Unusual Locations for Adenosine-Sensitive Accessory Atrioventricular Pathways with Decremental Conduction

Locations of Decremental Accessory Pathways. Introduction : Accessory AV pathways with decremental conduction are uncommon and, in particular, are thought not to occur at the anterior portion of the mitral annulus.
Methods and Results : This report describes successful catheter ablation in three patients with accessory AV pathways that were adenosine sensitive and showed decremental conduction properties. The pathways were located at the anteroseptal, anteroparaseptal, and anterolateral aspects of the mitral annulus.
Conclusion : Accessory pathways with decremental conduction do occur anywhere around the mitral annulus, even in the area of fibrous continuity between the aortic leaflet of the mitral valve and the aortic valve itself.     

Recurrence of Accessory Pathway Conduction After Successful Radiofrequency Ablation: Histological Findings

The histological findings from a patient with Wolff-Parkinson-White syndrome (right superior paraseptal accessory pathway) who underwent successful radiofrequency ablation and had recurrence of tachycardia one month later in the absence of overt pre-excitation are reported. Histology revealed three small, oval to circular shaped, whitish, smooth areas on the right endocardial surface, the one being situated at the atrial free wall, and the other two being at the ventricular aspect. A very small hole was present in the interventricular component of the membranus septum. The accessory pathway band passed to either side of the small hole albeit disrupted by fibrous tissue in places.These findings indicate that multiple applications may cause penetration of the myocardium, and to achieve success, complete disruption of the pathway at some point along its course is required. Recurrence of retrograde accessory pathway conduction can be explained with the impedance mismatch hypothesis.     

Catheter Ablation of the Atrial Origin of a Decrementally Conducting Atriofascicular Accessory Pathway by Radiofrequency Current

Radiofrequency Ablation of Pseudo-Mahaim Fibers. Introduction: A young woman with refractory recurrent supraventricular tachycardia was referred for catheter ablation. Methods and Results: Electrophysiologic studies revealed the mechanism of tachycardia to be atrioventricular (AV) reentry, utilizing a decrementally conducting atriofascicular accessory pathway as the anterograde limb of the circuit and the normal intraventricular conducting system as the retrograde limb. Pace mapping in the right atrium during sinus rhythm suggested an atrial origin of the accessory pathway several centimeters distant from the AV node. Multiple radiofrequency lesions at the distal insertion of the accessory pathway in or near the right bundle branch failed to abolish preexcitation. In contrast, radiofrequency current applied to the ventricular side of the anterolateral tricuspid ring, adjacent to the atrial origin of the accessory pathway, was successful in abolishing preexcitation and inducible supraventricular tachycardia without affecting AV nodal conduction. Conclusion: Radiofrequency ablation can provide curative therapy for intractable supraventricular tachycardia due to decrementally-conducting atriofascicular accessory pathways. The risk of AV block in such patients as a consequence of the procedure should be quite low.     

Case Report: Clinical AV Nodal Reentrant Tachycardia in a Patient with Left Sided Accessory Pathway and Immediate Occurrence of Antidromic AV Reentrant Tachycardia after Slow Pathway Ablation

The only inducible arrhythmia in a patient with exclusive antegrade conducting left anterolateral accessory pathway, consists of slow/fast atrioventricular nodal reentrant tachycardia. After radiofrequency catheter ablation of the slow pathway, true antidromic AV reentrant tachycardia was easily induced by atrial pacing. Following ablation of the accessory pathway no arrhythmia could be induced.     

Retrograde Supernormal Conduction in Concealed Accessory Atrioventricular Pathway Following Catheter Ablation

Supernormal Conduction in Concealed Kent Following Ablation. A case is presented of a 63-year-old woman with a concealed accessory pathway that exhibited retrograde supernormal conduction after radiofrequency catheter ablation. Although ventricular pacing at a slow rate revealed no retrograde conduction over the accessory pathway following ablation, the tachycardia recurred 15 months later. During ventricular pacing there was retrograde 1:1 conduction over the accessory pathway at a fast rate while there was intermittent VA dissociation with rare retrograde conduction at the slower rate. Ventricular extrastimulus testing demonstrated a supernormal conduction zone of the coupling interval. Thus, accessory pathways may exhibit supernormal conduction after catheter ablation. Pacing should be performed at both slow and fast rates to confirm the presence of conduction block following ablation.     

Electrophysiologic Characteristics and Radiofrequency Catheter Ablation in Atrioventricular Node Reentrant Tachycardia with Second-Degree Atrioventricular Block

Second-Degree AV Block During AVNRT. Introduction : Detailed electrophysiologic study of AV nodal reentrant tachycardia (AVNRT) with 2:1 AV block has been limited.
Methods and Results : Six hundred nine consecutive patients with AVNRT underwent electrophysiologic study and radiofrequency catheter ablation of the slow pathway. Twenty-six patients with 2:1 AV block during AVNRT were designated as group I, und those without this particular finding were designated as group II. The major findings of the present study were: (1) group I patients had better anterograde and retrograde AV nodal function, shorter tachycardia cycle length (during tachycardia with 1:1 conduction) (307 ± 30 vs 360 ± 58 msec, P < 0.001), and higher incidence of transient bundle branch block during tachycardia (18/26 vs 43/609, P < 0.001) than group II patients: (2) 21 (80.8%) group I patients had alternans of AA intervals during AVNRT with 2:1 AV block. Longer AH intervals (264 ± 26 vs 253 ± 27 msec, P = 0.031) were associated with the blocked beats. However, similar HA intervals (51 ± 12 vs 50 ± 12 msec, P = 0.363) and similar HV intervals (53 ± 11 vs 52 ± 12, P = 0.834) were found in the blocked and conducted beats; (3) ventricular extrastimulation before or during the His-bundle refractory period bundle could convert 2:1 AV block to 1:1 AV conduction.
Conclusions : Fast reentrant circuit, rather than underlying impaired conduction of the distal AV node or infranodal area, might account for second-degree AV block during AVNRT. Slow pathway ablation is safe and effective in patients who have AVNRT with 2:1 AV block.     

Clinical Recurrences After Successful Accessory Pathway Ablation:

Dormant Accessory Pathways. Introduction : Recurrence of clinical symptoms after radiofrequency catheter ablation of an accessory atrioventricular pathway (AP) may be due to the late manifestation of an additional AP that was not detected during the initial ablation session. It was the purpose of this study to elucidate the phenomenon of these "dormant" APs.
Methods and Results : Of 1280 consecutive patients who underwent radiofrequency catheter ablation of an AP, 54 patients (4.2 %) developed clinical symptoms postablation, necessitating a repeat ablation session. Recurrence of conduction over the AP targeted al the initial ablation session was found in 45 patients, whereas in the other 9 patients (0.7%) the manifestation of a previously unnoticed AP had caused symptom recurrence. Retrospective analysis of the data from these patients' ablation sessions revealed that the late manifesting AP was ablated at a site clearly different from that of the initially targeted AP, and that the manifestation of conduction over a previously "dormant" AP occurred significantly later than the recovery of a presumably ablated AP. Seven (78%) of the 9 "dormant" APs were concealed, and none exhibited decremental conduction properties.
Conclusion : The incidence of clinical recurrences mediated by the late manifestation of conduction over a previously "dormant" AP is low. The lack of an anatomic vicinity of these predominantly concealed APs with the initially targeted AP and the lack of evidence for their presence during the initial ablation session suggest intermittent conduction as the most likely explanation for their late manifestation.     

Atrioventricular Nodal Reentrant Tachycardia with Multiple Discontinuities in the Atrioventricular Node Conduction Curve: Immediate Success Rates of Radiofrequency Ablation and Long-Term Clinical Follow-up Results as Compared to Patients with Single or No AH-Jumps

Background: Some patients with atrioventricular nodal reentrant tachycardia (AVNRT) demonstrate multiple discontinuities (AH jump) in their antegrade AV node conduction curves. We evaluated and compared the immediate success rates, procedure-related complications, long-term clinical follow-up results and recurrence rates after slow pathway ablation in patients with multiple versus single or no AH jumps. Methods: The study group consists of 278 consecutive patients (mean age 36.6 ± 15.7) who underwent ablation for typical AVNRT, divided into three categories according to the number of AH jumps (50 ms) before ablation: Group-1 consisted of 63 patients (23%) with continuous AV node function curves; Group-2 of 183 patients (66%) with a single jump and Group-3 of 32 (12%) patients showing more than one AH jumps. Results: Age was significantly higher in Group-3 as compared to Group-1 (43 ± 18 years vs. 34 ± 16 years, p = 0.020). The electrophysiological features of AVNRT did not differ among groups. Before ablation, the maximum AH interval was significantly longer in Group-3 as compared to Groups-1 and -2 (p < 0.001 for both). AV node antegrade ERP was significantly shorter in Group-3 than in Group-2, both before and after ablation (p < 0.050 for both). AV node Wenckebach cycle length (WCL) was shorter in Group-3 as compared to both Groups-1 and -2, before and after ablation (p < 0.050 for all). AV node WCL was prolonged significantly in all groups after ablation (p < 0.001 for all). Residual dual pathways were present in 37 of 278 patients (13%) after ablation and were significantly more frequent in Group-3 than Group-2 (31% vs. 15%, p = 0.023). Conclusions: Patients with multiple AH jumps are older and more often have residual dual atrioventricular nodal pathway physiology after successful ablation but these features do not affect the immediate and long-term success rates of slow pathway ablation as compared to patients with single or no AH jumps.     

Radiofrequency Ablation of Concealed Left Free-Wall Accessory Pathways Without Coronary Sinus Catheterization:

Ablation of Concealed Accessory Pathways. Introduction: Feasibility of radiofrequency (RF) ablation using a two-catheter technique without coronary sinus catheterization was studied in 100 consecutive patients with a single concealed left free-wall accessory path-way.
Methods and Results: Tachycardia was induced by electrical stimulation in the right atrium/right ventricle, and the presence of a concealed left free-wall accessory pathway was suggested electrocardiographically (negative P wave in leads I and/or a VL during orthodromic tachycardia) or by earlier atrial activation in the pulmonary artery compared to the high right atrium. Mapping of the mitral annulus was performed during right ventricular pacing or orthodromic tachycardia, and RF energy was applied at the site with the earliest retrograde atrial activation. Ablation was considered effective if tachycardia could not be induced, and if VA dissociation or exclusive retrograde nodal conduction was observed. Ablation was initially successful in 98 of 100 patients. Mean number of radiofrequency pulses were 3.2 ± 2. Mean fluoroscopy time and total procedure time was 14 ± 9 and 107 ± 32 minutes, respectively. There were no complications related to the procedure. At a mean follow-up of 22 ± 13 months, two patients experienced tachycardia recurrence and required a second procedure, which was successful.
Conclusions: Our results suggest that RF catheter ablation of concealed left free-wall accessory pathways can be safely, effectively, and rapidly performed using a simplified two-catheter technique with no need for coronary sinus catheterization.     

Pseudo-Pacemaker Syndrome Following Inadvertent Fast Pathway Ablation for Atrioventricular Nodal Reentrant Tachycardia

Pseudo-Pacemaker Syndrome After AV Nodal Ablation. Atrioventricular nodal reentrant tachycardia that is refractory to drug treatment has recently been treated with radiofrequency catheter ablation. In this case report we describe a patient with atrioventricular nodal reentrant tachycardia in whom radiofrequency ablation of slow pathway was attempted, with inadvertent damage to the fast pathway. The patient developed marked first-degree atrioventricular block associated with symptoms mimicking pacemaker syndrome.     

Pathological Findings Following Slow Pathway Ablation for AV Nodal Reentrant Tachycardia

Pathology of Slow Pathway Ablation. Introduction : AV nodal reentrant tachycardia is routinely cured using radiofrequency catheter ablation techniques. However, there remains controversy as to whether the reentrant circuit for this tachycardia exists solely in the AV node or whether perinodal atrial tissues are vital to the circuit. In addition, the effects of radiofrequency ablation of the slow pathway of AV nodal reentrant tachycardia on the AV node are not known. We examined an autopsy specimen to determine the anatomical location and extent of AV nodal damage of radiofrequency slow pathway ablation for cure of AV nodal reentrant tachycardia.
Methods and Results : A 64-year-old woman with confirmed AV nodal reentrant tachycardia underwent a successful "slow pathway" AV modification with a single radiofrequency application. Five months after the procedure, the patient died from a spontaneous intracranial hemorrhage. Postmortem gross pathological examination of the heart was performed. The heart was then sectioned and stained for histologic examination. On gross examination, a pale lesion 0.5 cm in diameter was seen on the endocardial surface adjacent to the tricuspid annulus. approximately 0.85 cm anterior to the coronary sinus os and 1.15 cm from the apex of the triangle of Koch where the AV node resides. Histologic examination revealed a right atrial lesion composed of connective tissue and fat. The compact AV node and surrounding transitional cells were unaffected histologically, with normal atrial cells lying between the AV node and the lesion.
Conclusion : Ablation of the slow pathway to cure AV nodal reentrant tachycardia does not produce any gross or histologic damage to the AV node, suggesting that the AV nodal reentrant circuit does not exist in its entirety in the AV node.     

Successful Radiofrequency Catheter Ablation of Left Lateral Accessory Pathway Using Transseptal Approach During Pregnancy

Recurrent supraventricular tachycardia (SVT) associated with the Wolff-Parkinson-White syndrome during pregnancy may be difficult to manage, mainly due to concerns about the effects of pharmacotherapy on the fetus. We report on a 32 year old woman in her 22nd week of pregnancy with recurrent symptomatic SVT in which standard pharmacotherapy had been ineffectual, contraindicated or poorly tolerated and in whom we were able to perform a successful transseptal ablation of a left lateral accessory pathway.     

Radiofrequency Ablation of a Supra ventricular Tachycardia Due to Interatrial Conduction From the Recipient to Donor Atria in an Orthotopic Heart Transplant Recipient

Recipient-to-Donor Interatrial Tachycardia. Interatrial conduction of recipient atrial tachycardia to the donor atria of an orthotopic heart transplant recipient resulted in a unique cause of supraventricular tachycardia. An electrophysiologic study was performed, and the recipient atria was found to be in an atrial tachycardia, cycle length of 210 msec, with periods of both 2:1 and 1:1 conduction to the donor atria resulting in a donor atrial cycle length of 420 msec and 210 msec, respectively. The site of interatrial conduction was mapped to the right atrial suture line, along the atrial free wall, and was successfully disrupted with radiofrequency energy. Arrhythmias of a similar mechanism may also be observed in other postsurgical patients.     

Radiofrequency Catheter Ablation of Two Right Mahaïm-like Accessory Pathways in a Patient with Ebstein's Anomaly

A 17-year-old woman with Ebstein's anomaly and recurrent episodes of antidromic tachycardia with two distinct morphologies is described. The tachycardias were produced by two separate Mahaïm-like accessory pathways. These were localized by their activation potentials at the anterolateral ventricular margin of the tricuspid annulus and ablated in a single session using radiofrequency current.     

Inappropriate Sinus Tachycardia After Radiofrequency Ablation of Para-Hisian Accessory Pathways

Inappropriate Sinus Tachycardia After Catheter Ablation. Introduction : Inappropriate sinus tachycardia (IST) has been observed following radiofrequency ablation (RFA) of the AV nodal fast pathway. This study was aimed to prospectively analyze the incidence and clinical significance of IST following RFA of para-Hisian accessory pathways (APs).
Methods and Results : Twenty-eight patients (pts) with para-Hisian APs underwent RFA. An AP was defined as para-Hisian whenever its atrial and ventricular insertions were associated with a His-bundle potential ≥ 0.1 mV. RF current was always delivered at the atrial aspect of the tricuspid annulus. to a site where the His-bundle potential was < 0.15 mV. Time- and frequency-domain analysis of heart rate variability was performed in 22 patients, before and after RFA. Abolition of AP conduction was obtained in all pts, and no AV conduction alteration occurred. Six pts (21.4%) presented with IST 45 to 240 minutes after the ablation procedure. In 5 of them, IST disappeared spontaneously within 72 hours, whereas in 1 pt β-blockers were required for 2 months. The atrial potential amplitude (1.217 ± 0.264 mV vs 0.882 ± 0.173 mV, P = 0.009) and A/V potential amplitude ratio (2.633 vs 1.686, P = 0.05) were significantly higher in pts who developed IST than in those who did not. A marked decrease in heart rate variability was observed only in pts who developed IST.
Conclusion : IST is a relatively frequent complication after RFA of para-Hisian APs: it is generally short-lasting and usually does not require any treatment. IST after catheter ablation is likely to depend upon transient parasympathetic denervation of the sinus node.     

Interruption of the Inferior Extension of the Compact Atrioventricular Node Underlies Successful Radio Frequency Ablation of Atrioventricular Nodal Reentrant Tachycardia

A recent anatomic study has revived interest in the inferior extensions of the compact atrioventricular node in humans. The rightward extension is on the right atrial aspect, close to the septal attachment of the tricuspid valve leaflet and, hence, closely related to the anticipated slow pathway considered to play a role in atrioventricular nodal reentrant tachycardia (AVNRT). This report documents a patient, 65 years of age, with dilated cardiomyopathy and AVNRT. The tachycardia was successfully terminated using selective radiofrequency (RF) ablation, delivered at a site where a slow potential was recorded and validated by atrial pacing, located between the tricuspid valve and the os of the coronary sinus (CS), close to its superior rim. In subsequent years the patient developed progressive heart failure and eventually died. Histopathologic examination revealed extensive scar tissue at the site of the burn, extending onto the crest of the underlying ventricular septum. Serial sections revealed the compact AV node superiorly and an inferior extension surfacing from the scar which could be traced inferiorly beyond the os of the CS. This is the first documentation of RF ablation interrupting an inferior extension of the compact AV node in a patient successfully ablated for AVNRT. The observation suggests that the slow pathway in this patient found its anatomic substrate in the inferior extension of the compact AV node.     

射频消融阻断房室旁路后室房逆传的特点

以射频电流阻断90例预激综合征患者的房室旁路.62例(68.9%)于旁路消融后呈室房分离,28例(31.1%)呈室房递减性传导.室房分离与患者年龄、性别及旁路传导特性无关,但左或右游离壁旁路阻断 后室房分离者多于递减传导者,而间隔旁路阻断后差别不显著.3例复发均为室房递减传导者.本研究提示,心房激动长期经旁路下传致房室结功能废用性退化可能为室房分离的原因,旁路阻断后室房递减传导者应仔细检测以除外潜在的旁路逆传.     

Cure of Incessant Pacemaker Circus Movement Tachycardia by Radiofrequency Catheter Ablation

Ablation of Pacemaker Circus Movement Tachycardia. Introduction : Treatment of pacemaker circus movement tachycardia (PCMT) in patients with very long VA conduction times may present a problem.
Methods and Results : PCMT occurred in a 46-year-old woman with an uncommon AV nodal reentrant tachycardia who developed 2:1 AV block after fast pathway radiofrequency catheter (RF) ablation performed at another institution. Due to the long VA conduction time, PCMT could not be prevented by reprogramming the pacemaker or by the addition of antiarrhythmic drugs. Cure of the PCMT was obtained after selective RF ablation of the slow AV nodal pathway.
Conclusion : RF ablation of the retrograde conduction offers another alternative for treatment of PCMT.