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Radiofrequency catheter ablation of right atriofascicular (Mahaim) accessory pathways guided by accessory pathway
J H McClelland1, X Wang, K J Beckman
1Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City 73190.
Insights
Researchers recorded accessory pathway (AP) potentials from right atriofascicular pathways, enabling precise catheter ablation of Mahaim fiber physiology. This study successfully localized and ablated these accessory pathways, preventing tachycardia recurrence.
Area of Science:
- Electrophysiology
- Cardiology
- Medical Device Technology
Background:
- Accessory pathways (APs) with Mahaim fiber physiology connect the right atrium to the right bundle branch.
- These pathways exhibit antegrade conduction, prolonged conduction times, and decremental properties.
- Previously, potentials from these specific right atriofascicular pathways were not recorded.
Purpose of the Study:
- To determine if AP activation potentials could be recorded from right atriofascicular APs.
- To assess if recorded potentials could guide catheter ablation site localization.
Main Methods:
- Analysis of 26 patients undergoing ablation for preexcited atrioventricular reentrant tachycardia.
- Utilized atrial extrastimuli, recorded earliest ventricular activation, and identified distal right bundle branch activation.
- Recorded discrete, high-frequency AP potentials at the tricuspid annulus and right ventricular free wall.
Main Results:
- Identified right atriofascicular APs in 23 of 26 patients (88.5%).
- Recorded AP potentials in 22 of 23 patients, preceding ventricular activation.
- Radiofrequency ablation at the AP potential site eliminated AP conduction in all treated patients, with no recurrence during follow-up.
Conclusions:
- Right atriofascicular APs have proximal (tricuspid annulus) and distal (right ventricular free wall) components.
- The distal component generates a recordable AP potential crucial for ablation site identification.
- Successful catheter ablation using recorded AP potentials led to sustained tachycardia elimination.
Background:
Accessory pathways (APs) exhibiting "Mahaim fiber" physiology (antegrade conduction only, long conduction time, and decremental properties) often connect the lateral right atrium to the right bundle branch (right atriofascicular pathways). Potentials from these pathways have not been recorded previously. The purpose of this study was to determine whether AP activation potentials could be recorded from right atriofascicular APs and to determine whether these potentials could be used to localize a site for catheter ablation.
Methods And Results:
Of 26 consecutive patients referred for catheter ablation of an AP producing a preexcited (antidromic) atrioventricular (AV) reentrant tachycardia having a left bundle branch block pattern with short ventriculoatrial and long AV intervals, 23 (88.5%) were found to have a right atriofascicular AP. During antidromic AV reentrant tachycardia, (1) right atrial extrastimuli (that did not penetrant tachycardia, (1) right atrial extrastimuli (that did not penetrate the AV node) advanced the timing of the next QRS complex, indicating that the AP was connected to the right atrium; (2) earliest antegrade ventricular activation was recorded at the apical right ventricular free wall, and (3) ventricular activation was preceded by activation of the distal right bundle branch, indicating a fascicular insertion or a ventricular insertion close to the terminus of the right bundle branch. A single, discrete, high-frequency AP potential was recorded at the lateral, anterolateral, or posterolateral tricuspid annulus in 22 of the 23 patients 63 +/- 12 milliseconds after the local atrial potential and 83 +/- 23 milliseconds before the local ventricular potential during sinus rhythm. The AP potential was also recorded at sites along the right ventricular free wall between the tricuspid annulus and the site of earliest ventricular activation at the apical region. Programmed atrial stimulation and adenosine each produced prolongation of AP conduction time because of an increase in the A-AP interval and Wenckebach block proximal to the AP potential. Radiofrequency current applied at a site recording the AP potential (tricuspid annulus in 19 patients and right ventricular free wall in 3 patients) eliminated AP conduction in all 22 patients. Tachycardia has not recurred in any patient during 18 +/- 13 months of follow-up. AP conduction was absent in all 9 patients who had a follow-up electrophysiological study 3.8 +/- 1.7 months after ablation.
Conclusions:
Right atriofascicular APs consist of two components. The proximal component is located at the lateral, anterolateral, or posterolateral tricuspid annulus, does not generate an AP potential recordable by catheter electrodes, and is responsible for the decremental conduction properties. The "distal" component extends from the tricuspid annulus to the distal right bundle branch at the apical right ventricular free wall and generates a large, high-frequency AP potential that accurately identifies a site for ablation.