EP ROUNDS
Unusual Termination by Single Ventricular Extra-Stimulus Applied during Atrioventricular Reciprocating Tachycardia: What Is the Mechanism? YUKINORI IKEGAMI, M.D.,* SEIJI TAKATSUKI, M.D.,† TAKUO YOSHIDA, M.D.,* and YUKIHIKO MOMIYAMA, M.D.* From the *Department of Cardiology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan; and †Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
ablation, SVT
Case Presentation A 66-year-old man underwent electrophysiological study due to recurrent attacks of narrow QRS tachycardia. Multipolar electrode-catheters were placed in the high right atrium (RA), Hisbundle region (His), right ventricular (RV) apex, and coronary sinus (CS). At baseline, the atrialHis (AH) interval was 70 ms during normal sinus rhythm and ventricular preexcitation was not present. Narrow QRS tachycardia could be easily induced by a single extra-stimulus applied from the RV. Atrial activation during tachycardia was eccentric. A single ventricular extra-stimulus was applied from the RV just after His-bundle activation when the His-bundle was refractory during tachycardia (Fig. 1). This extra-stimulus shortened the A-A intervals at the RA and the His-bundle region from 400 ms to 380 ms. Hence, the RA was advanced by the ventricular extra-stimulus applied when the His-bundle was refractory, which indicated the existence of retrograde conduction via an accessory pathway (AP). Please note the A-A interval at the distal CS was unchanged by the ventricular extra-stimulus that produced the change in the atrial activation sequence. Considering the site, which was not advanced by the extra-stimulus, was exclusively at the distal CS, it was concluded that the patient had two APs. AP one was near the ventricular stimulation site (AP1) which was activated earlier by the ventricular extra-stimulus and the other Conflict of interest: None. Address for reprints: Seiji Takatsuki, M.D., Department of Cardiology, Keio University Hospital, 35 Shinanomachi, Shinjukuku, Tokyo, 160-8582 Japan. Fax: 81-3-5363-3875; e-mail: [email protected] Received November 6, 2013; revised December 16, 2013; accepted January 8, 2014. doi: 10.1111/pace.12364
was far from the ventricular stimulation site and near the distal CS (AP2). The next H-H interval was prolonged from 400 ms to 410 ms, which could be explained by the decremental conduction property of the atrioventricular (AV) node. This narrow QRS tachycardia was diagnosed as reciprocating tachycardia with two retrograde APs. Then another RV extra-stimulus was applied with a coupling interval of 350 ms, terminating the tachycardia in an unusual fashion (Fig. 2). How do you interpret this tracing? Commentary The ventricular extra-stimulus is useful for the diagnosis of narrow QRS tachycardia. If the tachycardia was reset or terminated by the ventricular extra-stimulus applied during Hisbundle refractoriness, the tachycardia must be AV reciprocating tachycardia. The tachycardia termination by the right ventricular extra-stimulus during the AV reciprocating tachycardia is quite common, but usually accompanies AH block due to earlier atrial activation by the ventricular extrastimulation. If we look at Figure 2, we see that the ventricular extra-stimulus was applied 20 ms earlier than Figure 1, however, the anterograde His-bundle activation was still able to be observed just after the spike of the ventricular stimulation without change in the H-H interval. Interestingly, the retrograde atrial activation sequence was clearly changed in which the distal CS was the earliest caused by A-A interval prolongation at the RA and His-bundle region, compatible with retrograde conduction block at the AP1. The AA interval at the distal CS was not perturbed by the ventricular extra-stimulus, hence AP2 was activated via the intrinsic His-Purkinje system. Then the tachycardia was terminated due to AH block. The tachycardia could be easily induced and this termination pattern was observed to be reproducible.
©2014 Wiley Periodicals, Inc. 774
June 2014
PACE, Vol. 37
UNUSUAL TERMINATION OF AVRT
Figure 1. A single ventricular extra-stimulus was applied with a coupling interval of 370 ms when the His-bundle was refractory.
Figure 2. A single ventricular extra-stimulus with coupling interval of 350 ms terminated the tachycardia with atrial-His block.
PACE, Vol. 37
June 2014
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IKEGAMI, ET AL.
Figure 3. Schematic illustration of atrial activation pattern.
The site of atrial pacing may influence the refractoriness by changing the direction of the stimulus into the AV node.1,2 In our case, the input to the AV node from lateral AP activation was clearly critical here and obviously this input was associated with longer effective refractory period than the septal one
that blocked, which paradoxically terminated the tachycardia with apparently a longer A-A interval at the His-bundle region (Fig. 3). Both the left lateral wall and septal APs were successfully ablated in this case. AV nodal reentrant tachycardia was not inducible after the ablation of the APs.
References 1. Bastford WP, Akhtar B, Caracta AR, Josephson ME, Deides SF, Damato AN. Effect of atrial stimulation site on the electrophysiological properties of the atrioventricular node in man. Circulation 1974; 50:283–292.
776
2. Aranda J, Castellanos A, Moleiro F, Befeler B. Effects of the pacing site on A-H conduction and refractoriness in patients with short P-R intervals. Circulation 1976; 53:33–39.
June 2014
PACE, Vol. 37
Unusual Termination by Single Ventricular Extra-Stimulus Applied during Atrioventricular Reciprocating Tachycardia: What Is the Mechanism? YUKINORI IKEGAMI, M.D.,* SEIJI TAKATSUKI, M.D.,† TAKUO YOSHIDA, M.D.,* and YUKIHIKO MOMIYAMA, M.D.* From the *Department of Cardiology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan; and †Department of Cardiology, Keio University School of Medicine, Tokyo, Japan
ablation, SVT
Case Presentation A 66-year-old man underwent electrophysiological study due to recurrent attacks of narrow QRS tachycardia. Multipolar electrode-catheters were placed in the high right atrium (RA), Hisbundle region (His), right ventricular (RV) apex, and coronary sinus (CS). At baseline, the atrialHis (AH) interval was 70 ms during normal sinus rhythm and ventricular preexcitation was not present. Narrow QRS tachycardia could be easily induced by a single extra-stimulus applied from the RV. Atrial activation during tachycardia was eccentric. A single ventricular extra-stimulus was applied from the RV just after His-bundle activation when the His-bundle was refractory during tachycardia (Fig. 1). This extra-stimulus shortened the A-A intervals at the RA and the His-bundle region from 400 ms to 380 ms. Hence, the RA was advanced by the ventricular extra-stimulus applied when the His-bundle was refractory, which indicated the existence of retrograde conduction via an accessory pathway (AP). Please note the A-A interval at the distal CS was unchanged by the ventricular extra-stimulus that produced the change in the atrial activation sequence. Considering the site, which was not advanced by the extra-stimulus, was exclusively at the distal CS, it was concluded that the patient had two APs. AP one was near the ventricular stimulation site (AP1) which was activated earlier by the ventricular extra-stimulus and the other Conflict of interest: None. Address for reprints: Seiji Takatsuki, M.D., Department of Cardiology, Keio University Hospital, 35 Shinanomachi, Shinjukuku, Tokyo, 160-8582 Japan. Fax: 81-3-5363-3875; e-mail: [email protected] Received November 6, 2013; revised December 16, 2013; accepted January 8, 2014. doi: 10.1111/pace.12364
was far from the ventricular stimulation site and near the distal CS (AP2). The next H-H interval was prolonged from 400 ms to 410 ms, which could be explained by the decremental conduction property of the atrioventricular (AV) node. This narrow QRS tachycardia was diagnosed as reciprocating tachycardia with two retrograde APs. Then another RV extra-stimulus was applied with a coupling interval of 350 ms, terminating the tachycardia in an unusual fashion (Fig. 2). How do you interpret this tracing? Commentary The ventricular extra-stimulus is useful for the diagnosis of narrow QRS tachycardia. If the tachycardia was reset or terminated by the ventricular extra-stimulus applied during Hisbundle refractoriness, the tachycardia must be AV reciprocating tachycardia. The tachycardia termination by the right ventricular extra-stimulus during the AV reciprocating tachycardia is quite common, but usually accompanies AH block due to earlier atrial activation by the ventricular extrastimulation. If we look at Figure 2, we see that the ventricular extra-stimulus was applied 20 ms earlier than Figure 1, however, the anterograde His-bundle activation was still able to be observed just after the spike of the ventricular stimulation without change in the H-H interval. Interestingly, the retrograde atrial activation sequence was clearly changed in which the distal CS was the earliest caused by A-A interval prolongation at the RA and His-bundle region, compatible with retrograde conduction block at the AP1. The AA interval at the distal CS was not perturbed by the ventricular extra-stimulus, hence AP2 was activated via the intrinsic His-Purkinje system. Then the tachycardia was terminated due to AH block. The tachycardia could be easily induced and this termination pattern was observed to be reproducible.
©2014 Wiley Periodicals, Inc. 774
June 2014
PACE, Vol. 37
UNUSUAL TERMINATION OF AVRT
Figure 1. A single ventricular extra-stimulus was applied with a coupling interval of 370 ms when the His-bundle was refractory.
Figure 2. A single ventricular extra-stimulus with coupling interval of 350 ms terminated the tachycardia with atrial-His block.
PACE, Vol. 37
June 2014
775
IKEGAMI, ET AL.
Figure 3. Schematic illustration of atrial activation pattern.
The site of atrial pacing may influence the refractoriness by changing the direction of the stimulus into the AV node.1,2 In our case, the input to the AV node from lateral AP activation was clearly critical here and obviously this input was associated with longer effective refractory period than the septal one
that blocked, which paradoxically terminated the tachycardia with apparently a longer A-A interval at the His-bundle region (Fig. 3). Both the left lateral wall and septal APs were successfully ablated in this case. AV nodal reentrant tachycardia was not inducible after the ablation of the APs.
References 1. Bastford WP, Akhtar B, Caracta AR, Josephson ME, Deides SF, Damato AN. Effect of atrial stimulation site on the electrophysiological properties of the atrioventricular node in man. Circulation 1974; 50:283–292.
776
2. Aranda J, Castellanos A, Moleiro F, Befeler B. Effects of the pacing site on A-H conduction and refractoriness in patients with short P-R intervals. Circulation 1976; 53:33–39.
June 2014
PACE, Vol. 37
