Te3/Bi2Te3 Topological Insulator Heterostructure for Spin-Charge Conversion

Properly tuning the Fermi level position in topological insulators is of vital importance to tailor their spin-polarized electronic transport and to improve the efficiency of any functional device based on them. Here, we report the full in situ metal organic chemical vapor deposition (MOCVD) and study of a highly crystalline Bi2Te3/Sb2Te3 topological insulator heterostructure on top of large area (4″) Si(111) substrates. The bottom Sb2Te3 layer serves as an ideal seed layer for the growth of highly crystalline Bi2Te3 on top, also inducing a remarkable shift of the Fermi level to place it very close to the Dirac point, as visualized by angle-resolved photoemission spectroscopy. To exploit such ideal topologically protected surface states, we fabricate the simple spin-charge converter Si(111)/Sb2Te3/Bi2Te3/Au/Co/Au and probe the spin-charge conversion (SCC) by spin pumping ferromagnetic resonance. A large SCC is measured at room temperature and is interpreted within the inverse Edelstein effect, thus resulting in a conversion efficiency of λIEEE ∼ 0.44 nm. Our results demonstrate the successful tuning of the surface Fermi level of Bi2Te3 when grown on top of Sb2Te3 with a full in situ MOCVD process, which is highly interesting in view of its future technology transfer.

Significant enhancement of ferromagnetism above room temperature in epitaxial 2D van der Waals ferromagnet Fe5-δGeTe2/Bi2Te3 heterostructures

Two-dimensional (2D) van der Waals (vdW) ferromagnetic metals Fe_xGeTe₂ with x = 3-5 have raised significant interest in the scientific community. Fe₅GeTe₂ shows prospects for spintronic applications since the Curie temperature T_c has been reported near or higher than 300 K. In the present work, epitaxial Fe_5-δGeTe₂ (FGT) heterostructures were grown by Molecular Beam Epitaxy (MBE) on insulating crystalline substrates. The FGT films were combined with Bi₂Te₃ topological insulator (TI) aiming to investigate the possible beneficial effect of the TI on the magnetic properties of FGT. FGT/Bi₂Te₃ films were compared to FGT capped only with AlO_x to prevent oxidation. SQUID and MOKE measurements revealed that the growth of Bi₂Te₃ TI on FGT films significantly enhances the saturation magnetization of FGT as well as the T_c well above room temperature (RT) reaching record values of 570 K. First-principles calculations predict a shift of the Fermi level and an associated enhancement of the majority spin (primarily) as well as the total density of states at the Fermi level suggesting that effective doping of FGT from Bi₂Te₃ could explain the enhancement of ferromagnetism in FGT. It is also predicted that strain induced stabilization of a high magnetic moment phase in FGT/Bi₂Te₃ could be an alternative explanation of magnetization and T_c enhancement. Ferromagnetic resonance measurements evidence an enhanced broadening in the FGT/Bi₂Te₃ heterostructure when compared to FGT. We obtain a large spin mixing conductance of g↑↓eff = 4.4 × 10²⁰ m^-2, which demonstrates the great potential of FGT/Bi₂Te₃ systems for spin-charge conversion applications at room temperature.

Recurrent arrhythmic storms and unsuccessful catheter ablation in chronic ischemic heart disease

The prototypical substrate for reentrant ventricular tachycardia (VT) is post-myocardial infarction (MI) scar. Catheter ablation is an important therapeutic option for recurrent VT but sometimes it is not effective despite the technical advances. Here we describe the case of a 60-year-old man who suffered a MI in 1998 and presented with recurrent arrhythmic storms during his long-term follow-up. Twenty years later, he underwent two catheter ablations with bipolar electroanatomic voltage mapping (EVM) demonstrating only an area of low voltages in the lateral left ventricular free wall. Both procedures were unsuccessful and the patient eventually underwent cardiac transplantation in 2019. Pathology examination revealed circumferential subendocardial scar with hypertrabeculation, so that the reentry substrate was unreachable by ablation with the use of standard techniques. The comparison of EVM findings with the morphologic ones in patients with chronic ischemic heart disease can help to better understand the feasibility and effectiveness of VT substrate ablation.

Matching Ablation Endpoints to Long-Term Outcome: The Prospective Multicenter Italian Ventricular Tachycardia Ablation Registry

BACKGROUND

Multicenter ventricular tachycardia (VT) ablation studies have shown poorer outcomes compared with single-center experiences. This difference could be related to heterogeneous mapping and ablation strategies.

OBJECTIVES

This study evaluated a homogenous simplified catheter ablation strategy for different substrates and compared the results with those of a single referral center.

METHODS

This was a multicenter prospective VT ablation registry of patients with the following 4 causes of VT: previous myocardial infarction; previous myocarditis; arrhythmogenic right ventricular dysplasia; or idiopathic dilated cardiomyopathy. The procedural protocol included precise mapping and ablation steps with the combined endpoint of late potential (LP) abolition and noninducibility of VT. The long-term primary efficacy endpoint was freedom from VT.

RESULTS

A total of 309 patients were enrolled. LPs were present in 70% of patients and were abolished in 83%. At the end of the procedure 74% of LPs were noninducible. The primary combined endpoint of LP abolition and noninducibility was achieved in 64% of patients with LPs at baseline. Freedom from VT at 12 months was observed in 67% of patients. In the overall study group, VT inducibility was the only predictor of freedom from VT (P = 0.013). In patients with LPs, the VT recurrence rate was lower both for patients with complete LP abolition (P = 0.040) and for patients meeting the composite endpoint (P = 0.035).

CONCLUSIONS

A standardized VT mapping and ablation technique reproduced the procedural outcomes of a single referral center in a multicenter prospective study. LP abolition and noninducibility were effective in reducing VT recurrences in patients with 4 causes of cardiomyopathy. (Ventricular Tachycardia Ablation Registry; NCT03649022).

Predictors of late arrhythmic events after generator replacement in Brugada syndrome treated with prophylactic ICD

Introduction

Predictors of late life-threatening arrhythmic events in Brugada syndrome (BrS) patients who received a prophylactic ICD implantation remain to be evaluated. The aim of the present long-term multicenter study was to assess the incidence and clinical-electrocardiographic predictors of late life-threatening arrhythmic events in BrS patients with a prophylactic implantable cardioverter defibrillator (ICD) and undergoing generator replacement (GR).

Methods

The study population included 105 patients (75% males; mean age 45 ± 14years) who received a prophylactic ICD and had no arrhythmic event up to first GR.

Results

The median period from first ICD implantation to last follow-up was 155 (128-181) months and from first ICD Implantation to the GR was 84 (61-102) months. During a median follow-up of 57 (38-102) months after GR, 10 patients (9%) received successful appropriate ICD intervention (1.6%/year). ICD interventions included shock on ventricular fibrillation (n = 8 patients), shock on ventricular tachycardia (n = 1 patient), and antitachycardia pacing on ventricular tachycardia (n = 1 patient). At survival analysis, history of atrial fibrillation (log-rank test; P = 0.02), conduction disturbances (log-rank test; P < 0.01), S wave in lead I (log-rank test; P = 0.01) and first-degree atrioventricular block (log-rank test; P = 0.04) were significantly associated with the occurrence of late appropriate ICD intervention. At Cox-regression multivariate analysis, S-wave in lead I was the only independent predictor of late appropriate ICD intervention (HR: 9.17; 95%CI: 1.15-73.07; P = 0.03).

Conclusions

The present study indicates that BrS patient receiving a prophylactic ICD may experience late appropriate intervention after GR in a clinically relevant proportion of cases. S-wave in lead I at the time of first clinical evaluation was the only independent predictor of persistent risk of life-threatening arrhythmic events. These findings support the need for GR at the end of service regardless of previous appropriate intervention, mostly in BrS patients with conduction abnormalities.

Detectable reentrant circuits in localized microreentrant tachycardias in the era of ultra high-density mapping

Funding Acknowledgements

Type of funding sources: None.

Background

Optimal criteria in clinical practice differentiating microreentrant atrial tachycardias (mAT) from macroreentrant atrial arrhythmias (MAT) have not yet been clarified. The use of multielectrode catheters and the recent development of ultra high-density mapping (UHDM) with automated features has improved our knowledge of mAT circuits and foci location.

Purpose

In the present study, we systematically evaluated AT mechanisms in a large consecutive cohort of patients with MAT identifying the precise mAT circuits using the Rhythmia mapping system.

Methods

Consecutive patients indicated for MAT ablation from January 2021 to November 2021 at 33 centers were prospectively included. All MATs were completely mapped in the left or right atrium by means of the Rhythmia mapping system and the 64-poles Orion basket catheter. For study purpose, a mAT was defined as an AT with slow continuous low fragmented potentials covering at least 50% of tachycardia cycle length (CL) in a small area (set as a circuit within &lt; 1 cm2) and in a couple of closed splines of the Orion catheter and a centrifugal activation pattern to the remainder of the atria. The Lumipoint tool was systematically used to confirm EGM fragmentation inside this area. Data are reported as mean±SD.

Results

One-hundred eighty-seven MATs were analyzed: 100 (53.7%) atypical left atrial flutter, 27 (14.3%) left AT and 60 (32%) right AT. A total of 7 MAT (prevalence of 3.7%) was identified as mATs (6 atypical left atrial flutter and 1 AT), with 5 out 7 with a previous history of AF ablation procedure. The percentage of atrial surface with a voltage level below 0.1 mV was 19±17%. The CL was 329±78ms. The electrical activity spanning the whole CL was detected by 2±0.6 pairs of close bipoles of the Orion catheter, and was actually confined to a region of 0.4±0.2cm2 with continuous highly fractionated potential covering 68±10% of the CL (longest component of fractionated EGM per spline=74±18% of the CL). Voltage level was 0.3±0.1mV at RF delivery site and 0.2±0.1mV at the site of longest duration of the fragmented potential, respectively. Targeted mAT activity was identified closer to PVs in three cases and at the mid portion of the anterior wall and at the roof in two cases each, respectively. In all cases a single shot RF delivery terminated each arrhythmia at targeted location. Consolidative RF ablations were then delivered in the adjacent area. No complication occurred. At three months follow-up all patients remained free from any AT recurrence.

Conclusions

In this standard of care clinical experience with UHDM system, the prevalence of mAT seems to be higher than previously reported in literature. A technique based on mAT identification through a novel automated algorithm and matched area of electrogram fractionation captured by the Orion catheter may limit the extent of ablation needed.

The impact of RF wattage level on local impedance and procedural parameters in AF ablation cases

Funding Acknowledgements

Type of funding sources: None.

Background

Local impedance (LI) measurement can provide information on catheter tip contact, but also changes in LI during ablation can inform the extent and effectiveness of RF energy delivery. To date the relationship between highly LI measurements and contact force (CF) during atrial fibrillation (AF) ablation at different levels of energy delivery is still lacking.

Purpose

We aimed to evaluate the impact of power setting on LI and key procedural parameters in AF ablation cases.

Methods

A novel CF ablation catheter equipped with dedicated algorithm was used to measure LI at the distal electrode of this catheter. Radiofrequency (RF) catheter applications ≥45 watts were categorized as high power (HP) and applications &lt;45w as standard power (SP). Ablations were also grouped according to different levels of CF (&lt;5g, 5-14g, 15-24g and ≥25g). Data are reported as mean±SD.

Results

Sixty-two consecutive pts undergoing RF catheter ablation of AF from the CHARISMA registry were included A total of 4619 ablation spots performed around PVs were analyzed (58% paroxysmal, 84% de novo, RF deliveries per pt=76±27, RF delivery time=9.1±5s, CF=12.3±8g). The majority of these were HP applications (n=4192, 91%). The mean LI was 158±17Ω prior to ablation and 138±14Ω after ablation (p&lt;0.0001, absolute LI drop of 21.9±8Ω) with a LI drop rate equal to 4.4±3Ω/s. HP ablations had significantly shorter RF delivery times, 8.8±4s vs 12±7s (p&lt;0.0001), larger LI drops (22.2±8Ω vs 19.3±9Ω, p&lt;0.0001) and higher LI drop rates (4.5±3Ω/s vs 3.6±2Ω/s, p&lt;0.0001) than SP, respectively. For both HP and SP settings, the magnitude of LI drop increased and RF delivery time decreased with increasing amounts of CF. The largest differences between HP and SP were found when CF was &lt;15g (RF delivery time: 9±5s at HP vs 12.9±7s at SP, percentage of difference 26.3%, p&lt;0.0001; LI drop: 21.2±8Ω at HP vs 18.6±9Ω, percentage of difference -14.3%, p&lt;0.0001). No major complications occurred during the procedures. All PVs were successfully isolated.

Conclusions

This preliminary experience suggests that, HP ablation is effective and safe and resulting in shorter RF delivery times and larger LI drops than SP ablation.

Visualization of pulmonary vein reconnections using dynamic mapping in redo procedures for patients with atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background/Introduction

Pulmonary vein (PV) reconnection is commonly associated with recurrence of atrial fibrillation (AF) after the initial catheter ablation procedure. Visualization and identification of PV reconnections are critical during repeat procedures.

Purpose

To examine the use of dynamic mapping (LiveView) in combination with a high-density mapping catheter (HD Grid) in the recognition of PV reconnections in redo AF ablation procedures.

Methods

Acute procedure data from 81 patients were prospectively collected. Mapping catheter selection and the use of LiveView was determined at the physician’s discretion. For cases where LiveView was used, the location and number of gaps from the previous procedure were identified using both standard mapping and dynamic mapping separately.

Results

Most of the patients included in the analysis were treated for paroxysmal AF (PAF: n=63/81, 77.8%). Dynamic mapping data was incorporated in 50 PAF cases and 15 persistent AF cases. Within these 65 cases, standard mapping identified a total of 120 PV gaps whereas LiveView identified a total of 138 PV gaps; gaps were most frequently identified on the right PVs, especially in the anterior region (Table1). A contact force-sensing ablation catheter was commonly (n=64/81, 79%) used by the operators. The right anterior region was ablated with an average contact force of 13.8±3.1g and Lesion index (LSI) of 5.2±0.7 at a power of 35.8±8.4W. Non-PV ablation was performed in 38 (46.9%) patients; the most common lesion sets were roofline, cavotricuspid isthmus (CTI) line, and mitral isthmus line. Acute PV isolation was achieved in all patients at the end of the procedure.

Conclusion

Data from this analysis suggest the incorporation of dynamic mapping data may help reveal more PV reconnections compared to standard mapping. Additional study is needed to assess the long-term clinical outcomes when regional dynamic mapping data is used to identify PV reconnections in repeat procedures.

Ventricular tachycardia channels ablation incorporating automated high-density mapping guidance: data from the CHARISMA registry

Funding Acknowledgements

Type of funding sources: None.

Background

Ventricular tachycardia (VT) ablation targeting conducting channels (CC)s based on timing of late potentials (LPs) during sinus rhythm (dechanneling) may facilitate a scar homogenization strategy without the need for extensive ablation and possibly lead to higher successful rate.

Purpose

We evaluated the feasibility and safety of a CC identification and ablation approach by means of an ultra-high density mapping system with a novel automated algorithm in ischemic VT procedures.

Methods

Consecutive patients indicated for ischemic VT ablation were prospectively included. A complete map of the left ventricle was performed prior and after ablation through the Rhythmia mapping system. Channels were defined as any signal activity bounded by anatomic and functional barriers and characterized through the Lumipoint (LM) tool and continuous activation was used on the whole ventricular substrate. Procedural end point was the elimination of all identified CCs by ablation at the CC entrance and exit followed by abolition of any residual LPs inside the CC. The ablation endpoint was noninducibility. Data are reported as mean±SD.

Results

A total of 36 channels were identified through LM from 28 patients (1.2±0.5 per patient): 21 (75%) patients had 1 CC, 6 (21.4%) had 2 CCs and 1 (3.6%) had 3 CCs. LPs were identified inside CCs in 19 cases (67.9%). In 8 cases (28.6%) LPs were present both inside and outside and in 1 (3.6%) case LPs were present only outside the CC. LPs inside channels covered an area of 7.6±5 mm2 with a ratio between LPs area and CCs’ area of 67.4±31.8%. In 12 (43%) cases LPs area covered more than 90% of the CCs’ area. At voltage map analysis a total of 34 CC were identified: 1 CC was present in 75% of the cases, 2 CCs in 17.9% and 3 CCs in 3.6%. LPs were identified only inside CCs in 46.4% of the cases, both inside and outside in 42.9% and only outside in 10.7%. Healthy tissue (voltage level≥0.5mV) was prevalent (68.2±17%), followed by intermediate voltage areas (0.5-0.05 mV; 31.1±17%) and very low voltage areas (&lt;0.05mV; 0.7±1%). LPs were found mostly at intermediate voltage areas (57.0±34% of the covered area; 39.1±33% at healthy tissue and 3.4±13% at very low voltage areas). LM was more accurate than traditional voltage mapping in identifying CCs: in 6 (21.4%) cases voltage map overestimated LPs areas, in 2 (7.1%) cases failed to fully identify LPs and only in 19 out 28 (67.8%) LM and voltage map had a complete agreement. All CCs’ entrance and exit were successfully ablated and abolition of any residual LPs inside the CC was achieved in all patients. No complication occurred. Noninducibility was achieved in all (100%) the cases.

Conclusions

In this experience, a channel identification approach through the advanced Lumipoint tool was more accurate than traditional voltage mapping and seems to be safe, feasible, and effective at least in the acute setting of ischemic VT ablation.

Implantation of cardiac electronic devices in active COVID-19 patients: Results from an international survey

BACKGROUND

Cardiac implantable electronic device (CIED) implantation rates as well as the clinical and procedural characteristics and outcomes in patients with known active coronavirus disease 2019 (COVID-19) are unknown.

OBJECTIVE

The purpose of this study was to gather information regarding CIED procedures during active COVID-19, performed with personal protective equipment, based on an international survey.

METHODS

Fifty-three centers from 13 countries across 4 continents provided information on 166 patients with known active COVID-19 who underwent a CIED procedure.

RESULTS

The CIED procedure rate in 133,655 hospitalized COVID-19 patients ranged from 0 to 16.2 per 1000 patients (P <.001). Most devices were implanted due to high-degree/complete atrioventricular block (112 [67.5%]) or sick sinus syndrome (31 [18.7%]). Of the 166 patients in the study survey, the 30-day complication rate was 13.9% and the 180-day mortality rate was 9.6%. One patient had a fatal outcome as a direct result of the procedure. Differences in patient and procedural characteristics and outcomes were found between Europe and North America. An older population (76.6 vs 66 years; P <.001) with a nonsignificant higher complication rate (16.5% vs 7.7%; P = .2) was observed in Europe vs North America, whereas higher rates of critically ill patients (33.3% vs 3.3%; P <.001) and mortality (26.9% vs 5%; P = .002) were observed in North America vs Europe.

CONCLUSION

CIED procedure rates during known active COVID-19 disease varied greatly, from 0 to 16.2 per 1000 hospitalized COVID-19 patients worldwide. Patients with active COVID-19 infection who underwent CIED implantation had high complication and mortality rates. Operators should take these risks into consideration before proceeding with CIED implantation in active COVID-19 patients.

Impact of channels identification and ablation in ventricular tachycardia patients through high-density mapping: preliminary experience from an Italian registry

Funding Acknowledgements

Type of funding sources: None.

Background

Ventricular tachycardia (VT) ablation techniques in ischemic cardiomyopathy have evolved during the recent years. However, the long-term success rate remains disappointing. A technique based on channel identification and ablation through a novel automated algorithm may limit the extent of ablation needed and possibly lead to higher successful rate.

Purpose

To report preliminary data on feasibility and safety of a channel identification approach and to characterize late potentials (LPs) features using an ultra-high density mapping system with a novel analysis tool in ischemic VT procedures.

Methods

Consecutive patients (pts) indicated for ischemic VT ablation were enrolled in the CHARISMA study. A complete map of the left ventricle was performed prior and after ablation through the Rhythmia mapping system. For our purpose channels were defined as any signal activity bounded by anatomic and functional barriers and characterized through a novel map analysis tool (Lumipoint-LM-) that automatically identifies fragmented late potentials (LPs) and continuous activation was used on the whole ventricular substrate. Procedural endpoint was the elimination of all identified conducting channels (CCs) by ablation at the CC entrance and exit followed by abolition of any residual LPs inside the CC. The ablation endpoint was noninducibility.

Results

A total of 18 channels were identified through LM from 14 pts: 71.4% of the pts had 1 CC, 28.6% had 2 CCs. In the majority of the cases LPs where identified only inside CCs (57.1%), whereas in 6 cases (42.9%) LPs were present both inside and outside. The mean conduction time inside CCs was 50.3 ± 30ms, the mean CC length was 32.6 ± 17mm and the conduction velocity was 0.8 ± 0.5 mm/ms. LPs covered a mean area of 7.0 ± 5mm2 (ratio between LPs area and CCs’ area = 52.4 ± 33.7%). At voltage map analysis 1 CC was present in 78.6% of the cases (2 CCs in 21.4%). LPs were identified only inside CCs in 42.9% of the cases, both inside and outside in 50% and only outside in 7.1%. Healthy tissue (voltage level≥0.5mV) was prevalent (61.2 ± 13.8%), followed by intermediate voltage areas (0.5-0.05mV; 37.5 ± 13.7%) and very low voltage areas (&lt;0.05mV; 1.2 ± 2%). LPs were found mostly at intermediate voltage areas (54.1 ± 31.7% of the covered area; 39.1 ± 28.4% at healthy tissue and 6.8 ± 17.8% at very low voltage areas). Agreement in CCs identification between advanced analysis through LM and voltage map was fair (9/14 with complete agreement). In 3 cases voltage map overestimated LPs areas, in 2 cases failed to fully identify LPs. All CCs’ entrance and exit were successfully ablated and abolition of any residual LPs inside the CC was achieved in all pts. No complication occurred. Noninducibility was achieved in all the cases.

Conclusions

In our preliminary experience, a new channel identification approach through the advanced Lumipoint algorithm seems to be safe, feasible and effective at least in the acute setting of ischemic VT ablation.

Assessment and incidence of PV gaps as determined by HD Grid and circular mapping catheters

Funding Acknowledgements

Type of funding sources: None.

Background

Many tools and techniques are utilized to assess pulmonary vein isolation (PVI), such as evaluation of entrance and exit block, voltage mapping, and use of drugs such as adenosine. It is unclear which tools and techniques may provide greater sensitivity in the identification and elimination of pulmonary vein (PV) gaps, leading to better long-term outcomes. The HD Grid simultaneously records orthogonal bipolar EGMs to reduce directional sensitivity. Previously published data suggest that the use of HD Grid may improve sensitivity for gap identification.

Purpose

To determine, in a large cohort of procedures, the rate of gap detection when using HD Grid to check for PVI as compared to circular mapping catheters (CMC).

Methods

Anonymized, acute procedural data was prospectively collected in de novo AF ablation procedures in which either a 10- or 20-pole CMC or HD Grid catheter was used to assess PVI. Procedural data including gap detection and PVI assessment method were analyzed using chi-squared test.

Results

559 cases from over 60 institutions in 8 countries were analyzed. Of the 559 cases, 47.4% (265/599) used HD Grid, and 52.6% (294/599) used a CMC. PV gaps were found in 52.5% (139/265) of HD Grid procedures and in 36.7% (108/294) of CMC procedures (p &lt; 0.001). The most common PVI assessment method in both HD Grid and CMC groups was entrance/exit block (90.9%, 92.5%, respectively). Mapping as a post-ablation assessment method was used in 69.1% (183/265) of HD Grid procedures whereas it was only used in 42.8% (126/294) of CMC procedures (p &lt; 0.001). Of the 183 HD Grid procedures that utilized mapping for PV assessment, 57.9% (106/183) used both voltage and activation mapping, 41.0% (75/183) used voltage only and 1.1% (2/183) used activation mapping only. Significantly more gaps were found in the HD Grid group that used both activation and voltage mapping (83.0%, 88/106) as compared to voltage mapping only (49.3%, 37/75, p &lt; 0.001). At the end of the procedure, 95.8% of patients in the HD Grid group were in sinus rhythm, as compared to 84.7% of the CMC group.

Conclusions

While this analysis does not represent a direct comparison of the sensitivity of the two different technologies, HD Grid detected significantly more PV gaps compared to CMC in AF procedures. Previous publications have attributed similar findings to HD Grid’s ability to reduce voltage amplitude dependence on wavefront directionality. The significantly larger number of HD Grid cases that utilized mapping as a method of determining PVI could be explained by the need to maneuver the HD Grid around the circumference of the vein, which may naturally lead to map collection. This data also suggests that using both voltage and activation mapping identifies significantly more gaps as compared to only voltage mapping, however, further analysis could be warranted to better understand how these maps were collected and what map settings were used.

Minimal fluoroscopic approaches and factors associated with radiation dose when high-definition mapping is used for supraventricular tachycardia ablation: insight from the CHARISMA registry

Funding Acknowledgements

Type of funding sources: None.

Background

Limited data exist on factors associated with radiation exposure during ablation procedures when a high definition mapping technology is used.

Purpose

To report factors associated with radiation exposure and data on feasibility and safety of a minimal fluoroscopic approach using the Rhythmia mapping system in supraventricular tachycardia (SVT) ablation procedures.

Methods

Consecutive patients indicated for arrhythmia ablation were enrolled in the CHARISMA study at 12 centers. We included in this analysis consecutive right-side procedures performed through a minimal fluoroscopy approach with the Rhythmia mapping system were analyzed. A 3D geometry of chambers of interest was reconstructed on the basis of the electroanatomic information taken from the mapping system. Fluoroscopy was used only if deemed necessary. The effective dose (ED) was calculated using accepted formula. For our purpose high dose exposure was defined as an ED greater than the median value of ED of the population exposed to radiation.

Results

This analysis included 325 patients (mean age = 56 ± 17 years, 57% male) undergoing SVT procedures (152 AVNRT, 116 AFL, 41 AP and 16 AT). During the study, 27481 seconds of fluoroscopy was used (84.6 ± 224 seconds per procedure), resulting in a mean equivalent ED of 1.1 ± 3.7 mSv per patient. The mean reconstructed RA volume was 99 ± 54 ml in a mean mapping time of 12.2 ± 7 min. The mean number of radiofrequency ablations (RFC) to terminate each arrhythmia was 9.4 ± 9 (mean RFC delivery time equal to 6.7 ± 6 min). 192 procedures (59.1%) were completed without any use of fluoroscopy; during the remaining 133 procedures (39.9%), 206.6 ± 313.4 seconds of fluoroscopy was used (median ED = 1.2 mSv). In a minority of the cases (n = 25, 7.7%) the fluoroscopy time was higher than 5 minutes (median ED = 6.5 mSv), whereas radiologic exposure time greater than 1 minute occurred in ninety cases (27.7%, median ED = 2.1 mSv). On multivariate logistic analysis adjusted for baseline confounders the RFC application time (OR = 1.0014, 95%CI: 1.0007 to 1.0022; p = 0.0001) was independently associated to an ED greater than 1.2 mSv, whereas female gender had an inverse association (0.54, 0.29 to 0.98; p = 0.0435). Acute success was reached in 97.8% of the cases. During a mean of 290.7 ± 169.6 days follow-up, no major adverse events related to the procedure were reported. Overall, the recurrence rate of the primary arrhythmia during follow-up was 2.5%.

Conclusions

In our experience, arrhythmias ablation through minimal fluoroscopy approach with the use of a novel ablation technology is safe, feasible, and effective in common right atrial arrhythmias. High-dose exposure occurred in a very limited number of cases, without any reduction of the safety and acute and long-term effectiveness profile.

Minimal fluoroscopy approach for right-sided supraventricular tachycardia ablation with a novel ablation technology: Insights from the multicenter CHARISMA clinical registry

BACKGROUND

No data exist on the ability of the novel Rhythmia 3-D mapping system to minimize fluoroscopy exposure during transcatheter ablation of arrhythmias. We report data on the feasibility and safety of a minimal fluoroscopic approach using this system in supraventricular tachycardia (SVT) procedures.

METHODS

Consecutive patients were enrolled in the CHARISMA registry at 12 centers. All right-sided procedures performed with the Rhythmia mapping system were analyzed. The acquired electroanatomic information was used to reconstruct 3-D cardiac geometry; fluoroscopic confirmation was used whenever deemed necessary.

RESULTS

Three hundred twenty-five patients (mean age = 56 ± 17 years, 57% male) were included: 152 atrioventricular nodal reentrant tachycardia, 116 atrial flutter, 41 and 16 right-sided accessory pathway and atrial tachycardia, respectively. Overall, 27 481 s of fluoroscopy were used (84.6 ± 224 s per procedure, equivalent effective dose = 1.1 ± 3.7 mSv per patient). One hundred ninety-two procedures (59.1%) were completed without the use of fluoroscopy (zero fluoroscopy, ZF). In multivariate analysis, the presence of a fellow in training (OR = 0.15, 95% CI: 0.05-0.46; p = .0008), radiofrequency application (0.99, 0.99-1.00; p = .0002), and mapping times (0.99, 0.99-1.00; p = .042) were all inversely associated with ZF approach. Acute procedural success was achieved in 97.8% of the cases (98.4 vs. 97% in the ZF vs. non-ZF group; p = .4503). During a mean of 290.7 ± 169.6 days follow-up, no major adverse events were reported, and recurrence of the primary arrhythmia was 2.5% (2.1 vs. 3% in the ZF vs. non-ZF group; p = .7206).

CONCLUSIONS

The Rhythmia mapping system permits transcatheter ablation of right-sided SVT with minimal fluoroscopy exposure. Even more, in most cases, the system enables a ZF approach, without affecting safety and efficacy.

Annealing studies combined with low temperature emission Mössbauer spectroscopy of short-lived parent isotopes: Determination of local Debye-Waller factors

An extension of the online implantation chamber used for emission Mössbauer Spectroscopy (eMS) at ISOLDE/CERN that allows for quick removal of samples for offline low temperature studies is briefly described. We demonstrate how online eMS data obtained during implantation at temperatures between 300 K and 650 K of short-lived parent isotopes combined with rapid cooling and offline eMS measurements during the decay of the parent isotope can give detailed information on the binding properties of the Mössbauer probe in the lattice. This approach has been applied to study the properties of Sn impurities in ZnO following implantation of ¹¹⁹In (T_½ = 2.4 min). Sn in the 4+ and 2+ charge states is observed. Above T > 600 K, Sn²⁺ is observed and is ascribed to Sn on regular Zn sites, while Sn²⁺ detected at T < 600 K is due to Sn in local amorphous regions. A new annealing stage is reported at T ≈ 550 K, characterized by changes in the Sn⁴⁺ emission profile, and is attributed to the annihilation of close Frenkel pairs.

Association Between Quality of Life and Procedural Outcome After Catheter Ablation for Atrial Fibrillation: A Secondary Analysis of a Randomized Clinical Trial

IMPORTANCE

Catheter ablation is effective in reducing atrial fibrillation (AF), but the association of ablation for AF with quality of life is unclear.

OBJECTIVE

To evaluate whether the procedural outcome of ablation for AF is associated with quality of life (QOL) measures.

DESIGN, SETTING, AND PARTICIPANTS

This was a prespecified secondary analysis of the Substrate and Trigger Ablation for Reduction of Atrial Fibrillation-Part II (STAR AF II) prospective randomized clinical trial, which compared 3 strategies for ablation of persistent AF. This analysis included 549 of the 589 patients enrolled in the trial who underwent ablation. Enrollment occurred at 35 centers in Europe, Canada, Australia, China, and Korea from November 2010 to July 2012. Data for the current study were analyzed on December 11, 2019.

INTERVENTIONS

Patients underwent AF ablation with 1 of 3 ablation strategies: (1) pulmonary vein isolation (PVI), (2) PVI plus complex fractionated electrograms, or (3) PVI plus linear lesions.

MAIN OUTCOMES AND MEASURES

Quality of life was assessed at baseline and at 6, 12, and 18 months after ablation for AF using the 36-Item Short Form Health Survey and the EuroQol Health-Related Quality of Life 5-Dimension 3-Level questionnaire. Scores were also converted to a physical health component score (PCS) and a mental health component score (MCS). Individual AF burden was calculated by the total time with AF from Holter monitors and the percentage of transtelephonic monitor recordings showing AF.

RESULTS

Among the 549 patients included in this secondary analysis, QOL was assessed in 466 (85%) at baseline and at 6, 12, and 18 months after ablation for AF. The mean (SD) age of the study population was 60 (9) years; 434 (79%) individuals were men, and 417 (76%) had continuous AF for 6 months or more before ablation. The AF burden significantly decreased from a mean (SD) of 82% (36%) before ablation to 6.6% (23%) after ablation (P < .001). Significant improvements in mean (SD) PCS (68.3 [20.7] to 82.5 [18.6]) and MCS (35.3 [8.6] to 37.5 [7.6]) occurred 18 months after ablation (P < .05 for both). Significant QOL improvement occurred in all 3 study arms and regardless of AF recurrence, defined as AF episodes lasting more than 30 seconds: for no recurrence, mean (SD) PCS increased from 66.5 (20.9) to 79.1 (19.4) and MCS from 35.3 (8.7) to 37.7 (7.7); for recurrence, mean (SD) PCS increased from 70.2 (20.4) to 86.4 (16.8) and MCS from 35.3 (8.6) to 37.1 (7.4) (P < .05 for all). When outcome was defined by AF burden reduction, in patients with less than 70% reduction in AF burden, the increase in PCS was significantly less than in those with greater than 70% reduction, and only 3 of 8 subscales showed significant improvement.

CONCLUSIONS AND RELEVANCE

In this secondary analysis, decreases in AF burden after ablation for AF were significantly associated with improvements in QOL. Quality of life changes were significantly associated with the percentage of AF burden reduction after ablation.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01203748.

Minimal fluoroscopy approach in current clinical practice with a novel ablation technology for supraventricular tachycardia: a large multicenter experience from an Italian registry

Background

Electrophysiological studies and ablation procedures expose both physicians and patients to a large amount of radiation. Most of 3-D mapping systems provide improved tracking of catheters, possibly allowing relevant reductions in radiation exposure. No data exists on the ability of the Rhythmia mapping system to minimize fluoroscopy time and dose.

Purpose

To report preliminary data on feasibility and safety of a minimal fluoroscopic approach using the Rhythmia mapping system in supraventricular tachycardia (SVT) procedures.

Methods

Consecutive patients indicated for arrhythmia ablation were enrolled in the CHARISMA study at 12 centers. For our purpose consecutive right-side procedures performed through a minimal fluoroscopy approach with the Rhythmia mapping system were analyzed. A 3D geometry of chambers of interest was reconstructed on the basis of the electroanatomic information taken from the mapping system. Fluoroscopy was used only if deemed necessary.

Results

This analysis included 266 patients (mean age = 57±17 years, 57% male) undergoing SVT procedures (120 AVNRT, 91 AFL, 32 AP, 11 AT and 12 other right atrial procedures). In all cases, diagnostic EP and ablation catheters were positioned using a low fluoroscopic electroanatomic guided approach. The mean fluoroscopy time needed for each procedure was 55±128 s. The median reconstructed RA volume was 92 [63–131] ml in a median mapping time of 11 [7–17] min. The median number of radiofrequency ablations to terminate each arrhythmia was 6 [3–12] (total RF delivery time of 291 [180–505] s). Sixty-five percent of the procedures (n=174) were completed with less than 10 s of fluoroscopy. Low fluoroscopy approach with less than 10 s (minimal fluoroscopy approach) was most frequently obtained in case of AVNRT (91, 76%) compared to other arrhythmias' ablation (83, 57%, p=0.001) Achievement of a minimal fluoroscopic approach was not affected by operator's experience (65% vs 66%, p=1.00, respectively within physician with more or less of 10 years of active practice), whereas it was affected by presence of a fellow in training during the procedure (72% without fellow vs 26% with fellow, p&lt;0.0001). A 100% rate of acute success was observed, and no procedure-related complications occurred. At multivariate logistic regression analysis adjusted for baseline confounders, both the total number of RF ablations (OR: 0.93 (95% CI:0.88 to 0.96; p=0.0053) and the presence of a fellow in training during the procedure (OR: 0.29; 95% CI: 0.1 to 0.87; p=0.0278) had an inverse association to the achievement of a minimal fluoroscopic approach.

Conclusions

In our preliminary experience, arrhythmias' ablation through minimal fluoroscopy approach with the use of a novel ablation technology seems to be safe, feasible, and effective in common right atrial arrhythmias. Use of fluoroscopy can be dramatically reduced in most cases, without any reduction of the safety and acute effectiveness profile.

Funding Acknowledgement

Type of funding source: None

P1452Low fluoroscopy approach with a novel ablation technology in right side procedures: a large multicenter experience from the CHARISMA registry

Funding Acknowledgements

NO FUNDING

Background

Electrophysiological studies and ablation procedures expose both physicians and patients to a significant amount of radiation. Nowadays, most of 3-D mapping systems allow for improved tracking of catheters with possible reduction in radiation exposure. No data exists on the ability to minimize fluoroscopy time and dose while using the Rhythmia mapping system.

Purpose

To report preliminary data on feasibility and safety of a low fluoroscopic approach using the Rhythmia mapping system in SVT procedures.

Methods

The CHARISMA study is a non-randomized, multicenter, prospective study in which consecutive patients indicated for arrhythmia were enrolled. For our purpose consecutive right-side procedures performed through a low fluoroscopy approach with the Rhythmia mapping system were analyzed. The mapping system was used to create the 3D geometry of chambers of interest and anatomic reference points and to visualize the catheters from the beginning to the end of the procedure. Fluoroscopy was used only if deemed necessary.

Results

204 unselected consecutive cases of SVT from 11 centers were included in the study (mean age = 55 ± 18 years, 53% male, 85 AVNRT, 75 AFL, 28 AP, 9 AT and 7 other right atrial procedures). In all the cases, diagnostic EP and ablation catheters were positioned using only the low fluoroscopic guided mapping approach. During the study, a total of 7157 s of fluoroscopy was needed in 204 patients (51 ± 137 s per procedure). One hundred fourty-one procedures (69%) were completed with less than 10 seconds of fluoroscopy, whereas in 169 (83%) of the cases the fluoroscopy time was lower than 60 seconds. Low fluoroscopy approach with less than 10 seconds was less frequently obtained in case of AFL (46, 61.3%) compared to AVNRT ablation (65, 76.5%, p = 0.041) whereas no differences were found comparing with AP (21, 75%, p = 0.248). The median reconstructed RA volume was 94[65-133] ml in a median mapping time of 11 [6-16] min. The median number of radiofrequency ablations to terminate each arrhythmia was 5 [3-12] (total RF delivery time of 293 [180-505] sec). A 100% rate of acute success was observed in our case series. No complications occurred.

Conclusions

In our preliminary experience, arrhythmias ablation through low fluoroscopy approach and the use of a novel ablation technology seems to be safe, feasible, and effective in common right atrial arrhythmias. Use of fluoroscopy can be nearly avoided in most cases, without any reduction of the safety and effectiveness profile.