Cavotricuspid Isthmus-dependent Atrial Flutter Research Articles

Acute decompensated heart failure in the setting of cavotricuspid isthmus-dependent atrial flutter and thyroid storm

Thyroid storm is an extreme form of hyperthyroidism associated with a high mortality rate. Heart failure is considered the leading cause of mortality in these patients. Atrial flutter is the second most common arrhythmia in patients with thyroid storms that can lead to cardiomyopathy and further complications, such as acute decompensated heart failure. In this report, we present a case of acute decompensated heart failure in the setting of cavotricuspid isthmus-dependent atrial flutter and thyroid storm. Keywords: Thyroid storm, Graves’ disease, cardiomyopathy, atrial flutter.

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.

Abstract 12930: Atrial Myopathy and the Risk of Incident Atrial Fibrillation in People With Newly Diagnosed Cavotricuspid Isthmus-Dependent Atrial Flutter

Background New cavotricuspid isthmus-dependent atrial flutter (AFL) is associated with increased risk of incident atrial fibrillation (AF). It is unclear which patients with AFL will develop AF. Hypothesis: Patients with new AFL who have co-existing atrial myopathy, detected by measuring left atrial emptying fraction (LAEF) and left atrial reservoir strain (LARS), may be at increased risk for developing AF. Methods: There were 210 patients who received an ablation or cardioversion for AFL at a tertiary care medical center between 2015-2022. Patients were excluded for prior AF (118), congenital heart disease (16), valve surgery and heart transplant (9), no echocardiogram available (9), and less than 6 months of follow up (9). Data was obtained by retrospective chart review. Covariates included coronary heart disease, heart failure, diabetes, age, sex, vascular disease, and stroke. Exposure variables included LAEF and LARS. We used Cox proportional hazards models to estimate the risk of AF for LAEF and LARS. Results: 49 patients (mean age 62.3 years, 18.3% female) met criteria for inclusion, and 18 developed atrial fibrillation over a mean follow up period of 29.9 months (19.7 months). Those who developed AF had lower LAEF and LARS compared to those who did not. For every 5% decrease in LAEF and LARS, there was a 1.79 (1.33, 2.38) and 5.26 (1.75, 16.67)-fold increase in risk of AF after adjustment for covariates. Conclusion: Co-existing atrial myopathy, measured by decreased LAEF and LARS, is associated with increased risk of AF in people with new AFL.

Different electrophysiological characteristics of cavo-tricuspid isthmus dependent atrial flutter guided by robotic magnetic navigation in patients with and without prior cardiac surgery.

Cavo- tricuspid isthmus dependent atrial flutter (CTI- AFL) is a common atrial arrhythmia in patients with prior cardiac surgery (postsurgical AFL) and without prior cardiac surgery (nonsurgical AFL). However, there is only limited data regarding the eletrophysiological differences between the CTI- AFL in the postsurgical patients and the nonsurgical patients. We aimed to investigate the differences in clinical and electrophysiological characteristics between the postsurgical group and nonsurgical group and to evaluate the acute and long-term outcomes after ablation guided by robotic magnetic navigation (RMN) in both the groups. Methods Fourty-two consecutive patients with nonsurgical AFL and 21 with postsurgical AFL were retrospectively analyzed in our center. Electrocardiographic (ECG) analysis and three-dimensional electrophysiological study were performed in all the patients. The results revealed that only 55.6% of postsurgical patients with proven counterclockwise (CCW) AFL presented with a typical ECG suggesting this mechanism. In contrast, 86.1% of nonsurgical patients demonstrated a typical ECG pattern for CCW AFL. In addition, we employed a reverse "U-curve" to facilitate radiofrequency delivery when ablating near the inferior vena cava ostium in the present study. Compared with the nonsurgical group, electroanatomical mapping showed the mean AFL cycle length was significantly longer (253.3 ± 40.4 vs. 234.1 ± 24.2 ms, p = 0.03) and the right atrium volume was larger (114.8 ± 26.0 vs. 97.5 ± 19.1 mL, p = 0.004) in the postsurgical group. Additionally, the procedural time (75.9 ± 21.3 vs. 61.6 ± 26.6 minutes, p = 0.03) and ablation time (53.0 ± 21.4 vs. 36.7 ± 25.6 minutes, p = 0.02) are much longer in the postsurgical group. However, the navigation index in the postsurgical group was significantly smaller (0.35 ± 0.08 vs. 0.43 ± 0.13, p = 0.01). Moreover, the acute and long-term success rates were comparable between the two groups. Catheter ablation of CTI-AFL with and without prior cardiac surgery guided by RMN are associated with high acute and long-term success rates, despite the procedural and ablation times are much longer in the postsurgical patients. However, ECG characteristics of the tachycardia may be misleading as they are more often atypical in patients after cardiac surgery.

Prediction of atrioventricular conduction disturbance after ablation of persistent atrial fibrillation.

The prevalence of atrioventricular conduction disturbance (AVCD) in patients with persistent atrial fibrillation (AF) has not yet been fully investigated. We sought to identify the predictors of AVCD in patients with AF by analyzing the relationship between pre-ablation heart rate during AF and the PR interval in sinus rhythm after ablation. We analyzed pre-ablation 24-h Holter electrocardiogram (ECG) and 12 lead ECG 12months after ablation of 121 consecutive patients with persistent AF who underwent their first ablation procedure and maintained sinus rhythm at 12months. AVCD was defined as a first-degree atrioventricular block (AVB), second-degree AVB, high-degree AVB, or third-degree AVB observed on ECG at 12months after ablation. Seventeen out of 121 patients (14.0%) had AVCD at 12months. In the group with AVCD, total heartbeat (THB) and maximum heart rate (Max HR) were significantly lower, and the prevalence of concomitant Cavo-tricuspid isthmus-dependent atrial flutter before ablation and the appearance of macro reentrant atrial tachycardia (AT) during the procedure were significantly higher than those in the group without AVCD. Multiple regression analysis revealed that maximum HR and macro reentrant AT were significant predictors of AVCD. Receiver operating characteristic curve analysis revealed that Max HR of <165.0bpm predicts AVCD with a sensitivity of 76.47% and a specificity of 74.00%. In patients with persistent AF, low Max HR and the presence of macro reentrant AT during the ablation procedure were predictors of AVCD.

Are reentrant atrial tachycardias sensitive to adenosine administration?

Abstract Funding Acknowledgements Type of funding sources: None. Background Adenosine (ADN) infusion may terminate focal atrial tachycardia (AT). However, the effect of ADN on reentrant atrial tachycardia (RAT) is unclear and based on case reports and small series. These latter included mostly patients with cavotricuspid isthmus-dependent atrial flutter and provided conflicting results, with RAT termination found when it involved the septal or the tricuspid/mitral valve regions. Purpose The aim of this study was to test the response (termination, transient suppression or no effect) to ADN infusion on RATs and to evaluate differences according to the AT location. Methods The effect of ADN was prospectively studied at the time of catheter ablation in consecutive patients with AT. Only patients with RAT were included. This latter mechanism was established by activation and entrainment mapping and confirmed by catheter ablation. A 10 mg adenosine 5'-triphosphate (ATP) bolus was administered in all to evaluate the effects on AT cycle length and termination. Additional ATP bolus of 20 or 30 mg was administered if no AV block for at least 2 secs was obtained with the former ones. Results 58 patients (67, ±13 years old; 11 female) with 79 RAT were included. 38 RATs were right sided (34 cavotricuspid isthmus-depend atrial flutters, 1 lateral right atrium reentry, 1 upper loop reentry, 1 superior vena cava reentry, and 1 septal reentry around the coronary sinus) and 41 were left sided (21 perimitral reentry, 16 peripulmonary vein reentry and 4 with a small free wall reentry). No RAT was terminated or had a &amp;gt;20 ms cycle length prolongation following ADN administration. There was no transformation of the RAT into other mechanisms of AT or atrial fibrillation by ADN in any case. There were no complications. Conclusion RATs are insensitive to ADN infusion, with neither termination nor cycle length prolongation.

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.

Wave speed guided point-by-point cavo-tricuspid isthmus ablation to reduce ablation and fluoroscopy in typical atrial flutter

Abstract Funding Acknowledgements Type of funding sources: None. Background Ablation procedures for cavo-tricuspid isthmus (CTI) dependent typical atrial flutter (AFL) have traditionally been performed with conventional electrophysiology mapping guided by fluoroscopy. Three-dimensional electroanatomical mapping (EAM) systems have routinely been used to guide ablation of more complex arrhythmias, but in recent years, have been used for simple ablations with the aim of reducing irradiation. High voltage regions in the CTI have been described as a target in order to minimize procedure times, but there is a lack of knowledge regarding the utility of slow conduction zones for this purpose. Methods In a prospective cohort of patients undergoing 3D EAM assisted AFL ablation, we evaluated a novel strategy (NS) based on omnipolar vectors, using both wave speed and voltage information to focus radiofrequency (RF) lesions (see figure), and compared with a recent retrospective cohort of patients undergoing voltage-guided ablation (VG). Results A group of 26 consecutive patients with mean age 68±12 years and 88% male, underwent NS ablation, and were compared to 23 patients undergoing VG ablation, with no differences among patient characteristics. Of the 26 patients in group NS, 16 (53.9%) were successfully ablated targeting only 2 sites, representing the 2 most confluent areas of low wave speed and high voltage. A total of 24 (92.5%) were ablated successfully with targeting all sites of low wave speed. Only a single patient in the NS group required the completion of a classic CTI line. Average fluoroscopy time and radiation dose were lower in the NS group compared to VG group (1.1±2.4 min 19.5±41.7 mGray vs 8.2±10.2 min and 64.4±76.5 mGray, p=0.0014 and p=0.013, respectively). Furthermore, RF time trended towards reduction in the NS group. Conclusions A strategy based on targeting only areas of low wave speed is effective, limiting the need to complete a traditional CTI line, and reducing fluoroscopy in patients undergoin CTI ablation.

PO-03-004 VISITAG SURPOINT GUIDED HIGH-POWER SHORT-DURATION ABLATION FOR CAVOTRICUSPID ISTHMUS DEPENDENT ATRIAL FLUTTER

VISITAG SURPOINT (VS) guided high-power short-duration (HPSD) ablation has been shown to be safe and effective for the treatment of paroxysmal atrial fibrillation. However, there is limited data on its utility in guiding ablation of cavotricuspid isthmus (CTI) dependent atrial flutter and the effect of CTI anatomy on HPSD procedural success. The purpose of this study was to assess the safety and efficacy of VS guided HPSD ablation for CTI dependent atrial flutter compared to standard ablation strategies and determine the impact of CTI anatomy on reconnection rates. Sixty-four consecutive patients underwent HPSD ablation for atrial flutter at 50W, with a target VS index of 400 and an inter-lesion distance < 6mm. Retrospective data from 35 patients receiving standard CTI ablation at 40W without VS were analyzed as controls. CTI anatomy was assessed using intracardiac echocardiography and categorized as either flat/concave, discrete diverticulum or having an underlying vascular structure. CTI morphology, radiofrequency (RF) time, first-pass bidirectional block (BDB), reconnection rates and ablation complications were compared. CTI morphology, mean CTI length and post-CTI waiting period were not significantly different between HPSD and standard 40W groups. Four patients (7%) in the HPSD group had CTI reconnection. Of these, 3 had evidence of a diverticulum and 1 had an underlying vascular structure. None of the HPSD patients with flat/concave CTI morphology had reconnection. In the standard 40W ablation group, 7 patients (20%) had reconnection (p < 0.05). Of these, 3 were flat/concave, 3 had a diverticulum and 1 had an underlying vascular structure. First pass BDB was achieved in 88% of HPSD patients and 77% of standard 40W patients (p = 0.18). Total RF delivery was significantly shorter in the HPSD group (p < 0.001) with a mean time of 3.65 ± 1.27 minutes, corresponding to 21 ± 10 ablation lesions. Durable bidirectional block was achieved in all HPSD and standard ablation patients, including those with reconnection. There were no complications in either group. HPSD with a target VS index of 400 is safe and effective for typical flutter ablation, with a lower rate of CTI reconnection and shorter RF time compared to standard ablation. The presence of diverticula or underlying vascular structures decreases procedural success. The absence of these anatomical variants may preclude the need for a standard waiting period when using VS guided HPSD technique.Tabled 150W (n = 64)40W (n = 35)p-valueAge (years)66 ± 1065 ± 100.81Gender (male)37 (58%)19 (54%)0.74Flat/Concave39 (61%)22 (63%)0.85Diverticulum22 (34%)11 (31%)0.77Underlying Vessel3 (5%)2 (6%)0.82CTI Length (cm)3.16 ± 0.623.21 ± 0.780.67RF Time (min)3.65 ± 1.278.73 ± 2.77< 0.001First Pass Block56 (88%)27 (77%)0.18Reconnection Rate4 (7%)7 (20%)< 0.05 Open table in a new tab

Comparison of Intra Cardiac Echo (ICE) Guided Verses Non- Intra Cardiac Echo Radiofrequency Catheter Ablation of Cavotricuspid Isthmus Dependent Atrial Flutter

The isthmus-dependent atrial flutter can be effectively treated with Radiofrequency (RF) catheter ablation. Objectives: To compare the ICE guided versus non-ICE radiofrequency catheter ablation of Cavo tricuspid isthmus dependent atrial flutter. Methods: A cross-sectional study was carried out on 40 patient’s atrial flutter data in the Cardiac Electrophysiology Department, Hayatabad medical Complex Peshawar, Pakistan from August 2017 to August 2022. Patients were categorized into two groups: Group-I (ICE-guided RF catheter ablation) and Group-II (non-ICE RF catheter ablation). The standard protocol of ablation was followed using 40-50 watts power at temperature 60oC. In the case of an irrigated cooled tip catheter, the flow was limited to 30 mL/hour and the power was limited to 30 watts. Results: The overall mean ablation and flouro time was 9.44 ± 6.93 minutes and 20.64 ± 9.77 minutes respectively. The frequency of patients in Group-I and Group-II was 29 (72.5%) and 11 (27.5%) respectively. Out of the total patients, about 8 (20%) patients had shown failed status in terms of procedure success, out of which 5 (62.5%) were from Group-II. Compared to non-ICE guided procedure, the ICE guided procedure had lesser flouro and ablation time with higher rate of success and lower complications and recurrence. Conclusions: The present study observed that intracardiac echocardiography (ICE) can effectively disclose the Cavo tricuspid isthmus and guide ablation anatomy. Additionally, ICE guided radiofrequency catheter ablation had higher success rate, less flouro and ablation time, and lower complications than non-ICE guided radiofrequency catheter ablation.

Achieving bi-directional conduction block during catheter ablation is not enough to prevent recurrence of cavo-tricuspid isthmus dependant atrial flutter: Role of subclinical conduction.

Achieving bi-directional conduction block, as assessed by differential pacing and change in activation along tricuspid annulus (TA), across the cavo-tricuspid isthmus (CTI), is considered a satisfactory end point during catheter ablation of atrial flutter (AFL). To assess role of subclinical conduction by observing polarity reversal of local bipolar signals from RS to QR pattern lateral to the line of ablation, in predicting recurrence of CTI dependant AFL after ablation in patients with bidirectional conduction block. Of 683 patients undergoing ablation of CTI dependent AFL, 73 (10.6%) patients underwent redo flutter ablation and were evaluated further. The mean age was 60.8 years and 51% were males. Evidence of bidirectional block by differential pacing and change is activation along multipolar catheter and reversal of local bipolar signals from RS to QR pattern lateral to the line of ablation, during the 1st and subsequent procedure, were studied. 60% patients had confirmed bidirectional block of which 71% had lack of voltage reversal, at the end of 1st procedure. All patients with bidirectional block with lack of reversal of bipolar signals, after the first procedure had recurrence of AFL whereas only 3/11 (27%) people with bidirectional block and with absence of subclinical conduction had recurrence of AFL. Achieving bidirectional conduction block is not sufficient to prevent recurrence of AFL after CTI ablation. Reversal of local bipolar signals, from RS to QR pattern along with achieving bidirectional conduction delay would reduce recurrence of AFL, post ablation.

657 RECURRENT TYPICAL ATRIAL FLUTTER UNDERGOING ABLATION IN A JUVENILE PATIENTS’ SERIES

Abstract Aims Cavotricuspid isthmus ablation is a routine procedure in electrophysiology laboratories. It is mainly performed as treatment for cavotricuspid isthmus-dependent atrial flutter, which is rare in young patients without structural heart disease. Safety and efficacy data regarding this procedure in such patients are scarce. In this case series we present the clinical characteristics and procedure related outcomes of 3 juvenile patients without overt structural heart disease who underwent cavotricuspid isthmus ablation in our Hospital for recurrent typical atrial flutter. Methods and Results Of the 1217 flutter ablation procedures performed in our Hospital from 2003 to 2022, 3 were on juvenile, otherwise healthy patients. The median patient age was 19.3 years old. All of them had a history of recurrent paroxysmal typical atrial flutter, which was initially terminated with electrical cardioversion. Given the young age no pharmacological prophylaxis was initiated, but on the subsequent recurrence we decided for an ablative strategy. Echocardiography and/or MRI excluded structural heart disease. One of them had experienced flutter induced tachycardiomyopathy, while one underwent previous cavotricuspid isthmus ablation with subsequent arrhythmia relapse. All the procedures were conducted using standard electrophysiology equipment successfully, without significant complications. Baseline electric characteristics of cavotricuspid isthmus were recorded and block of conduction was confirmed using standard protocols. Conclusion Recurrent cavotricuspid isthmus-dependent atrial flutter in young Patients without structural heart disease is exceptionally rare, and ablation is seldom performed. In this case series we present 3 patients with such characteristics, and in whom cavotricuspid isthmus radiofrequency ablation was successfully performed.

Predictors of the presence of typical atrial flutter in patients undergoing atrial fibrillation ablation

Abstract Background Typical cavotricuspid isthmus (CTI) dependent atrial flutter (Afl) may develop spontaneously in patients undergoing atrial fibrillation (AF) ablation and it is also responsible for a significant portion of recurrences after AF ablation. In this situation, the second ablation for typical Afl is frequently needed. If the predictors of typical Afl can be known in such patients, CTI ablation for typical Afl can also be performed in the same session as AF ablation. Thus, the risks and increased costs of the second ablation procedure can be avoided. There is insufficient data related to the predictors of typical Afl in patients undergoing AF ablation. Purpose In this study, we aimed to investigate the predictors of typical Afl in patients undergoing catheter ablation for AF. Methods In this retrospective study, we consecutively enrolled 135 patients with AF undergoing index catheter ablation. Patients who did not come regular follow-up after ablation were excluded. Thus, 131 patients were included. The patients were divided two groups according to spontaneous typical Afl development before or after AF ablation. They were compared in terms of baseline characteristics and procedural features. Results The mean age of the patients was 58 (48–62), 65 of them (49.6%) were male, typical Afl was observed in 20 patients (15.2%). The frequency of male gender was higher (80.0% vs 44.1%, p=0.003), the left ventricular (LV) ejection fraction was lower (56.2±10.9% vs 60.7±6.7%, p=0.015), LV end-diastolic diameter was higher [50.0 (48.2–53.0) vs 47.0 (44.0–49.0), p&amp;lt;0.001), the left atrium diameter was higher (41.4±4.5 vs 38.4±4.5, p=0.008), and the right atrium (RA) diameter was higher (41.6±3.5 vs 36.8±3.7, p&amp;lt;0.001) in patients with typical Afl than in those without it (Figure 1a). Laboratory measurements, drug use, and procedural characteristics were similar between groups. A logistic regression analysis demonstrated that male gender [OR: 4.5, 95% CI: 1.01–20.03, p=0.048) and the RA diameter [OR: 1.57, 95% CI: 1.22–2.02, p&amp;lt;0.001] were independent predictors of the presence of typical Afl (Figure 1b). A Receiver Operating Characteristic curve showed that optimal cut-off value of the RA diameter to predict the presence of typical atrial flutter was 40.5 mm (AUC: 0.843, sensitivity %80, specificity %85, p&amp;lt;0.001) (Figure 2). Conclusion A RA diameter greater than 40.5 mm may predict the presence of spontaneous typical Afl in patients undergoing catheter ablation for AF. This information can help to identify patients who would benefit from CTI ablation in the same session as AF ablation. Funding Acknowledgement Type of funding sources: None.

Feasibility and safety of interventional electrophysiology and catheter ablation in the South African public sector: Challenges and opportunities for comprehensive cardiac electrophysiology in South Africa.

The spectrum and outcomes of catheter ablation procedures performed in South Africa are unknown, and therefore, the feasibility of interventional electrophysiology in the South African public sector is undetermined. This study was a retrospective review of all patients that underwent invasive electrophysiology procedures and catheter ablation at Groote Schuur Hospital (GSH) and the University of Cape Town Private Academic Hospital (UCTPAH) between 01 January 2013 and 31 December 2020.One thousand one hundred eighty-six invasive electrophysiology procedures were performed during the study period. Of these were 1102 catheter ablation procedures. There were 76 redo catheter ablation procedures, predominantly for atrial fibrillation (AF), which accounted for 39% (30/76) of the repeat procedures. There were only 0.8% (9/1102) catheter ablation related complications which were mostly access related. Atrial fibrillation accounted for most of the ablation procedures, 28.9% (318/1102); these were mainly performed at UCTPAH than at GSH, 300 vs 18 p< .0001. Cavotricuspid isthmus (CTI) dependent atrial flutter ablation was the second most commonly performed catheter ablation procedure, accounting for 21.6% (238/1102) of the catheter ablation procedures. More CTI dependent atrial flutter ablations were performed at GSH than a UCTPAH, 156 vs 82 p< .0001. The overall success rate of catheter ablation was 92%. A broad spectrum of catheter ablation procedures was performed with a high success rate and limited complications, thus demonstrating the feasibility of safe cardiac electrophysiology and catheter ablation in the South African public sector.

Characteristics and Ablation Outcomes of Atrial Tachycardia in Patients with Prior Cardiac Surgery vs. Spontaneous Scars: Where Are the Differences?

(1) Background: Atrial scars play an important role in atrial tachycardia (AT). They can not only be found in patients with prior cardiac surgery (PCS) but also in patients without PCS or significant structural heart disease, in which case the scar is called a spontaneous scar (SS). This study aims to compare the characteristics, mechanisms and ablation outcomes of AT in patients with PCS and SS. (2) Methods: We retrospectively reviewed electrophysiological and ablative characteristics of ATs in 46 patients with PCS and 18 patients with SS. (3) Results: There were averages of 1.52 and 2.33 ATs per patient in the PCS group and SS group, respectively (p < 0.01). Cavo-tricuspid isthmus dependent atrial flutter (CTI-AFL) was presented in most patients in both groups (93.50% vs. 77.80%, p = 0.17), whereas the SS group had a higher occurrence of scar-mediated reentrant AT (SMAT) and focal AT (FAT) compared with the PCS group (88.90% vs. 39.10%, p < 0.01; 22.2% vs. 2.2%, p < 0.05). There were no significant differences in acute success rate between the two groups, whereas patients with SS had lower long-term success rate (87.0% vs. 61.1%, p < 0.05) and higher occurrence of sinus node dysfunction (SND) (4.3% vs. 22.2%, p < 0.05). (4) Conclusions: CTI-AFL is common in both patients with PCS and SS, and routine CTI ablation is recommended. Compared with patients with PCS, patients with SS have more ATs, especially with higher occurrence of SMAT and FAT, and had a lower long-term success rate and higher incidence of SND.

Local impedance-guided ablation and ultra-high density mapping versus conventional or contact force-guided ablation with mapping for treatment of cavotricuspid isthmus dependent atrial flutter

Introduction– Local impedance (LI) guided ablation as a method of judging lesion effectiveness for cavotricuspid isthmus dependent atrial flutter (CTI-AFL), and ultra-high density (UHD) mapping when breakthrough occurred across an ablation line has not previously been assessed. MethodsThis retrospective observational study evaluated patients undergoing CTI-AFL ablation using conventional, contact force (CF) and LI guided strategies. Ablation metrics were collected, and in the LI cohort, the use of UHD mapping for breakthrough evaluated. Results30 patients were included, 10 per group. Mean total ablation time was significantly shorter with LI (3.2 ± 1.3min) vs conventional (5.6 ± 2.7min) and CF (5.7 ± 2.0min, p = 0.0042). Time from start of ablation to CTI block was numerically shorter with LI (14.2 ± 8.0min) vs conventional and CF (19.7 ± 14.1 and 22.5 ± 19.1min, p = 0.4408). Mean lesion duration was significantly shorter with LI, but there were no differences in the number of lesions required to achieve block, procedural success, complication rates or recurrence. 15/30 patients did not achieve block following first-pass ablation. UHD mapping rapidly identified breakthrough in the five LI patients, including epicardial-endocardial breakthrough (EEB). Conclusion– The use of LI during ablation for real-time lesion assessment was as efficacious as the conventional and CF methods. UHD mapping rapidly identified breakthrough, including EEB.

Incidence and Predictors of Left Atrial Appendage Thrombus before Catheter Ablation of Thrombogenic Arrhythmias.

Introduction: Transesophageal echocardiography (TEE) is routinely performed before catheter ablation of atrial tachyarrhythmias to rule out the presence of left atrial thrombi. However, data to support this practice are inconsistent. Methods: We analyzed consecutive pre-procedural TEE in a high-volume electrophysiology center for the presence of left atrial thrombi and a relevant flow reduction in the left atrial appendage (LAA) defined as LAA sludge or LAA emptying velocity (LAAEV) < 20 cm/s. The possible predictors of reduced flow were recorded and compared in a multivariate logistic regression analysis. Results: 1676 TEE were included (1122 before pulmonary vein isolation, 436 before atrial flutter ablation, 166 before other ablations). 543 patients (32%) were female and 991 (59%) were on DOAC. Nine patients (0.5%) had an LAA thrombus on pre-procedural TEE. Ninety-five further patients (5.7%) had a relevant reduction in LAA flow. The underlying rhythm showed a significant association with the presence of LAA thrombus or reduced LAA flow (p = 0.003). Patients in sinus rhythm and cavotricuspid isthmus-dependent atrial flutter exhibited the lowest risk. Additionally, reduced kidney function was associated with a reduction in LAA flow velocities (p = 0.04). Of note, two LAA thrombi occurred in patients in sinus rhythm and six out of nine patients with an LAA thrombus were on vitamin-K antagonists. Conclusions: LAA thrombus is a rare occurrence before an elective catheter ablation. The underlying rhythm and kidney function may serve as markers of a higher likelihood of significantly reduced LAAEV and LAA thrombus.

Paradoxical delayed capture proved the dual-loop tachycardia mechanism of a cavotricuspid isthmus-dependent atrial flutter

A 37-year-old man underwent catheter ablation for a cavotricuspid isthmus-dependent atrial flutter. Two 20-pole deflectable electrode catheters were placed in a parallel position on the tricuspid annulus and right atrial lateral wall. The dual-loop tachycardia mechanism of the atrial flutter was suggested by paradoxical delayed capture of the lateral wall of the right atrium during entrainment pacing from the lateral tricuspid annulus.

Prospective Evaluation of a Standardized Screening for Atrial Fibrillation after Ablation of Cavotricuspid Isthmus Dependent Atrial Flutter.

Aims: We aimed to prospectively investigate the effectiveness of a standardized follow-up for AF-detection after common atrial flutter (cAFL) ablation. Methods: A total of 309 patients after cAFL ablation without known AF, from 5 centers, and at least one completed, standardized follow-up at 3, 6 and 12 months, including a 24 h Holter-electrocardiogram (ECG), were included. The primary outcome was incident atrial fibrillation (AF), or atrial tachycardia (AT). Predictors were investigated by Cox proportional-hazards models. Results: The mean age was 67.9 years; 15.2% were female and the mean CHA2DS2-VASc (Congestive heart failure, Hypertension, Age, Diabetes, Stroke, Vascular disease, Sex category) score was 2.4 points. The great majority of patients (90.3%) were anticoagulated. Over a mean follow-up of 12.2 months with a standardized approach, AF/AT was detected in 73 patients, corresponding to 11.7% at 3 months, 18.4% at 6 months and 28.2% at 12 months of follow-up. AF was found in 64 patients, AT in 9 and both in 2 patients. Occurrence of AF was recorded in 40 (60.6%) patients by Holter-ECG and in the remaining 26 (39.4%) by clinical follow-up only. There was no difference in male versus female (p = 0.08), or in younger versus older patients (p = 0.96) for AF/AT detection. Only coronary artery disease (hazard ratio [95% confidence intervals] 1.03 [1.01–1.05], p = 0.01) was associated with the primary outcome. Conclusions: AF or AT was detected in a large proportion of cAFL patients after cavotricuspid-isthmus (CTI) ablation, using a standardized follow-up over 1 year. This standardized screening can be easily implemented with high patient acceptance. The high proportion of post-ablation AF needs to be taken into consideration when deciding on long-term oral anticoagulation.

B-PO04-108 FIRST IN CLINICAL ROUTINE ISTHMUS-DEPENDENT ATRIAL FLUTTER ABLATION ENTIRELY PERFORMED IN THE INTERVENTIONAL MRI SUITE USING ACTIVE CATHETER IMAGING

Recently, magnetic resonance imaging (MRI) has been established as a radiation-free alternative to fluoroscopy to image anatomy and structural alterations causative for arrhythmogenesis during cavotricuspid isthmus (CTI) dependent atrial flutter (AFl) ablation procedures. Describe the first real-world experience of CTI ablations performed completely in the interventional cardiac magnetic resonance (iCMR) suite using active catheter imaging. Fifteen patients (73% male, median age 70 yrs (IQR 67-82) underwent ablations in the iCMR suite. Procedures were performed in a 1.5T MRI with MR-conditional ablation catheters. Catheter guidance was performed using active catheter imaging leveraging MR receive coils within the catheter tip [Figure]. Ablation success, complications, and time for procedure were collected. All 15 patients achieved acute procedure success without complication. Median procedure time was 43min (IQR 33-58) with an RF delivery time of 18 min (interquartile range (IQR) 12-26). Post-procedure lesion visualization scanning was 32 min (IQR 10-42). In 5 patients left ventricular ejection fraction improved from 28±7 % to 47±6% after ablation. Of the13 patients that made it to 6 month follow up (1 lost to follow up, 1 death at 6 months), none of the patients had AFl recurrence. CTI-dependent AFl ablation using active catheter imaging can successfully be performed entirely in the iCMR suite. The MR environment allows anatomic visualization of the CTI, intra-procedural lesion visualization, and exclusion of a pericardial effusion.