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 VAbl‐RVApex intervals were −12 and 64 ms (p = .007), the median QRS‐V(His) intervals were 16 and 86 ms (p = .120), and the median VAbl‐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.

Comprehensive assessment of Mahaim accessory pathways’ anatomic distribution

“…A comparison of right-sided and left-sided Mahaim pathways in a series of patients revealed that left-sided Mahaim pathways ( n = 4) were all clustered in the left lateral annulus. 39 Conversely, the present study found only two out of four left-sided Mahaim pathways located at the left lateral annulus.…”

Left Free Wall-Sided Mahaim Type Fiber and Av Nodal Reentry Tachycardia -- Unusual but Not Impossible Combination

“…The left-sided location of Mahaim APs may be due to leftward extension of the A-V node or to a defect in embryological migration accompanied by an A-V isolation defect, as it is with left-sided AVNRTs. 2 We describe an unusual, previously unreported, left free wall-sided AP conducting only antegradely with slow decremental properties, in combination with dual A-V nodal pathway and previously ablated AVNRT. The AP was successfully and uncomplicatedly ablated on the left free wall of the mitral ring.…”

“…The most frequent coexisting arrhythmia is AV node reentrant tachycardia (AVNRT) which is a common finding in right sided Mahaim type APs, but has not been described in leftsided free wall fibers. 2 We present a patient with a unique combination of AVNRT and left-sided Mahaim type AP.…”

“…These APs comprise less than 3%-6% of all. [1][2][3] Most Mahaim type APs are right sided with atrial insertion points at various sites along the tricuspid annulus. Left-sided Mahaim fibers have been occasionally reported with a prevalence of 1.6%.…”

“…Left-sided Mahaim fibers have been occasionally reported with a prevalence of 1.6%. 2 The preferred treatment is radiofrequency ablation. The most frequent coexisting arrhythmia is AV node reentrant tachycardia (AVNRT) which is a common finding in right sided Mahaim type APs, but has not been described in leftsided free wall fibers.…”