Reentrant Tachycardia Research Articles

Abstract 16255: Unraveling the Complex Interplay: Atrial Flutter in a Patient With Prior Double Outlet Right Ventricular Repair

Introduction: Double Outlet Right Ventricle (DORV) is a rare complex congenital heart disease (CHD) in which both the great arteries arise predominantly or entirely from the right ventricle. It is one of the rare CHD lesions with a prevalence of about 0.9%. These patients have complex anatomy, which increases their risk of recurrent arrhythmias. We present a challenging case of Atrial Flutter (AFL) in a patient with DORV. Case: A 31-year-old male with a history of DORV repair presented with palpitations and chest pain for 2 days. His heart rate (HR) was 240 bpm. EKG showed AFL with variable block [Figure 1]. Labs were unremarkable. The patient remained in AFL with HR above 120 bpm despite receiving diltiazem and adenosine. Considering his underlying complex anatomy, ablation was deferred, and the patient was cardioverted to sinus rhythm [Figure 1]. A loop monitor was placed and was started on flecainide with outpatient follow-up at a higher centre. Discussion: Infundibulotomy, removal of obstructive muscle bundles, and a patch to widen the passageway from the right ventricle to the pulmonary arteries are all steps in DORV repair. These surgeries result in scar tissue, an akinetic right ventricular outflow tract, and pulmonary valve insufficiency. Reentrant tachycardias may form due to surgical scars. In DORV patients, Atrial tachyarrhythmias have undesirable outcomes resulting in congestive heart failure, stroke, and mortality. Antiarrhythmics and cardioversion are the cornerstones of managing AFL in patients with DORV due to increased failure rates of catheter ablation. Conclusion: This case illustrates persistent atrial arrhythmias more likely due to DORV repair, resulting in cardiac remodeling. The abnormal anatomy makes localization of irritated ectopic foci and ablations ineffective and difficult.

Medical cardioversion of atrial fibrillation and flutter with class IC antiarrhythmic drugs in young patients with and without congenital heart disease.

The use of flecainide and propafenone for medical cardioversion of atrial fibrillation (AF) and atrial flutter/intra-atrial reentrant tachycardia (IART) is well-described in adults without congenital heart disease (CHD). Data are sparse regarding their use for the same purpose in adults with CHD and in adolescent patients with anatomically normal hearts and we sought to describe the use of class IC drugs in this population and identify factors associated with decreased likelihood of success. Single center retrospective cohort study of patients who received oral flecainide or propafenone for medical cardioversion of AF or IART from 2000 to 2022. The unit of analysis was each episode of AF/IART. We performed a time-to-sinus rhythm analysis using a Cox proportional hazards model clustering on the patient to identify factors associated with increased likelihood of success. We identified 45 episodes involving 41 patients. As only episodes of AF were successfully cardioverted with medical therapy, episodes of IART were excluded from our analyses. Use of flecainide was the only factor associated with increased likelihood of success. There was a statistically insignificant trend toward decreased likelihood of success in patients with CHD. Flecainide was more effective than propafenone. We did not detect a difference in rate of conversion to sinus rhythm between patients with and without CHD and were likely underpowered to do so, however, there was a trend toward decreased likelihood of success in patients with CHD. That said, medical therapy was effective in >50% of patients with CHD with AF.

Radiofrequency Catheter Ablation of Mahaim Tachycardia in Adult Patients

Mahaim pathways causing reentrant tachycardia are rare but potentially dangerous arrhythmia. Catheter ablation is the definitive treatment option for individuals with this kind of tachycardia. Objective: To evaluate the efficacy and safety of radiofrequency catheter ablation of mahaim tachycardia in adult patients. Methods: A retrospective study investigated total of 40 adult patients referred to the Cardiac Electrophysiology Department of Hayatabad medical Complex Peshawar from 4th January 2017 to 21st September 2022 were enrolled. Patient’s age (20-68 years) of both male and female genders referred for radiofrequency ablation of mahaim tachycardia were studied. The tachycardia was invariably antidromic, resulting from anterograde conduction via the Mahaim pathway. All the cases were followed for complications. Results: The overall mean age was 43.60 ± 12.4 years. The mean ablation and flouro time was 9.44± 6.93 minutes and 20.64 ± 9.77 minutes respectively. Hypertension and diabetes were found in 11 (27.5%) and 6 (15%) patients respectively. The successful ablation was achieved in 31 (77.5%) patients whereas 1 case was abandoned. During follow-up, one patient developed femoral hematoma as a complication. Typical Atrioventricular nodal reentry tachycardia (AVNRT) and atrial fibrillation were other tachycardia found in 3 (7.5%) and 4 (10%) respectively. The incidence of congenital anomalies such as ASD Secundum, HOCM, DCM, and Ebstein Anomaly was 2 (5%), 1 (2.5%), 1 (2.5%), and 1 (2.5%) respectively. Conclusion: The present study found that Radiofrequency ablation is effective and safe for treating Mahaim tachycardia. The success rate of RFA was 77.5%.

Fetal Supraventricular Tachycardia: Histologic Evidence of Accessory Pathways Due to Incomplete Annulus Fibrosus Formation.

Atrioventricular (AV) reentrant tachycardia is a common type of supraventricular tachycardia (SVT) that occurs in the fetus and neonate. Although many tachycardias resolve within several weeks of birth or respond to medical management, disruptions in the cardiac annulus fibrosus and development of additional accessory pathways may lead to refractory dysrhythmia resulting in fetal hydrops and ultimately, fetal death. While accessory pathways have been well documented anatomically in adult and childhood tachyarrhythmias, there are no reports of the histology of these pathways in human fetuses with SVT. This is a small case series of 2 fetuses with a history of SVT that resulted in fetal hydrops. In both cases, examination of the cardiac conduction system was unremarkable and examination of the atrioventricular junction revealed a focally thinned and/or discontinuous annulus fibrosus with documented direct continuity between the atrial and ventricular myocardium in 1 case. This case series demonstrates that thinning or absence of the annulus fibrosus is a feature seen in fetal SVT, and the development of subsequent aberrant AV connections due to defective formation of the annulus fibrosus suggests a possible cause for these arrhythmias.

Peculiarities of surgical treatment of atrial macro reentry tachyarrhythmia in elderly patients with implanted pacemaker

Atrial macro reentry tachycardias are the most common tachyarrhythmias in the structure of cardiac arrhythmias in the elderly. Catheter ablations are the gold standard for the treatment of atrial macro reentry arrhythmias, but in the elderly group, the risks of complex ablations often outweigh the benefits. Aim: to determine the optimal volume of catheter ablation in atrial tachyarrhythmia using an implanted pacemaker in elderly patients. Materials and methods. The work is based on a retrospective analysis of the results of surgical treatment of (n = 45) elderly patients (75–90 years) with atrial macro reentry tachycardia, who were previously identified as an artificial pacemaker at the National M. Amosov Institute of Cardiovascular Surgery Affiliated to National Academy of Medical Sciences of Ukraine. Patients were divided into 3 groups depending on the response of the reentry tachycardia to electrical pacing (assessed by the difference between postpacing interval (PPI) and tachycardia cycle lens (CL): group І – PPI-CL 20–40 ms; group ІІ – PPI–CL 20–40 ms; group ІІІ – PPI-CL 60 ms and more. Results. In the group I (n = 20) in 100 % of the patients isthmus-dependent reentry tachyarrhythmia was diagnosed and cava-tricuspid isthmus was ablated. In the group ІІ (n = 12) 4 (33 %) patients were diagnosed with reentry tachycardia around the right pulmonary veins, in 8 (67 %) patients – reentrant tachycardia around the mitral valve. In the group ІІІ (n = 13) in 8 (62 %) patients macro reentry around the mitral valve was found, in 3 (23 %) – reentry around the left pulmonary veins, in another 2 (15 %) of the patients – reentry of the left atrial roof. Conclusions. Non-invasive electrophysiological study with pacemaker can be an effective way to study atrial macro reentry tachyarrhythmias. Electrophysiological PPI-SI criteria less than 20 ms can be used as an additional diagnostic criterion for the selection of patients for surgical treatment. Catheter ablation is recommended for elderly patients when the reentry circle is located in the right atrium.

Role of Scar and Border Zone Geometry on the Genesis and Maintenance of Re-Entrant Ventricular Tachycardia in Patients With Previous Myocardial Infarction.

In patients with healed myocardial infarction, the left ventricular ejection fraction is characterized by low sensitivity and specificity in the prediction of future malignant arrhythmias. Thus, there is the need for new parameters in daily practice to perform arrhythmic risk stratification. The aim of this study is to identify some features of proarrhythmic geometric configurations of scars and border zones (BZ), by means of numerical simulations based on left ventricular models derived from post myocardial infarction patients. Two patients with similar clinical characteristics were included in this study. Both patients exhibited left ventricular scars characterized by subendo- and subepicardial BZ and a transmural BZ isthmus. The scar of patient #1 was significantly larger than that of patient #2, whereas the transmural BZ isthmus and the subdendo- and subepicardial BZs of patient #2 were thicker than those of patient #1. Patient #1 was positive at electrophysiologic testing, whereas patient #2 was negative. Based on the cardiac magnetic resonance (CMR) data, we developed a geometric model of the left ventricles of the two patients, taking into account the position, extent, and topological features of scars and BZ. The numerical simulations were based on the anisotropic monodomain model of electrocardiology. In the model of patient #1, sustained ventricular tachycardia (VT) was inducible by an S2 stimulus delivered at any of the six stimulation sites considered, while in the model of patient #2 we were not able to induce sustained VT. In the model of patient #1, making the subendo- and subepicardial BZs as thick as those of patient #2 did not affect the inducibility and maintenance of VT. On the other hand, in the model of patient #2, making the subendo- and subepicardial BZs as thin as those of patient #1 yielded sustained VT. In conclusion, the results show that the numerical simulations have an effective predictive capability in discriminating patients at high arrhythmic risk. The extent of the infarct scar and the presence of transmural BZ isthmuses and thin subendo- and subepicardial BZs promote sustained VT.

Bundle Branch Re-Entrant Ventricular Tachycardia after Minimal Invasive Cardiac Surgery

Background: Bundle branch re-entrant ventricular tachycardia (BBRVT) is a monomorphic ventricular arrhythmia with wide QRS complexes caused by re-entrant tachycardia between both bundle branches. BBRVT can occur in a variety of cardiac pathologies with His–Purkinje system (HPS) conduction abnormalities such as dilated cardiomyopathy, coronary artery disease, hypertrophic cardiomyopathy, valvular heart disease and even after aortic valve surgery. Case report: A 62-year-old male patient with an ischemic cardiomyopathy and implantable cardioverter defibrillator (ICD) underwent minimal invasive aortic valve replacement (Yil-AVR) and coronary artery bypass graft (CABG). He was remitted a week later because of relapsing sustained ventricular tachycardia (VT). Electrocardiogram showed a wide QRS tachycardia, which was remarkably similar to the patient’s sinus rhythm. Analysis of ICD revealed the presence of BBRVT. Catheter ablation of the right bundle branch (RBB) was performed. He is currently in clinical follow-up and no reoccurrence of VT has been recorded so far. Conclusion: Patients with known cardiomyopathy can develop BBRVT early after cardiac surgery. To our knowledge, this is the first time that BBRVT occurred after Yil-AVR.

Environmental Fe, Ti, Al, Cu, Hg, Bi, and Si Nanoparticles in the Atrioventricular Conduction Axis and the Associated Ultrastructural Damage in Young Urbanites: Cardiac Arrhythmias Caused by Anthropogenic, Industrial, E-Waste, and Indoor Nanoparticles.

Air pollution exposure is a risk factor for arrhythmia. The atrioventricular (AV) conduction axis is key for the passage of electrical signals to ventricles. We investigated whether environmental nanoparticles (NPs) reach the AV axis and whether they are associated with ultrastructural cell damage. Here, we demonstrate the detection of the shape, size, and composition of NPs by transmission electron microscopy (TEM) and energy-dispersive X-ray spectrometry (EDX) in 10 subjects from Metropolitan Mexico City (MMC) with a mean age of 25.3 ± 5.9 and a 71-year-old subject without cardiac pathology. We found that in every case, Fe, Ti, Al, Hg, Cu, Bi, and/or Si spherical or acicular NPs with a mean size of 36 ± 17 nm were present in the AV axis in situ, freely and as conglomerates, within the mitochondria, sarcomeres, lysosomes, lipofuscin, and/or intercalated disks and gap junctions of Purkinje and transitional cells, telocytes, macrophages, endothelium, and adjacent atrial and ventricular fibers. Erythrocytes were found to transfer NPs to the endothelium. Purkinje fibers with increased lysosomal activity and totally disordered myofilaments and fragmented Z-disks exhibited NP conglomerates in association with gap junctions and intercalated disks. AV conduction axis pathology caused by environmental NPs is a plausible and modifiable risk factor for understanding common arrhythmias and reentrant tachycardia. Anthropogenic, industrial, e-waste, and indoor NPs reach pacemaker regions, thereby increasing potential mechanisms that disrupt the electrical impulse pathways of the heart. The cardiotoxic, oxidative, and abnormal electric performance effects of NPs in pacemaker locations warrant extensive research. Cardiac arrhythmias associated with nanoparticle effects could be preventable.

Ablation of incisional re-entrant atrial tachycardia via superior approach in heterotaxy syndrome.

Ablation of incisional re-entrant atrial tachycardia via superior approach in heterotaxy syndrome.

Falling off a limit cycle using phase-agnostic stimuli: Applications to clinical oscillopathies

For over a century, physiological studies have shown that precisely timed pulses can switch off a biological oscillator. This empiric finding has shaped our mechanistic understanding of how perturbations start, stop, and reset biological oscillators and has led to treatments that suppress pathological oscillations using electrical pulses given within specified therapeutic phase windows. Here, we present evidence, using numerical simulations of models of epileptic seizures and reentrant tachycardia, that the phase window can be opened to the entire cycle using novel complex stimulus waveforms. Our results reveal that the trajectories are displaced by such phase-agnostic stimuli off the oscillator's limit cycle and corralled into a region where oscillation is suppressed, irrespective of the phase at which the stimulus was applied. Our findings suggest the need for broadening theoretical understanding of how complex perturbing waveforms interact with biological oscillators to access their arrhythmic states. In clinical practice, oscillopathies may be treated more effectively with non-traditional stimulus waveforms that obviate the need for phase specificity.

Pediatric catheter ablation at the beginning of the 21st century: results from the European Multicenter Pediatric Catheter Ablation Registry 'EUROPA'.

Contemporary data from prospective multicentre registries on catheter ablation in pediatric patients are sparse. Aim of the European Pediatric Catheter Ablation Registry EUROPA was to contribute data to fill this gap of knowledge. From July 2012 to June 2017, data on catheter ablation in pediatric patients (≤18 years of age) including a 1-year follow-up from five European pediatric EP centres were collected prospectively. A total of 683 patients (mean age 12.4 ± 3.9 years, mean body weight 50.2 ± 19 kg) were enrolled. Target tachycardia was WPW/atrioventricular-nodal re-entrant tachycardia (AVRT) in 380 (55.7%) patients, AVNRT in 230 (33.8%) patients, ventricular tachycardia (VT) in 24 (3.5) patients, focal atrial tachycardia (FAT) in 20 (2.9%) patients, IART in 14 (2%) patients, and junctional ectopic tachycardia in 3 (0.45) patients. Overall procedural success was 95.6%. Compared with all other substrates, success was significantly lower in FAT patients (80%, n = 16, P = 0.001). Mean procedure duration was 136 ± 67 min and mean fluoroscopy time was 4.9 ± 6.8 min. Major complications occurred in 0.7% of the patients. No persisting AV block requiring permanent pacing was reported. At 1-year follow-up (605/683 patients, 95%), tachycardia recurrence was reported in 7.8% of patients. Recurrence after VT ablation (33%) was significantly higher (P = 0.001) than after ablation of all other substrates. The present study proves overall high efficacy and safety of catheter ablation of various tachycardia substrates in pediatric patients. Of note, complication rate was exceptionally low. Long-term success was high except for patients after VT ablation.

Acute and long-term outcome of redo catheter ablation for recurrent atrial tachycardia and recurrent atrial fibrillation in patients with prior atrial fibrillation ablation.

Organized atrial tachycardia (AT) accounts for a substantial proportion of recurrence after radiofrequency catheter ablation (RFCA) for atrial fibrillation (AF). We sought to analyze the characteristics and long-term outcome of redo RFCA for recurrent AT compared with those for recurrent AF. We analyzed 133 patients who underwent prior AF ablation and presented for redo RFCA procedure. Documented rhythm at recurrence was AT in 50 patients (37.6%) and AF in 83 patients (62.4%). Redo ablation was conducted using a stepwise approach in all subjects. Recurrent arrhythmia was more frequently a persistent type in the AT group (70.0% vs. 36.1% in the AT and AF group, respectively, p < 0.001). Fifty mappable ATs were identified in the AT group. Perimitral reentry was most common (19/50), followed by PV-related focal or reentrant tachycardia (16/50). During the redo RFCA, PV reconnection rate and linear ablation rate were similar in the two groups, while the focal target ablation tended to be conducted more frequently in the AF group (26.0% vs. 42.2%, p = 0.060). The AT group showed a higher acute success rate (92.0% vs. 75.9%, p = 0.019) and higher arrhythmia freedom during a mean of 30months (76.0% vs. 55.4%, p = 0.030), compared with the AF group. The AT group and de novo AF type (paroxysmal) were independent predictors for higher arrhythmia freedom. RFCA for recurrent AT following AF ablation showed favorable acute and long-term success rates and was associated with superior procedural outcomes compared with those for recurrent AF.

127Diastolic window of interest mapping for fast identification of the critical isthmus in re-entrant ventricular tachycardia

Abstract Background/Introduction Identification of the critical isthmus in re-entrant ventricular tachycardia (VT) should be fast and accurate as the tachycardia is often tolerated for a limited period of time. Using the standard window of interest (WOI) setting with the beginning and end of the window set at mid diastole, mapping systems may incorrectly annotate far field systolic signals instead of smaller diastolic local bipolar signals. The resulting activation map may not show activation pathways through the scar area. Purpose We aimed to study if adjustment of the WOI to the diastolic part of the VT cycle during automatic annotated mapping could aid critical tachycardia isthmus identification. Methods Consecutive patients with ischemic cardiomyopathy undergoing endocardial VT ablation between January 2018 and July 2019 were studied. VT mapping was performed using a multipolar mapping catheter. All signals were automatically annotated using the algorithm provided by the 3D mapping system which uses the maximum negative slope of the unipolar signal (-dV/dT) concomitant with a bipolar signal to calculate local activation times. Location of the critical isthmus was either identified or confirmed by pacing showing concealed entrainment. Acquired maps were analysed retrospectively using three methods: (1) automatically annotated using conventional WOI settings with onset of the window fixed in mid-diastole and a window duration spanning the tachycardia cycle length minus 20 ms, (2) similar conventional WOI settings with manual correction assuring annotation of the near field signal and (3) automatically annotated with an adjusted WOI focused on the diastolic part of the VT, thus excluding its systolic part. Results Forty ischemic cardiomyopathy patients underwent endocardial VT ablation, of which 8 procedures were identified that included activation mapping of re-entrant VT’s. Using conventional WOI settings, local activation was automatically annotated on far field instead of the actual local bipolar activation signal in a mean of 92 (14%) points, range 17 to 260 (3 to 21 %). In all cases, the resulting map did not show diastolic pathways through the scar (Figure A). After manual correction of annotated signals, maps depicted pathways through the scar area (Figure B). All automatically annotated maps with a diastolic WOI indicated the location of the critical isthmus (Figure C). Diastolic pathways are shown by isochronals coloured red/yellow (early diastolic entry) going over in green to light blue (mid-diastolic) adjacent to blue (late diastolic) to pink (exit area), instead of blue/pink and red/yellow (‘early meets late’) during standard WOI mapping. Conclusions Diastolic WOI mapping improves rapid critical isthmus identification in re-entrant ventricular tachycardia, without the need for manual correction. Resulting activation maps may require familiarisation as colour coding differs from standard WOI maps. Abstract Figure. Standard versus diastolic WOI map

Pulmonary vein-gap re-entrant atrial tachycardia following atrial fibrillation ablation: an electrophysiological insight with high-resolution mapping.

The circuit of pulmonary vein-gap re-entrant atrial tachycardia (PV-gap RAT) after atrial fibrillation ablation is sometimes difficult to identify by conventional mapping. We analysed the detailed circuit and electrophysiological features of PV-gap RATs using a novel high-resolution mapping system. This multicentre study investigated 27 (7%) PV-gap RATs in 26 patients among 378 atrial tachycardias (ATs) mapped with Rhythmia™ system in 281 patients. The tachycardia cycle length (TCL) was 258 ± 52 ms with P-wave duration of 116 ± 28 ms. Three types of PV-gap RAT circuits were identified: (A) two gaps in one pulmonary vein (PV) (unilateral circuit) (n = 17); (B) two gaps in the ipsilateral superior and inferior PVs (unilateral circuit) (n = 6); and (C) two gaps in one PV with a large circuit around contralateral PVs (bilateral circuit) (n = 4). Rhythmia™ mapping demonstrated two distinctive entrance and exit gaps of 7.6 ± 2.5 and 7.9 ± 4.1 mm in width, respectively, the local signals of which showed slow conduction (0.14 ± 0.18 and 0.11 ± 0.10m/s) with fragmentation (duration 86 ± 27 and 78 ± 23 ms) and low-voltage (0.17 ± 0.13 and 0.17 ± 0.21 mV). Twenty-two ATs were terminated (mechanical bump in one) and five were changed by the first radiofrequency application at the entrance or exit gap. Moreover, the conduction time inside the PVs (entrance-to-exit) was 138 ± 60 ms (54 ± 22% of TCL); in all cases, this resulted in demonstrating P-wave with an isoelectric line in all leads. This is the first report to demonstrate the detailed mechanisms of PV-gap re-entry that showed evident entrance and exit gaps using a high-resolution mapping system. The circuits were variable and Rhythmia™-guided ablation targeting the PV-gap can be curative.

P4839Identification of the best ablation target and its relationship with mid-diastolic activity in re-entrant intra-atrial tachycardia

P4839Identification of the best ablation target and its relationship with mid-diastolic activity in re-entrant intra-atrial tachycardia

Anticoagulation practices in adults with congenital heart disease and atrial arrhythmias in Switzerland.

In adults with congenital heart disease (CHD) and atrial arrhythmias, recommendations for thromboprophylaxis are vague and evidence is lacking. We aimed to identify factors that influence decision-making in daily practice. From the Swiss Adult Congenital HEart disease Registry (SACHER) we identified 241 patients with either atrial fibrillation (Afib) or atrial flutter/intraatrial reentrant tachycardia (Aflut/IART). The mode of anticoagulation was reviewed. Logistic regression models were used to assess factors that were associated with oral anticoagulation therapy. Compared with patients with Aflut/IART, patients with Afib were older (51 ± 16.1 vs 37 ± 16 years, P < .001) and had a higher CHA2 DS2 -VASc (P < .001) and HAS-BLED scores (P = .005). Patients with Afib were more likely on oral anticoagulation than patients with Aflut/IART (67% vs 43%, P < .001). In a multivariate logistic regression model, age [odds ratio (OR) 1.03 per year, 95%CI (1.01-1.05), P = .019], atrial fibrillation [OR 2.75, 95%CI (1.30-5.08), P = .007], non-paroxysmal atrial arrhythmias [OR 5.33, 95%CI (2.21-12.85)], CHA2 DS2 -VASc-Score >1 [OR 2.93, 95%CI (1.87-4.61), P < .001], and Fontan palliation [OR 17.5, 95%CI (5.57-54.97), P < .001] were independently associated with oral anticoagulation treatment, whereas a HAS-BLED score >1 was associated with absence of thromboprophylaxis [OR 0.32, 95%CI (0.17-0.60), P < .001]. In this multicenter study, age, type, and duration of atrial arrhythmias, CHA2 DS2 -VASc and HAS-BLED scores as well as a Fontan palliation had an impact on the use of thromboprophylaxis in adult CHD patients with atrial arrhythmias. In daily practice, anticoagulation strategies differ between patients with Afib and those with Aflut/IART. Prospective observational studies are necessary to clarify whether this attitude is justified.

693Identification of the best ablation target and its relationship with mid-diastolic activity in re-entrant intra-atrial tachycardia

693Identification of the best ablation target and its relationship with mid-diastolic activity in re-entrant intra-atrial tachycardia

P932Successful one-point ablation for three circuits of reentrant atrial tachycardia

P932Successful one-point ablation for three circuits of reentrant atrial tachycardia

We Must Believe in BELIEF: Left Atrial Appendage as a Source of Arrhythmogenesis

Background: Catheter ablation of persistent and longstanding persistent AF usually requires substrate modification, as well as the elimination of non–pulmonary vein triggers. In this regard, the left atrial appendage (LAA) may represent a site of frequent ectopy and re-entrant tachycardia in some individuals. The results of the recent BELIEF study suggest that empirical isolation of the LAA at the time of AF ablation may be important in preventing AF recurrence.

Arrhythmias Originating in the Atria.

Atrial flutter, atrial tachycardias, and atrial fibrillation are the main sustained atrial tachycardias. Reentry, increased automaticity, and triggered activity are atrial arrhythmia's main mechanisms. Atrial flutter is the clinical and theoretical model of reentry. Its classification is based on the atrial chamber involved and the arrhythmia's anatomic path. Ablative procedures for atrial fibrillation have created several new reentrant tachycardias. Electrocardiography (ECG) identifies the site of origin of focal atrial tachycardias and the mechanism of these arrhythmias. ECG is fundamental in the diagnosis of atrial fibrillation and often allows understanding of its mechanism of origin and maintenance.