Kazumasa Hiejima

Heterogeneity of anterograde fast-pathway and retrograde slow-pathway conduction patterns in patients with the fast–slow form of atrioventricular nodal reentrant tachycardia: electrophysiologic and electrocardiographic considerations

OBJECTIVES This study sought to define the electrophysiologic and electrocardiographic characteristics of fast-slow atrioventricular nodal reentrant tachycardia (AVNRT). BACKGROUND In fast-slow AVNRT the retrograde slow pathway (SP) is located in the posterior septum, whereas the anterograde fast pathway (FP) is located in the anterior septum; however, exceptions may occur. METHODS Twelve patients with fast-slow AVNRT were studied. To determine the location of the retrograde SP, atrial activation during AVNRT was examined while recording the electrograms from the low septal right atrium (LSRA) on the His bundle electrogram and the orifice of the coronary sinus (CS). Further, to investigate the location of the anterograde FP, single extrastimuli were delivered during AVNRT both from the high right atrium and the CS. RESULTS The CS activation during AVNRT preceded the LSRA in six patients (posterior type); LSRA activation preceded the CS in three patients (anterior type), and in the remaining three both sites were activated simultaneously (middle type). In the anterior type, CS stimulation preexcited the His and the ventricle without capturing the LSRA electrogram (atrial dissociation between the CS and the LSRA), suggesting that the anterograde FP was located posterior to the retrograde SP. In the posterior and middle types, high right atrial stimulation demonstrated atrial dissociation, suggesting that the anterograde FP was located anterior to the SP. In the posterior and middle types, retrograde P waves in the inferior leads were deeply negative, whereas they were shallow in the anterior type. CONCLUSIONS Fast-slow AVNRT was able to be categorized into posterior, middle and anterior types according to the site of the retrograde SP. The anterior type AVNRT, where an anteriorly located SP is used in the retrograde direction and a posteriorly located FP in the anterograde direction, appears to represent an anatomical reversal of the posterior type which uses a posterior SP for retrograde and an anterior FP for anterograde conduction. Anterior type AVNRT should be considered in the differential diagnosis of long RP (RP > PR intervals) tachycardias with shallow negative P waves in the inferior leads.

NONFLUOROSCOPIC GUIDANCE FOR CATHETER PLACEMENT INTO THE CORONARY SINUS UNDER DIRECT VISION USING A BALLOON-TIPPED CARDIOSCOPE

The right atrial posterior septum, including the coronary sinus (CS) ostium, is an important landmark in radio frequency catheter ablation therapy for supraventricular tachycardia or atrial flutter. The anatomical findings around the CS ostium would be useful to determine a target site or line during catheter ablation. The aim of the study was to test the ability of the imaging catheter to identify structures in the posterior septal area of the right atrium and to evaluate the feasibility of guidance for catheter placement in the CS using a cardiosccpe that we recently developed. In 12 anesthetized dogs, the Cardioscope, consisting of a deflectable 7 Fr fiberoptic endoscope with an inflatable and transparent balloon, was introduced into the right atrium via the femoral vein. The cardioscope was manipulated to observe the right atrial posterior septum. A deflectable electrode catheter was inserted via the jugular vein and positioned in the CS under cardioscopic guidance. In 10 of 12 dogs, the right atrial posterior septum, including the CS ostium, and the tendon of Todaro could be anatomically identified by cardioscopy. It was possible to position an electrode catheter in the CS in all 10 dogs under direct vision without fluoroscopy. But the CS ostium could not be detected in the remaining two dogs, although the cardioscope was placed at as many sites as possible. No complication occurred. The balloon‐tipped cardioscope appears to be useful in observing the right atrial posterior septum and in guiding an electrode catheter into the CS.

Retrograde Supernormal Conduction, Gap Phenomenon in Concealed Accessory Atrioventricular Pathways

We present four patients with the Wolff‐Parkinson‐White syndrome who exhibited retrograde supernormal conduction or gap phenomenon in concealed accessory pathways. In the first patient, ventricular extrastimulus testing revealed retrograde block at the coupling interval of 520 msec and reappearance of conduction at the coupling interval of 370 msec. In a second patient, 1:1 retrograde conduction was not present but supernormal conduction was demonstrated at coupling intervals of 360 msec to 310 msec during the ventricular extrastimulus testing when the basic drive consisted of atrioventricular (AV) simultaneous pacing. In a third patient, ventricular extrastimulus testing demonstrated retrograde conduction through the accessory pathway only at coupling intervals of 400 msec to 360 msec. In a fourth patient, retrograde block occurred at the coupling interval of 340 msec and retrograde “slow” conduction reappeared at coupling intervals of 300 msec to 250 msec (gap phenomenon) only when the basic drive consisted of AV simultaneous pacing. Thus, concealed accessory pathways may exhibit retrograde supernormal conduction or gap phenomenon. Ventricular extrastimulus testing consisting of AV simultaneous pacing during the basic drive may facilitate demonstration of these unusual properties.

Electrophysiological Demonstration of Anterograde Concealed Conduction in Accessory Atrioventricular Pathways Capable Only of Retrograde Conduction

Anterograde concealed conduction into the concealed accessory atrioventricular (AV) pathway has been postulated to be one of the factors preventing the reciprocating process via the accessory pathway in patients with the concealed Wolff‐Parkinson‐White(WPW) syndrome but its presence has not been documented. To demonstrate the occurrence of anterograde concealment, 12 patients with the concealed WPW syndrome were selected for study. A pacing protocol was designed in which the retrograde conduction of the ventricular extrastimulus over the accessory pathway was assessed during ventricular pacing aione (conventional method) and during the AV simultaneous pacing (simultaneous method); the results were then compared. When the high right atrium was simultaneously paced, the effective refractory period of the concealed accessory pathway shortened as compared with the conventional method in five of 12 patients (from 341.7 ± 110.8 to 312.5 ± 108.2 msec, n = 12), whereas, it decreased in all patients studied when the coronary sinus near the accessory pathway was simultaneously paced (from 375.7 ± 135.0 to 287. ± 116.1 msec, n = 7). These results demonstrate that the AV simultaneous pacing frequently shortens the refractoriness of the concealed accessory AV pathway and such facilitation seems to he well explained by the probable anterograde concealment in it and peeling back of the refractory barrier.

Ventricular Fibrillation Induced by Conducted Sinus or Supraventricular Beat

We report a case of a 35-year-old housewife who had a repetitive ventricular fibrillation following cardiac surgery. This arrhythmia was induced by sinus or supraventricular ectopic beats conducted to the ventricles and interrupting the preceding T or T+U wave during incomplete A-V dissociation. The cycle length (Q-Q) and the Q-Q/Q-T ratio of the beats preceding fibrillation were significantly shorter than the Q-Q and Q-Q/Q-T ratio of the beats not preceding fibrillation. These findings suggest that ventricular fibrillation is more likely to occur when the supraventricular impulse is conducted to the ventricles early in the cycle and interrupts the T or T+U wave.

Coronary Sinus Pacing Initiates Counterclockwise Atrial Flutter While Pacing From the Low Lateral Right Atrium Initiates Clockwise Atrial Flutter Analysis of Episodes of Direct Initiation of Atrial Flutter

INTRODUCTION Rapid atrial pacing in sinus rhythm may directly induce atrial flutter without provoking intervening atrial fibrillation, or initiate atrial flutter indirectly, by a conversion from an episode of transient atrial fibrillation provoked by rapid atrial pacing. The present study was performed to examine whether or not the direct induction of clockwise or counterclockwise atrial flutter was pacing-site (right or left atrium) dependent. METHODS AND RESULTS We analyzed the mode of direct induction of atrial flutter by rapid atrial pacing. In 46 patients with a history of atrial flutter, rapid atrial pacing with 3 to 20 stimuli (cycle length = 500 - 170 ms) was performed in sinus rhythm to induce atrial flutter from 3 atrial sites, including the high right atrium, the low lateral right atrium, and the proximal coronary sinus, while recording multiple intracardiac electrograms of the atria. Direct induction of atrial flutter by rapid atrial pacing was a rare phenomenon and was documented only 22 times in 15 patients: 3, 11, and 8 times during stimulation, respectively, from the high right atrium, low lateral right atrium, and the proximal coronary sinus. Counterclockwise atrial flutter (12 times) was more frequently induced with stimulation from the proximal coronary sinus than from the low lateral right atrium (8 vs 1, P = .0001); clockwise atrial flutter (10 times) was induced exclusively from the low lateral right atrium (P = .0001 for low lateral right atrium vs proximal coronary sinus, P = .011 for low lateral right atrium vs high right atrium). CONCLUSIONS Direct induction of either counterclockwise or clockwise atrial flutter was definitively pacing-site dependent; low lateral right atrial pacing induced clockwise, while proximal coronary sinus pacing induced counterclockwise atrial flutter. Anatomic correlation between the flutter circuit and the atrial pacing site may play an important role in the inducibility of counterclockwise or clockwise atrial flutter.

Demonstration of Right and Left Atrial Dissociation by Atrial Rapid Pacing or Extrastimulation During Fast‐Slow (Uncommon) Form of Atrioventricular Nodal Reentrant Tachycardia

Some recent works suggest that extranodal atrial fibers may form part of the reenlry circuit in the atrioventricular (AV) nodal reentrant tachycardia (AVNRT). This hypothesis is based on the fact that the perinodal dissection successfully abolished AVNRT while preserving intact AV conduction. Apart from the surgical success, the electrophysiological evidence supporting this hypothesis has not been demonstrated, especially in the uncommon (fast‐slow) form of AVNRT. We present some electrophysiological evidence suggesting atrial participation in eight patients with the fast‐slow form of AVNRT. During the tachycardia, rapid pacing or extrastimulation was done from the orifice of the coronary sinus (CS) and the right atrium (RA), while recording the electrograms of the CS and the low septal RA. In seven patients, right and left atrial dissociation was demonstrated during pacing from the RA, while in the remaining one this was demonstrated from the CS. The interatrial dissociation will be unlikely if the intranodal reentry circuit connects with the atria via a single upper common pathway. This suggests that the upper turnaround of the reentry circuit involves atrial tissue and that the extranodal accessory pathway with long conduction times may form the ascending limb of the circuit (atrionodal reentry). Alternatively, the reentry circuit is entirely intranodal and two or more connecting pathways are present between the atria and the circuit.

NEW DIAGNOSTIC FINDING TO ASSESS PARA-HISIAN PACING OBSERVED IN A PATIENT WITH A PERMANENT FORM OF JUNCTIONAL RECIPROCATING TACHYCARDIA

Morphologic Change During Para‐Hisian Pacing. Para‐Hisian pacing, a useful method to differentiate conduction over an accessory pathway from conduction over the AV node, is assessed essentially by comparing the timing of local atrial electrograms between Hisbundle captured heats and His‐bundle noncaptured heats. We describe the case of a patient with a permanent form of junctional reciprocating tachycardia, in whom an atrial double potential was recorded only during the tachycardia at the right posterior septum. During para‐Hisian pacing, a morphologic change in the atrial electrogram at the posterior septum was also identified, as well as a change in the retrograde atrial sequence. Since the morphologic change of atrial electrograms during para‐Hisian pacing cannot be demonstrated in a patient without an accessory pathway, this new finding could he considered a new additional diagnostic criterion suggesting the presence of an accessory pathway.

Catheter Ablation of Idiopathic Left Ventricular Tachycardia with Multiple Breakthrough Sites Guided by an Electroanatomical Mapping System

Idiopathic ventricular tachycardia (VT) has been considered to be amenable to radiofrequency catheter ablation guided by Purkinje potentials. However, there appear to be various types of reentrant circuits associated with this VT deduced from the results of the successful radiofrequency catheter ablation cases. We describe in this report a patient with idiopathic left ventricular tachycardia which was electrically inducible and verapamil sensitive. Multiple earliest ventricular activation sites during tachycardia were detected with electroanatomical mapping using the CARTO system. Multiple applications at these sites failed to eliminate the VT. The earliest Purkinje potential was recorded at least 1.5[emsp4 ]cm away from the earliest ventricular activation sites, and the radiofrequency current application at this site resulted in the complete abolition of this VT. The reentrant circuit of this tachycardia seemed to have multiple breakthrough sites to the ventricular myocardium, which were distant from the requisite part of the reentrant circuit of this VT involving the Purkinje fiber network conduction system.

Marked anterograde decremental conduction over a rapidly conducting accessory pathway after radiofrequency ablation

We report on a patient with the Wolff-Parkinson-White syndrome who temporarily exhibited a marked anterograde decremental conduction over a rapidly conducting accessory atrioventricular pathway after successful radiofrequency ablation. By recording the intracardiac electrogram via the ablation catheter placed at the successful ablation site, we were able to exclude the possibility of the occurrence of anterograde decremental conduction in the atrial or ventricular myocardium between the accessory pathway and the recording electrodes.