Miniseries 2-septal and paraseptal accessory pathways-Part I: The anatomic basis for the understanding of para-Hisian accessory atrioventricular pathways

Comparison between cryotherapy and radiofrequency energy sources for parahisian accessory pathway percutaneous ablation

BACKGROUND

Catheter ablation of parahisian accessory pathways (PHAP) are challenging due to their proximity to the normal conduction system. Retrospective studies suggest that cryoablation has a better safety profile but a higher recurrence rate when compared to radiofrequency ablation (RFCA). The objective of this study was to compare the results of parahisian AP ablation performed by electrophysiologists with experience in both technologies.

METHODS

Prospective single-center, non-blinded and 1:1 model was used. Patients included had parahisian AP confirmed by an electrophysiological study and referred for radiofrequency or cryotherapy ablation according to current guidelines, under fluoroscopic guidance. No electroanatomic mapping was used.

RESULTS

A total of 30 patients (mean age of 25±9.4 years; 90% male) were enrolled between Oct/2018 to Feb/2020. Acute success rate between RFCA and CRYO were similar (93% vs. 87%, p = 0.54). A nonsignificant reduction in short-term recurrence rate for RFCA (14% vs. 30%, p = 0.3) and mechanical trauma (6% vs. 20%; p = 0.28) was observed. Long-term recurrence rate and event-free survival time were similar in both groups after 1-year follow-up (p = 0.286). No persistent complete AV block or conduction disturbance was also observed.

CONCLUSION

Considering the limitation of a small sample size and the lack of use of electroanatomic mapping for RFCA, the efficacy and safety profile of parahisian AP ablation with RFCA was not different from CRYO, when performed by experienced electrophysiologists. No cases of permanent complete AV block were reported with either energy modalities.

Iatrogenic cardiomyopathy in patients with manifest right supero-paraseptal accessory pathways

INTRODUCTION

We describe two patients with right supero-paraseptal accessory pathway (SPAP) who developed left ventricular dysfunction associated with an increased degree of ventricular pre-excitation and frequent orthodromic reciprocating tachycardia (ORT) due to worsening atrioventricular (AV) node conduction.

METHODS AND RESULTS

Case 1: 48-year-old female with a history of normally functioning mechanical mitral valve, CABG, and ventricular pre-excitation that worsened after her open heart surgery. She presented with frequent palpitations with documented supraventricular tachycardia (SVT) and found to have a new left ventricular dysfunction with decrease in left ventricular ejection fraction (LVEF) from 55% to 46% with dyssynchrony. An electrophysiological study confirmed a right SPAP and ORT. The pathway was successfully ablated from the antegrade approach after careful mapping. After ablation and 6-month follow up echocardiogram showed improvement of EF to 54% and the LV dyssynchrony resolved. Case 2: 51-year-old male with a history of frequent SVT with recent unsuccessful ablations that resulted in worsening ventricular pre-excitation, more frequent SVT, and new left ventricular dysfunction (LVEF from 60% to 40%). He was started on amiodarone which resulted in significant sinus bradycardia, intermittent ventricular pre-excitation, and first degree AV block with significant increase in ORT events. His electrophysiology study confirmed SPAP which was successfully ablated from the antegrade approach after careful mapping. After 1 month, follow-up echocardiogram showed an improved ejection fraction to 60%.

CONCLUSION

Left ventricular dysfunction due to dyssynchrony and symptomatic frequent ORT of right SPAP can develop in the setting of new iatrogenic diminished AV node conduction. Successful ablation will result in LV function recovery to baseline.

Case report: A case of perinodal atrial tachycardia and review of the relevant clinical anatomy surrounding the retroaortic node

A 70-year-old female presented with incessant supraventricular tachycardia that was refractory to metoprolol and sotalol. ECG revealed a narrow complex tachycardia with a rate of 163 beats per minute with a short RP relationship. She had salvos of atrial tachycardia which led to a severe reduction in ejection fraction as noted on echocardiography and hemodynamic instability. An electrophysiological study was performed, and findings suggested this to be an atrial tachycardia with earliest activation in the perinodal area. Radiofrequency ablation was carried out along the septum and associated structures to surround this region including the right atrium, non-coronary sinus of Valsalva, and the left atrium (anterior wall outside of the right superior pulmonary vein) to isolate this area and surround the focus with ablation lesions. The patient has done well post-procedure and continues to do well without any recurrence on low-dose flecainide at 8 months.

Evidence for concealed fasciculo-ventricular connections as revealed by His bundle pacing

BACKGROUND

It is almost 100 years ago since Mahaim described the so-called paraspecific connections between the ventricular conduction axis and the crest of the muscular ventricular septum, believing such pathways to be ubiquitous. These pathways, however, have yet to be considered as potential pathways for septal activation during His bundle pacing.

MATERIALS

So as to explore the hypothesis that specialised septal pathways might provide the substrate for septal activation during His bundle pacing, we compared the findings from 22 serially sectioned histological datasets and 34 different individuals undergoing His bundle pacing.

RESULTS

We found histologically specialised pathways connecting the branching component of the atrioventricular conduction axis with the crest of the muscular ventricular septum in almost four-fifths of the histological datasets. In 32 of 34 patients undergoing His bundle pacing, the QRS complex closely resembled published images of known conduction through fasciculo-ventricular pathways. In only two patients was a delta wave not seen at any pacing voltages. Capture of these connections varied according to pacing voltage, a finding which correlated with the distance of the pathways from the site of penetration of the ventricular conduction axis. Ventricular activation times remained normal in the presence of the delta wave at higher pacing voltage but were prolonged at lower voltages.

CONCLUSIONS

Our histologic findings confirm fasciculo-ventricular connections, initially described by Mahaim as being paraspecific, are likely ubiquitous. Analysis of 12-lead electrocardiograms leads us to conclude that fasciculo-ventricular pathways, concealed during sinus rhythm, become manifest with His bundle pacing.

New insights into atrioventricular nodal anatomy, physiology, and immunochemistry: A comprehensive review and a proposed model of the slow-fast atrioventricular nodal reentrant tachycardia circuit in agreement with direct potential recordings in the Koch's triangle area

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.

Miniseries 1-Part III: 'Behind the scenes' in the triangle of Koch

AIMS

To take full advantage of the knowledge of cardiac anatomy, structures should be considered in their correct attitudinal orientation. Our aim was to discuss the triangle of Koch in an attitudinally appropriate fashion.

METHODS AND RESULTS

We reviewed our material prepared by histological sectioning, along with computed tomographic datasets of human hearts. The triangle of Koch is the right atrial surface of the inferior pyramidal space, being bordered by the tendon of Todaro and the hinge of the septal leaflet of the tricuspid valve, with its base at the inferior cavotricuspid isthmus. The fibro-adipose tissues of the inferior pyramidal space separate the atrial wall from the crest of the muscular interventricular septum, thus producing an atrioventricular muscular sandwich. The overall area is better approached as a pyramid rather than a triangle. The apex of the inferior pyramidal space overlaps the infero-septal recess of the subaortic outflow tract, permitting the atrioventricular conduction axis to transition directly to the crest of the muscular ventricular septum. The compact atrioventricular node is formed at the apex of the pyramid by union of its inferior extensions, which represent the slow pathway, with the septal components formed in the buttress of the atrial septum, thus providing the fast pathway.

CONCLUSIONS

To understand its various implications in current cardiological catheter interventions, the triangle of Koch must be considered in conjunction with the inferior pyramidal space and the infero-septal recess. It is better to consider the overall region in terms of a pyramidal area of interest.