Bidirectional Cavotricuspid Isthmus Block Research Articles

Validation of bidirectional cavotricuspid isthmus block using electrocardiographic imaging

Abstract Background The validation of bidirectional cavotricuspid isthmus (CTI) block following catheter ablation for typical atrial flutter (AFL) involves endocavitary manoeuvres using multiple catheters. The diagnostic capacity of electrocardiographic imaging (ECGi) as a non-invasive tool to confirm bidirectional CTI block may simplify the procedure but its benefit has not been investigated so far. Purpose To evaluate the diagnostic capacities of a novel imageless ECGi system in detecting bidirectional CTI block during AFL catheter ablation. Methods A total of 34 patients were consecutively included in a prospective single-centre study. Atrial activation maps were derived from a novel imageless ECGi system when pacing the septal and lateral aspects of the CTI, gauging the technology's capacities to detect bidirectional block by measuring transisthmic intervals (TII) and observing wave-front collision patterns. TII reflects the time taken for electrical activation to cross the CTI during pacing and we measured both the absolute value and the increase relative to its baseline value. The bidirectional CTI block was assessed by endocavitary manoeuvres using a multipole catheter as the gold-standard. We conducted a blind assessment of the diagnostic capacities of ECGi over endocavitary manoeuvres considering maps from the septal and lateral pacing to determine clockwise and counterclockwise CTI block, respectively. Results Our study established clear benchmarks for diagnosing CTI block using ECGi (Figure 1). Regarding the assessment of clockwise CTI block, the presence of a wave-front collision pattern at the CTI yielded a positive predictive value (PPV) of 91% and negative predictive value (NPV) of 69%. Furthermore, ROC analysis pinpointed 100 ms and 30 ms as the optimal threshold for TII absolute value (PPV=89%, NPV =78%) and TII increase from baseline (PPV=91%, NPV =65%), respectively. Taking together, the combination of these three parameters offered high diagnostic capacities (PPV=87%, NPV=90%). Regarding counterclockwise CTI block, the TII absolute value alone was a reliable predictor, with a threshold derived from ROC analysis of 115 ms providing a PPV of 77% and a NPV of 83% (Graphical abstract). Conclusion These results highlight the efficacy of ECGi in CTI block assessment, promising a streamlined and accurate diagnostic approach (Graphical abstract). The use of a single ablation catheter coupled with ECGi to assess the bidirectional CTI block offers a simplified and efficient alternative to traditional dual catheter techniques.ECGi-based CTI block assessment methodGraphical abstract

Application of virtual navigation in the treatment of macro-re-entrant atrial tachyarrhythmias

Macro-re-entrant atrial tachyarrhythmias occupy the leading positions in the structure of tachyarrhythmias, and one of the most common in this group is atrial flutter. These abnormal rhythms lead to a significant decrease in the quality of patients’ life, and sometimes, indirectly due to complications, can lead to disability and fatal consequences. Medical treatment for this group of arrhythmias has limited effectiveness, and the surgical method of treatment – catheter ablation – comes to the first place. Ablation of atrial flutter is traditionally performed under the guidance of fluoroscopy without the use of a navigation system, but this is associated with increased radiation exposure to patients and staff. Advances in modern arrhythmology make it possible to create anatomical models of heart chambers and activation models of the excitation spreading along anatomical models, reducing the radiation load, but requiring additional equipment and skills. Aim: to compare the procedure duration and radiation load during radiofrequency catheter ablation of the cavo-tricuspid isthmus using 3D navigation with traditional methods. Materials and methods. The work was based on the analysis of treatment results in 84 patients at National M. Amosov Institute of Cardiovascular Surgery affiliated to National Academy of Medical Sciences of Ukraine in the period from 2014 to 2021. Depending on the imaging method, patients were divided into 2 groups. Group I included 31 patients who underwent radiofrequency cavo-tricuspid isthmus (CTI) ablation according to the traditional method under fluoroscopic control without using a navigation system. Group II comprised 27 patients in whom an anatomical model of the right atrium was created. Results. Success criteria were achieved in all groups, bidirectional block line was created at the level of the CTI. In group I, the average time from the first application to the restoration of sinus rhythm was 325 ± 25 s with an average number of applications of 7.4 ± 0.6 (from 5 to 10). The average procedure time was 43.0 ± 3.3 min, with an average X-ray time of 572 ± 44 s and an average dose area product (DAP) was 62.0 ± 5.0 Gy.cm2. In group II, the total duration of the first stage of the intervention was 312 ± 26 s. The average time to stopping tachycardia and restoring sinus rhythm was 230 ± 19 s. The average time from sinus rhythm restoration to confirmation of bidirectional CTI block was 71 ± 6 s with an average number of applications of 3.2 ± 3.0 per the procedure. The average procedure time was 41.5 ± 3.5 min, the average X-ray time was 120 ± 10 s, the average DAP was 15.0 ± 1.3 Gy.cm2. Conclusions. The usage of the anatomical model of the right atrium reduces X-ray exposure by 75.8 %, in comparison to the traditional technique, during radiofrequency catheter ablation of the cavo-tricuspid isthmus with similar procedure time. The anatomical model can be recommended for ablation of the cavo-tricuspid isthmus.

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

Identification of cavotricuspid isthmus conduction block, pitfall of differential pacing maneuver

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Differential pacing (DP) maneuver was generally used to assess bidirectional block of cavotricuspid isthmus (CTI) after catheter ablation. Purpose The purpose of the study is to identify limitation of DP maneuver and suggest continuous sequence (CS) maneuver as a complement of differential pacing. Methods Patients who were diagnosed to typical atrial flutter and underwent catheter ablation were enrolled. CTI conduction block was evaluated by two maneuver, DP and CS maneuver. We tried to identify CTI conduction block for each patient with both maneuvers. With CS maneuver, CTI conduction block was assessed with the recorded sequence of diagnostic catheter. Results Sixty two patients were investigated. Two maneuvers were performed in all patients. There were 8 cases (8/62, 12.9%) of discrepancy between the result of CS and DP maneuver. One of discrepancy cases, CTI conduction block was identified with CS maneuver, but insufficient conduction block with DP maneuver. The rest of discrepancy (11.2%) cases were the opposite. Conclusion DP could not guarantee bidirectional block of CTI because of anatomical complexity and catheter instability. CS maneuver found incomplete block over 10% of conventional maneuver. CS maneuver is simple and can be complement to overcome limitation of DP maneuver.

Incremental value of maximum voltage and activation-guided ablation for cavotricuspid isthmus-dependent atrial flutter

Abstract Funding Acknowledgements Type of funding sources: None. Radiofrequency (RF) catheter ablation is an effective method for treatment of typical cavo-tricuspid isthmus (CTI) dependent atrial flutter. However, despite the widespread use of contact force irrigated catheter, 11% of patients don’t achieve a first-pass CTI block, requiring additional RF applications or additional line during the same or a second procedure. From an anatomical point of view, CTI is composed of discrete bundles of muscle with intervening connective tissue, suggesting that its conduction proprieties are dependent of the anatomic architecture of the bundles. The maximum voltage-guided (MGV) ablation technique targets high-voltage electrograms along CTI to ablate the functionally active anatomic muscle bundle, without drawing a complete anatomic line. [1;2] Purpose The aim of this study was to evaluate the efficacy of maximum voltage and activation-guided ablation (MVG/LAT) for CTI atrial flutter in real-world setting. Methods This was a prospective observational study in which all patients undergoing CTI atrial flutter ablation at the Electrophysiology Laboratory of our Department from 01/2021 to 10/2022 were recruited. Patients who were undergoing the ablation procedure after having already made an unsuccessful attempt of the same were excluded from the study. Substrate and activation mapping of CTI, both during flutter and during pacing from the proximal coronary sinus (CSp), was performed in all patients, identifying the earliest activated high-voltage channels, without the use of fluoroscopy, using the Smart-Touch SF catheter (CARTO 3, V7, Biosense Webster). High-voltage channels were validate also during lateral RA pacing. CTI ablation was performed only in channels with high voltage and early activation (W 45, AI 500). Bidirectional CTI block were validate by differential atrial pacing maneuvers and activation mapping during pacing from CSp. Results Procedural data of 39 patients were evaluated (mean age 68±13 years; men 92.6%; mean right atrium volume 149 mL). The mean number of points taken per map per patient was 1151. Bipolar thresholds were customized (0.5-2.5 mV) with the aim of better visualizing high-voltage channels. In 20/39(51.2%) patients ablation was performed during atrial flutter, in 19/39(48.8%) during pacing from proximal CS. In 19/39(48.8%) patients high-voltage channels were not detected at the central isthmus line (6 o'clock, LAO). The median number of RF applications to achieve bidirectional block of the CTI were 6 (1-20) in all patients (p=NS) (Figure 1,2). During a mean follow-up of 260 days (90-531) no recurrences were documented in any patient. Conclusions MVG/LAT-guided ablation, targeting selectively conductive muscle fibers, decreases the number of RF applications and improves efficacy, mostly in patients with challenging anatomies.

PO-05-224 IDENTIFICATION OF CAVOTRICUSPID ISTHMUS CONDUCTION BLOCK – PITFALL OF DIFFERENTIAL PACING MANEUVER.

Differential pacing (DP) maneuver was generally used to assess bidirectional block of cavotricuspid isthmus (CTI) after catheter ablation. Nevertheless, in some cases, DP maneuver could be inaccurate in identification of bidirectional CTI block. The purpose of the study is to identify limitation of DP maneuver and suggest continuous sequence (CS) maneuver as a complement of differential pacing maneuver. Patients who were diagnosed to typical atrial flutter and underwent catheter ablation were enrolled. CTI conduction block was evaluated by two maneuvers, DP and CS maneuver. We tried to identify CTI conduction block for each patient with both maneuvers. Differential pacing maneuver was conducted according to conventional protocol. With CS maneuver, CTI conduction block was assessed with the recorded sequence of diagnostic catheter. Sixty two patients were investigated. Two maneuvers were performed in all patients. There were 8 cases (8/62, 12.9%) of discrepancy between the result of CS and DP maneuver. One of discrepancy cases, CTI conduction block was identified with CS maneuver, but insufficient conduction block with DP maneuver. The rest of discrepancy (11.2%) cases were the opposite. DP could not guarantee bidirectional block of CTI because of anatomical complexity and catheter instability. CS maneuver found incomplete block over 10% of conventional maneuver. CS maneuver is simple and can be complement to overcome limitation of DP maneuver.

Lesion size index-guided cavotricuspid isthmus linear ablation.

The lesion size index (LSI) predicts radiofrequency (RF) ablation lesion size and is an established parameter for pulmonary vein isolation. However, the effectiveness and safety of LSI for cavotricuspid isthmus (CTI) linear ablation remain unclear. This single-center retrospective study included 50 of patients (67 ± 10years, 68% male) who underwent de novo CTI linear ablation between July 2020 and December 2020. The LSI target was set at 5.0 and 4.0 for the anterior 2/3 and posterior 1/3 segments, respectively. Acute procedural parameters of ablation were evaluated. Acute bidirectional CTI block was achieved in all patients with an RF application time of 4.0min (3.1-5.0min), RF application number of 15 ± 7, and length of CTI of 36.9 ± 9.3mm. First-pass bidirectional conduction block of the CTI was achieved in 39/50 (78%) patients. No major complications were observed. The contact force (CF) per application was significantly lower in the gap tag group than in the non-gap tag group (7g [7-8g] vs. 10g [7-12g], P = 0.0284). LSI-guided CTI linear ablation is an effective and safe treatment approach. CF affects gap formation, even when the target LSI is the same.

First clinical experience with cardiac magnetic resonance guided typical atrial flutter ablation with the integration of active catheter tracking and electro-anatomical mapping

Abstract Funding Acknowledgements Type of funding sources: None. Background In our university hospital, we previously implemented cardiac magnetic resonance (CMR) guided typical atrial flutter ablation in a pre-existing MRI suite which was transformed into an interventional cardiac MRI (iCMR) suite. Purpose To describe our first clinical experience with integration of active catheter tracking and dedicated electro-anatomical mapping (EAM) system for the treatment of typical atrial flutter in a transformed pre-existing MRI suite. Methods Between February 2021 and December 2021, all consecutive patients planned for CMR guided typical atrial flutter ablation were included in this analysis. The procedure was performed under general anaesthesia. Feasibility and safety of active catheter tracking and the integration with a dedicated EAM was evaluated. All patients provided written informed consent. Results In total, nine patients underwent CMR guided atrial flutter ablation. Procedural characteristics are presented in Table 1. In all patients, both active catheter tracking and the integration with EAM were performed successfully. Bidirectional cavo-tricuspid isthmus block was achieved in eight out of nine patients and confirmed by differential pacing using intracardiac electrograms and EAM. In one of these eight patients, the registration of intracardiac electrograms was not possible due to technical problems and the patient was transferred to a conventional electrophysiology lab to complete the ablation following our predefined bailout procedure. Seven out of nine patients were in sinus rhythm at the start of the procedure, one in nodal rhythm with atrial bigeminy, one patient required electrical cardioversion for atrial fibrillation prior to the procedure. No periprocedural complications occurred. Conclusion CMR guided typical atrial flutter ablation in a transformed pre-existing MRI suite using active catheter tracking and a dedicated EAM system is feasible and safe based on this small population. It allows for detailed visualisation of catheters and individual patients anatomy. Further studies in larger patient populations are required to evaluate whether iCMR is cost effective and can improve clinical outcome of typical atrial flutter ablation and other arrhythmias.

Dielectric-based tissue thickness measured during radiofrequency ablation catheter

Abstract Funding Acknowledgements Type of funding sources: None. A new dielectric-based method of KODEX-EPD mapping system (EPD Solutions) for measuring tissue thickness at the catheter-tissue interface has recently been developed. We reported preliminary data on real-time catheter-based measuring myocardial wall thickness in vivo, during typical atrial flutter (AFL) RF ablation. The Kodex version used to perform this type of analysis is a version not commercially available yet but only for case replay and research purpose, not used in clinical practice. The study population consisted of 12 consecutive patients, suffering from symptomatic paroxysmal or persistent cavo-tricuspid isthmus (CTI) dependent. The Wall Viewer (WV) function is measured by assessing a series of dielectric signals derived directly from real-time local interrogation of the catheter-tissue interface. WV is displayed in millimeters, with either high or low confidence levels per met or unmet prerequisite acquisition criteria respectively and it is displayed as a color code scale (Fig. 1, A). The anatomy of the CTI was identified using the 4mm MAP-iT irrigated ablation catheter. A suitable starting point for the ablation, in the proximity of the tricuspid valve, and a final location in the junction between the inferior vena cava and the right atrium, were precisely defined based on electrograms recorded. Subsequently, "point by point" CTI ablation was performed delivering RF energy with 30/40 Watts for 20-40 seconds with an interlesion distance ≤6 mm. 9 patients had paroxysmal common AFL, 3 persistent common AFL. The mean age was 64±9 years, 10 (83%) were male. The mean body mass index was 30±6, 9 (75%) patients had hypertension, and 1 (8%) had coronary artery disease. The mean procedure time was 37±13 min, the mean fluoroscopic time was 690±378 s, the mean RF time 763±205 s, with a mean number of RF pulses of 28±7. The mean cavo-tricuspid isthmus length was 29.5±2.6 mm. The atrial wall thickness was significantly higher close to the tricuspid annulus than close to the inferior vena cava (3.6±0.5 mm vs 2.4±0.3 mm, p<0.001) and a trend towards a progressive decrease of atrial wall thickness was observed moving the mapping catheter from the tricuspid valve to the inferior vena cava (Fig. 1, B). Acute bidirectional cavo-tricuspid isthmus block was achieved in all patients without any complications. We first describe a new mapping technology that allows atrial wall thickness measurement and, as expected, the wall thickness was higher close the tricuspid annulus and lower towards the inferior vena cava. The possibility to calculate the substrate thickness before RF delivery could deeply change the way to perform RF ablation, allowing a tailored energy delivery thus increasing the efficiency of the procedures and potentially reduction of the risk of complications.

B-IN02-02 DIELECTRIC-BASED TISSUE THICKNESS MEASURED WITH A RADIOFREQUENCY ABLATION CATHETER: INITIAL CLINICAL RESULTS

Current algorithms that indicate adequacy of radiofrequency (RF) lesion formation incorporate parameters such as contact force, power, and duration, but omit tissue thickness. A new dielectric-based method for measuring tissue thickness (DTT, Wall Viewer™) at the catheter-tissue interface has recently been developed (pre-market). DTT performance in clinically relevant atrial anatomy, such as the cavotricuspid isthmus (CTI), is unknown. To evaluate the correlation between DTT and tissue thickness measured with intracardiac echocardiography (ICE) in subjects undergoing CTI ablation. Eight subjects at two centers underwent a CTI ablation (NCT03858361 and NCT04438395). Right atrial maps were created with an electroanatomic mapping system (KODEX-EPD). The DTT algorithm is based on a pre-trained algorithm model that incorporates real-time catheter position and local dielectric tissue interrogation by catheter electrodes. Prior to ablation, DTT measurements were taken with an ablation catheter (ThermoCool® SF) along the CTI by blinded operators and compared with tissue thickness determined on stored CTI ICE images after the procedure. Bi-directional CTI block was confirmed with differential pacing. Average RA mapping time was 23 ± 5 min. Acute bi-directional block was confirmed in all subjects. CTI thickness measured with ICE (range 1.3 - 5.0 mm) was compared to DTT tissue thickness at 43 points. There was a significant linear correlation between DTT and ICE tissue thicknesses (p < 0.001, slope: 0.73 and r: 0.57). In total, 86.0% (37/43) of DTT values fell within 1.5 mm of ICE measurements with the largest deviation of 2.1 mm. Clinically relevant atrial tissue thickness was accurately measured by a dielectric-based method with a commercially available RF ablation catheter. Real-time tissue thickness measurement may better inform RF dosing to ensure lesion transmurality while limiting collateral structure damage.

B-PO01-072 DIELECTRIC-BASED TISSUE THICKNESS MEASURED WITH A RADIOFREQUENCY ABLATION CATHETER: INITIAL CLINICAL RESULTS

Current algorithms that indicate adequacy of radiofrequency (RF) lesion formation incorporate parameters such as contact force, power, and duration, but omit tissue thickness. A new dielectric-based method for measuring tissue thickness (DTT, Wall Viewer™) at the catheter-tissue interface has recently been developed (pre-market). DTT performance in clinically relevant atrial anatomy, such as the cavotricuspid isthmus (CTI), is unknown. To evaluate the correlation between DTT and tissue thickness measured with intracardiac echocardiography (ICE) in subjects undergoing CTI ablation. Eight subjects at two centers underwent a CTI ablation (NCT03858361 and NCT04438395). Right atrial maps were created with an electroanatomic mapping system (KODEX-EPD). The DTT algorithm is based on a pre-trained algorithm model that incorporates real-time catheter position and local dielectric tissue interrogation by catheter electrodes. Prior to ablation, DTT measurements were taken with an ablation catheter (ThermoCool® SF) along the CTI by blinded operators and compared with tissue thickness determined on stored CTI ICE images after the procedure. Bi-directional CTI block was confirmed with differential pacing. Average RA mapping time was 23 ± 5 min. Acute bi-directional block was confirmed in all subjects. CTI thickness measured with ICE (range 1.3 - 5.0 mm) was compared to DTT tissue thickness at 43 points. There was a significant linear correlation between DTT and ICE tissue thicknesses (p < 0.001, slope: 0.73 and r: 0.57). In total, 86.0% (37/43) of DTT values fell within 1.5 mm of ICE measurements with the largest deviation of 2.1 mm. Clinically relevant atrial tissue thickness was accurately measured by a dielectric-based method with a commercially available RF ablation catheter. Real-time tissue thickness measurement may better inform RF dosing to ensure lesion transmurality while limiting collateral structure damage.

A simplified differential pacing technique for the evaluation of bidirectional cavo-tricuspid isthmus block during ablation of typical atrial flutter.

Bidirectional block of the cavo-tricuspid isthmus (CTI) is an established endpoint of CTI-dependent atrial flutter (AFl) ablation. Differential pacing has been used to evaluate the CTI block. The purpose of this study is to describe a modified differential pacing technique to evaluate the CTI block. Sixty-two patients underwent radiofrequency (RF) ablation of CTI-dependent AFl. The acute endpoints were non-inducibility of the AFl, and verification of the bidirectional CTI block by our methodology. Pacing was performed in the CS with an ablation catheter positioned immediately lateral to the CTI ablation line, and then 1-2 cm more laterally. The stimulus-to-ablation catheter atrial electrogram intervals were measured at these sites (StimCS-Abl1 and StimCS-Abl2, respectively). Pacing with the ablation catheter also was performed at these 2 sites, and the stimulus-to-CS electrogram intervals (StimABL1-CS and StimABL2-CS) were measured. The criteria for the bidirectional block were StimCS-Abl1 > StimCS-Abl2, and StimABL1-CS > StimABL2-CS. Clinical efficacy was defined as freedom from recurrent AFl during follow-up. Following 12.2 ± 3.7 min of RF delivery across the CTI, intervals were StimCS-Abl1 = 181.2 ± 22.7 ms and StimABL1-CS = 181.0 ± 23.6 ms, and StimCS-Abl2 = 152.2 ± 26.5 ms and StimABL2-CS = 151.2 ± 22.7 (P < 0.001). Atrial flutter was rendered not inducible in all patients, and no procedural complications were encountered. During the next 15.9 ± 0.7 months, two patients were lost to follow-up, and among the 62 other patients, one (1.7%) had flutter recurrence. The bidirectional CTI block can be assessed quickly and easily using only the ablation and CS catheters for differential pacing.

Abstract 15658: Anatomical Characteristics of the Cavotricuspid Isthmus and Their Correlation With Obstructive Sleep Apnea

Introduction: Macro-reentrant arrhythmias involving the cavo-tricuspid isthmus (CTI) are common in patients with atrial fibrillation (AF). Bidirectional CTI block is the ablation strategy of choice, but it can be surprisingly difficult to obtain at times. Objective: Aim of this study was to systematically assess the characteristics of the CTI to determine its most common anatomical variants to be anticipated for ablation. Methods: This is a prospective observational study in which intracardiac echocardiography (ICE) was used to visualize the CTI of patients undergoing AF ablation. The presence of anatomical variants was recorded, and length was measured along the central CTI in atrial systole. CTI systolic shortening measured in sinus rhythm and defined as: [(diastolic length - systolic length)/(diastolic length)]x100. Results: 180 patients (65±9 years old, 31% female, 37% paroxysmal AF) are included in the study. Mean CTI length was 31±9 mm, with a systolic shortening of 25±13%. A prominent Eustachian ridge was present in 32%, a Chiari network in 11%, and at least one pouch-like recess in 35%, with a mean depth of 5.3±2.5 mm (Figure). A longer CTI was observed in patients with non-PAF compared with patients with PAF (33 vs. 27 mm, P&lt;0.0001) and in patients with known obstructive sleep apnea (OSA; 37 vs. 32 mm, P=0.0077). Of note, after excluding patients with heart failure, ROC analysis showed that a CTI length ≥ 33 mm was predictive of the presence of OSA (67 % sensitivity and specificity, AUC = 0.71). Less CTI systolic shortening was observed in patients with non-PAF compared those with PAF (22 vs. 32%; P&lt;0.0001). Conclusion: Anatomical variants of the CTI are common and should be anticipated in case of a challenging CTI ablation. A long CTI is associated with OSA and might warrant further clinical screening to identify this common AF comorbidity. CTI systolic shortening correlates with the type of AF and could represent a measure of right atrial contractility.

Definition of success criteria for ablation of typical right atrial flutter with a single-catheter approach: A pilot study

The success rate of cavotricuspid isthmus ablation to treat right common flutter is high (up to 95%), but needs bidirectional block confirmation, requiring two or three catheters. To describe a new pacing technique using a single catheter to ablate and confirm cavotricuspid isthmus block with differential PR interval measurements. We included 61 patients from five centres, who were referred for cavotricuspid isthmus ablation. All patients had cavotricuspid isthmus ablation, and the cavotricuspid isthmus block was confirmed by differential pacing using two or three catheters. The new method consisted of measuring the PR interval on the surface electrocardiogram using pacing from the tip of the ablation catheter on the lateral side (lateral delay) and the septal side (coronary sinus ostium) of the cavotricuspid isthmus line (difference=delta PR interval), before and after cavotricuspid isthmus ablation. We analysed the value of the delta PR interval in predicting bidirectional cavotricuspid isthmus block as confirmed by standard methods. Among our patient population (mean age 63±12 years), 39 patients were ablated during sinus rhythm, and 22 during common flutter. Cavotricuspid isthmus block was achieved in all patients but one. Lateral delay and delta PR interval increased significantly after validation of cavotricuspid isthmus block (257±42 vs. 318±50ms and 32±23 vs. 96±22ms, respectively; P<0.0001). A delta PR interval cut-off of ≥70ms had 100% sensitivity and specificity to predict bidirectional cavotricuspid isthmus block. A single-catheter ablation approach to performing cavotricuspid isthmus line based on surface electrocardiogram PR interval measurement is feasible. After ablation, cavotricuspid isthmus block was systematically obtained when the delta PR interval was>70ms.

Effectiveness and safety of high‐power and short‐duration ablation for cavotricuspid isthmus ablation in atrial flutter

Despite many studies on new tools and strategies for cavotricuspid isthmus (CTI) ablation, there is an unmet need to improve the CTI ablation procedure. Recently, high-power short-duration (HPSD) ablation has been widely used for pulmonary vein (PV) isolation in atrial fibrillation. We evaluated the effectiveness and safety of HPSD for CTI ablation in atrial flutter (AFL). Eighty-four patients who underwent CTI ablation with or without simultaneous PV isolation between January 2018 and February 2019 were enrolled in this prospective cohort study. We compared procedural characteristics, periprocedural complications, and recurrence of atrial tachyarrhythmia (ATa) between the HPSD group (50 W for 15s) and conventional group (30 W for 60s). A total of 84 patients were divided into the HPSD (n=42) and conventional (n=42) groups. Bidirectional CTI block was achieved in all patients and 95% achieved bidirectional block after the first-line ablation in both groups. Although there was no difference in the total number of ablation lines between the two groups (1.17 ± 0.7vs 1.38 ± 0.8, P=.067), HPSD ablation significantly reduced total ablation time compared to the conventional group (236.0 ± 85.6vs 534.2 ± 235.2s, P<.001). One pericardial tamponade was reported in the HPSD group. During the mean follow-up of 9.3 ± 4.8 months, CTI-dependent AFL recurrence occurred in one patient in the HPSD group. Recurrence of ATa developed in 14 patients with no significant difference between the groups. Our study demonstrates that HPSD CTI ablation is safe and can shorten procedure time.

Ablation of typical atrial flutter guided by the paced PR interval on the surface electrocardiogram: a proof of concept study.

We aimed to assess the novel concept of using the paced PR interval (PRI) on the surface electrocardiogram (ECG) to prove trans-isthmus block after cavotricuspid isthmus (CTI) ablation for typical atrial flutter (AFl). Consecutive patients with AFl underwent linear radiofrequency ablation of the inferior CTI (6 o'clock). After AFl termination and/or presumed completion of the CTI line, CTI block was proven by atrial pacing by the ablation catheter medial (5 o'clock) and lateral to the line (7 and 9 o'clock). Corresponding PRIs were measured on the surface ECG. CTI block was assumed, if a sudden increase in the PRI was observed by moving the pacing site from 5 to 7 o'clock, and if the latter was longer than at 9 o'clock. Afterwards, bidirectional CTI block was confirmed by differential pacing. Thirty-one patients (mean age 67 ± 16 years, 81% male) underwent CTI ablation, and 18/31 (58%) were in AFl at the time of ablation (cycle length 249 ± 31 ms). Successful CTI block as defined by the PRI method was achieved in 31/31 (100%), and the mean PRIs during pacing at 5, 7, and 9 o'clock were 203 ± 56 ms, 329 ± 70 ms, and 296 ± 66 ms, respectively. Cavotricuspid isthmus block was confirmed in all patients (100%) by coronary sinus pacing with a reversal of the local activation sequence lateral to the isthmus line. The method of PRI analysis on the surface ECG to guide CTI ablation is easy to apply and highly accurate in confirming CTI block. This simple technique enables the novel concept of CTI ablation and proof of block with a single catheter.

Interest of waiting time for spontaneous early reconnection after cavotricuspid isthmus ablation: A monocentric randomized trial.

The aim of this study was to determine the rate of recurrent atrial flutter (AFl) after isolated cavotricuspid isthmus (CTI) ablation and to evaluate the impact of a waiting period with the search for early resumption of the CTI block on the long-term outcome. Three hundred and nineteen consecutive patients referred for typical AFl ablation were randomly assigned to CTI ablation with continuous reevaluation of the CTI block during 30 minutes and early reablation if needed (waiting time [WT] + group, n=155) or to CTI ablation with no waiting period after proven bidirectional CTI block (WT-group, n=164). All patients were regularly followed-up. In the WT+ group, 10 patients (6%) presented a recovery across the CTI (time to recovery: 17 ± 7') and were reablated at the end of the waiting period. After a median follow-up of 21 months, the rate of recurrent AFl was significantly higher in the WT-group as compared to the WT+ group (11.6% [19/164] vs 2.5% [4/155], respectively; P=0.007). However, no significant differences in the subsequent rate of AF were observed between the two groups (29% [WT-] vs 32% [WT+], P=0.66). During the follow-up, 28 patients from the WT-group underwent a second ablation procedure (16 AFl redo and 12 AF ablation) versus 10 patients form the WT+ group (three AFl redo and seven AF ablation). Waiting 30 minutes after CTI ablation to check for early resumption and early reablation allows for decreasing significantly the rate of recurrent atrial flutter.

Anatomic characterization of cavotricuspid isthmus by 3D transesophageal echocardiography in patients undergoing radiofrequency ablation of typical atrial flutter.

Radiofrequency ablation (RFA) is the treatment of choice of cavotricuspid isthmus (CTI)-dependent atrial flutter. Procedural time is highly variable due to anatomical structures. This study aimed to characterize CTI anatomy by transesophageal 3D echocardiography imaging (3D-TEE) to identify anatomic structures related to longer ablation time. Thirty-one consecutive patients (mean age 67.3 ± 11.5 years, 22 males) underwent CTI-ablation procedure. Before ablation, TEE was performed and 3D-TEE images were acquired to evaluate CTI anatomy qualitatively as well as perform measures of CTI morphological features. The electrophysiologist performing RFA was blinded to 3D-TEE data. Bidirectional block of CTI was achieved in all patients without procedural complications after a median ablation time of 11 (IQR 7-14) min. Patients with RFA time ≥11 min (Group 2) presented lower left ventricular ejection fraction (51.1 ± 17.0 vs. 59.5 ± 6.6%, P < 0.010), a larger left atrium (46.2 ± 8.4 vs. 39.9 ± 9.4 mm, P < 0.058), and, more frequently, a right atrial pouch (12/16 patients vs. 4/15, P = 0.012) compared with patients with RFA time < 11 min (Group 1); CTI pouch was significantly deeper in Group 2 compared with Group 1: telediastolic (TD) pouch depth was 10.4 ± 4.5 vs. 6.3 ± 1.5 mm (P = 0.003) and telesystolic (TS) depth 12.8 ± 4.4 vs. 7.0 ± 1.4 mm (P < 0.001), respectively. TD isthmus length, prominent pectinate muscle, and presence of an Eustachian ridge (ER) did not differ between the two groups. Routine pre-procedural 3D-TEE imaging is extremely helpful in qualitative and quantitative evaluation of CTI anatomy in patients undergoing RFA for symptomatic typical atrial flutter. Detection of a deep right atrial pouch was found to be associated with significantly prolonged CTI ablation time to achieve bidirectional block.

Impact of cavotricuspid isthmus morphology in CRYO versus radiofrequency ablation of typical atrial flutter

Objectives. Cryoablation (CRYO) is an alternative to radiofrequency (RF) for catheter ablation of cavotricuspid isthmus (CTI)-dependent atrial flutter (AFL). We aimed to study whether different CTI morphologies had different impacts on procedural success for CRYO and RF. Design. This study randomized 153 patients with CTI-dependent AFL (median age 65 years; range 34–82) to RF or CRYO (78 CRYO; 75 RF). Biplane angiography (RAO 30° and LAO 60°) was done before the ablation procedure and isthmuses were classified as straight (n = 81), concave (n = 43) or pouch-like (n = 29). RF was performed with a 3.5-mm open-irrigated tip catheter and CRYO was performed with a 9 F, 8-mm tip catheter. The ablation endpoint was bidirectional block of CTI. Results. Acute procedural success was achieved in 70/75 patients in the RF group and in 72/78 patients in the CRYO group. With regard to CRYO or RF, acute procedural success rates were similar between the three isthmus types: straight: CRYO (92%) and RF (96%); concave: CRYO (92%) and RF (94%); and pouch-like: CRYO (94%) and RF (85%). There were no significant differences regarding success rate between the different morphologies in the CRYO or the RF group. The CTI was longer in patients with acute failure compared to the patients with acute success (38 ± 7 mm versus 33 ± 6 mm, p = 0.045). Conclusion. The CTI morphology did not influence the acute success rate for either the CRYO or the RF ablation of CTI-dependent AFL. A longer CTI was associated with a lower success rate regardless of energy source.

Characteristics of Cavotricuspid Isthmus Ablation for Atrial Flutter Guided by Novel Parameters Using a Contact Force Catheter.

This study sought to investigate specific contact force (CF) parameters to guide cavotricuspid isthmus (CTI) ablation and compare the outcome with a historical control cohort. Patients (30) undergoing CTI ablation were enrolled prospectively in the Study cohort and compared with a retrospective Control cohort of 30 patients. Ablation in the Study cohort was performed using CF parameters >10 g and <40 g and a Force Time Integral (FTI) of 800 ± 10 g. The Control cohort underwent traditionally guided CTI ablation. Traditional parameters (electrogram and impedance change) were assessed in both cohorts. All ablations regardless of achieving targets were included in data analysis. Bidirectional CTI block was achieved in all of the Study and 27 of the Control cohort. Atrial flutter recurred in 3 (10%) patients (follow-up 564 ± 212 days) in the study cohort and in 3 (10%) patients (follow-up 804 ± 540 days) in the Control cohort. There were no major complications in either cohort. Traditional parameters correlated poorly with CF parameters. In the Study cohort, flutter recurrence was associated with significantly lower FTI and ablation duration, but was not associated with total average CF. CTI ablation can be safely performed using CF parameters guiding ablation, with similar long-term results to a historical ablation control group. Potentially CF parameters may provide adjunctive information to enable a more efficient CTI ablation. Further research is required to confirm this.