Comparison of electrophysiological characteristics of right- and left-sided Mahaim-type accessory pathways

Abstract

Aims: Mahaim-type accessory pathways (MAPs) are generally right-sided due to the embryological differentiation, but left-sided localization is also possible. This study aims to compare the clinical and electrophysiological characteristics of right- and left-sided MAPs. Methods: Of 251 patients diagnosed with AP by electrophysiological study between November 2015 and February 2020, 12 patients with MAP were included (right sided n = 8, left sided n = 4). MAP was diagnosed if, (1) no retrograde conduction, (2) anterograde decremental conduction, (3) adenosine sensitivity, and (4) Mahaim potential at successful ablation site were present. Results: Ten of twelve MAPs were clustered on the lateral walls of the mitral (n = 3, 75%) and tricuspid annuli (n = 7, 87.5%). Right-sided MAPs were mostly long pathways extending toward the conduction system whereas left-sided MAPs were short extending toward the neighboring myocardium. For right- and left-sided APs, the median QRS times were 129 and 156 ms (p =.042), the median V<inf>Abl</inf>-RV<inf>Apex</inf> intervals were −12 and 64 ms (p =.007), the median QRS-V<inf>(His)</inf> intervals were 16 and 86 ms (p =.120), and the median V<inf>Abl</inf>-QRS interval was −8 and 12 ms (p =.017), respectively. Coexistence of dual atrioventricular node physiology was observed only in right-sided APs (n = 3, 37.5%). Conclusion: MAPs are more typically located on the right but may rarely be seen on the left. Catheter ablation was associated with high success without complications. © 2021 Elsevier B.V., All rights reserved.