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In patients with no evidence for structural heart disease, idiopathic ventricular fibrillation and polymorphic ventricular tachycardia (PVT) are frequently triggered by ventricular premature beats (VPBs) arising from the Purkinje system or the right ventricular outflow tract that can be successfully eliminated by radiofrequency (RF) catheter ablation.1, 2 Such triggers of malignant arrhythmias have also been demonstrated and successfully eliminated in patients with Brugada, long QT, and early repolarization syndromes.3, 4, 5 We report a case involving a patient with Brugada syndrome in whom malignant PVT was eliminated by RF ablation of VPBs as a trigger originating from the left fascicular conduction system.

Atrial tachycardias (ATs) are relatively uncommon and their mechanisms include reentry or may be focal. The characteristics and radiofrequency (RF) ablation of adenosine-sensitive AT arising near the apex of Koch’s triangle have been reported. We report a case of successful RF ablation of this tachycardia by using a retrograde transaortic/transmitral approach. An electrophysiological study performed during sinus rhythm showed continuous anterograde atrioventricular nodal and no ventriculoatrial conduction. The tachycardia could be induced and terminated by atrial extrastimulation and rapid atrial pacing. Although inverse resetting response pattern was observed, tachycardia termination by intravenous low-dose adenosine was rather suggestive of triggered activity as the mechanism. The earliest atrial activation was recorded in the His-bundle region. After ineffective right-sided attempts and failure to find earlier atrial activity during mapping the noncoronary sinus of Valsalva, this tachycardia was successfully ablated from the left atrial septum by using a retrograde transaortic/transmitral approach. This report demonstrates the feasibility of a novel retrograde left atrial approach for RF ablation of adenosine-sensitive AT originating from the apex of Koch’s triangle. Cardiol Res. 2019;10(1):48-53 doi: https://doi.org/10.14740/cr806

Most tachycardias in the pulmonary venous atrium are inaccessible by direct means and require either a retrograde approach or a transseptal approach for ablation. We present a case in which successful radiofrequency ablation of common atrioventricular nodal reentrant tachycardia was accomplished via a retrograde transaortic approach guided by nonfluoroscopic mapping with use of the NavX™ mapping system. The patient was a 49-year-old woman who at the age of 4 years had undergone Mustard repair for complete dextrotransposition of the great arteries. Three-dimensional reconstructions of the ascending aorta, right ventricle, systemic venous atrium, left ventricle, and superior vena cava–inferior vena cava baffle complex were created, and the left-sided His bundle was marked. After a failed attempt at ablation from the systemic venous side, we eliminated the atrioventricular nodal reentrant tachycardia by ablation from the pulmonary venous side. This case is, to our knowledge, the first report of successful radiofrequency ablation of common atrioventricular nodal reentrant tachycardia after Mustard repair for this congenital cardiac malformation in which ablation was guided by 3-dimensional nonfluoroscopic imaging. This imaging technique enabled accurate anatomic location of the ablation catheters in relation to the His bundle marked from the systemic venous side.

Introduction Decremental conduction in short anterograde atrioventricular accessory pathways (AV-APs) is rare. Case presentation We report on two cases with radiofrequency (RF) ablation of anterograde fast non-decremental AV-AP conduction. In Case 1, electrophysiological testing revealed fast non-decremental conduction over an anterograde short right posteroseptal AV-AP. During ablation, latent pre-excitation due to anterograde adenosine-sensitive slow decremental conduction over the same AV-AP manifested after eliminating its non-decremental conduction. Complete abolition of AP conduction was achieved by additional ablation. In Case 2, overt pre-excitation disappeared after the first ablation session for an anterograde short non-decremental right mid-septal AV-AP. However, latent pre-excitation due to markedly decremental conduction over the same AV-AP unmasked by intravenous adenosine and atrial pacing manoeuvers could be eliminated in a second session. Discussion This report describes unusual anterograde short non-decremental AV-APs, developing markedly slow adenosine-sensitive decremental conduction during ablation. Such AV-AP conduction properties due to RF injury may be overlooked and mask incomplete ablation and point-out careful testing including stimulation techniques and low and higher dose adenosine administration post-ablation.

We present the first description of successful radiofrequency (RF) ablation of a bidirectional atrioventricular accessory pathway (AP) guided by nonfluoroscopic mapping with use of three-dimensional magnetic resonance imaging integrated into the Nav-X system (MRI/Nav-X fusion) in a 13-year-old boy with remote surgical palliation for cyanotic criss-cross heart with atrioventricular discordance, double-outlet right ventricle, and a large ventricular septal defect. Due to complex anatomy, a unique finding was that the eliminated left lateral AP electrically connected the left atrium to the antero-superior morphologic right ventricle prior to ablation.

Nodofascicular and Atriofascicular Pathway Ablation. Introduction: True nodoventricular or nodofascicular pathways and left-sided anterograde decremental accessory pathways (APs) are considered rare findings. Methods and Results: Two unusual patients with paroxysmal supraventricular tachycardia were referred for radiofrequency (RF) ablation. Both patients had evidence of dual AV nodal conduction. In case 1, programmed atrial and ventricular stimulation induced regular tachycardia with a narrow QRS complex or episodes of right and left bundle branch block not altering the tachycardia cycle length and long concentric ventriculoatrial (VA) conduction. Ventricular extrastimuli elicited during His-bundle refractoriness resulted in tachycardia termination. During the tachycardia, both the ventricles and the distal right bundle were not part of the reentrant circuit. These findings were consistent with a concealed nodofascicular pathway. RF ablation in the right atrial mid-septal region with the earliest atrial activation preceded by a possible AP potential resulted in tachycardia termination and elimination of VA conduction. In case 2, antidromic reciprocating tachycardia of a right bundle branch block pattern was considered to involve an anterograde left posteroseptal atriofascicular pathway. For this pathway, decremental conduction properties as typically observed for right atriofascicular pathways could be demonstrated. During atrial stimulation and tachycardia, a discrete AP potential was recorded at the atrial and ventricular insertion sites and along the AP. Mechanical conduction block of the AP was reproducibly induced at the annular level and at the distal insertion site. Successful RF ablation was performed at the mitral annulus. Conclusion: This report describes two unusual cases consistent with concealed nodofascicular and left anterograde atriofascicular pathways, which were ablated successfully without impairing normal AV conduction system.

This report describes the case of a 19-year-old patient with Ebstein's anomaly, who had an unusual combination of a right atriofascicular (Mahaim) and two ipsilateral right atrioventricular (Kent) accessory pathways participating in three types of antidromic and orthodromic reciprocating tachycardias in the absence of retrograde conduction over the bundle of His-atrioventricular node axis. All three pathways were ablated in a single session using temperature-guided radiofrequency current.

The Brugada syndrome (BS) is characterized by distinctive ST-segment abnormalities, malignant ventricular arrhythmias, and sudden cardiac death and is attributed to a sodium channelopathy. Additionally, right ventricular wall motion abnormalities have been described by previous studies.

Concealed Nodoventricular Mahaim Fiber. Introduction: We present the case of a 17-year-old woman who underwent an electrophysiological study and radiofrequency (RF) ablation of supraventricular tachycardia refractory to medical treatment. Two right-sided, concealed, nondecremental atrioventricular accessory pathways (AV-APs) involved in ortho-dromic circus movement tachycardias were identified. After RF ablation of both AV-APs, evidence of bidirectional dual AV nodal conduction was demonstrated and regular narrow complex tachycardia was induced. Methods and Results: During the tachycardia, retrograde slow and fast AV nodal pathway conduction with second-degree ventriculoatrial (VA) block and VA dissociation were observed. During the tachycardia with second-degree VA block, ventricular extrastimuli elicited during His-bundle refractoriness advanced the next His potential or terminated the tachycardia. Mapping the right atrial mid-septal region, a distinct high-frequency activation P potential was recorded in a discrete area, two thirds of the way from the His bundle toward the os of the coronary sinus. Detailed electrophysiologic testing with the recordahle P potential demonstrated that the tachycardia utilized a concealed nodoventricular AP arising from the proximal slow AV nodal pathway. Conclusion: The tachycardia with slow 1:1 VA conduction could be reset by ventricular extrastimuli elicited during His-bundle refractoriness advancing the subsequent activation P potential and atrial activation. RF ablation guided by recording of the activation P potential resulted in elimination of both the slow AV nodal pathway and the nodoventricular connection with preservation of the normal AV conduction system.

This paper reports the case of a 63-year-old female patient with Wolff-Parkinson-White syndrome who underwent an electrophysiologic study (EPS) and ablation using temperature-guided radiofrequency current for atrial fibrillation with a shortest preexcited RR interval of 160 ms. Detailed EPS and mapping demonstrated an unusual, complex left-sided accessory pathway, with the two distinct branches having two remote atrial insertions and a narrow common ventricular isthmus associated with the manifestation of atrial double potentials recorded from the coronary sinus. Simple ablation at the left lateral side from the ventricular aspect completely eliminated complex accessory pathway conduction, resulting in the disappearance of atrial double potentials.

An electrophysiologic study of atrial tachycardia is presented. During tachycardia, transient entrainment and sinus rhythm, two patterns of persistent double potentials in the high right atrium and fragmented activity in the low atrial septum were observed. No activity was recorded from multiple areas of the right atrium with endocardial apping during sinus rhythm. The observations suggest that persistent fragmented activity represents slow conduction within the circuit which could be orthodromically entrained. Persistent double potentials probably represent slow conduction orthodromically and/or antidromically activated outside the circuit. However, a wave front from pacing impulses travelling through this area could entrain the circuit.