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

Changes in QRS morphology during antidromic atrioventricular reentrant tachycardia

We report a case of a 44-year-old male who underwent an electrophysiological study for symptomatic supraventricular tachycardia (SVT) with wide QRS complex. The SVT was diagnosed as an antidromic atrioventricular reentrant tachycardia (AVRT) via antegrade conduction of left-sided accessory pathway (AP). However, the QRS morphology changed during the SVT, and then the SVT was terminated spontaneously. The mapping of AP was performed during sinus rhythm, and the radiofrequency application successfully eliminated the AP, which rendered tachycardias non-inducible. This was a rare case of antidromic AVRT during which the QRS morphology changed.

Challenging wide QRS tachycardia diagnosis: One trigger two mechanisms

The coexistence of different types of wide QRS complex tachycardias induced by the same trigger has rarely been observed. The electrical instability and incessant nature of tachycardias can cause tachycardiomyopathy and will not allow accurate diagnosis during an electrophysiological study (EPS). In case of an electrical storm, elimination of the trigger may be the first approach to provide patient stability. We report a successfully managed case of repetitive initiation of pleomorphic ventricular tachycardia and Mahaim-type antidromic atrioventricular reentrant tachycardia, induced by a premature ventricular complex in the right ventricular outflow tract.

Electrophysiological characteristics of right- and left-sided Mahaim accessory pathways: A single-center experience in China

Background

Mahaim-type accessory pathways (MAPs) are rare accessory pathways (APs) with specific properties. They are mostly located in the right side of the heart but rarely exist on the left side.

Objectives

This study aims to analyze the clinical and electrophysiological (EP) characteristics of both-sided MAPs.

Methods

A total of 2,249 patients with AP from our center were enrolled between 1 January 2011 and 27 March 2022. During the EP study (EPS) 17 patients were diagnosed with MAPs (right-sided: n = 13, left-sided: n = 4) according to the properties of Mahaim fibers.

Results

MAPs constitute 0.75% of all APs. Out of 1,553 patients with left-sided APs, four patients (0.26%) were diagnosed with Mahaim fiber-mediated tachycardia. Out of 696 patients with right-sided APs, 13 patients (1.9%) were diagnosed with Mahaim fiber. Most Mahaim fibers were located at the free wall of the tricuspid and mitral annuli. Seven patients of right-sided MAPs were of atriofasicular type, six patients had right-sided MAPs, and all of the patients with left-sided MAPs were of atrioventricular (AV) type. The M potential only was detected in long-length MAPs. Coexistence with other supraventricular tachycardias (SVTs) was also observed both in patients with right-sided and left-sided MAPs. All the patients underwent radiofrequency ablation successfully. Only one patient had tachycardia recurrence during a follow-up.

Conclusion

Although MAPs are commonly located at right sides, left sites are not impossible. The M potential contributes to the improvement of the successful ablation.

Comprehensive assessment of Mahaim accessory pathways' anatomic distribution

Objective

To present the authors’ experience of Mahaim-type accessory pathways (MAPs), focusing on anatomic localizations.

Methods

Data from consecutive patients who underwent electrophysiological study (EPS) for MAP ablation in two tertiary centres, between January 1998 and June 2020, were retrospectively analysed.

Results

Of the 55 included patients, 27 (49.1%) were male, and the overall mean age was 29.5 ± 11.6 years (range, 12–66 years). MAPs were ablated at the tricuspid annulus in 43 patients (78.2%), mitral annulus in four patients (7.3%), paraseptal region in three patients (5.5%), and right ventricle mid-apical region in five patients (9.1%). Among 49 patients who planned for ablation therapy, the success rate was 91.8% (45 patients).

Conclusion

MAPs were most often ablated at the lateral aspect of the tricuspid annuli, sometimes at other sides of the tricuspid and mitral annuli, and infrequently in the right ventricle. The M potential mapping technique is likely to be a useful target for ablation of MAPs.