- Email: [email protected]
Reply to the Editor—Differentiating Orthodromic Reciprocating Tachycardia From Atrioventricular Nodal Reentrant Tachycardia
e2
Heart Rhythm, Vol 8, No 2, February 2011
References 1.
2.
3.
4.
Leftheriotis D, Yoshiga Y, Kuck K-H, Ouyang F. Masked left atrial appendage isolation during ablation of persistent atrial fibrillation. Heart Rhythm 2010;8: 137–141. Di Biase L, Burkhardt JD, Mohanty P, et al. Left atrial appendage: an underrecognized trigger site of atrial fibrillation. Circulation 2010;122:109 – 118. Tilz RR, Chun KR, Schmit B, et al. Catheter ablation of long-standing persistent atrial fibrillation: a lesson from circumferential pulmonary vein isolation. J Cardiovasc Electrophysiol 2010;21:1085–1093. Tilz RR, Schmidt B, Menon S, et al. Left atrial appendage function and clinical outcome after electrical isolation of left atrial appendage in patients undergoing atrial fibrillation ablation. Circulation 2008;118:S694 –S695.
paced morphology. We would like to present this exception as an example of the need to exercise when using this response, especially in ORT where the response depends on multiple variables such as site of pacing, relative distance and conduction time to the His-Purkinje system, and the accessory pathway. Krishnakumar Nair, MD, CCDS† [email protected] Raja Selvaraj, MD* Kah Len Ho, MD† Kumaraswamy Nanthakumar, MD, FRCPC†
To the Editor—His Capture and Entrainment
†
In their article entitled “A novel approach to differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia” in the September 2010 issue of Heart Rhythm, Dandamudi et al1 report that in all 23 patients with orthodromic reciprocating tachycardia (ORT) in their study, atrial entrainment occurred before or within one beat after a fully paced right ventricular (RV) complex, whereas in atrioventricular nodal reentrant tachycardia (AVNRT), atrial entrainment occurred more than one beat after a fully paced RV complex. This maneuver is especially useful when RV overdrive pacing terminates tachycardia, making interpretation of the response to pacing termination impossible to use. In AVNRT, atrial entrainment has to occur through the His–Purkinje system. Therefore, antidromic His capture, which results in a fully paced RV complex, necessarily precedes atrial entrainment. In ORT, on the other hand, atrial entrainment can occur by the pathway or by the His-Purkinje system. Entrainment usually occurs through the pathway, followed by orthodromic His capture. A fixed fusion type of RV morphology develops only after orthodromic His capture and therefore typically after atrial entrainment. This is the basis of the maneuver detailed by Dandamudi et al. Because antidromic His capture is essential before atrial entrainment in AVNRT, we agree with the authors that the appearance of a fully paced RV morphology before or within one beat of atrial entrainment excludes AVNRT. However, we disagree with the conclusion that this finding identifies all patients with ORT. Especially in the case of left lateral accessory pathways, the time taken for the RV paced impulse to reach the pathway may be greater than the time needed for the impulse to capture the His. Therefore, the His bundle can be captured retrogradely with a fully paced morphology seen several beats prior to atrial entrainment. We recently reported one such case,2 and this phenomenon can be seen clearly in Figure 2 of our report. This figure shows the beginning of entrainment, and a fully paced RV morphology is seen in beat 3, preceded by antidromic His capture as evidenced by shortening of the H-H interval, His morphology different from anterograde His, and shorter AH interval (compared to Figure 1 in the same report). However, the atrium is entrained two cycles after this fully
Division of Cardiology University Health Network Toronto General Hospital Toronto, Ontario, Canada *Department of Cardiology Jawaharlal Institute of Postgraduate Medical Education and Research Puducherry, India
References 1.
2.
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. Nair K, Selvaraj R, Farid T, Nanthakumar K. Antidromic His capture during entrainment of orthodromic AVRT. Pacing Clin Electrophysiol 2010;33:1153– 1156.
Reply to the Editor—Differentiating Orthodromic Reciprocating Tachycardia From Atrioventricular Nodal Reentrant Tachycardia In our series,1 there were 15 left free-wall accessory pathways, with the remaining being either septal (right or left) or right free-wall accessory pathways (APs). In all patients with left free-wall APs, we were able to demonstrate acceleration of the tachycardia cycle length (TCL) to the paced cycle length (PCL) with the first fixed morphology right ventricular (RV) paced beat. However, we also showed that with most septal and right free-wall pathways, TCL was accelerated to the PCL even prior to achieving fixed RV pacing morphology. In order for our maneuver to work, it is critical to assess all QRS morphologies to determine the first fixed RV paced morphology beat. Also, it is important that synchronized pacing be performed because asynchronous pacing could reset atrioventricular nodal reentry tachycardia (AVNRT) or orthodromic reentry tachycardia (ORT) based on timing of the RV pacing stimulus. Finally, the first entrained atrial complex is determined by a fixed RV pacing stimulus to atrial electrogram interval. These factors will clearly determine which fixed RV morphology stimulus beat entrained the first atrial complex during tachycardia. It is likely that with left lateral APs, there could be exceptions where acceleration of TCL to the PCL with fixed RV fusion could
Letters to the Editor take more than one beat due to the distance of the AP from the pacing site. Our population included both left lateral APs and left posterior APs, which may yield different results. Our sample size was small, and we did not encounter any exceptions likely due to this reason. However, demonstration of acceleration of TCL to the PCL by the first fixed morphology RV paced beat during SVT has a very high positive predictive value in confirming ORT as the correct diagnosis because this observation in AVNRT is highly unlikely.
e3 Gopi Dandamudi, MD On behalf of the authors [email protected] Geisinger Heart Institute Wilkes-Barre, Pennsylvania
Reference 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.
Heart Rhythm, Vol 8, No 2, February 2011
References 1.
2.
3.
4.
Leftheriotis D, Yoshiga Y, Kuck K-H, Ouyang F. Masked left atrial appendage isolation during ablation of persistent atrial fibrillation. Heart Rhythm 2010;8: 137–141. Di Biase L, Burkhardt JD, Mohanty P, et al. Left atrial appendage: an underrecognized trigger site of atrial fibrillation. Circulation 2010;122:109 – 118. Tilz RR, Chun KR, Schmit B, et al. Catheter ablation of long-standing persistent atrial fibrillation: a lesson from circumferential pulmonary vein isolation. J Cardiovasc Electrophysiol 2010;21:1085–1093. Tilz RR, Schmidt B, Menon S, et al. Left atrial appendage function and clinical outcome after electrical isolation of left atrial appendage in patients undergoing atrial fibrillation ablation. Circulation 2008;118:S694 –S695.
paced morphology. We would like to present this exception as an example of the need to exercise when using this response, especially in ORT where the response depends on multiple variables such as site of pacing, relative distance and conduction time to the His-Purkinje system, and the accessory pathway. Krishnakumar Nair, MD, CCDS† [email protected] Raja Selvaraj, MD* Kah Len Ho, MD† Kumaraswamy Nanthakumar, MD, FRCPC†
To the Editor—His Capture and Entrainment
†
In their article entitled “A novel approach to differentiating orthodromic reciprocating tachycardia from atrioventricular nodal reentrant tachycardia” in the September 2010 issue of Heart Rhythm, Dandamudi et al1 report that in all 23 patients with orthodromic reciprocating tachycardia (ORT) in their study, atrial entrainment occurred before or within one beat after a fully paced right ventricular (RV) complex, whereas in atrioventricular nodal reentrant tachycardia (AVNRT), atrial entrainment occurred more than one beat after a fully paced RV complex. This maneuver is especially useful when RV overdrive pacing terminates tachycardia, making interpretation of the response to pacing termination impossible to use. In AVNRT, atrial entrainment has to occur through the His–Purkinje system. Therefore, antidromic His capture, which results in a fully paced RV complex, necessarily precedes atrial entrainment. In ORT, on the other hand, atrial entrainment can occur by the pathway or by the His-Purkinje system. Entrainment usually occurs through the pathway, followed by orthodromic His capture. A fixed fusion type of RV morphology develops only after orthodromic His capture and therefore typically after atrial entrainment. This is the basis of the maneuver detailed by Dandamudi et al. Because antidromic His capture is essential before atrial entrainment in AVNRT, we agree with the authors that the appearance of a fully paced RV morphology before or within one beat of atrial entrainment excludes AVNRT. However, we disagree with the conclusion that this finding identifies all patients with ORT. Especially in the case of left lateral accessory pathways, the time taken for the RV paced impulse to reach the pathway may be greater than the time needed for the impulse to capture the His. Therefore, the His bundle can be captured retrogradely with a fully paced morphology seen several beats prior to atrial entrainment. We recently reported one such case,2 and this phenomenon can be seen clearly in Figure 2 of our report. This figure shows the beginning of entrainment, and a fully paced RV morphology is seen in beat 3, preceded by antidromic His capture as evidenced by shortening of the H-H interval, His morphology different from anterograde His, and shorter AH interval (compared to Figure 1 in the same report). However, the atrium is entrained two cycles after this fully
Division of Cardiology University Health Network Toronto General Hospital Toronto, Ontario, Canada *Department of Cardiology Jawaharlal Institute of Postgraduate Medical Education and Research Puducherry, India
References 1.
2.
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. Nair K, Selvaraj R, Farid T, Nanthakumar K. Antidromic His capture during entrainment of orthodromic AVRT. Pacing Clin Electrophysiol 2010;33:1153– 1156.
Reply to the Editor—Differentiating Orthodromic Reciprocating Tachycardia From Atrioventricular Nodal Reentrant Tachycardia In our series,1 there were 15 left free-wall accessory pathways, with the remaining being either septal (right or left) or right free-wall accessory pathways (APs). In all patients with left free-wall APs, we were able to demonstrate acceleration of the tachycardia cycle length (TCL) to the paced cycle length (PCL) with the first fixed morphology right ventricular (RV) paced beat. However, we also showed that with most septal and right free-wall pathways, TCL was accelerated to the PCL even prior to achieving fixed RV pacing morphology. In order for our maneuver to work, it is critical to assess all QRS morphologies to determine the first fixed RV paced morphology beat. Also, it is important that synchronized pacing be performed because asynchronous pacing could reset atrioventricular nodal reentry tachycardia (AVNRT) or orthodromic reentry tachycardia (ORT) based on timing of the RV pacing stimulus. Finally, the first entrained atrial complex is determined by a fixed RV pacing stimulus to atrial electrogram interval. These factors will clearly determine which fixed RV morphology stimulus beat entrained the first atrial complex during tachycardia. It is likely that with left lateral APs, there could be exceptions where acceleration of TCL to the PCL with fixed RV fusion could
Letters to the Editor take more than one beat due to the distance of the AP from the pacing site. Our population included both left lateral APs and left posterior APs, which may yield different results. Our sample size was small, and we did not encounter any exceptions likely due to this reason. However, demonstration of acceleration of TCL to the PCL by the first fixed morphology RV paced beat during SVT has a very high positive predictive value in confirming ORT as the correct diagnosis because this observation in AVNRT is highly unlikely.
e3 Gopi Dandamudi, MD On behalf of the authors [email protected] Geisinger Heart Institute Wilkes-Barre, Pennsylvania
Reference 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.