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IntroductionThe assessment of the ventricular myocardial substrate critically depends on the size of mapping electrodes, their orientation with respect to wavefront propagation, and interelectrode distance. We conducted a dual-center study to evaluate the impact of microelectrode mapping in patients undergoing catheter ablation (CA) of ventricular tachycardia (VT). MethodsWe included 21 consecutive patients (median age, 68 [12], 95% male) with structural heart disease undergoing CA for electrical storm (n = 14) or recurrent VT (n = 7) using the QDOT Micro catheter and a multipolar catheter (PentaRay, n = 9). The associations of peak-to-peak maximum standard bipolar (BVc) and minibipolar (PentaRay, BVp) with microbipolar (BV mu Max) voltages were respectively tested in sinus rhythm with mixed effect models. Furthermore, we compared the features of standard bipolar (BE) and microbipolar (mu BE) electrograms in sinus rhythm at sites of termination with radiofrequency energy. ResultsBV(mu Max) was moderately associated with both BVc (beta = .85, p < .01) and BVp (beta = .56, p < .01). BV mu Max was 0.98 (95% CI: 0.93-1.04, p < .01) mV larger than corresponding BVc, and 0.27 (95% CI: 0.16-0.37, p < .01) mV larger than matching BVp in sinus rhythm, with higher percentage differences in low voltage regions, leading to smaller endocardial dense scar (2.3 [2.7] vs. 12.1 [17] cm(2), p < .01) and border zone (3.2 [7.4] vs. 4.8 [20.1] cm(2), p = .03) regions in microbipolar maps compared to standard bipolar maps. Late potentials areas were nonsignificantly greater in microelectrode maps, compared to standard electrode maps. At sites of VT termination (n = 14), mu BE were of higher amplitude (0.9 [0.8] vs. 0.4 [0.2] mV, p < .01), longer duration (117 [66] vs. 74 [38] ms, p < .01), and with greater number of peaks (4 [2] vs. 2 [1], p < .01) in sinus rhythm compared to BE. Conclusionmicroelectrode mapping is more sensitive than standard bipolar mapping in the identification of viable myocytes in SR, and may facilitate recognition of targets for CA.

Ablation targets of persistent atrial fibrillation remain poorly understood nowadays: due to structural alterations of the left atrium, isolation of the pulmonary veins alone has proved ineffective. New ablation targets such as the posterior wall, coronary sinus, and left atrial appendage were then sought. A new catheter (QDOT Micro™) has recently been released, which has the potential to increase the safety and efficacy of the procedure: it is connected to a new radiofrequency generator that allows for temperature-controlled ablation by reducing power and increasing irrigation with the increase in tissue temperature and allows to deliver power up to 90 W for few seconds (very high-power short-duration).

Nowadays, the pathophysiology mechanism of initiation and maintenance of reentrant arrhythmias, including atrial flutter, is well characterized. However, the anatomic and functional elements of the macro reentrant arrhythmias are not always well defined. In this article, we illustrate the anatomic structures that delineate the typical atrial flutter circuit, both clockwise and counterclockwise, paying attention to the inferior vena cava-tricuspid isthmus (CTI) and crista terminalis crucial role. Finally, we describe the left atrial role during typical atrial flutter, electrophysiologically a by-stander but essential in the phenotypic electrocardiogram (ECG).

"Despite being one of the best understood cardiac arrhythmias, the clinical meaning of atrial flutter varies according to the specific context, and its optimal treatment may be limited by both the suboptimal response to rate/rhythm control drugs and by the complexity of the underlying substrate. In this article, we present a state-of-the-art overview of mechanisms, prognostic impact, and medical/interventional management options for atrial flutter in several specific patient populations, including heart failure, cardiomyopathies, muscular dystrophies, posttransplant patients, patients with respiratory disorders, athletes, and subjects with preexcitation, aiming to stimulate further research in this challenging field and facilitate appropriate patient care."

Background Provide a brief overview of recent technological advances that can potentially give information for treatment of different kind of arrhythmias. Methods In this report, we describe the features of Omnipolar technology (OT) using high density mapping catheter and we report five different scenario in which this new tool can give some important information to understand arrhythmia’s substrate and guide the treatment. OT combine three unipolar and two bipolar signals and provides maximum voltage regardless of electrode-wavefront orientation, local wavefront activation direction and local measurements of wave speed: it allow to create a velocity map. Results OT has been used to study different types of supraventricular tachycardias. Regarding reentry tachycardias, velocity map has allowed the characterization and definition of the impulse velocity along the dual nodal pathway and the accessory pathways (AP). As regards atrial flutter, it has successfully allowed the definition of the slowest zone of the critical isthmus and radiofrequency (RF) delivery at that point resulted in termination of the arrhythmia. During mapping of the left atrium in sinus rhythm, the velocity map allowed the identification of the course of the Bachmann’s bundle, which could potentially play a role during the ablation of persistent atrial fibrillation (AF). Conclusion OT and velocity map offer significant advantages in the management of challenging arrhythmias, and can potentially improve the efficacy of the treatment of some arrhythmias such as atrial flutter and AF.

Background atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice. Predisposing factors for priming and maintenance of AF include increased left atrial (LA) size, which correlates with LA disease and is a major risk factor for recurrence after AF catheter ablation (CA). The role of inflammation in the pathogenesis of AF and the associated atrial cardiomyopathy has been ill-defined Objective we hypothesized that simply-detected inflammatory blood markers could correlate with left atrial volume, and thus with the severity of AF-associated atrial cardiomyopathy. Methods we conducted a retrospective, observational study enrolling 472 consecutive patients (male gender, n= 357, 76%; mean age, 61±11 years) who underwent paroxysmal (n=318) or persistent (n=154) AF CA at our institution. In each patient, widely available laboratory markers of inflammation (C-reactive protein (PCR), uric acid, and red blood cells distribution width [RDW]) were measured prior to CA and correlated to LA volume, using univariable and stepwise multivariable linear regression. Results the mean left ventricular ejection fraction (EF) was 57,4±7,6%, whereas the mean indexed LA volume was 35,3±11,9 ml/m2. The mean RDW measured 13,5±1,3, the mean PCR value was 0,5±1 mg/L, and the mean uric acid value was 5,2±1,4 mg/dl. In univariable linear regression analysis, RDW (β 2.65; 95% CI [1.81-3.49]; p=0.0002), PCR (β 1.2; 95% CI [0.02-2.38]; p=0.047), CHA2DS2VASc (β 2,17; 95% CI [1.42-2.94]; p 0.001), uric acid (β 0.85; 95% CI [0.01-1.69]; p=0.05), EF (β -0.37; 95% CI [-0.51-0.23]; p=0.002) and age (β 0.35; 95% CI [0.25-0.45]; p=0.00004) were significantly related to LA volume. In multivariable linear regression model, EF (β -0.24; 95% CI [-0.39- -0.09]; p 0.002), age (β 02; 95% CI [0.08-0.32]; p 0.0017) and RDW (β 1.5; 95% CI [0.62-2.38]; p 0.00093) retained their independent association with LA volume. Conclusion RDW, a simple-detected blood marker, proved to be an independent predictor of LA size, suggesting a mechanistic link between inflammation and the severity of atrial cardiomyopathy. These observations may allow a very simple and low-cost identification of AF patients at higher risk of adverse outcomes and recurrences after CA, facilitating treatment plan decisions (e.g., rate vs. rhythm control).

Background Due to the complexity of the underlying substrate and to the difficulty in characterizing the arrhythmia mechanism and circuitry, every ventricular tachycardia (VT) catheter ablation (CA) represents a challenge. Nowadays VT CA is an increasingly recommended and used procedure. Objective Investigate whether VT interruption during radiofrequency (RF) delivery can be regarded as a marker indicating a lower risk VT recurrence at follow-up. Methods We conducted a retrospective cohort study and we enrolled 69 patients with VTs treated with CA using RF energy, from November 2018 to July 2022. First, in all patient substrate and late potential map was performed; than VT induction was attempted. In patients in whom activation mapping could be performed, we first targeted VT interruption, followed by substrate modification (fragmented/late potential elimination and/or dechanneling of the entire pathologic zone) [group1]. In 15 patients, it was not possible to perform activation mapping due to the poor hemodynamic VT tolerance and/or to the absence of VT inducibility with programmed ventricular stimulation. In these cases, substrate CA was performed, aiming to eliminate fragmented and/or late potentials [group2]. Recurrences were assessed with ICD in office interrogations and remote monitoring for a median of 12 (IQR 5-20) months of follow-up. Results Sixty-nine patients were included in the study. Respectively for the group1 and for the group2, the mean age at baseline was 60 ± 18,3 and 63 ± 12,3 p > 0,05) and the mean left ventricular ejection fraction was 41,3 ± 12,6% and 38,2 ± 11,8% (p > 0,05). In 41 (59%) patients, the indication for the procedure was electrical storm refractory to pharmacological therapies or multiple ICD shocks due to VT/VF. 12 (17%) patients underwent endo-epicardial CA due to the presumed epicardial VT origin and only 9 (13%) underwent right ventricular CA. Among the 31 patients in which it was possible to interrupt the arrhythmia through RF delivery, we observed 9 (23%) sustained VT recurrence at follow-up. Among the 38 patients in which VT was not interrupted with RF delivery or the VT had poor hemodynamic tolerance, there were 16 (42%) sustained VT recurrences at follow-up. Risk of recurrence at follow-up was numerically lower in patients in which VT was interrupted with RF delivery during the procedure, but not statistically significant (p value > 0,05). Conclusions In patients undergoing CA for VTs, activation mapping is useful to enhance the understanding of the arrhythmia circuitry. Our preliminary results seem to suggest that VT interruption during RF delivery may represent a positive prognostic marker, pointing to better outcomes and lower recurrence rates, even if the results were not statistically significant. Further investigations with a larger cohort of patients is required to confirm these findings.

Introduction: Recently, a novel non-thermal ablation modality, Pulse Field Ablation (PFA), has been introduced in clinical practice. Case report: Because there were multiple recurrences of ischemic stroke despite adequate anticoagulant therapy , a 64-year-old male was admitted to AF PFA and concomitant left atrial appendage (LAA) closure. An intense smoke effect was detected in the LAA and a cerebral protection device (CPD) was positioned. Catheter AF PFA and LAA closure were performed. One little thrombus had been collected into the CPD at the end of procedure. Conclusion: Combined procedure seems to be safe and feasible.

Aims Catheter ablation (CA) is an important therapeutic option for patients with recurrent ventricular tachycardia (VT). Recently, a novel contact-force sensing catheter (QDOT, Biosense Webster) allowing radiofrequency ablation in a temperature-controlled fashion, equipped with microelectrodes and thermocouples has been developed and tested in very-high power short duration CA of atrial fibrillation. As of today, this catheter has never been used for VT ablation. To describe the safety and short-term clinical performance of the novel QDOT catheter for the ablation of recurrent VT/electrical storm. Methods and results Case 1: a 43-year-old male patient with prior anterior myocardial infarction (MI), left ventricular (LV) dysfunction with an apical aneurysm, and recurrent VT episodes was admitted to our hospital for CA of VT. The patient underwent high-density electroanatomical mapping of the left ventricle using a multipolar catheter (PentaRay, Biosense Webster), which showed an extensive apical dense scar region, corresponding to the ventricular aneurysm. When the QDOT catheter was advanced in that region, late/fragmented potentials were detected by microelectrodes as well as by conventional electrodes. During the procedure, a sustained VT with right bundle branch block (RBBB)-inferior axis morphology and transition in V2 could be induced. We recorder diastolic fragmented potentials inside the aneurysm, where the novel catheter previously showed late/fragmented potentials; radiofrequency energy delivery with conventional settings (40 W) in that area led to rapid arrhythmia termination (Figure A). At the end of the procedure, VTs were no more inducible. Case 2: a 79-year-old male patient with prior inferior MI, mild LV dysfunction with a 5 cm × 5 cm × 3 cm aneurysm of the basal-mid inferior wall, and two previous CAs for recurrent VT presented to our hospital for electrical storm due to multiple episodes of slow VT (cycle, 470 ms, RBBB morphology, inferior axis, transition in V6), which were refractory to antiarrhythmic drug treatment. We decided to perform redo CA using the QDOT catheter, which revealed long and fragmented low-amplitude diastolic potentials inside the LV aneurysm (Figure B). VT was rapidly terminated by means of radiofrequency energy delivery with usual settings (40 W) in this region, and was no more inducible afterwards. Conclusions The novel ablation catheter showed favourable manoeuverability in the ventricle, while also allowing a precise characterization of the tachycardia circuitry and of the arrhythmogenic myocardial substrate, which was enhanced by the availability of microelectrodes. We believe that this preliminary experience may pave the way for further assessments of this new technology in the so far unexplored ventricular milieu.

Aims Left atrial appendage aneurysm (LAAA) is a rare condition mostly due to congenital malformations or secondary causes. Methods and results Since very few cases are described in the literature, there is uncertainty in treatment and prognosis. Diagnosis is achieved by advanced imaging as transesophageal echocardiography (TEE), which also allows the detection of thrombus, moreover cardiac magnetic resonance (CMR) could be more specific in describing sizes and relationships with surrounding anatomical structures. Surgical aneurysmectomy could be indicated in the majority of cases, especially if compression of other cardiac chambers or mediastinal structures are present. Medical therapy can include tromboprophylaxys and arrhythmias management. Since high quality evidence is scarce, a shared decision making by Heart Team approach should be considered. We present the case of a 47 years old male who came to our attention for palpitations and epigastric pain. The ECG showed high ventricular rate atrial fibrillation (AF) with wide QRS (left bundle branch block morphology). Due to haemodynamic instability the patient underwent urgent electrical cardioversion and coronary angiography showed patent coronary arteries. He had a giant left auricle appendage diagnosed twelve years before and was on antiarrhythmic prophylaxis for previous AF episodes. A TEE was performed and confirmed the diagnosis of LAAA also showing hypokinetic anterior-apical wall due to the interplay with the giant aneurysm. Subsequent CMR showed no LGE and confirmed the absence of thrombus in the LAAA. After Heart Team consultation surgical treatment was proposed to the patient who refused any invasive procedure. Therefore medical treatment was achieved by direct oral anticoagulation and antiarrhythmic therapy with betablockers and flecainide per os. Moreover, a loop recorder for longitudinal monitoring was implanted. At 6 months of follow-up the patient was asymptomatic except for a brief paroxysm of self-limited AF. 510 Figure 1CMR scan showing giant left atrial appendage aneurysm. (A) Transversal view. (B) Frontal view. (C) Sagittal view.510 Figure 2TOE mid oesophageal 57° showing giant left atrial appendage.

A radiofrequency energy lesion transmurality marker incorporating power, contact force, and time (Ablation Index, AI) was shown to be associated with outcomes of catheter ablation (CA) of multiple arrhythmias, but was never systematically assessed in the CA of focal atrial tachycardias (AT). We aimed to evaluate the role of AI as a predictor of outcomes in focal AT CA, and therefore, retrospectively included 45 consecutive patients undergoing CA for focal AT in four referral electrophysiology laboratories. Clinical and procedural information were collected. For each patient, maximum and mean (by averaging maximum AI values for each radiofrequency ablation lesion) AI were measured. The primary outcome was focal AT-free survival, and was systematically assessed with periodical Holter monitors or cardiac implantable electronic devices. CA was acutely effective in each case; however, 20% (n = 9) of the study population experienced a focal AT recurrence over a median follow-up of 288 days. Both maximum and mean AI values were significantly higher among patients without AT recurrences (maximum AI = 568 ± 91, mean AI = 426 ± 105) than in patients with AT relapses (maximum AI = 447 ± 142, mean AI = 352 ± 76, p = 0.036, and p = 0.028, respectively). The optimal cutoffs associated with freedom from recurrences were 461 for maximum AI (sensitivity, 0.89; specificity, 0.56) and 301 for mean AI (sensitivity, 0.97; specificity, 0.44). In a time-to-event analysis, maximum AI was significantly associated with survival free from AT recurrence (p = 0.001), whereas mean AI was not (p = 0.08). In summary, maximum AI is the best procedural parameter associated with the outcomes of CA for focal AT, and may help standardize the procedural approach.