Advances in Physiological Cardiac Stimulation

Advances in cardiac stimulation demonstrate that bradyarrhythmia treatments go beyond heart rate control. The concern with the ventricular stimulation site and, consequently, with the maintenance of intraventricular synchrony has become routine in most services. Techniques of physiological cardiac stimulation, such as stimulation of the bundle of His and the left branch, have been improved. Despite the indisputable benefits of these therapeutic modalities, there are technical difficulties that limit systematic use. In this sense, to make physiological cardiac stimulation more practical and reproducible, the concept of parahissian stimulation was expanded and studied. The technique, simpler and reproducible, contemplates a conventional approach of the right ventricle. The big difference is the use of QRS spatial variance analysis technology (Synchromax®, Exo S.A., Argentina) to confirm the maintenance of ventricular synchrony according to the implanted site.

Exercise-Induced Bundle Branch Block - an Infrequent Incidence

We describe an elderly woman who underwent a treadmill test preoperatively and was found to have Exercise-induced Left Bundle Branch Block without chest pain. Coronary angiogram was done which revealed a 70% stenosis in the fi rst diagonal branch of Left Anterior Descending Artery and a 40% lesion in proximal Right Coronary Artery. Available literature attributes rate-dependent transient conduction defects to obstructive lesions of coronary arteries, slow arterial blood fl ow, vasospasms as well as pathology in the Bundle of His.

Re-evaluation of the structure of the atrioventricular node and its connections with the atrium

Aims The anatomic substrates for atrioventricular nodal re-entry remain enigmatic, but require knowledge of the normal arrangement of the inputs and exist from the atrioventricular node. This knowledge is crucial to understand the phenomenon of atrioventricular nodal re-entry. Methods and results We studied 20 human hearts with serial sections covering the entirety of the triangle of Koch and the cavotricuspid isthmus. We determined the location of the atrioventricular conduction axis and the connections between the specialized cardiomyocytes of the conduction axis and the adjacent working atrial myocardium. The atrioventricular node was found at the apex of the triangle of Koch, with entry of the conduction axis to the central fibrous body providing the criterion for distinction of the bundle of His. We found marked variation in the inferior extensions of the node, the shape of the node, the presence or absence of a connecting bridge within the myocardium of the cavotricuspid isthmus, the connections between the compact node and the myocardium of the atrial septum, the presence of transitional cardiomyocytes, and the ‘last’ connection between the working atrial myocardium and the conduction axis before it became the bundle of His. Conclusion The observed variations of the inferior extensions, combined with the arrangement of the ‘last’ connections between the atrial myocardium and the conduction axis prior to its insulation as the bundle of His, provide compelling evidence to support the concept for atrioventricular nodal re-entry as advanced by Katritsis and Becker.

Cartilaginous Metaplasia Involving the Atrioventricular Node and Bundle of His Contributing to Sudden Early Neonatal Death

Cartilaginous metaplasia involving the atrioventricular (AV) node is an uncommon entity that may cause sudden cardiac death secondary to dysrhythmias. We report 2 autopsy cases of full-term male newborns: 1 stillborn and 1 live-born, with antemortem bradycardia who died in the peripartum period. An examination of the cardiac conduction system in both cases demonstrated extensive cartilaginous metaplasia of the central fibrous body and involvement of the AV node and bundle of His. The cases highlight the recognition of cardiac conduction system anomalies as a cause of sudden perinatal death. In cases of perinatal death with preceding arrhythmia, postmortem sections of the cardiac conduction system are recommended to examine for cardiac conduction system anomaly.

Cryoablation of the para-Hisian region

Basis: the ablation of the para-Hisian region is a challenge due to the risk of inadvertent lesion of a bundle of His. Cryoablation, due to its slower progression, allows interruption of the application in case of signs of undesired lesions and catheter adhesion during the applications, which has made cryoablation the ideal method for these patients. Objectives: to demonstrate the results of an initial series of patients referred for cryoablation of para-Hisian pathways. Patients and methods: From April 2015 to August 2017, 13 patients were referred for cryoablation due to the necessity for a para-Hisian approach detected in previous ablation procedures. Of the 13 patients, seven were submitted a radiofrequency ablation attempt (RF) and presented failure or recurrence, five performed only electrophysiological studies, and no ablation was attempted, and one was indicated primarily. The mean age was 32 ± 16 years. Eleven patients had manifest anomalous pathways (APs), one hidden and one nodal reentrant tachycardia (NRT) with a transient atrioventricular block (AB) during RF. A cycle of 4 minutes followed by one more cycle in case of a positive result. Results: Of the 13 patients, 11 had an acute success in eliminating the accessory pathway. One patient had multiple accessory pathways, one right side, and one left side. In this patient, it was possible only the ablation of the left pathway. In all others, it was observed exuberant Hisian potential at the point of application with success. The patient with NRT was ablated in the M region without intercurrences. Four applications were required on average to eliminate the accessory pathway successfully. The mean local temperature was -74 ºC. In five patients, the occurrence of third-degree right branch block (RBB) was observed. In one patient, early application of RBB was interrupted and the bonus application was not applied. This wasthe only acutely successful patient who presented clinical recurrence. Transient AB was not observed in any patient. No complications were observed. Conclusion: Cryoablation of para-Hisian pathways and NRTs in regions surrounding the His was an effective method for treatment in this population of patients refractory or refused for RF treatment. The occurrence of acute RBB does not seem to be a criterion for the interruption of applications.