Response

Abstract

We appreciate Dr. Gomes’s interest in our report on the participation of a concealed atriohisian tract in the typical atrioventricular nodal reentrant tachycardia (AVNRT), 1 Otomo K. Suyama K. Okamura H. et al. Participation of a concealed atriohisian tract in the reentrant circuit of the slow-fast type of atrioventricular nodal reentrant tachycardia. Heart Rhythm. 2007; 4: 703-710 Abstract Full Text Full Text PDF PubMed Scopus (17) Google Scholar which suggested the participation of a concealed atriohisian tract as a retrograde limb in the reentrant circuit of one-third of the typical AVNRT cases. In the Letter to the Editor, Dr. Gomes pointed out a possibility that an insulated intranodal tract with Purkinje muscle-like properties formed the retrograde pathway in the reentrant circuit. 2 Gomes J.A. Dhatt M.S. Damato A.N. et al. Incidence, determinants and significance of fixed retrograde conduction in the region of the atrioventricular node Evidence for retrograde atrioventricular nodal bypass tracts. Am J Cardiol. 1979; 44: 1089-1098 Abstract Full Text PDF PubMed Scopus (47) Google Scholar , 3 Gomes J.A. Dhatt M.S. Rubenson D.S. et al. Electrophysiologic evidence for selective retrograde utilization of a specialized conducting system in atrioventricular nodal reentrant tachycardia. Am J Cardiol. 1979; 43: 687-698 Abstract Full Text PDF PubMed Scopus (59) Google Scholar Actually, the data in our article did not convincingly rule out a possibility that a retrograde fast pathway was an insulated intranodal tract with electrophysiological properties of Purkinje muscle or working atrial myocardium. We considered that those retrograde tracts were concealed atriohisian tracts because they showed resistance to adenosine triphosphate with little or no decremental property in the retrograde direction and the H-A interval during the entrainment pacing from the parahisian right ventricle (H-Ae) was shorter than that during the tachycardia (H-At) (H-Ae-HAt <0 ms). Recent data from the animal experiments also supported our hypothesis. 4 Patterson E. Scherlag B.J. Fast pathway-His bundle connections in the rabbit heart. J Interv Cardiol Electrophysiol. 2004; 10: 121-129 Crossref PubMed Scopus (7) Google Scholar , 5 Patterson E. Scherlag B.J. Anatomic and functional fast atrioventricular conduction pathway. J Cardiovasc Electrophysiol. 2002; 13: 945-949 Crossref PubMed Scopus (16) Google Scholar As Dr. Gomes perceptively pointed out, however, an insulated intranodal tract with Purkinje muscle-like properties originating from the proximal portion of the His bundle (below the junction between the AV node and His bundle) would be also compatible with the electrophysiological behaviors of the concealed atriohisian tract. Morphologic and cellular studies would be required to settle this controversy. To the EditorHeart RhythmVol. 5Issue 2PreviewIn their article published in the June 2007 issue of Heart Rhythm, Otomo et al1 provide evidence for participation of a concealed atriohisian tract in the reentrant circuit of the slow–fast form of atrioventricular nodal reentrant tachycardia (AVNRT). They studied the electrophysiologic characteristics of the retrograde fast pathway in 74 patients with AVNRT after administering adenosine triphosphate (ATP). In 27 patients (36.5%) who showed ATP resistance, and therefore muscle-like properties, entrainment pacing from the parahisian region suggested the absence of a lower common pathway. Full-Text PDF