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Atrioventricular nodal reentrant tachycardia (AVNRT) is the most frequent regular tachycardia in humans. In this review, we describe the most recent discoveries regarding the anatomical, physiological, and molecular biological features of the atrioventricular junction that could underlie the typical slow-fast AVNRT mechanisms, as these insights could lead to the proposal of a new theory concerning the circuit of this arrhythmia. Despite several models have been proposed over the years, the precise anatomical site of the reentrant circuit and the pathway involved in the slow-fast AVNRT have not been conclusively defined. One possible way to evaluate all the hypotheses regarding the nodal tachycardia circuit in humans is to map this circuit. Thus, we tried to identify the slow potential of nodal and inferior extension structures by using automated mapping of atrial activation during both sinus rhythm and typical slow-fast AVNRT. This constitutes a first step toward the definition of nodal area activation in sinus rhythm and during slow-fast AVNRT. Further studies and technical improvements in recording the potentials of the atrioventricular node structures are necessary to confirm our initial results., (Copyright © 2023 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Atrial activation during typical atrioventricular nodal reentrant tachycardia (AVNRT) exhibits anatomic variability and spatially heterogeneous propagation inside the Koch's triangle (KT). The mechanism of the reentrant circuit has not been elucidated yet. Aim of this study is to describe the distribution of Jackman and Haïssaguerre potentials within the KT and to explore the activation mode of the KT, in sinus rhythm and during the slow-fast AVNRT., Methods: Forty-five consecutive cases of successful slow pathway (SP) ablation of typical slow-fast AVNRT from the CHARISMA registry were included., Results: The KT geometry was obtained on the basis of the electroanatomic information using the Rhythmia mapping system (Boston Scientific) (mean number of points acquired inside the KT = 277 ± 47, mean mapping time = 11.9 ± 4 min). The postero-septal regions bounded anteriorly by the tricuspid annulus and posteriorly by the lateral wall toward the crista terminalis showed a higher prevalence of Jackman potentials than mid-postero-septal regions along the tendon of Todaro and coronary sinus (CS) (98% vs. 16%, p < 0.0001). Haïssaguerre potentials seemed to have a converse distribution across the KT (0% vs. 84%, p < 0.0001). Fast pathway insertion, as located during AVNRT, was mostly recorded in an antero-septal position (n = 36, 80%), rather than in a mid-septal (n = 6, 13.3%) or even postero-septal (n = 3, 7%) location. During typical slow-fast AVNRT, two types of propagation around the CS were discernible: anterior and posterior, n = 31 (69%), or only anterior, n = 14 (31%). During the first procedure, the SP was eliminated, and acute procedural success was achieved (median of 4 [3-5] RF ablations)., Conclusion: High-density mapping of KT in AVNRT patients both during sinus rhythm and during tachycardia provides new electrophysiological insights. A better understanding and a more precise definition of the arrhythmogenic substrate in AVNRT patients may have prognostic value, especially in high-risk cases., Trial Registration: Catheter Ablation of Arrhythmias With High Density Mapping System in the Real World Practice (CHARISMA) URL: http://clinicaltrials.gov/ Identifier: NCT03793998., (© 2020. Springer Science+Business Media, LLC, part of Springer Nature.)

Despite the technical improvements made in recent years, the overall long-term success rate of ventricular tachycardia (VT) ablation in patients with ischemic cardiomyopathy remains disappointing. This unsatisfactory situation has persisted even though several approaches to VT substrate ablation allow mapping and ablation of noninducible/nontolerated arrhythmias. The current substrate mapping methods present some shortcomings regarding the accurate definition of the true scar, the modality of detection in sinus rhythm of abnormal electrograms that identify sites of critical channels during VT and the possibility to determine the boundaries of functional re-entrant circuits during sinus or paced rhythms. In this review, we focus on current and proposed ablation strategies for VT to provide an overview of the potential/real application (and results) of several ablation approaches and future perspectives., (© 2019 The Authors. Clinical Cardiology published by Wiley Periodicals, Inc.)

The mechanisms of atrial fibrillation (AF) induction and maintenance, including those involved in paroxysmal atrial fibrillation, are not completely known; this limits our ablation strategies and prevents us from understanding what we are actually doing when performing pulmonary vein isolation. In this report, we focus on the commonly used ablation strategies for AF and question the importance of complete pulmonary vein isolation in achieving lasting success in the ablation of AF. We also discuss in detail the absence of durable pulmonary vein isolation in patients without arrhythmic recurrences after AF ablation and the possibility to cure paroxysmal AF without concomitant pulmonary vein isolation, provocatively questioning the dogma of pulmonary vein isolation as the cornerstone of AF ablation. Finally, a prospective personalized approach in the individual patient is advocated., (© 2019 Wiley Periodicals, Inc.)

The discrimination between ventricular (VT) and supraventricular tachycardia (SVT) and the evaluation of their hemodynamic impact are essential issues in the arrhythmia management. A new pacing device features a tachycardia diagnostic system relying on simultaneous recording of the transvalvular impedance (TVI) and a special integrated electric signal derived by the whole set of endocardial electrodes (iECG). The iECG waveform is sensitive to the pattern of ventricular activation, similarly to the surface ECG. The TVI increases in systole and decreases in diastole and the amplitude of this cyclic fluctuation is an expression of the effectiveness of the pump function. In order to test the value of these signals in the analysis of a tachycardia, we have assessed the iECG and TVI modifications induced by different SVTs and tolerated and non-tolerated VTs, during electrophysiological (EP) studies. In case of SVT, the ventricular component of the iECG maintained the same morphology as in sinus rhythm. The peak-peak amplitude of the TVI fluctuation was reduced to 66 ± 11 % of the individual sinus rhythm reference, but the signal was present at every beat and showed a remarkable stability (variation coefficient 0.19 ± 0.01). In case of VT, the ventricular component of the iECG was strikingly different than in sinus rhythm. Regular TVI fluctuation was observed with tolerated VTs (peak-peak amplitude 74 ± 6 %; variation coefficient 0.21 ± 0.04). In contrast, with non-tolerated VTs the TVI amplitude was depressed below 40%, and the signal was virtually absent in the event of very fast VT or VF. Our results confirm that the iECG is a reliable tool to quickly discriminate VTs from SVTs and that TVI can provide information on the severity of the hemodynamic impairment produced by a tachycardia, with potential clinical benefit in the follow-up of pacemaker patients. Furthermore, the application of these signals to automatic algorithms of arrhythmia recognition might improve the specificity of therapy administration by an implantable defibrillator (ICD).

Aims: Evaluation of ambulatory blood pressure monitoring (ABPM), two-dimensional (2D) echo and clinical variables in predicting cardiac death and acute decompensated heart failure in patients with ischaemic cardiomyopathy and receiving a cardioverter-defibrillator implantation., Methods and Results: We studied 180 consecutive patients (169 men) on an out-patient basis, with systolic dysfunction (ejection fraction ≤35%) and previous myocardial infarction. All received a cardioverter defibrillator (ICD) (116 dual chamber, 36 monocameral and 28 biventricular), for primary prevention of sudden death and standard medical therapy for heart failure. Mean follow-up was 11.7 months. Two-dimensional echo was performed just before ICD implantation, ABPM and haematological samples 2 weeks later. Age, ejection fraction, creatinine, haemoglobin concentration, mean 24-h systolic blood pressure, mean 24-h diastolic blood pressure, mean 24-h heart rate, brain natriuretic peptide, QRS duration, % paced beats, ventricular scar, biventricular pacing, sex and diabetes were considered. Cox proportional hazards regression analysis was used to explore the relationship between events. ROC curves were built for each independent variable. Events occurred in 47 patients (26%); 7 deaths for refractory heart failure and 40 hospitalizations for acute decompensated heart failure. Low mean 24-h systolic blood pressure [hazard ratio 0.96, 95% confidence interval (CI) 0.93-0.99, P = 0.02], high creatinine (hazard ratio 1.61, 95% CI 1.06-2.47, P = 0.01), low haemoglobin concentration (hazard ratio 0.81, 95% CI 0.65-0.99, P = 0.04) and older age (hazard ratio 1.04, 95% CI 1.01-1.08, P = 0.02) were independent predictors of events., Conclusions: Ambulatory systolic blood pressure, haemoglobin, creatinine and age can stratify risk of death and acute decompensated heart failure in patients with ischaemic cardiomyopathy and ICD in whom 2D-echo ejection fraction is not predictive.

Background: The presence of a conduction block at the level of the Koch triangle (KT) and the origin of the multicomponent potentials inside this area are controversial issues. We investigated the propagation of the sinus impulse into the KT and the characteristics of multicomponent potentials recorded in that area in patients with and without atrioventricular nodal reentrant tachycardia (AVNRT)., Methods and Results: Thirty-two patients (16 with AVNRT, 16 without AVNRT) underwent a sinus rhythm electroanatomic mapping of the right atrium (RA). Conduction velocities in the RA and in the KT were evaluated quantitatively on activation maps and qualitatively on isochronal and propagation maps. The presence, location, and timing of different types of multicomponent potentials were evaluated. A mean of 149±44 points were sampled in the RA, whereas a mean of 79±21 points were collected inside the KT. Propagation block at the level of crista terminalis was not found in any patient, whereas slow conduction inside the KT was found in all (median conduction velocity, 122 cm/s [110 to 135 cm/s] outside KT versus 60 cm/s [48 to 75 cm/s] inside KT; P<0.0001). Jackman potentials were identified inside KT in almost all the patients and were invariably found on the line of collision between the wavefronts activating the KT in opposite directions., Conclusions: No conduction block was detected inside the KT in patients with and without AVNRT. Conduction slowing was demonstrated during propagation of the sinus impulse inside the KT. The genesis of the Jackman potential may be related to the collision of the wavefronts activating KT in opposite directions.

We report a patient with clinical manifestation of arrhythmias and evidence of noncompacted myocardium in both left and right ventricular apex. The diagnosis was made with intracardiac echo performed during the electrophysiologic study. This method has allowed the diagnosis of noncompaction of the ventricular myocardium due to its high resolution. Color Doppler showed trabecular recesses in communication with the ventricular cavity that could not be identified with transthoracic echocardiography.

Radiofrequency ablation procedures inside the left atrial appendage (LAA) are likely to involve dangerous complications because of a high thrombogenic effect. Cryoablation procedures are supposed to be safer. We describe two cases of successful cryoablation procedures. Two NavX-guided cryoablations of permanent focal atrial arrhythmias arising from the LAA were performed. Left atrial reconstruction and mapping allowed the zone of the earliest atrial potential to be recorded; the entire course of the ablation catheter was monitored. The arrhythmias were successfully ablated; no thrombotic complications were observed.

Purpose: The purpose of the study is to evaluate the feasibility and utility of magnetic resonance (MR) image and electroanatomic (EA) maps integration in guiding detailed left ventricle (LV) anatomical and substrate mapping, identifying the most accurate registration strategy., Methods: Twenty-five patients with dilated ischemic or non-ischemic cardiomyopathy were enrolled. We first verified the feasibility and accuracy of EA mapping and MR image integration using four different strategies (15 patients). Different EA maps were performed according to the strategy in exam: aortic map, collected from the descending portion of the arch to the ascending one; partial or complete LV map, reconstructed with a minimum of 40 widely distributed points or 200 points, respectively. We then evaluated the utility in LV substrate mapping of the most accurate integration method identified (ten patients)., Results: Strategy III, based on aortic map and a partial LV map, allowed us to obtain an accurate integration with MR images of aorta and LV with a lower number of EA LV points; we therefore used this strategy during phase II of the study. Both mean LV end diastolic volume and long- and short-axis LV end diastolic diameters obtained by MR were not significantly different compared with Carto measurements. Eighty-eight percent of the segments with transmural/subendocardial scar detected by delayed enhanced MR were localized on bipolar voltage maps projected on MR-integrated images., Conclusion: This study shows that integration strategy III represents the optimal registration method. Its clinical utility consists on guiding the catheter roving inside the chamber, mapping all areas of the LV and optimizing scar reconstruction.

Purpose: We investigated the relationship among esophageal warming, pain perception, and the site of radiofrequency (RF) delivery in the left atrium (LA) during the course of catheter ablation of atrial fibrillation. Such a procedure in awake patients is often linked to the development of visceral pain and esophageal warming. As a consequence, potentially dangerous complications have been described., Methods: Twenty patients undergoing RF ablation in the LA were studied. An esophageal probe (EP) capable of measuring endoesophageal temperature (ET) was positioned before starting the procedure. The relative position of the EP and the tip of the ablator were evaluated through fluoroscopy imaging before starting each RF delivery, during which the highest value of the temperature was collected. After RF withdrawal, the patients were asked to define the intensity of the experienced pain by using a score index ranging from 0 (no pain) to 4 (pain requiring immediate RF interruption)., Results: The mean ET value during ablation was 39.59 +/- 4.71 degrees C. The EP proximity to the ablator's tip showed a high correlation with the development of the highest ET values (Spearman's rank correlation coefficient r = 0.49, confidence interval (CI) 0.55-0.41). Moreover, the highest values of pain intensity were reported when the RF was delivered to the atrial zones close to the EP projection (r = 0.50, CI 0.55-0.42) and when the highest ET levels were reached (r = 0.38, CI 0.30-0.45)., Conclusions: Pain perception in LA ablation is significantly related to esophageal warming and is higher when the RF is delivered near the esophagus. It seems advisable to perform ET monitoring in sedated patients to avoid short- and long-term jeopardizing of the esophageal wall.

A 48-year-old man with an episode of syncope and family history of sudden cardiac death was evaluated. The ECG showed negative T waves from V1 to V3 with evidence of epsilon-wave. Magnetic resonance imaging showed replacement with fibrofatty tissue in midapical regions of free wall of the right ventricle with dyskinesia. Transthoracic echocardiography revealed only mild enlargement of the middle right ventricular cavity. A programmed ventricular stimulation induced only an unsustained monomorphic ventricular tachycardia. Intracardiac echocardiography showed mild right ventricular enlargement and outflow dilatation (26 mm), microaneurysms with systolic bulging along the apical segment of the right ventricle. Bipolar voltage mapping, performed by the Carto system, detected a circumscribed low potential (<1.5 mV) area at the same level of the right ventricular apex. Cardiovascular imaging improves the detection of abnormal myocardial areas. Further studies are warranted to support this hypothesis.

This article describes a case of cardiac resynchronization therapy (CRT) performed with dual site left ventricular pacing. The main clinical and functional long-term results are in agreement with the most recent data regarding traditional CRT. Furthermore, this innovative pacing modality allowed optimal inter- and intraventricular resynchronization.

Objectives: The aim of the study was to evaluate the effectiveness of cardiac resynchronization therapy (CRT) in patients with refractory heart failure (HF) and incomplete left bundle branch block ("narrow" QRS), together with echocardiographic evidence of interventricular and intraventricular asynchrony., Background: Cardiac resynchronization therapy has been proven effective in patients with HF and wide QRS by ameliorating contraction asynchrony., Methods: Fifty-two patients with severe HF received biventricular pacing. The patients were eligible in the presence of echocardiographic evidence of interventricular and intraventricular asynchrony, regardless of QRS duration. The patient population was divided into group 1 (n = 38), with a QRS duration >120 ms, and group 2 (n = 14), with a QRS duration < or =120 ms., Results: The baseline parameters considered in the study were similar in both groups. At follow-up, CRT determined narrowing of the QRS interval in the entire population and in group 1 (p < 0.001), whereas a small increase in QRS duration was observed in group 2 (p = NS); in all patients and within groups, we observed improvement of New York Heart Association functional class (p < 0.001 in all), left ventricular ejection fraction (p < 0.001 in all), left ventricular end-diastolic and end-systolic diameter (p < 0.05 within groups), mitral regurgitation area (p < 0.001 in all), interventricular delay (p < 0.001 in all), and deceleration time (group 1: p < 0.001, group 2: p < 0.05), with no significant difference between groups. The 6-min walking test improved in both groups (group 1: p < 0.001; group 2: p < 0.01)., Conclusions: Cardiac resynchronization therapy determined clinical and functional benefit that was similar in patients with wide or "narrow" QRS. Cardiac resynchronization therapy may be helpful in patients with echocardiographic evidence of interventricular and intraventricular asynchrony and incomplete left bundle branch block.