UNKNOWN OF THE MONTH
Narrow complex tachycardia after ablation of the left lateral accessory pathway: What is the mechanism? Martin Eisenberger, MD, PhD,*† Alan Bulava, MD, PhD,*† Jiri Hanis, MD,* Adam Novotny, MS* From the *South Bohemia Cardiac Centre, Budweis Hospital, Budweis, Czech Republic, and †Faculty of Health and Social Studies, South Bohemia University, Budweis, Czech Republic.
Case presentation A 24-year-old patient with history of palpitations underwent ablation of the concealed left lateral accessory pathway that was rather difficult, requiring multiple radiofrequency (RF) energy applications. A narrow complex tachycardia with a heart rate of 240 beats/min with no visible P waves was recorded the next morning. The patient was brought back to the electrophysiology laboratory for a redo procedure. Catheters were positioned in the right ventricular apex (RVa) and in the coronary sinus (CS); retrograde conduction during pacing from the RVa was found to be nondecremental, and the atrial signals noted in the CS catheter showed a proximal to distal activation pattern. The clinical tachycardia was easily induced with incremental atrial pacing. Figure 1 shows the electrocardiogram and intracardiac electrograms during tachycardia after a 20-pole Halo catheter had been positioned in the right atrium around the tricuspid annulus. Figure 2 shows an activation map of the left atrium during tachycardia obtained using the CARTO 3 electroanatomical system (Biosense Webster Inc., Diamond Bar, CA). Figure 3 shows electrograms obtained during pacing from the RVa during sinus rhythm. What is the mechanism for the tachycardia?
Commentary The most likely cause of the tachycardia after accessory pathway ablation is the recurrence of the pathway. One would expect eccentric atrial activation distal to proximal in the CS with a short ventriculoatrial (VA) interval in the distal CS during tachycardia. However, in this case, a completely different CS activation pattern was observed. Concentric proximal to distal activation during tachycardia can suggest coexistence of another accessory pathway. KEYWORDS Catheter ablation; Accessory pathway; Tachycardia; Mitral isthmus; CARTO ABBREVIATIONS CS ¼ coronary sinus; RF ¼ radiofrequency; RVa ¼ right ventricular apex; VA ¼ ventriculoatrial (Heart Rhythm 2015;12:455–457) This work was supported by South Bohemia University (grant no. BOV2012_001). Address reprint requests and correspondence: Dr Martin Eisenberger, South Bohemia Cardiac Centre, B Nemcove 585/54, 370 01 Budweis, Czech Republic. E-mail address: martineisenberger@ hotmail.com.
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
A differential diagnosis also includes typical cavotricuspid isthmus–dependent atrial flutter and atypical atrioventricular nodal reentrant tachycardia. A duodecapolar Halo catheter was positioned in the right atrium around the tricuspid annulus to see whether a right-sided accessory pathway could be diagnosed. The earliest atrial activation during tachycardia was found high on the interatrial septum with a long VA interval (Figure 1). A right-sided accessory pathway would be expected to have a short VA interval; however, at this point, we could not rule out a slowly conducting septal pathway. In addition, a cavotricuspid isthmus–dependent atrial flutter would have counterclockwise or clockwise macroreentrant activation on the Halo catheter, the absence of which meant that it could be excluded. The previous ablations on the lateral mitral annulus could have created an area of slow conduction that might facilitate a perimitral reentry circuit. Therefore, a diagnosis of perimitral flutter was a plausible explanation at this point. A single transseptal puncture was performed, and the CARTO 3 electroanatomical system was used to reconstruct the geometry of the left atrium with an activation map during tachycardia (Figure 2). A low-voltage region was actually found in the area between the mitral annulus and the left inferior pulmonary vein, which was most likely due to the extensive ablations of the accessory pathway performed the day before. During detailed activation mapping, the earliest atrial signal was recorded superior to this low-voltage region (red region on the activation map). However, the activation map covered only 143 ms, which was just slightly more than half of the 250-ms tachycardia cycle length, making perimitral flutter unlikely. To confirm this, entrainment pacing can be done at different sites around the mitral annulus. Indeed, entrainment from the inferior and anterior mitral annulus showed that the postpacing interval was more than 50 ms longer than the tachycardia cycle length, which definitively excluded perimitral reentry as the cause of the tachycardia. Another possible diagnostic consideration was focal atrial tachycardia originating from the anterolateral region of the mitral annulus with a conduction block over the mitral isthmus, which could have been inadvertently caused by the
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Figure 1 Narrow complex tachycardia showing proximal to distal activation on the coronary sinus (CS) catheter (CS9,10 to CS1,2). A 20pole Halo catheter was situated in the right atrium around the tricuspid annulus. The earliest atrial signal is recorded high on the interatrial septum on Halo15,16. The tachycardia cycle length (CL) was 250 ms. RVa ¼ right ventricular apex.
previous ablations. Serial pacing during sinus rhythm from the ablation catheter positioned in the region superior to the previous accessory pathway ablation site showed proximal to distal activation in the CS, suggesting transmitral conduction block. To confirm the conduction block across the mitral isthmus line and to avoid the most common pitfalls, the usual criteria of differential pacing were used.1 A reversal in the CS activation sequence could also be explained by ablation of the distal connection between the CS and the left atrium, provided that there was a discrete muscular connection. However, double potentials in the CS catheter reflecting both the activation of the CS musculature itself and the far-field activation of the adjacent left atrium would be observed in such cases, and no double potentials were seen in our patient. A very early atrial signal was noted in the ablation catheter positioned superior to the previous accessory pathway ablation site during pacing from the right ventricle (Figure 3). The only possible way to observe this very early atrial signal on the lateral mitral isthmus during pacing from the right ventricle is through a retrograde conducting accessory pathway; therefore, the correct diagnosis could only be a recurrence of the left-sided accessory pathway. Two RF applications in this region interrupted the conduction through the accessory pathway, and a VA block was subsequently observed during ventricular pacing.
Heart Rhythm, Vol 12, No 2, February 2015
Figure 2 An activation CARTO 3 map of the left atrium shows a scar region, most likely owing to the previous ablations of the accessory pathway (gray dots) between the mitral annulus and the lower pole of the left inferior pulmonary vein. Tachycardia activation was counterclockwise around the mitral annulus, covering only 143 ms (97 to 46 ms) of the 250-ms tachycardia cycle length.
Figure 3 Pacing from the right ventricular apex (RVa) during sinus rhythm. A proximal to distal activation pattern on the coronary sinus catheter and a very early atrial signal (black arrow) were recorded from the distal ablation catheter (MAPd) positioned superior to the mitral isthmus (white arrow in Figure 2).
Eisenberger et al
Tachycardia After Pathway Ablation
A change in the activation pattern on the CS catheter after ablation of the concealed left lateral accessory pathway, during ventricular pacing, is usually considered an “easy-tobe-recognized” end point for successful ablation. However, an inadvertent block of conduction across the mitral isthmus can cause the same change in CS activation and mimic accessory pathway interruption. An unintended mitral isthmus conduction block, which can occur after RF ablations on the lateral mitral annulus, is more likely to occur in younger
457 patients, since they are more likely to have a shorter mitral isthmus, or after extensive ablations.2
References 1. Shah AJ, Pascale P, Miyazaki S, et al. Prevalence and types of pitfall in the assessment of mitral isthmus linear conduction block. Circ Arrhythm Electrophysiol 2012;5:957–967. 2. Bulava A, Hanis J, Sitek D. Mitral isthmus conduction block: intriguing result of radiofrequency catheter ablation for a left concealed accessory pathway. Europace 2010;12:579–581.
Narrow complex tachycardia after ablation of the left lateral accessory pathway: What is the mechanism? Martin Eisenberger, MD, PhD,*† Alan Bulava, MD, PhD,*† Jiri Hanis, MD,* Adam Novotny, MS* From the *South Bohemia Cardiac Centre, Budweis Hospital, Budweis, Czech Republic, and †Faculty of Health and Social Studies, South Bohemia University, Budweis, Czech Republic.
Case presentation A 24-year-old patient with history of palpitations underwent ablation of the concealed left lateral accessory pathway that was rather difficult, requiring multiple radiofrequency (RF) energy applications. A narrow complex tachycardia with a heart rate of 240 beats/min with no visible P waves was recorded the next morning. The patient was brought back to the electrophysiology laboratory for a redo procedure. Catheters were positioned in the right ventricular apex (RVa) and in the coronary sinus (CS); retrograde conduction during pacing from the RVa was found to be nondecremental, and the atrial signals noted in the CS catheter showed a proximal to distal activation pattern. The clinical tachycardia was easily induced with incremental atrial pacing. Figure 1 shows the electrocardiogram and intracardiac electrograms during tachycardia after a 20-pole Halo catheter had been positioned in the right atrium around the tricuspid annulus. Figure 2 shows an activation map of the left atrium during tachycardia obtained using the CARTO 3 electroanatomical system (Biosense Webster Inc., Diamond Bar, CA). Figure 3 shows electrograms obtained during pacing from the RVa during sinus rhythm. What is the mechanism for the tachycardia?
Commentary The most likely cause of the tachycardia after accessory pathway ablation is the recurrence of the pathway. One would expect eccentric atrial activation distal to proximal in the CS with a short ventriculoatrial (VA) interval in the distal CS during tachycardia. However, in this case, a completely different CS activation pattern was observed. Concentric proximal to distal activation during tachycardia can suggest coexistence of another accessory pathway. KEYWORDS Catheter ablation; Accessory pathway; Tachycardia; Mitral isthmus; CARTO ABBREVIATIONS CS ¼ coronary sinus; RF ¼ radiofrequency; RVa ¼ right ventricular apex; VA ¼ ventriculoatrial (Heart Rhythm 2015;12:455–457) This work was supported by South Bohemia University (grant no. BOV2012_001). Address reprint requests and correspondence: Dr Martin Eisenberger, South Bohemia Cardiac Centre, B Nemcove 585/54, 370 01 Budweis, Czech Republic. E-mail address: martineisenberger@ hotmail.com.
1547-5271/$-see front matter B 2015 Heart Rhythm Society. All rights reserved.
A differential diagnosis also includes typical cavotricuspid isthmus–dependent atrial flutter and atypical atrioventricular nodal reentrant tachycardia. A duodecapolar Halo catheter was positioned in the right atrium around the tricuspid annulus to see whether a right-sided accessory pathway could be diagnosed. The earliest atrial activation during tachycardia was found high on the interatrial septum with a long VA interval (Figure 1). A right-sided accessory pathway would be expected to have a short VA interval; however, at this point, we could not rule out a slowly conducting septal pathway. In addition, a cavotricuspid isthmus–dependent atrial flutter would have counterclockwise or clockwise macroreentrant activation on the Halo catheter, the absence of which meant that it could be excluded. The previous ablations on the lateral mitral annulus could have created an area of slow conduction that might facilitate a perimitral reentry circuit. Therefore, a diagnosis of perimitral flutter was a plausible explanation at this point. A single transseptal puncture was performed, and the CARTO 3 electroanatomical system was used to reconstruct the geometry of the left atrium with an activation map during tachycardia (Figure 2). A low-voltage region was actually found in the area between the mitral annulus and the left inferior pulmonary vein, which was most likely due to the extensive ablations of the accessory pathway performed the day before. During detailed activation mapping, the earliest atrial signal was recorded superior to this low-voltage region (red region on the activation map). However, the activation map covered only 143 ms, which was just slightly more than half of the 250-ms tachycardia cycle length, making perimitral flutter unlikely. To confirm this, entrainment pacing can be done at different sites around the mitral annulus. Indeed, entrainment from the inferior and anterior mitral annulus showed that the postpacing interval was more than 50 ms longer than the tachycardia cycle length, which definitively excluded perimitral reentry as the cause of the tachycardia. Another possible diagnostic consideration was focal atrial tachycardia originating from the anterolateral region of the mitral annulus with a conduction block over the mitral isthmus, which could have been inadvertently caused by the
http://dx.doi.org/10.1016/j.hrthm.2014.11.029
456
Figure 1 Narrow complex tachycardia showing proximal to distal activation on the coronary sinus (CS) catheter (CS9,10 to CS1,2). A 20pole Halo catheter was situated in the right atrium around the tricuspid annulus. The earliest atrial signal is recorded high on the interatrial septum on Halo15,16. The tachycardia cycle length (CL) was 250 ms. RVa ¼ right ventricular apex.
previous ablations. Serial pacing during sinus rhythm from the ablation catheter positioned in the region superior to the previous accessory pathway ablation site showed proximal to distal activation in the CS, suggesting transmitral conduction block. To confirm the conduction block across the mitral isthmus line and to avoid the most common pitfalls, the usual criteria of differential pacing were used.1 A reversal in the CS activation sequence could also be explained by ablation of the distal connection between the CS and the left atrium, provided that there was a discrete muscular connection. However, double potentials in the CS catheter reflecting both the activation of the CS musculature itself and the far-field activation of the adjacent left atrium would be observed in such cases, and no double potentials were seen in our patient. A very early atrial signal was noted in the ablation catheter positioned superior to the previous accessory pathway ablation site during pacing from the right ventricle (Figure 3). The only possible way to observe this very early atrial signal on the lateral mitral isthmus during pacing from the right ventricle is through a retrograde conducting accessory pathway; therefore, the correct diagnosis could only be a recurrence of the left-sided accessory pathway. Two RF applications in this region interrupted the conduction through the accessory pathway, and a VA block was subsequently observed during ventricular pacing.
Heart Rhythm, Vol 12, No 2, February 2015
Figure 2 An activation CARTO 3 map of the left atrium shows a scar region, most likely owing to the previous ablations of the accessory pathway (gray dots) between the mitral annulus and the lower pole of the left inferior pulmonary vein. Tachycardia activation was counterclockwise around the mitral annulus, covering only 143 ms (97 to 46 ms) of the 250-ms tachycardia cycle length.
Figure 3 Pacing from the right ventricular apex (RVa) during sinus rhythm. A proximal to distal activation pattern on the coronary sinus catheter and a very early atrial signal (black arrow) were recorded from the distal ablation catheter (MAPd) positioned superior to the mitral isthmus (white arrow in Figure 2).
Eisenberger et al
Tachycardia After Pathway Ablation
A change in the activation pattern on the CS catheter after ablation of the concealed left lateral accessory pathway, during ventricular pacing, is usually considered an “easy-tobe-recognized” end point for successful ablation. However, an inadvertent block of conduction across the mitral isthmus can cause the same change in CS activation and mimic accessory pathway interruption. An unintended mitral isthmus conduction block, which can occur after RF ablations on the lateral mitral annulus, is more likely to occur in younger
457 patients, since they are more likely to have a shorter mitral isthmus, or after extensive ablations.2
References 1. Shah AJ, Pascale P, Miyazaki S, et al. Prevalence and types of pitfall in the assessment of mitral isthmus linear conduction block. Circ Arrhythm Electrophysiol 2012;5:957–967. 2. Bulava A, Hanis J, Sitek D. Mitral isthmus conduction block: intriguing result of radiofrequency catheter ablation for a left concealed accessory pathway. Europace 2010;12:579–581.
