Isthmus-dependent Atrial Flutter Research Articles

Atrial voltage analysis following vein of marshall alcohol infusion predicts mitral line block

Abstract Background The vein of Marshall (VOM) is a promising therapeutic target for the atrial fibrillation (AF) treatment, fitting perfectly with the "Coumel triangle" as it contains triggers of focal activities and stable reentries, autonomic parasympathetic and sympathetic connection and it represents substrate for perimitral flutters. Lateral mitral line (ML) represents a fundamental part of the anatomical ablation setup for the treatment of AF but its bidirectional block is very difficult to achieve by endocardial ablations. Ethanol infusion into the VoM (VOM-EI) has demonstrated high effectiveness in facilitating ML block. Newly-formed bipolar lesion after VOM-EI is considered an index of effectiveness of the alcoholization procedure. Voltage analysis assessment after VOM-EI in predicting ML block is poorly investigated. Purpose To compare unipolar and bipolar low-voltage areas (LVAs) along VOM trajectory after VOM-EI, and their role in predicting ML block. Methods We enrolled 59 patients undergoing catheter ablation for persistent AF or mitral isthmus dependent atrial flutter. We performed first a high-density voltage map of the left atrium. After VOM-EI, a LA remap was performed. The area width difference was obtained and defined as ∆LVA (see Figure 1). Normal Bipolar voltage cutoffs were 0.50 mV in case of sinus rhythm or 0.29 mV in case of AF. Unipolar cutoffs were respectively 2.7 mV in sinus rhythm and 1.1 mV in AF. The anatomical lesions set, after VOM-EI, included wide antral PVI, linear lesion for dome and ML isthmus following the newly-formed lesion after the VOM-EI. Systematic lines block validation was performed. ML block was defined after coronary sinus electrograms sequence inversion (septal-to-lateral) during left atrial appendage pacing. In case of residual conduction gaps, RF applications into the coronary sinus-great cardiac vein were done to target residual epicardial gaps. Ablation time to obtain ML block (AblTime) was obtained. Results In our group, 56/59 patients (94.5%) achieved mitral isthmus block. Bipolar and unipolar low voltage areas after VOM-EI were 9.9 ± 6.9 cm2 and 12.2 ± 5.9 cm2 respectively. Bipolar ∆LVAs were significantly lower compared with unipolar ∆LVA (8.2 ± 6.5 cm2 vs 9.4 ± 6.0 cm2; p= 0.03). A strong linear correlation between AblTime and bipolar ∆LVA (R: 0.76) and a significant correlation between AblTime and unipolar ∆LVA (R: 0.6) were found (Figure 2). Patients that required coronary sinus applications to reach ML block (13/59, 22%), presented lower ∆LVAs at logistic regression both at bipolar (p<0.01) and unipolar (p=0.03) analysis. Conclusions Unipolar and bipolar voltage analysis along the mitral isthmus trajectory predicts ML block achievement, with VOM-EI inducing wider unipolar LVAs than bipolar LVAs. Furthermore, wider unipolar and bipolar LVAs post VOM-EI are linked to a shorter AblTime and an increased probability of avoiding the need to target epicardial gaps via the CS musculature.LVA along VOM territory after VOM EI∆LVAs linear correlation with AblTime

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.

Long-term outcomes after catheter ablation for idiopathic atypical atrial flutter

BackgroundIdiopathic atypical (non–cavotricuspid isthmus–dependent) atrial flutter (IAAFL) may be seen in patients without structural heart disease and without previous cardiac surgery or ablation. ObjectiveThis study sought to determine the patient characteristics, electrophysiologic and electroanatomic properties, and clinical outcomes after ablation in patients with IAAFL. MethodsWe retrospectively compared IAAFL patients with cavotricuspid isthmus–dependent AFL (C-AFL) patients undergoing catheter ablation. The primary outcome was a composite of death from cardiovascular causes, ischemic stroke, and hospitalization for worsening of heart failure. ResultsOf 180 patients who underwent catheter ablation for AFL, 89 were included in this study (22 IAAFL and 67 C-AFL). Electrophysiologic study showed significantly longer intra-atrial conduction time and lower atrial voltage during sinus rhythm in the IAAFL group compared with the C-AFL group. The atrial scar was observed in all 22 IAAFL patients, with the most common sites being the posterior or lateral wall of the right atrium in 10 (45.5%) and the anterior wall of the left atrium in 8 (36.4%). During 3.5 ± 2.8 years of follow-up, the composite primary end point occurred significantly more frequently in the IAAFL group (hazard ratio [HR], 3.45; 95% confidence interval [CI], 1.20–9.89; P = .015). In multivariable analysis, brain natriuretic peptide levels (HR, 1.01; 95% CI, 1.00–1.01, per 1 pg/mL; P = .01) and IAAFL (HR, 4.14; 95% CI, 1.21–14.07; P = .02) were independently associated with the primary outcome. ConclusionIAAFL in patients had distinct electrophysiologic features suggestive of atrial cardiomyopathy. These patients are at risk for development of cardiovascular adverse events after ablation.

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.

Risk of atrial arrhythmias in patients with ventricular tachycardia in arrhythmogenic right ventricular cardiomyopathy

BackgroundIn arrhythmogenic right ventricular cardiomyopathy (ARVC), risk of atrial arrhythmias (AAs) persists after ventricular tachycardia (VT) ablation. ObjectiveThe purpose of this study was to determine the type, prevalence, outcome, and risk correlates of AA in ARVC in patients undergoing VT ablation. MethodsProspectively collected procedural and clinical data on ARVC patients undergoing VT ablation were analyzed. Risk score for typical atrial flutter was determined from univariate logistic regression analysis. ResultsOf 119 consecutive patients with ARVC and VT ablation, 40 (34%) had AA: atrial fibrillation (AF) in 31, typical isthmus-dependent atrial flutter (AFL) in 27, and atrial tachycardia/atypical flutter (AT) in 10. Seventeen patients (43%) with AA experienced inappropriate defibrillator therapy, with 15 patients experiencing shocks. Ablation was performed for typical AFL in 21 (53%), AT in 5 (13%), and pulmonary vein isolation for AF in 4 (10%) patients and prevented AA in 78% and all AFL during additional mean follow-up of 65 months. Risk score for typical flutter included age >40 years (1 point), ≥moderate right ventricular dysfunction (2 points), ≥moderate tricuspid regurgitation (2 points), ≥moderate right atrial dilation (2 points), and right ventricular volume >250 cc (3points), with score >4 identifying 50% prevalence of typical flutter. ConclusionAAs are common in patients with ARVC and VT, can result in inappropriate implantable cardioverter-defibrillator shocks, and typically are controlled with atrial ablation. A risk score can be used to identify patients at high risk for typical AFL who may be considered for isthmus ablation at the time of VT 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.

Abstract 17847: Typical Right Atrial Flutter Ablation Using Subclavian Venous Access in Patients With Interrupted or Occluded Inferior Vena Cava

Introduction: Ablation for typical atrial flutter (AFL) traditionally involves vascular access from the femoral vein to facilitate advancing catheters through the Inferior Vena Cava (IVC) to the right atrium (RA). In patients with interrupted or occluded IVC, this procedure is challenging to perform. We report a case series of typical right AFL ablation using subclavian access in interrupted or occluded IVC. Cases: A 63-year-old female with typical AFL refractory to medical therapy was referred for radiofrequency ablation (RFA). She had a history of surgically corrected atrial septal defect at age 4 years with known IVC interruption draining into RA via an azygous venous extension. Another case involved a 41-year-old male with quadriplegia and typical AFL who underwent an attempted RFA from femoral access that was aborted due to massive thrombosis of IVC. Decision making: In both cases, two sheaths were placed into the left subclavian venous system using ultrasound guidance. A coronary sinus catheter and irrigated tip ablation catheter were advanced into the coronary sinus and RA respectively. Additionally, in the second case, an intracardiac echocardiography probe was inserted via separate venous access. Using the electroanatomic mapping system, entrainment and activation mapping confirmed a tricuspid isthmus-dependent AFL. RFA was performed using an open irrigated RFA catheter in a linear fashion resulting in the termination of the tachycardia to sinus rhythm. In the first case, ablation extended from the tricuspid annulus to the os of the hepatic vein at the 06:00 position. Post ablation, hemostasis was achieved using a suture-mediated closure device. At follow-up, both patients were asymptomatic without evidence of AFL on extended-duration cardiac monitoring. Conclusion: In patients with interrupted or occluded IVC, the subclavian veins can be accessed for mapping and ablation of typical AFL when traditional femoral venous access is challenging.

Features of Catheter Treatment of Non-Isthmus-Dependent Atrial Flutter

Atrial flutter (AF) is caused by the re-circulation of the wave of electrical excitation of the myocardium (reentry) around the anatomical substrate which circulates within the atrial tissues. This is always a macro re-entry. Such an anatomical barrier, around which circulation can occur, can be the superior or inferior vena cava, rings of the tricuspid or mitral valves, the mouth of the coronary sinus, pulmonary veins, postoperative scar.&#x0D; The aim. To determine the specifics of elimination, success rate, and long-term outcome with various preablation and postablation diagnostic techniques for non-isthmus-dependent atrial flutter (NIDAFL).&#x0D; Materials and methods. The study included 26 patients who underwent radiofrequency ablation of atypical NIDAFL.&#x0D; Results. As a result of radiofrequency ablation, a sinus rhythm was restored in 17 patients during the procedure. In 7 cases, when the typical, isthmus-dependent AF was removed, the tachycardia cycle and the morphology of the R wave changed. Mapping showed that in 7 cases the direction of the re-entry front changed, and instead of the circulation of excitation through the cavatricuspid isthmus, it then passed around the atriotomy scar. In 2 cases, a change in the cardiac cycle was observed after radiofrequency ablation, but the excitation circulation was the same around the atriotomy scar, only the tachycardia cycle increased. As a result of the use of our techniques, arrhythmia was eliminated in all 21 patients with an atriotomy AF during one procedure. Five patients with AF of a different localization of the re-entry circuit also had their arrhythmia eliminated, although 8 procedures (for five patients) were performed (on average 1.6). There were no complications. During the follow-up period of 1.8±0.7 years, 2 patients had a recurrence of arrhythmia, and they underwent a repeat procedure to eliminate the arrhythmia. One patient developed typical AF that had not been observed before, which was successfully eliminated.&#x0D; Conclusion. Catheter treatment of atypical NIDAFL is quite a non-trivial task, because, as our experience shows, several types of tachycardia occur in a significant number of patients. In cases of restoration of sinus rhythm as a result of the application, it is necessary to check the inducibility of another arrhythmia. But despite everything, catheter removal of NIDAFL is quite effective, especially for atriotomy AF, although it requires more X-ray exposure and a relatively large number of applications. The use of navigation systems has helped to improve the results of such interventions in more complex cases.

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.

Tissue characterisation of acute ablation lesions in the right atrium during CMR-guided atrial flutter ablation

Abstract Funding Acknowledgements Type of funding sources: None. Background Cardiac magnetic resonance (CMR)-guided ablation therapy offers a unique opportunity and incentive to investigate acute ablation lesions. Until present, human studies only used T2-weighted imaging (T2WI) and late gadolinium enhancement (LGE) to assess acute ablation lesions. Purpose To investigate the tissue characteristics of acute ablation lesions during CMR-guided atrial flutter ablation, by combining T2WI and LGE with first-pass perfusion and T1 mapping. Methods Thirteen patients with typical isthmus-dependent atrial flutter were prospectively enrolled and treated with CMR-guided ablation. Pre-ablation tissue characterisation consisted of T2WI and T1 mapping. Postablation imaging was performed directly after application of the primary ablation lesions and included T2WI (n=12), first-pass perfusion (n=9), LGE (n=9) and T1 mapping (n=7). For analysis of T2WI an edema ratio (ER; i.e. the signal intensity ratio between myocardium and reference skeletal muscle) &amp;gt; 2.0 was considered indicative of edema. Post-processing comprised native T1 measurements in three regions of the ablation line (near the tricuspid annulus, mid region, near the caval vein) on pre- and post-ablation images by two independent observers. For each region, the change in T1 value was expressed as the absolute increase (in ms) and the relative increase (in %). A third observer, blinded to the CMR results, reviewed which region(s) had required additional RF lesions after post-ablation CMR imaging. Results In 12 out of 13 patients CMR-guided atrial flutter ablation was successful, resulting in bidirectional conduction block. In 1 patient the ablation procedure was completed in the conventional electrophysiology lab, hampering acute post-ablation imaging. In all patients T2WI demonstrated edema in the ablation region. The ER increased from 1.6 ± 0.3 to 3.3 ± 0.5 post-ablation (p&amp;lt;0.001). Perfusion defects were present in 9/9 patients. The LGE images demonstrated hyperenhancement with a central area of hypo-enhancement in 9/9 patients, suggestive of ablation necrosis and previously reported areas of microvascular damage and hemorrhage. Right atrial T1 mapping was feasible in 20/21 regions (in 1 case artifacts from the adjacent catheter hampered analysis) and reproducible (r 0.981, ICC 0.939). The post-ablation increase in T1 value was significantly different between regions that did (n=10) and did not (n=10) require additional RF lesions, T1 increase was 46 ± 90ms versus 133 ± 69ms (p = 0.026), and 4.7 ± 9.1% versus 13.2 ± 6.8% (p = 0.028) respectively. Conclusion CMR tissue characterisation of acute ablation lesions during CMR-guided atrial flutter ablation demonstrates edema, perfusion defects, and necrosis with a core of microvascular damage. Atrial T1 mapping of the acute ablation lesion is feasible and reproducible, and might distinguish regions that require additional RF applications.

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.

Familial cardiolaminopathy due to a previously undescribed LMNA gene mutation

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Cardiolaminopathies are rare genetic alterations, which present diverse mechanical and electrical alterations. OBJECTIVE To present a family carrying an LMNA gene mutation that although not described manifest clinical and electrocardiographic characteristics of the disease. Methods We present the case of two sisters and one brother, aged 65, 57 and 51 years, respectively. At the beginning of their fourth decade, all of them debuted with atrial flutter associated with second and third degree atrioventricular block. Two of them (one or the sisters and the brother) underwent ablation of isthmus-dependent atrial flutter. However, in both, the flutter recurred and no new interventional treatment was further offered. The male subject received a pacemaker implant for treatment of AV block; some years later, he presented a cerebrovascular event and subsequently a recurrence, both while in oral anticoagulation and, actually remains with moderate motor deficit and dysarthria. The youngest woman suffered an embolic cerebrovascular event when she was 50 y/o; she remained asymptomatic in relation to the rhythm disorder and refused a pacemaker. The oldest sister who is asymptomatic, received a pacemaker when she was 45 y/o and now is anticoagulated. By echocardiography, all siblings presented left ejection fraction in between 40 and 50% with decreased strain values and normal left ventricular geometry. Results Recently in our country it is possible to carry out a genetic test, for which the three were subjected to it. In this family, the genetic testing was done using a comercial kit for 172 genes. The result was a Frameshift Indels (non misense) mutation NM_170707.3 c.1526del p.(Pro509LeufsTer39) Exon:9/12, in all three. The caveat is that this LMNA gene mutation has not been previously described. In light of these results, the youngest woman with total AV block and sequelae of cerebrovascular disease and mild left ventricular dysfunction, received an implantable cardiac defibrillator (ICD) implant for primary prevention of sudden death and her siblings are undergoing an upgrade to ICD. Conclusion The mutation found in this family is unique and for the first time reported in the LMNA gene in the world. Genetic diagnosis is limited in our country, which makes it difficult to determine this type of pathology. However, given the clinical presentation of an electrical disorder in all the siblings of a family, in this particular case, it was mandatory to perform this test. These results allow us to better understand the prognosis and intervene appropriately to prevent sudden death, even though there is no treatment to avoid the progression of the disease.

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.

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

PO-01-192 USE OF A LARGE-FOOTPRINT FOCAL LATTICE CATHETER FOR MAPPING AND ABLATION OF ATRIAL FLUTTERS

Catheter ablation of atrial flutters (AFL), in particular atypical (ie non-cavotricupid isthmus dependent) AFL, can be eliminated with high-density electroanatomical mapping using multielectrode catheters used in concert with radiofrequency ablation (RFA). However, this requires 2 separate complex catheters: for mapping and for ablation. Further challenges include difficulties in establishing durable block across the isthmus of identified circuits, in particular (but not exclusively) the mitral isthmus. Recently, a large footprint lattice-tip catheter (Sphere-9, Affera-Medtronic Inc.) has been developed capable of both delivering either pulsed field (PF) energy or high-power RF energy, and performing high-density mapping using mini-electrodes located throughout the lattice-tip. To determine the feasibility and efficacy, both acute and chronic, of mapping and ablation of AFL using the lattice-tip catheter. As part of a 3-center, single-arm, first-in-human study of AF ablation with the lattice-tip catheter (NCT04141007, NCT04194307), spontaneous or induced AFLs were mapped and ablated using the lattice-tip catheter, in conjunction with a compatible mapping-system. The 7Fr lattice-tip catheter has a compressible 9-mm nitinol tip with 9 embedded mini-electrodes, and is able to deliver either RF or PF energy (each lesion 2-5 sec). During AF ablation in the 178-pt cohort (39% paroxysmal, 61% persistent), AFL was identified in 47 (26%) pts. This included typical AFL in 22 (12%) pts, peri-mitral AFL in 17 (10%) and other AFLs in 26 (15%). Mapping of the AFL circuits was performed exclusively using the lattice catheter. Cavo-tricuspid isthmus (CTI), LA roof, and mitral isthmus lines were targeted in 94%, 83%, and 70% of patients in whom AFLs were identified (some flutters were not targeted flutters if not considered clinically-relevant). Bidirectional conduction block was achieved in all (100%) of attempted lines. Over a 12-month follow-up, 37 of 47 pts (79%) were free from AFL recurrence. Atrial flutters are noted in a substantial number of patients undergoing catheter ablation of atrial fibrillation. The flexibility of a large-tip focal lattice catheter allows for facile post-PVI mapping and ablation of such flutters, while minimizing the need for additional equipment and catheter exchanges. Ablation using either RF or PF energy resulted in successful block across attempted linear lesions and excellent long-term success.

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.

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.