CTI-dependent Atrial Flutter Research Articles

Impact of the underlying rhythm during cavotricuspid isthmus ablation on the incidence of future new-onset atrial fibrillation: insights from an international multi-centre registry

Abstract Background Radiofrequency catheter ablation of the cavotricuspid isthmus (RF-CTI) is the estabslished treatment of typical atrial flutter (AFL). After RF-CTI for AFL patients without previously documented atrial fibrillation (AF) may also develop AF. It is unknown whether the presence or absence of AFL at the time of ablation can predict the future occurence of AF. Purpose To compare baseline characteristics, procedural data, and long-term follow-up (FU) of patients with AFL. Methods Consecutive patients with documented AFL undergoing RF-CTI were enrolled in a multi-center registry in five centers in two countries between February 2017 and July 2023. For patients with AFL, entrainment mapping was performed for confirming CTI dependent AFL. Patients were categorized into two groups, those with AFL and those with sinus rhythm (SR) during RF-CTI. FU data were collected, including clinical assessments, 12-lead electrocardiogram (ECG) and 24-hour Holter-ECGs during each visit. Results Of the 949 subjects, 36% were excluded from the analysis due to a history of AF. A total of 574 patients were included (mean age 68 +/- 11 yrs, 14% females), 62% presented in AFL group and 38 % SR group during CTI. Median FU was 364 days. Patients in AFL group were older (P < 0.029), more likely to have diabetes (P = 0.026), and were less frequently treated with antiarrhythmic drugs (P < 0.001). In the first 12 months of FU, 40% of the patients underwent three FU examinations, while 77% of the patients underwent at least one 24-hour Holter-ECGs during FU. In the Kaplan-Meier analysis patients in AFL group significantly less often developed AF during FU (log-rank, P < 0.016, central ). In the multivariate Cox regression analysis, sinus rhythm during ablation (hazard ratio 1.474; 95% CI 1.043-2.084; P = 0.028), male gender (hazard ratio 1.722; 95% CI 1.116-2.658; P = 0.014) and coronary artery disease (hazard ratio 1.711; 95% CI 1.145-2.555; P = 0.009) were identified as predictors for the occurence of AF during FU. Conclusion Over a one year follow-up, new onset AF occurs significantly less frequently in patients with ongoing atrial flutter during RF-CTI ablation.

Comparative Efficacy of Cavotricuspid Isthmus Ablation in Sinus Rhythm Versus Typical Atrial Flutter

Background: Cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL) is the most common atrial macro-reentrant tachycardia, characterized by a typical ECG pattern (type I ECG). Often, tachycardia terminates before it can be confirmed by an electrophysiological study (EPS), necessitating CTI ablation in sinus rhythm (SR). This study aims to compare the success rate of CTI ablation in patients with type I ECG during SR versus ongoing CTI-dependent AFL, focusing on arrhythmia recurrence. Methods: We screened patients at Ulm University Heart Center from January 2010 to November 2020 with type I ECG who underwent CTI ablation. Patients were divided into two groups: those whose tachycardia terminated before EPS and underwent ablation in SR, and those with ongoing CTI-dependent AFL during EPS. CTI ablation was deemed complete when a bidirectional conductance block was achieved, confirmed after 30 min. Results: A total of 230 patients were included, all showing typical AFL in ECG recordings. Of these, 67 patients underwent ablation in SR, while 163 were ablated during ongoing AFL. The median follow-up time was 2.7 years. Recurrence of CTI-dependent AFL occurred in 8.3% of patients: 4.5% in the SR ablation group and 9.8% in the ongoing AFL group. Kaplan–Meier estimation showed similar efficacy for both methods regarding arrhythmia recurrence (log-rank p = 0.07). Conclusions: Our decade-long study indicates that CTI ablation during SR is as effective as ablation during ongoing CTI-dependent AFL in achieving long-term freedom from arrhythmia. This research supports the efficacy of both techniques in clinical settings, validating a widely practiced approach.

Feasibility and safety of cavotricuspid isthmus ablation using exclusive intracardiac echocardiography guidance: a proof-of-concept, observational trial

Abstract Introduction Catheter ablation is the preferred treatment for typical atrial flutter (AFl), although it can pose challenges due to anatomical abnormalities. The integration of 3D electroanatomical mapping systems (EAMS) has notably diminished the need for fluoroscopy in AFl ablation procedures. Intracardiac echocardiography (ICE) has also demonstrated advantages in reducing radiation exposure during AFl ablation. Nevertheless, there is a lack of evidence on the feasibility of ICE-guided, zero-fluoroscopy AFl ablation without the use of EAMS. Methods In this prospective study, we enrolled 80 patients with CTI-dependent AFl. The initial 40 patients underwent ablation guided by standard fluoroscopy along with ICE (Standard ICE group), whereas the remaining 40 patients underwent zero-fluoroscopy ablation exclusively using ICE (Zero ICE group). Procedure outcomes, including acute success, procedural duration, fluoroscopy duration, radiation dose, and any associated complications, were compared between the groups. Results Both groups achieved a 100% acute success rate. In the Zero ICE group, the zero-fluoroscopy approach was successfully executed in 39 out of 40 cases (97.5%). There were no significant differences in procedure time (55.5 (46.5; 66.8) min vs. 51.5 (44.0; 65.5), p=0.50) and puncture to first ablation time (18 (13.5; 23) min vs. 19 (15; 23.5) min, p=0.50) between the groups. The Zero ICE group had significantly lower fluoroscopy time (57 (36.3; 90) sec vs. 0 (0; 0) sec, p<0.001) and dose (3.17 (2.27; 5.63) mGy vs. 0 (0; 0) mGy, p<0.001 compared to the Standard ICE group. Total ablation time was longer in the Standard ICE group (597 (447; 908) sec vs. 430 (260; 750), p=0.02), but total ablation energy (22458 (14836; 31116) Ws vs. 17043 (10533; 29302) Ws, p=0.10) did not differ significantly. First-pass bidirectional conduction block of the CTI and acute reconnection rates were comparable between the groups. No complications or recurrences were noted during the follow-up period. Conclusion ICE-guided, zero-fluoroscopy CTI ablation for AFl using only ICE is feasible and safe. This method effectively eliminates radiation exposure without compromising procedural duration, total ablation time, or acute success rates.isthmus ablation by ICE

Tissue characterization of acute lesions during cardiac magnetic resonance-guided ablation of cavo-tricuspid isthmus-dependent atrial flutter: a feasibility study.

To characterize acute lesions during cardiac magnetic resonance (CMR)-guided radiofrequency (RF) ablation of cavo-tricuspid isthmus (CTI)-dependent atrial flutter by combining T2-weighted imaging (T2WI), T1 mapping, first-pass perfusion, and late gadolinium enhancement (LGE) imaging. CMR-guided catheter ablation offers a unique opportunity to investigate acute ablation lesions. Until present, studies only used T2WI and LGE CMR to assess acute lesions. Fifteen patients with CTI-dependent atrial flutter scheduled for CMR-guided RF ablation were prospectively enrolled. Directly after achieving bidirectional block of the CTI line, CMR imaging was performed using: T2WI (n = 15), T1 mapping (n = 10), first-pass perfusion (n = 12), and LGE (n = 12) imaging. In case of acute reconnection, additional RF ablation was performed. In all patients, T2WI demonstrated oedema in the ablation region. Right atrial T1 mapping was feasible and could be analysed with a high inter-observer agreement (r = 0.931, ICC 0.921). The increase in T1 values post-ablation was significantly lower in regions showing acute reconnection compared with regions without reconnection [37 ± 90 ms vs. 115 ± 69 ms (P = 0.014), and 3.9 ± 9.0% vs. 11.1 ± 6.8% (P = 0.022)]. Perfusion defects were present in 12/12 patients. The LGE images demonstrated hyper-enhancement with a central area of hypo-enhancement in 12/12 patients. Tissue characterization of acute lesions during CMR-guided CTI-dependent atrial flutter ablation demonstrates oedema, perfusion defects, and necrosis with a core of microvascular damage. Right atrial T1 mapping is feasible, and may identify regions of acute reconnection that require additional RF ablation.

Catheter ablation of typical atrial flutter improves cardiac chamber size and function.

Cavo-tricuspid isthmus (CTI) dependent atrial flutter (AFL) is one of the most common atrial arrhythmias involving the right atrium (RA) for which radiofrequency catheter ablation has been widely used as a therapy of choice. However, there is limited data on the effect of this intervention on cardiac size and function. A retrospective study was conducted on 468 patients who underwent ablation for CTI dependent typical AFL at a single institution between 2010 and 2019. After excluding patients with congenital or rheumatic heart disease, heart transplant recipients, or those without baseline echocardiogram, a total of 130 patients were included in the analysis. Echocardiographic data were analyzed at baseline before ablation, and at early follow-up within 1-year postablation. Follow-up echocardiographic data was available for 55 patients. Of the 55 patients with CTI-AFL, the mean age was 64.2 ± 14.8 years old with 14.5% (n = 8) female. The average left ventricular ejection fraction (LVEF) significantly improved on follow-up echo (40.2 ± 16.9 to 50.4 ± 14.9%, p < .0001), of which 50% of patients had an improvement in LVEF of at least 10%. There was a significant reduction in left atrial volume index (82.74 ± 28.5 to 72.96 ± 28 mL/m2 , p = .008) and RA volume index (70.62 ± 25.6 to 64.15 ± 31 mL/m2 , p = .046), and a significant improvement in left atrial reservoir strain (13.04 ± 6.8 to 19.10 ± 7.7, p < .0001). Patients who underwent CTI dependent AFL ablation showed an improvement in cardiac size and function at follow-up evaluation. While long-term results are still unknown, these findings indicate that restoration of sinus rhythm in patients with typical AFL is associated with improvement in atrial size and left ventricular function.

Feasibility and safety of cavotricuspid isthmus ablation using exclusive intracardiac echocardiography guidance: a proof-of-concept, observational trial.

Catheter ablation is the preferred treatment for typical atrial flutter (AFl), but it can be challenging due to anatomical abnormalities. The use of 3D electroanatomical mapping systems (EAMS) has reduced fluoroscopy exposure during AFl ablation. Intracardiac echocardiography (ICE) has also shown benefits in reducing radiation exposure during AFl ablation. However, there is a lack of evidence on the feasibility of ICE-guided, zero-fluoroscopy AFl ablation without the use of EAMS. In this prospective study, we enrolled 80 patients with CTI-dependent AFl. The first 40 patients underwent standard fluoroscopy + ICE-guided ablation (Standard ICE group), while the other 40 patients underwent zero-fluoroscopy ablation using only ICE (Zero ICE group). Procedure outcomes, including acute success, procedure time, fluoroscopy time, radiation dose, and complications, were compared between the groups. The acute success rate was 100% in both groups. Out of the 40 cases, the zero-fluoroscopy strategy was successfully implemented in 39 cases (97.5%) in the Zero ICE group. There were no significant differences in procedure time [55.5 (46.5; 66.8) min vs. 51.5 (44.0; 65.5), p = 0.50] and puncture to first ablation time [18 (13.5; 23) min vs. 19 (15; 23.5) min, p = 0.50] between the groups. The Zero ICE group had significantly lower fluoroscopy time [57 (36.3; 90) sec vs. 0 (0; 0) sec, p < 0.001] and dose [3.17 (2.27; 5.63) mGy vs. 0 (0; 0) mGy, p < 0.001] compared to the Standard ICE group. Total ablation time was longer in the Standard ICE group [597 (447; 908) sec vs. 430 (260; 750), p = 0.02], but total ablation energy [22,458 (14,836; 31,116) Ws vs. 17,043 (10,533; 29,302) Ws, p = 0.10] did not differ significantly. First-pass bidirectional conduction block of the CTI and acute reconnection rates were similar between the groups. No complications or recurrences were observed during the follow-up period. Our study suggests that zero-fluoroscopy CTI ablation guided solely by ICE for AFl is feasible and safe. Further investigation is warranted for broader validation.

Intracardiac Echocardiography Guidance Improves Procedural Outcomes in Patients Undergoing Cavotricuspidal Isthmus Ablation for Typical Atrial Flutter.

Atrial flutter (AFL) represents a prevalent variant of supraventricular tachycardia, distinguished by a macro-reentrant pathway encompassing the cavotricuspid isthmus (CTI). Radiofrequency (RF) catheter ablation stands as the favored therapeutic modality for managing recurring CTI-dependent AFL. Intracardiac echocardiography (ICE) has been proposed as a method to reduce radiation exposure during CTI ablation. This study aims to comprehensively compare procedural parameters between ICE-guided CTI ablation and fluoroscopy-only procedures. A total of 370 consecutive patients were enrolled in our single-center retrospective study. In 151 patients, procedures were performed using fluoroscopy guidance only, while 219 patients underwent ICE-guided CTI ablation. ICE guidance significantly reduced fluoroscopy time (73 (36; 175) s vs. 900 (566; 1179) s; p < 0.001), fluoroscopy dose (2.45 (0.6; 5.1) mGy vs. 40.5 (25.7; 62.9) mGy; p < 0.001), and total procedure time (70 (52; 90) min vs. 87.5 (60; 102.5) min; p < 0.001). Total ablation time (657 (412; 981) s vs. 910 (616; 1367) s; p < 0.001) and the time from the first to last ablation (20 (11; 36) min vs. 40 (25; 55) min; p < 0.01) were also significantly shorter in the ICE-guided group. Acute success rate was 100% in both groups, and no major complications occurred in either group. ICE-guided CTI ablation in patients with AFL resulted in shorter procedure times, reduced fluoroscopy exposure, and decreased ablation times, compared to the standard fluoroscopy-only approach.

Dual linear lesions for right atrial flutter after mitral valve surgery via the superior transseptal approach.

The superior transseptal approach (STA) for mitral valve surgery is associated with a higher risk of developing macroreentrant incisional atrial flutter (AFL) than the left atrial approach. This study aimed to describe the linear lesions for the complex AFL circuit after the STA and to propose an option for the linear ablation target site. Of the 26 patients who underwent radiofrequency catheter ablation for AFL after mitral valve surgery, data from seven patients with STA incisions were retrospectively analyzed. All patients who had undergone the STA had incisional AFL rotated in a long loop within the right atrium (RA) and cavo-tricuspid isthmus (CTI)-dependent AFL. The linear lesions were created in the CTI, the superior RA vestibule, and between the RA-free wall incision or the septal incision and the inferior vena cava. Procedural success was achieved with dual linear lesions in the CTI and superior RA vestibule. Two of seven patients had AFL recurrence during a mean observation period of 22.5 ± 16.7months. The circuits of recurrent AFL were CTI-dependent AFL and perimitral AFL, respectively. No AFL recurrence was noted with reconduction of the superior RA vestibular lesion. Dual linear lesions in the CTI and superior RA vestibule are an effective treatment option for RA macroreentrant AFL after the STA.

Catheter navigation by intracardiac echocardiography enables zero-fluoroscopy linear lesion formation and bidirectional cavotricuspid isthmus block in patients with typical atrial flutter

IntroductionOne of the most helpful aspects of intracardiac echocardiography (ICE) implementation in electrophysiological studies (EPS) is the real-time visualisation of catheters and cardiac structures. In this prospective study, we investigated ICE-guided zero-fluoroscopy catheter navigation during radiofrequency (RF) ablation of the cavotricuspid isthmus (CTI) in patients with typical atrial flutter (AFL).Methods and resultsThirty consecutive patients (mean age 72.9 ± 11.4 years, 23 male) with ongoing (n = 23) or recent CTI-dependent AFL underwent an EPS, solely utilizing ICE for catheter navigation. Zero-fluoroscopy EPS could be successfully accomplished in all patients. Mean EPS duration was 41.4 ± 19.9 min, and mean ablation procedure duration was 20.8 ± 17.1 min. RF ablation was applied for 6.0 ± 3.1 min (50W, irrigated RF ablation). Echocardiographic parameters, such as CTI length, prominence of the Eustachian ridge (ER), and depth of the CTI pouch on the ablation plane, were assessed to analyse their correlation with EPS- or ablation procedure duration. The CTI pouch was shallower in patients with an ablation procedure duration above the median (4.8 ± 1.1 mm vs. 6.4 ± 0.9 mm, p = 0.04), suggesting a more lateral ablation plane in these patients, where the CTI musculature is stronger. CTI length or ER prominence above the respective median did not correlate with longer EPS duration.ConclusionsZero-fluoroscopy CTI ablation guided solely by intracardiac echocardiography in patients with CTI-dependent AFL is feasible and safe. ICE visualisation may help to localise the optimal ablation plane, detect and correct poor tissue contact of the catheter tip, and recognise early potential complications during the ablation procedure.Graphical

PO-01-119 CATHETER STABILITY ANALYSIS IN ABLATION OF PAROXYSMAL ATRIAL FIBRILLATION: IMPACT OF A NOVEL FLEXIBLE ELECTRODE TIP

Catheter electrode stability is a key factor of a successful radiofrequency (RF) ablation lesion formation. Current techniques to enhance or monitor catheter stability include the use of steerable introducers, high-frequency jet ventilation, and the incorporation of objective lesion marker placement via Electroanatomic Mapping (EAM) Systems. In addition to automatic lesion marker placement, the EnSite™ AutoMark Module records catheter location during RF energy delivery, providing insight into catheter electrode stability during ablation. To demonstrate improved stability during ablation with a flexible laser cut tip electrode vs. a solid-6-hole electrode tip during de novo PVI ablation for the treatment of PAF and concomitant CTI-lines for the treatment of typical AFL. AutoMark™ ablation data gathered during the TactiFlex AF IDE NCT04356040 (flex tip catheter) and TactiSense IDE NCT03354663 (solid tip catheter) trials was analyzed (FIGURE). Both trials were prospective, non-randomized multicenter clinical studies which enrolled 355 and 150 subjects worldwide, respectively. PVI and CTI lesions from point-by-point ablation style operators with discrete lesions were included. Anatomic region assignment of each RF episode was accomplished using machine learning. Average distance and standard deviations of the ablation electrode movement from the mean positional centroid were calculated for each RF episode. Stability was evaluated as the percent of time during an RF episode where the ablation electrode remained within 2.5mm of the ablation lesion centroid. A total of 10285 flexible tip and 2141 solid tip RF episodes were analyzed from 112 and 21 cases, respectively. The average RF episode duration for the flexible tip and solid tip lesions, was 10.6 ± 4.8 and 17.1 ± 9.8 seconds, respectively. The flexible tip and solid tip catheters remained positionally stable within a 2.5 mm sphere for 85.3% ± 22.7 and 79.9% ± 26.1 of the RF episode duration, respectively, (p <0.001) (FIGURE). In the subset of lesions <10 seconds, the difference in stability was even more pronounced (TABLE). A flexible tip ablation catheter (TactiFlex™ SE) demonstrated greater stability than a solid tip ablation catheter (TactiCath™ SE) during ablation of atrial fibrillation and CTI-dependent atrial flutter. Greater stability during lesion formation may result in more durable lesions and better patient outcomes.Tabled 1Catheter# RF EpisodesRF Episode Duration, sec (SD)Mean (SD)Median [Q1, Q3]p-valueAll RF EpisodesFlexible Tip1028510.6 (4.8)85.3% (22.7)96.9% [79.9, 100]< 0.001Solid Tip214817.1 (9.8)79.9% (26.1)92.6% [66.7, 100]< 0.001RF Episodes < 10 secFlexible Tip43406.4 (2.8)85.0% (24.2)98.7% [80.7, 100]< 0.001Solid Tip5427.3 (2.3)73.6% (32.9)89.8% [51.7, 100]< 0.001Stability of a solid tip (TactiCath™ Contact Force Ablation Catheter, Sensor Enabled™) versus flexible tip (TactiFlex™ Contact Force Ablation Catheter, Sensor Enabled™), reported as the percent time the catheter tip remained within a 2.5 mm radius sphere. Open table in a new tab

Effect of contact vector direction on achieving cavotricuspid isthmus block

Cavotricuspid isthmus (CTI) ablation is an important treatment strategy for CTI-dependent atrial flutter (AFL). The location of the catheter contact area is confirmed by the contact vector direction (CVD) through three-dimensional mapping during the procedure. However, the relationship between CVD during radiofrequency ablation and its efficacy in achieving CTI block has not been clarified. This study aimed to investigate the relationship between CVD and efficacy in achieving CTI block. CVDs during radiofrequency ablation were divided into proximal vectors against the distal tip (P-vector) and other vectors (normal-vector). In 39 patients who underwent CTI linear ablation, the CTIs were divided into two segments: the tricuspid valve area (anterior) and inferior vena cava area (posterior). The frequency of the residual conduction gap was compared between segments in which the P- and normal-vectors were observed. P-vectors were observed in 13 of the 78 segments. The median ablation index was not significantly different between segments in which the P-vector and normal-vector were observed (398.2 [384.2–402.2] vs. 393.3 [378.3–400.1], p = 0.15). However, residual conduction gaps were significantly more frequently observed in the segment in which the P-vector was observed than those in which only the normal-vector was observed (6/13, 46.2% vs. 3/65, 4.6%; p < 0.01). During a 6-month follow-up, two patients required a second session of ablation due to AFL recurrence. A residual conduction gap was observed in one patient at the site where the P-vector was observed in the first session. Avoiding the P-vector might be an important factor in improving CTI block and reducing AFL recurrence.

Right atrial tachycardia after atrial fibrillation ablation: prevalence, clinical characteristics, electrophysiological mechanisms, and long-term outcomes.

This study aims to evaluate the prevalence, clinical characteristics, electrophysiological mechanisms, and long-term outcomes of right atrial tachycardia (AT) in patients who underwent ablation for atrial fibrillation (AF). From March 2010 to December 2020, 220 consecutive patients undergoing index AF ablation were referred for post-ablation AT recurrence. Thirty-five patients (35/220, 15.9%) with right AT recurrence (25 men; mean age 59.3 ± 10.2years) were enrolled. These patients were divided into groups with right ATs exclusively (group 1) and right combined with left ATs (group 2). Fifty-three ATs were mapped in all patients, with thirty-nine ATs originating from the right atrium. The detailed distribution of all right ATs was 22 in the cavo-tricuspid isthmus (CTI), 6 in the ostium of superior vein cava (SVC), 4 in the right free wall, 4 in the right anterior atrial septum, 2 in coronary sinus ostium, and 1 in crista terminalis. Group 2 had a significantly higher incidence of typical atrial flutter (AFL) than group 1 (11/12, 90.9% vs. 12/24, 50.0%, P = 0.03). During the mean follow-up of 43.6 ± 25.2months after the index AT ablation, the recurrence rate of AT/AF was 22.9% (8/35), and it was lower in group 1 than in group 2 (8.3% vs. 54.5%, P = 0.01). Right AT is relatively less common post-AF ablation. The CTI-dependent AFL and the ostium of SVC-derived focal AT constituted the major components of right ATs, suggesting the importance of ablation- and anatomy-related arrhythmogenic effects in the right atrium.

Cryoballoon Pulmonary Vein Isolation as First-Line Treatment for Typical Atrial Flutter

ObjectiveWe aimed to compare cryoballoon pulmonary vein isolation (PVI) with standard radiofrequency cavotricuspid isthmus (CTI) ablation as first-line treatment for typical atrial flutter (AFL).MethodsCryoballoon Pulmonary Vein Isolation as First-Line Treatment...

Zero-fluoroscopy ablation of the cavotricuspid isthmus guided by intracardiac echocardiography in patients with typical atrial flutter

Abstract Introduction In previous studies we have demonstrated the advantages of electrophysiology catheter navigation by intracardiac echocardiography (ICE). In this prospective study we investigated ICE-guided zero-fluoroscopy ablation of the cavotricuspid isthmus (CTI) involving a decapolar diagnostic and an irrigated radiofrequency (RF) ablation catheter in patients with typical atrial flutter (AFL). Methods and results Twenty-seven consecutive patients (mean age 73.4±11.6 years, 18 male) with ECG-recordings suggesting ongoing (n=19) or recent CTI-dependent AFL underwent an electrophysiological study (EPS) utilizing solely ICE for catheter navigation. All EPS could be successfully accomplished without the need for fluoroscopy. CTI-dependent AFL was confirmed by entrainment manoeuvre in all patients with ongoing AFL. Mean EPS duration was 44.0±20.3 minutes and mean ablation procedure duration was 22.3±16.4 minutes. RF ablation was applied for 6.3±3.1 minutes (50 Watts, irrigated RF-ablation in all patients). After the last RF application, bidirectional CTI-Block was confirmed by differential pacing in all patients. Echocardiographic parameters such as CTI-length, prominence of the eustachian ridge (ER), and depth of the CTI-pouch on the ablation plane (Figure 1) were assessed to analyse their correlation with EPS- or ablation procedure duration. CTI-pouch was shallower in patients with ablation procedure duration above median (4,9±1.09mm vs. 6.3±0.9mm, p=0.048), suggesting a more laterally ablation plane in these patients, where the CTI musculature is stronger. CTI-length or ER-prominence above the respective median did not correlated with longer EPS duration. However, in some cases with prominent ER inversion of the ablation catheter was needed to achieve contact of catheter-tip to the tissue. An asymptomatic intramural hematoma was diagnosed by ICE after successful ablation in one patient, no other major or minor complications were documented in this study. Conclusions Zero-fluoroscopy CTI ablation guided solely by intracardiac echocardiography in patients with CTI-dependent AFL is feasible and safe. ICE visualisation may help to localize the optimal ablation plane, to detect and correct poor tissue contact of the catheter tip and recognise early potential complications during the ablation procedure. Funding Acknowledgement Type of funding sources: None.

Paroxysmal atrial fibrillation ablation with a novel flexible tip radiofrequency catheter incorporating contact force sensing: acute results of the TactiFlex AF IDE trial

Abstract Background Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex™ Ablation Catheter, Sensor-Enabled™ (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating highly accurate fiber optics-based contact force sensing technology with a flexible, laser-cut tip. Purpose To demonstrate that ablation with TactiFlex SE is safe and effective for the treatment of drug refractory, symptomatic PAF. Methods The TactiFlex AF IDE is a prospective, non-randomized, multi-center clinical study which enrolled 355 subjects worldwide. Enrollment in the main study began on June 26, 2020 and completed on June 18, 2021. Subjects underwent de novo Pulmonary Vein Isolation (PVI) and, if indicated, a Cavotricuspid Isthmus ablation (CTI line) for CTI-dependent atrial flutter. Results Subjects were divided into two as treated subgroups: High Standard Power (HSP, n=189), defined as subjects with 100% of left atrial lesions ablated at ≥40 W, and Low Standard Power (LSP, n=119), defined as subjects with at least one left atrial lesion ablated at &amp;lt;40W. First pass success, defined as isolation of all pulmonary veins (PVs) confirmed after a minimum 20 min waiting period was achieved in 93.5% (175/186) and 84.5% (98/116) of HSP and LSP subjects, respectively (p=0.0104). Significant decreases in the HSP versus LSP procedures were also seen in total procedure time (112.0 min [89.0, 139.5] and 149.0 [115.0, 182.0], respectively [p&amp;lt;0.001]), total RF time for PV ablation (14.0 min [11.0, 19.0] and 29.0 [19.0, 41.0], respectively [p&amp;lt;0.0001]), total fluoroscopy time (4.0 min [0.0, 11.0] and 8.0 [3.0, 17.0], respectively [p&amp;lt;0.0001]) and irrigation fluid volume (378.0 mL [310.0, 466.0] and 636.0 [476.0, 829.0], respectively [p&amp;lt;0.0001]) (values given as Median [Q1, Q3]), see Figure 1. Both HSP and LSP subjects had a low rate of repeat procedures (1.6% [3/182] and 4.3% [5/115], respectively [p=0.2684]) and primary safety endpoint events (4.8% [9/189] and 4.2% [5/119], respectively [p=0.8182]) through 90 days post-index procedure. Conclusion The acute data on the TactiFlex SE catheter demonstrates safe and effective treatment of PAF using either a HSP or LSP ablation strategy. Ablation procedures performed using a HSP strategy were shorter and required less irrigation fluid and fluoroscopy. It is anticipated these results will be reflected in the 12-month safety and effectiveness primary endpoints. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): Abbott

Magnetic resonance imaging-guided conventional catheter ablation of isthmus-dependent atrial flutter using active catheter imaging.

Interventional cardiac magnetic resonance (iCMR) has been established as a radiation-free alternative compared to standard fluoroscopy-guided catheter ablation for cavotricuspid isthmus (CTI)-dependent atrial flutter to image anatomy, structural alterations, and further catheter guidance. The purpose of this study was to explore the safety, feasibility, and efficacy of CTI ablations performed completely in the iCMR suite using active catheter imaging. Consecutive patients underwent iCMR-guided catheter ablation for CTI-dependent atrial flutter. Procedures were performed in a 1.5-T magnetic resonance (MR) imaging unit with MR-conditional ablation catheters. Catheter guidance was achieved using active catheter imaging via integrated MR receive tip coils. Acute success, periprocedural complications, and short-term follow-up were collected for further analysis. All patients (N = 15; 73% male; median age 70 years; interquartile range [67-82]) achieved acute procedural success without any complication. Median procedural time was 43 minutes [33-58] with median radiofrequency delivery time of 18 minutes [12-26]. Postprocedural lesion visualization scanning was completed in a median of 32 minutes [10-42]. None of the patients with 6-month follow-up had atrial flutter recurrence. In the iCMR suite, CTI-dependent atrial flutter ablation could be achieved safely using active catheter imaging without any complication. It further allows detailed anatomic visualization of the CTI, intraprocedural lesion visualization, and exclusion of pericardial effusion.

Artificial intelligence-enabled electrocardiogram to distinguish cavotricuspid isthmus dependence from other atrial tachycardia mechanisms.

Accurately determining atrial arrhythmia mechanisms from a 12-lead electrocardiogram (ECG) can be challenging. Given the high success rate of cavotricuspid isthmus (CTI) ablation, identification of CTI-dependent typical atrial flutter (AFL) is important for treatment decisions and procedure planning. We sought to train a convolutional neural network (CNN) to classify CTI-dependent AFL vs. non-CTI dependent atrial tachycardia (AT), using data from the invasive electrophysiology (EP) study as the gold standard. We trained a CNN on data from 231 patients undergoing EP studies for atrial tachyarrhythmia. A total of 13 500 five-second 12-lead ECG segments were used for training. Each case was labelled CTI-dependent AFL or non-CTI-dependent AT based on the findings of the EP study. The model performance was evaluated against a test set of 57 patients. A survey of electrophysiologists in Europe was undertaken on the same 57 ECGs. The model had an accuracy of 86% (95% CI 0.77-0.95) compared to median expert electrophysiologist accuracy of 79% (range 70-84%). In the two thirds of test set cases (38/57) where both the model and electrophysiologist consensus were in agreement, the prediction accuracy was 100%. Saliency mapping demonstrated atrial activation was the most important segment of the ECG for determining model output. We describe the first CNN trained to differentiate CTI-dependent AFL from other AT using the ECG. Our model matched and complemented expert electrophysiologist performance. Automated artificial intelligence-enhanced ECG analysis could help guide treatment decisions and plan ablation procedures for patients with organized atrial arrhythmias.

Termination of macroreentrant atrial arrhythmias by pacing stimuli without global propagation.

Electrical stimulation during ventricular tachycardia resulting in tachycardia termination without global propagation (TWGP) is a well-recognized phenomenon. However, there is a paucity of literature showing a similar phenomenon in atrial arrhythmias. The purpose of the study was to evaluate the significance of TWGP in atrial arrhythmias. Electrophysiological studies performed from 2000 to 2019 at Methodist Hospital, Indiana University were reviewed retrospectively. Thirty-four patients were identified in whom stimulation during atrial tachycardia/flutter resulted in TWGP. Of the 34 patients, 12 (29%) had cavotricuspid isthmus (CTI)-dependent atrial flutter and 22 (71%) had other atrial arrhythmias during which TWGP was seen. Mean age of the population was 53 ± 13 years; and 68% were male. Previous catheter ablation for atrial fibrillation, atrial flutter, or other atrial tachyarrhythmias had been performed in 70.5%, and 44% previously had undergone cardiac surgery involving the atria. Congenital heart disease was present in 20.5%; 3 patients were status post lung transplant. Mean cycle length of atrial arrhythmia in which TWGP was seen was 317 ± 76 ms. The sites at which TWGP was seen reproducibly were highly specific for successful termination of the arrhythmias with radiofrequency energy. The arrhythmia circuits were 12 CTI-dependent atrial flutter, 11 left atrial macroreentrant atrial tachycardia (MRAT), 1 involving both left and right atria, and 8 were other right atrial MRAT. Termination of macroreentrant atrial arrhythmias by pacing stimuli without global propagation identifies a narrow diastolic isthmus at which catheter ablation is highly effective.

Classification of organised atrial arrythmias using explainable artificial intelligence

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): BHF NIHR Background Accurately determining atrial arrhythmia mechanisms from a 12-lead ECG can be challenging. Given the high success rate of cavotricuspid isthmus (CTI) ablation, accurate identification of CTI-dependent typical atrial flutter (AFL) is important for treatment decisions and procedure planning. Machine learning, with convolutional neural networks (CNNs) in particular, has been used to classify arrhythmias using the 12-lead ECG with great accuracy. However, most studies use human interpretation of the ECG as the ground truth to label the arrhythmia ECGs. Therefore, these neural networks can only ever be as good as expert human interpretation. We hypothesised a convolutional neural network could be trained to match or even exceed expert human performance in classifying CTI-dependent AFL vs. non-CTI dependent atrial tachycardia (AT), when using findings from the invasive electrophysiology (EP) study as the gold standard. Methods Figure 1 summarises the study methodology. We trained a CNN on data from 231 patients undergoing EP studies for atrial tachyarrhythmia. A total of 13500 5-second 12-lead ECG segments were used for training. Each case was labelled CTI-dependent AFL or non-CTI dependent AT based on the findings of the EP study. The model performance was evaluated against a test set of 57 patients. A survey of electrophysiologists and cardiologists in Europe was undertaken on the same 57 ECGs. Results The model had an accuracy of 86% (95% CI 0.77-0.95). The F1 score was 0.87.The AT/AFL network correctly identified AT 82% and AFL 90% of the time. A saliency map can be used to help understand why a CNN predicted a particular outcome. This is achieved by mapping the outcome back to key areas of the input that most influenced the network in producing the classification result. Figure 2 presents the saliency mappings of an example 12-lead ECG for each class of AFL and AT. The network used the expected sections of the ECGs for diagnoses; these were the P-wave segments and not the QRS or other unexpected segments. There were twelve respondents in the clinician survey. These respondents included nine electrophysiologists. The median accuracy was 78% (range 70-86%). The electrophysiologists had a median accuracy of 79%, (range 70-84%). Humans were more likely to incorrectly diagnose AFL as AT (on average incorrect diagnoses: 9 AFL, 1 AT). In comparison, the neural network most often incorrectly diagnosed AT as AFL (incorrect diagnoses: 5 AT, 3 AFL). Conclusion We describe the first neural network trained to differentiate CTI-dependent AFL from other atrial tachycardias. We found that our model surpassed expert human performance. Automated artificial intelligence enhanced ECG analysis could help guide treatment decisions and plan ablation procedures for patients with organised atrial arrhythmias.

Acute results of a novel flexible tip radiofrequency catheter incorporating contact force sensing

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Background Catheter ablation is an established therapy for paroxysmal atrial fibrillation (PAF). The TactiFlex Ablation Catheter, Sensor-Enabled (TactiFlex SE) is a next-generation radiofrequency ablation catheter incorporating highly accurate fiber optics-based contact force sensing technology with a flexible, laser-cut tip. This is the first report of results from the TactiFlex IDE clinical study. Purpose To demonstrate that ablation with TactiFlex SE is safe and effective for the treatment of drug refractory, symptomatic PAF. Methods The TactiFlex IDE (NCT04356040) is a prospective, non-randomized, multi-center clinical study which enrolled 305 subjects worldwide in the main study. Enrollment in the main study began on June 26, 2020 and completed on June 8, 2021. Subjects underwent de novo Pulmonary Vein Isolation (PVI) and, if indicated, a Cavotricuspid Isthmus ablation (CTI line) for CTI-dependent atrial flutter. Results Acute procedural success was achieved in 98.6% (274/278) of the main study cohort who underwent an ablation procedure using the TactiFlex SE. First pass success, defined as isolation of all pulmonary veins (PVs) confirmed after a minimum 20 min waiting period was achieved in 89.6% (249/278) of subjects. This was a significant improvement versus the TactiSense IDE trial (TactiCath Ablation Catheter, Sensor-Enabled). Significant decreases were also seen in total procedure time (123 min [101.0, 163.5]), total PV ablation time (55.5 min [35.0, 81.0]), total fluoroscopy time (6.0 min [0.0, 13.0]) and irrigation fluid volume (450.0 mL [346.0, 636.0]) (values given as Median [Q1, Q3]), see FIGURE. All subjects have completed at least 90 days of follow-up. Only 2.6% (7/271) of subjects required a repeat procedure during the 90-day blanking period. The primary safety and effectiveness endpoints will be evaluated at 12-months. At 90 days, 4.3% (12/281) subjects had experienced a primary safety endpoint event. Conclusions The acute data from the TactiFlex IDE clinical study demonstrate safety and effectiveness of the TactiFlex SE catheter in the treatment of PAF. Ablation procedures performed using the next-generation TactiFlex SE catheter were shorter and had improved acute clinical effectiveness outcomes versus the TactiSense IDE. It is anticipated these results will also be reflected in the 12-month safety and effectiveness endpoints.