Mahaim Accessory Pathways

Dear Sir,

I read with great interest the review article ‘Mahaim Accessory Pathways’ by D. Katritsis, et al.,1 in a past issue of Arrhythmia & Electrophysiology Review (AER 6(1):29-32). In this concise paper a systematic approach to electrophysiological diagnosis and differential diagnosis of these rare, but characteristic, pathways is presented. As the authors point out, pathways with Mahaim characteristics can be atriofascicular, atrioventricular, nodofascicular and nodoventricular, depending on their variable proximal and distal insertions. In my opinion, nodoventricular and nodofascicular pathways deserve special interest because they are often associated with regular wide complex tachycardia, which is difficult to differentiate from ventricular tachycardia (VT). Mahaim accessory pathways during tachycardia may exhibit atrioventricular dissociation since the atria are not integral to the circuit. Although this helps to rule out other forms of decremental pathways, mediated atrioventricular tachycardias may also be confused with VT, especially in nodoventricular tachycardias which often display a wide broad QRS complex tachycardia implying ventricular tachycardia. One criterion that distinguishes nodoventricular and nodofascicular tachycardia from intramyocardial VT is that QRS fusion from atrial activation during tachycardia is not possible in the first case wheras it is possible during VT.2,3 Therefore thorough observation during clinical tachycardia for possible fusion beats may provide the hallmark for the origin of tachycardia and may help significantly in the ablation procedure. Furthermore, induction of fusion systole with atrial extrasystoles during tachycardia is also very useful for distinguishing between these two tachycardias.

Nikolaos Fragakis

Assistant Professor of Cardiology, Aristotle University of Thessaloniki, Thessaloniki, Greece

References

1. Katritsis DG, Wellens HJ, Josephson MA. Mahaim Accessory Pathways. Arrhythmia & Electrophysiology Review 2017;6(1):29–32.
   Crossref | PubMed
2. Tchou P, Lehmann MH, Jazayeri M, Akhtar M. Atriofascicular connection or a nodoventricular Mahaim fiber? Electrophysiologic elucidation of the pathway and associated reentrant circuit. Circulation 1988;77:837–48.
   Crossref | PubMed
3. Grogin HR, Lee RJ, Kwasman M, et al. Radiofrequency catheter ablation of atriofascicular and nodoventricular Mahaim tracts. Circulation 1994;90:272–81
   Crossref | PubMed

Authors’ reply:

We thank Professor Fragakis for his kind words regarding our article on Mahaim pathways.1 We do concur with his comments. Demonstration of fusion is indeed a criterion of VT diagnosis, in general, and he is very right to point it out. Mahaim pathways are typical examples of electrophysiology entities that demand analytical and constructive thinking that may not always be found in our current era of computerised, video-game-like approaches. They also keep reminding us of the relevance and importance of the profound article by our sorely missed friend Mark Josephson: learn electrophysiology.2

Demosthenes G Katritsis, Hygeia Hospital, Greece

Hein J J Wellens, University of Maastricht, The Netherlands