To the editor: Differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia

Abstract

I read the article by Dandamudi et al 1 Dandamudi G. Mokabberi R. Assal C. et al. A novel approach to differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia. Heart Rhythm. 2010; 7: 1326-1329 Abstract Full Text Full Text PDF PubMed Scopus (53) Google Scholar with great interest. Congratulations for exploiting a very well known phenomenon in the electrophysiology laboratory and setting up criteria on the basis of that, and then validating this on a good number of patients to differentiate orthodromic reciprocating tachycardia (ORT) and atrioventricular nodal reentrant tachycardia (AVNRT). A few points are worth mentioning. 1It would be difficult to differentiate between completely paced right ventricular (RV) complex and mildly less completely paced complex; the criteria depend highly upon identifying the first beat with either completely paced or fixed fusion, and this may give rise to spurious results. 2If the tachycardia terminates before acceleration of A, which is common in cases of ORT, then the criteria are not valid. It is surprising that in 23 cases of ORT the tachycardia did not terminate in a single case before acceleration of A. In this scenario, the mode of termination is quite helpful. If the tachycardia terminates without producing a complete RV pacing complex (this can be documented by comparing the RV pacing morphology during tachycardia and RV pacing once the tachycardia has terminated), then the tachycardia is ORT because the only way the tachycardia can be terminated in AVNRT is an RV paced complex penetrating through the His bundle, which will produce a complete RV pacing complex. (Unless coincidentally the tachycardia terminates spontaneously, which is uncommon if tachycardia is reasonably sustained.) A novel approach to differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardiaHeart RhythmVol. 7Issue 9PreviewVarious diagnostic maneuvers have been proposed to help differentiate orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal reentrant tachycardia (AVNRT) prior to ablation. However, not all criteria are applicable in every situation as each has limitations. Full-Text PDF To the Editor—Response: Orthodromic reciprocating tachycardiaHeart RhythmVol. 8Issue 3PreviewWe would like to thank the author for the kind comments. We agree with the author that care needs to be taken when assessing electrocardiographic (ECG) morphologies. All 12 ECG leads would need to be reviewed carefully to ascertain the first purely paced right ventricular (RV) beat or fixed fusion RV beat. However, in most of our cases of orthodromic reciprocating tachycardia (ORT), the tachycardia cycle length (TCL) was advanced to the paced cycle length (PCL) even before achieving fixed fusion in patients with right-sided as well as septal accessory pathways (AP). Full-Text PDF