A Case Series of Very Slow Atrioventricular Nodal Reentrant Tachycardia Resembling Junctional Tachycardia

Introduction: The surface EKG of typical atrioventricular nodal reentrant tachycardia (AVNRT) shows simultaneous ventricular-atrial (RP) activation with pseudo R’ in V1 and typical heart rates ranging from 150-220/min. Slower rates are suspicious for junctional tachycardia (JT). However, occasionally we encounter typical AVNRT with slow ventricular rates. We describe a series of typical AVNRT cases with heart rates under 110/min. Methods: A total of 1972 patients with AVNRT who underwent slow pathway ablation were analyzed. Typical AVNRT was diagnosed when; 1) evidence of dual atrioventricular nodal conduction, 2) tachycardia initiation by atrial drive train with A-H-A response, 3) septal ventriculoatrial (VA) time < 70 ms, and 4) ventricular-atrial-ventricular (V-A-V) response to ventricular overdrive (VOD) pacing with post pacing interval-tachycardia cycle length (PPI-TCL) > 115ms. JT was excluded by either termination or advancement of tachycardia by atrial extrastimuli (AES) or atrial overdrive (AOD) pacing. Results: We found 11 patients (Age 20-78 years old, 6 female) who met the above-mentioned criteria. The TCL ranged from 560ms to 782ms. Except for one patient showing tachycardia termination, all patients demonstrated a V-A-V response and PPI-TCL over 115ms with VOD. AES or AOD pacing successfully excluded JT by either advancing the tachycardia in 10 patients or by tachycardia termination in one patient. Slow pathway was successfully ablated, and tachycardia was not inducible in all patients. Conclusions: This case series describes patients with typical AVNRT with slow ventricular rate (less than 110/min) who may mimic JT. We emphasize the importance of using pacing maneuvers to exclude JT.

Atrioventricular Nodal Reentrant Tachycardia Ablation Using Mini-Electrode Recordings

Catheter ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT) is mainly performed using anatomical landmarks. We sought to see whether a new ablation catheter equipped with mini-electrodes may facilitate the mapping of slow pathway potentials for AVNRT ablation. We prospectively included patients referred for AVNRT in our center. Mapping and ablation were performed using an irrigated catheter equipped with 3 insulated mini-electrodes on the distal tip. Thirteen consecutive patients were included (85% female, median age 46 years). Slow pathway potentials could be identified in 77% of cases on mini-electrode bipolar tracings, versus 15% on conventional bipolar tracings (p = 0.0009). At the end of the procedure, double potentials on the ablation line were identified in all patients, only on mini-electrode bipolar tracings. Following ablation, an interval separating double potentials in sinus rhythm ≥15% of baseline tachycardia cycle length was associated with non-inducibility in all patients (p < 0.0001). No recurrence occurred during 1 year of follow-up. The use of mini-electrodes may help target slow pathway potentials during AVNRT ablation. Identification of sufficiently split double potentials on the ablation line might represent an electrophysiological endpoint in these patients.

Inferior Extensions of the Atrioventricular Node

The pathways for excitation of the atrioventricular node enter either superiorly, as the so-called ‘fast’ pathway, or inferiorly as the ‘slow’ pathway. However, knowledge of the specific anatomical details of these pathways is limited. Most of the experimental studies that established the existence of these pathways were conducted in mammalian hearts, which have subtle differences to human hearts. In this review, the authors summarise their recent experiences investigating human cardiac development, correlating these results with the arrangement of the connections between the atrial myocardium and the compact atrioventricular node as revealed by serial sectioning of adult human hearts. They discuss the contributions made from the atrioventricular canal myocardium, as opposed to the primary ring. Both these rings are incorporated into the atrial vestibules, albeit with the primary ring contributing only to the tricuspid vestibule. The atrial septal cardiomyocytes are relatively late contributors to the nodal inputs. Finally, they relate our findings of human cardiac development to the postnatal arrangement.

Post-cardiac injury syndrome triggered by radiofrequency ablation for AVNRT

Background Post-cardiac injury syndrome (PCIS) is an inflammatory condition following myocardial or pericardial damage. In response to catheter ablation, PCIS most frequently occurs after extensive radiofrequency (RF) ablation of large areas of atrial myocardium. Minor myocardial injury from right septal slow pathway ablation for atrioventricular nodal reentrant tachycardia (AVNRT) is not an established cause of the syndrome. Case presentation A 62-year-old women with a 6-year history of symptomatic narrow-complex tachycardia was referred to perform an electrophysiological study. During the procedure AVNRT was recorded and a total of two RF burns were applied to the region between the coronary sinus and the tricuspid annulus. Pericardial effusion was routinely ruled out by focused cardiac ultrasound. In the following days, the patient developed fever, elevated inflammatory and cardiac markers, new-onset pericardial effusion, characteristic ECG changes, and complained of pleuritic chest pain. An extensive workup for infectious, metabolic, rheumatologic, neoplastic, and toxic causes of pericarditis and myocarditis was unremarkable. Cardiac magnetic resonance imaging showed no signs of ischemia, infiltrative disease or structural abnormalities. The patient was diagnosed with PCIS and initiated on aspirin and low-dose colchicine. At a 1-month follow-up visit the patient was free of symptoms but still had a small pericardial effusion. After three months of treatment the pericardial effusion had resolved completely. Conclusions Inflammatory pericardial reactions can occur after minor myocardial damage from RF ablation without involvement of structures in close proximity to the pericardium.

703 Koch’s triangle voltage mapping for cryoablation of slow pathway in children: preliminary data of a novel high density technique

Aims Different authors have described three-dimensional (3D) voltage mapping of the Koch’s triangle (KT) in order to find low-voltage bridges (LVBs) as targets for a successful transcatheter ablation (TCA) of the slow pathway (SP) in children. Recently, the advisor high density (HD) Grid™ mapping catheter was introduced as new multipolar catheter for HD mapping. The aim of the study was to describe our preliminary experience with the use of HD Grid™ catheter in LVB and electrophysiologically guided cryoablation of SP in children. Methods and results Twenty-one children (mean age 13 ± 3 years) with atrioventricular nodal re-entrant tachycardia (AVNRT) underwent cryoablation of SP guided by voltage HD mapping of the KT using HD Grid™ catheter. In order to better highlight the differences with conventional mapping, point collection was performed in each patient with this new multipolar catheter and with a quadripolar catheter. The conventional mapping collected 871 ± 262 points and used 211 ± 80 points in 887 ± 275 s, whereas HD mapping collected 7468 ± 2947 points, using 604 ± 165 points in 513 ± 181 s (P &lt; 0.001). Moreover, the LVB area mapped with HD Grid™ was about one-half smaller and clearly delineated. Cryoablation acute success rate was 100%. Overall median fluoroscopy exposure was 0.08 (0.01–5.42) µGy/m2, with a median fluoroscopy time of 0.1 (0.0–0.6) min. During the follow-up (4.8 ± 3.7 months), there were no recurrences. No complications occurred. Conclusions Our preliminary experience shows that HD mapping is faster and offers higher spatial resolution and definition. Procedural time can be reduced maintaining the TCA safe, with reduced fluoroscopy use, and successful.

Not-so-typical typical atrioventricular nodal re-entrant tachycardia in an adolescent

Dysrhythmias are commonly encountered in the Emergency Department (ED). Timely management and recognition of dysrhythmia in the ED is essential and crucial. Physicians working in the ED should be familiar with atypical presentation of common dysrhythmias. This case report illustrates atrioventricular nodal re-entrant tachycardia (AVNRT) with an unusually slow heart rate in an adolescent. A 16-year-old male presented to the ED twice for palpitations. His electrocardiograms showed narrow complex tachycardia with absent P waves. Electrophysiology studies confirmed typical slow-fast AVNRT which was treated successfully with radiofrequency ablation of the slow pathway. Diagnosing rare dysrhythmias or common dysrhythmias which manifest atypically can be challenging for non-cardiologists. Although AVNRT generally occurs with a heart rate of >130 bpm, emergency physicians should be aware that AVNRT can take place with a relatively slower rate in both the elderly and young.

New Onset of AV- Nodal Reentrant Tachycardia (AVNRT) in the elderly – an uncommon diagnosis?

Background Arrhythmias in elderly patients (&gt;70 years) are common in daily clinical practice. Most frequently, they are based on atrial fibrillation or other atrial tachycardia with an indication for oral anticoagulation and specific antiarrhythmic medications. The electrographic (ECG) documentation related to symptoms is essential before therapy initiation. In case of suspected AVNRT based on surface ECG, an electrophysiological study (EP) with ablation as curative strategy should be planned. Methods We analysed all patients &gt;70 years with AVNRT diagnosed by electrophysiologic (EP) studies between May 2018 and December 2020. Results An EP study for suspected AVNRT was performed in 27 patients &gt;70 years. The diagnosis of AVNRT was confirmed in 20 patients (75%). From all EP- studies with the diagnosis of AVNRT (n=93) in this period, 20 patients (22%) were older than 70 years (mean age 77 years with a range of 70–85 years), 12 were women. In most of the patients, the duration of symptoms was short (3 month). Only 4 patients had symptoms of paroxysmal tachycardia longer than 10 years. Except for 2 patients, all patients had at least one ECG- documentation (12- lead- ECG, Holter- ECG, telemetric ECG and/or in the loop recorder). In 12 patients, a 12- lead- ECG- documentation was available, in 5 patients the tachycardia has been registered in the Holter-ECG and in 1 in a loop recorder. In the 12- lead- ECG before ablation in sinus rhythm the PQ interval was with 196 (120- 300) ms in the upper range. In 16/ 20 patients was during the EP- study a sustained AVNRT (CL 410, 314- 538 ms) inducible. In the others, up to 3 typical AV- nodal- echo beats were induced in the EP- study. A slow pathway ablation/ modification was performed in all patients in typical position. In 2 patients, the implantation of a dual- chamber- pacemaker was necessary due to intermittent high- degree AV-nodal-block during the same hospital stay. In both patients, a first degree AV-block with PQ- interval of 250 and 300 ms was pre-existing. Discussion Especially for the elderly patients with new onset of clinical symptoms of arrhythmia, clinical anamnesis including an ECG- documentation is required for planning the therapeutic strategy. A borderline long PQ- interval as sign of an age- dependent fibrosis in the AV- node and, therefore, altered conduction properties in the AV node can be a cause of AVNRT in these older patients. In patients with pre-existing long PQ- interval (&gt;250 ms), the risk of pacemaker implantation after successful ablation is higher. In this group of patients, medical therapeutic options are limited and often associated with the need of pacemaker implantation. FUNDunding Acknowledgement Type of funding sources: None.