Atypical bypass tracts: can they be recognized during sinus rhythm?

• Published in: Europace (London, England) England), 2019-02, Vol.21 (2), p.208-218
• Main Authors: de Alencar Neto, José Nunes, Ramalho de Moraes, Saulo Rodrigo, Back Sternick, Eduardo, Wellens, Hein J J
• Format: Article
• Language: English
• ISSN: 1099-5129; 1532-2092
• DOI: 10.1093/europace/euy079

Abstract Atypical bypass tracts or variants of ventricular pre-excitation are rare anatomic structures often with rate-dependent slowing in conduction, called decremental conduction. During sinus rhythm, electrocardiographic recognition of those structures may be difficult because unlike in the Wolff–Parkinson–White syndrome where usually overt ventricular pre-excitation is present, the electrocardiogram (ECG) often shows a subtle pre-excitation pattern because of less contribution to ventricular activation over the slow and decrementally conducting bypass. Following the structure described by Ivan Mahaim and Benatt corresponding to a fasciculoventricular pathway, several other new variants of ventricular pre-excitation were reported. In this review, we aim to discuss the electrocardiographic pattern of the different subtypes of variants of ventricular pre-excitation, including the atriofascicular pathway, long and short decrementally conducting atrioventricular pathways, fasciculoventricular pathway, the atrio-Hisian bypass tract, and nodoventricular and nodofascicular fibres. Emphasis will be on the ECG findings during sinus rhythm.