Differential Entrainment Distinguishes Atrioventricular Nodal Reentry Tachycardia from Atrioventricular Reentrant Tachycardia

Background: Entrainment from the right ventricular (RV) apex and the base has been used to distinguish atrioventricular reentrant tachycardia (AVRT) from atrioventricular nodal reentry tachycardia (AVNRT). The difference in the entrainment response from the RV apex in comparison with the RV base has not been tested. Methods: Fifty‐nine consecutive patients referred for ablation of supraventricular tachycardia (SVT) were included. Entrainment of SVT was performed from the RV apex and base, pacing at 10–40‐ms faster than the tachycardia cycle length. SA interval was calculated from stimulus to earliest atrial electrogram. Ventricle to atrium (VA) interval was measured from the RV electrogram (apex and base) to the earliest atrial electrogram during tachycardia. The SA‐VA interval from apex and base was measured and the difference between them was calculated. Results: Thirty‐six AVNRT and 23 AVRT patients were enrolled. Mean age was 44 ± 12 years; 52% were male. The [SA‐VA]apex–[SA‐VA]base was demonstrable in 84.7% of patients and measured ?9.4 ± 6.6 in AVNRT and 10 ± 11.3 in AVRT, P < 0.001. The difference was negative for all AVNRT cases and positive for all septal accessory pathways (APs). Conclusion: The difference between entrainment from the apex and base is readily performed and is diagnostic for all AVNRTs and septal APs. (PACE 2010; 1335–1341)     

Histopathological Study Following Catheter Guided Radiofrequency Current Ablation of the Slow Pathway in a Patient with Atrioventricular Nodal Reentrant Tachycardia

The present study examined histological changes induced by catheter guided radiofrequency current in a patient with AV nodal reentrant tachycardia who underwent cardiac transplantation 1 week after ablation of the slow pathway. During the electrophysiology study AV nodal conduction curves were discontinuous and AV nodal reentry was induced. At the conclusion of the procedure there was no evidence of slow pathway function. Histological sections from the explanted heart demonstrated a sharply demarcated atrial lesion (5 × 5 × 4 mm) extending from the septal portion of the tricuspid annulus to the posterior border of the AV node. The lesion did not encompass the compact AV node. These observations support the hypothesis that the slow pathway is comprised of atrial approaches to the AV node and is distinct from the compact AV node.     

Upper and Lower Common Pathways in Atrioventricular Nodal Reentrant Tachycardia:

The concepts of upper and lower common pathways represent long-standing controversies of atrioventricular nodal reentrant tachycardia (AVNRT). Over the last years there has been considerable evidence against the presence of a lower and, especially, an upper common pathway as distinct entities that can be identified in most patients with atrioventricular reentrant tachycardia. The mechanism and relevance of these concepts remain speculative.     

Electrophysiological Behavior of Atrioventricular Node After Selective Fast or Slow Pathway Ablation in Patients with Atrioventricular Nodal Reentrant Tachycardia

One hundred twenty consecutive patients with symptomatic atrioventricular nodal reentrant tachycardia (AVNRT) underwent catheter ablation using radiofrequency energy. Fast pathway ablation was attempted in the first 16 consecutive patients by application of radiofrequency current in the anterior and superior aspect of the tricuspid annulus. Successful results were accomplished in 13 patients, complete atrioventricular (AV) block occurred in three. One hundred four patients underwent ablation of the slow pathway in the posterior and inferior aspect of the tricuspid annulus, which was successful in 98 patients. The remaining six patients subsequently underwent a fast pathway ablation with successful results in four and AV block in two. Therefore. 102 (98%) of the last 104 patients became free of AVNRT while maintaining intact AV conduction. This study characterizes the electrophysiological properties of the residual AV node following a selective fast or slow pathway ablation.     

Atrioventricular Nodal Physiology After Slow Pathway Ablation

The A V nodal physiology before and 1 week after “slow pathway potential” guided catheter ablation was examined in 32 patients with AV nodal reentrant tachycardia. A mean of 4.9 applications of radiofrequency energy eliminated AV nodal reentrant tachycardia in all patients. There were no significant differences in sinus cycle length (815 ± 159 msec vs 813 ± 162 msec;P = NS) and fast pathway conduction properties before and 1 week after ablation. Slow pathway conduction was completely eliminated in 10 (31%) (group I) of 32 patients after ablation. In the remaining 22 patients residual slow pathway conduction associated with one AV node echo was observed. In 15 patients (47%) (group II), the effective refractory period of the slow pathway showed a change of < 30 msec (265 ± 51 vs 266 ± 51 msec; P = NS), and in 7 patients (22%) (group III), a prolongation of more than 80 msec (247 ± 56 vs 340 ± 42 msec; P = 0.0001) before and 1 week after ablation. Minimal and maximal A₂-H₂ interval over the slow pathway in group II was not significantly changed (Min A₂-H₂:241 ± 37 vs 247 ± 40 msec; P = NS, Max A₂-H₂: 346 ± 79 vs 350 ± 60 msec; P = NS), while a significant prolongation was measured in group III (Min A₂-H₂: 261 ± 53 VS 373 ± 107 msec; P < 0.01. Max A₂-H₂: 359 ± 41 vs 427 ± 63 msec; P < 0.05) before and after ablation. Conclusion: In group II patients there was no evidence shown of impairment of the slow pathway. This suggests that disruption of the link between fast and slow pathways may be responsible for the elimination of AV nodal reentrant tachycardia, besides the elimination or impairment of the slow pathway itself, in “slow pathway potential” guided catheter ablation, and that the slow pathway potential may not necessarily represent activation of the slow pathway itself or of its atrial connection.     

Coincident Idiopathic Left Ventricular Tachycardia and Atrioventricular Nodal Reentrant Tachycardia: Control by Radiofrequency Catheter Ablation of the Slow Atrioventricular Nodal Pathway

A healthy 37-year-old male presented with a history of frequent palpitations and sustained wide QRS complex tachycardia with a right bundle branch block and left axis morphology. Serial electrophysiological studies revealed two inducible tachycardias, which were shown to represent atrioventricular nodal reentrant tachycardia and idiopathic left ventricular tachycardia. Transformation from one tachycardia to the other occurred spontaneously as well as following atrial or ventricular pacing. Radiofrequency catheter ablation of the slow atrioventricular nodal pathway resulted in cure of atrioventricular nodal reentrant tachycardia and the prevention of spontaneous recurrence of ventricular tachycardia, suggesting a role of atrioventricular nodal reentrant tachycardia in triggering the clinical episodes of ventricular tachycardia. The patient has remained asymptomatic without antiarrhythmic therapy for 8 months.     

Slow Potential-Guided Radiofrequency Catheter Ablation in Atrioventricular Nodal Reentrant Tachycardia: Characteristics of the Potential Associated with Successful Ablation

To examine the characteristics of Haïssaguerre's slow potential (SP) specific to effective catheter ablation of the slow pathway in AV nodal reentrant tachycardia, the properties of SP and its recording site ware analyzed in 52 patients who underwent successful SP-guided ablation. The properties of SP included the ratio of the amplitude of SP to that of atrial potential (A)(SP/A), the SP duration, the interval between His-bundle potential (HP) and SP (HP-SP), the interval between A and SP (A-SP), the interval between SP and ventricular potential (V) (SP-V), and the ratio of A-SP to the interval between A and the V (A-SP/A-V). The SP recording site was determined by the ratio of the amplitude of A to that of V (A/V) and by the relative position of the ablation catheter on X ray (right anterior oblique projection), expressed as the ratio of the distance between the coronary sinus ostium and SP site to that between the coronary sinus ostium and HP recording site (relative SP position). Twenty-eight slow pathways were ablated with a single energy application, while the other 24 required applications ≥ 2. In all successful applications, SP/A, SP duration, HP-SP, A-SP. SP-V, A-SP/A-V, A/V, and relative SP position were 51 %± 25%, 28 ± 5 ms, -11 ± 9 ms, 57 ± 25 ms, 68 ± 13 ms, 46%± 9%, 15%± 13%, and 51%± 13%, respectively. A significant correlation was observed between the relative SP position and A-SP, and between the relative SP position and A-SP/A-V (r = 0.60 and 0.37, respectively), while it was not between the relative SP position and HP-SP, nor between the relative SP position and SP-V. When the characteristics of SP were comparatively analyzed between the effective and ineffective applications in 24 patients in whom applications ≥ 2 were required, there was no difference observed in HP-SP, A-SP, SP-V, A-SP/A-V, and A/V. However, SP/A, SP duration, and the relative SP position in the effective applications were all greater than those in the ineffective ones (56%± 20% vs 35%± 18%, P < 0.001; 29 ± 4 vs 26 ± 5 ms, P < 0.01; and 52%± 15% vs 33%± 11%, P < 0.001, respectively). These results indicate that SP with an amplitude over a half of A amplitude and recorded at the mid-septum of the tricuspid annulus can be a marker for successful slow pathway ablation. Although the local atrial electrogram appears late as the SP recording site shifts to the lower position, the timing of SP relative to HP and V remained unchanged, suggesting that SP is independent of the local atrial activation.     

Ablation of Atrioventricular Nodal Reentrant Tachycardia in a Patient with Reversal of Slow and Fast Pathways Inputs into the Atrioventricular Node

We report a case of atrioventricular nodal reentrant tachycardia (AVNRT) coexistent with His bundle anomaly and atrial septal defects. The His‐bundle potential was recorded at the coronary sinus (CS) ostium. Fractionated atrial potentials and an A:V electrogram ratio 1:3 were recorded at the anterior septum of the tricuspid annulus approximately 2 cm from CS ostium. Radiofrequency catheter ablation at the anterior septum of the tricuspid annulus effectively eliminated AVNRT. (PACE 2012; 35:e17–e19)     

房室折返性心动过速合并房室结双径路的射频消融治疗

目的:探讨房室折返性心动过速(AVRT)合并房室结双径路(AVNDP)的电生理特征和射频消融术式的选择。方法:对640例阵发性室上性心动过速(PSVT)进行电生理检查,观察PSVT发作时传导的顺序,然后进行消融治疗。结果:640例PSVT中检出AVRT AVNDP 68例,检出率为10.6%;有8例诱发房室结折返性心动过速,对此类患者进行慢径消融治疗。随访所有经治患者均无复发。结论:AVRT合并AVNDP者阻断房室旁道是消融成功的关键;房室旁道作为"旁观者"时也应作房室旁道消融;如仅有(AH)跳跃但无心动过速者无需接受房室结改良。     

Analysis of Atrioventricular Nodal Reentrant Tachycardia with Variable Ventriculoatrial Block: Characteristics of the Upper Common Pathway

Background: The precise nature of the upper turnaround part of atrioventricular nodal reentrant tachycardia (AVNRT) is not entirely understood.
Methods: In nine patients with AVNRT accompanied by variable ventriculoatrial (VA) conduction block, we examined the electrophysiologic characteristics of its upper common pathway.
Results: Tachycardia was induced by atrial burst and/or extrastimulus followed by atrial-His jump, and the earliest atrial electrogram was observed at the His bundle site in all patients. Twelve incidents of VA block: Wenckebach VA block (n = 7), 2:1 VA block (n = 4), and intermittent (n = 1) were observed. In two of seven Wenckebach VA block, the retrograde earliest atrial activation site shifted from the His bundle site to coronary sinus ostium just before VA block. Prolongation of His-His interval occurred during VA block in 11 of 12 incidents. After isoproterenol administration, 1:1 VA conduction resumed in all patients. Catheter ablation at the right inferoparaseptum eliminated antegrade slow pathway conduction and rendered AVNRT noninducible in all patients.
Conclusion: Selective elimination of the slow pathway conduction at the inferoparaseptal right atrium may suggest that the subatrial tissue linking the retrograde fast and antegrade slow pathways forms the upper common pathway in AVNRT with VA block.     

Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in Children

Radiofrequency (RF) catheter ablation has been widely used in the treatment of cardiac arrhythmias. In atrioventricular nodal reentrant tachycardia (AVNRT), the experience has been predominantly in adults. The cardiac electrophysiological records of 18 consecutive children undergoing RF catheter AV node modification for AVNRT were reviewed. The patients (10 females, 8 males) were 8.2–17.9 years of age (mean 13.6 ± 3.0), weight 15.2–88.1 kg (mean 52.2 ± 20.8), and height 103–190 cm (mean 157.1 ± 21.7). Thirteen were on antiarrhythmic medications (1–3, average 1.5 drugs/day). All drugs were discontinued 48 hours prior to the ablations. The procedures were performed under sedation and local anesthesia. Pre- and post-AV node modification electrophysiological studies were performed in all procedures. The 18 patients underwent a total of 25 procedures (1.39 ± 0.61 per patient): the anterior approach aimed at the antegrade fast pathway in the first four patients and the posterior approach aimed at the slow pathway in the remainder. Thenumber of energy applications was 8–54 (19.8 ± 10.7) per procedure. The maximum energy used in each procedure was 30–50 watts (33.8 ± 8.4). The average energy was 24–50 watts (33.0 ± 6.8). The fluoroscopy time was 7.1–73.4 minutes (29.9 ± 20.0) per procedure, for a total catheterization time of 228–480 minutes (300.3 ± 59.1). Preablation spontaneous or induced AVNRT (cycle length 310.4 ± 55.0 msec) was seen in all except one who had the arrhythmia (cycle length 270 msec) on surface ECG. In 22 of 25 studies, the AH interval measured 67.4 ± 13.2 msec pre- and 98.7 ± 58.4 msec post-AV node modification (P < 0.02). Procedures were initially successful in 16 (89%) of 18 patients. One patient developed complete AV block requiring DDD pacemaker and has since recovered normal AV conduction. Transient third- or second-degree block was seen in four. Other complications included airway obstruction in one and excessive emesis in another. In follow-up of 2–26 months (13.0 ± 7.3), one patient underwent surgical ablation for failed initial RF catheter ablation, and two underwent successful RF procedures for recurrences. RF catheter AV node modification for AVNRT in children is a useful technique. Under ideal circumstances, it is safe and efficacious. Follow-up to determine the potential long-term complications is necessary.     

Effect of Pacing Site on the Atrial Electrogram at Target Sites for Slow Pathway Ablation in Patients with Atrioventricular Nodal Reentrant Tachycardia

Atrial electrograms recorded from target sites during radiofrequency catheter ablation of the slow atrioventricular (AV) nodal pathway are often fractionated and may be associated with a late, high frequency component (the slow pathway potential). The purpose of the current study was to assess the effects of slow pathway ablation on the morphology of the atrial electrogram and to determine whether target site electrograms display direction dependent changes in morphology during atrial pacing maneuvers. Twenty-six patients with typical AV nodal reentry had electrograms recorded from target sites before and after successful ablation of the slow A V nodal path way and during pacing from the high right atrium and distal coronary sin us at cycle lengths of 500 and 300 msec. There was no significant change in the duration or degree of fractionation of the atrial electrogram as the result of slow pathway ablation. In contrast, the duration and degree of fractionation were less when pacing from the coronary sinus compared with sinus rhythms or right atrial pacing. Pacing rate did not affect electrogram morphology. These data suggest that the morphology of the slow pathway target site electrogram is dependent on the direction of atrial activation and that the "slow pathway potential" does not represent activation of an anatomically discrete pathway.     

交界性心律在射频消融治疗房室结折返性心动过速中的临床意义

房室结折返性心动过速是临床上较为常见的一种快速性心律失常，射频消融技术是根治此类心律失常的首选方法，对慢径消融常选用中下位法，消融的终点为慢径消失，包括心房回波。与消融房室旁道的操作不同，房室结双径路的消融需要在窦性心律下放电，以保证整个放电过程中对正常房室传导功能的监测，在选择慢径消融时，有     

Shortcut Link Between the Fast and Slow Pathways and the Mechanism of Cure in Atrioventricular Nodal Reentrant Tachycardia by Catheter Ablation

The mechanism of cure in AV nodal reentrant tachycardia (AVNRT) by catheter ablation has not been fully clarified. We hypothesized that disruption of a shortcut link between the fast and slow pathways is responsible for the elimination of tachycardia. Results: AVNRT was eliminated in 20 patients by catheter ablation. In five patients (25%; group 1) slow pathway conduction disappeared 1 week after ablation. In six patients (30%; group II), the effective refractory period of the slow pathway was prolonged by more than 50 ms (212 ± 81 ms vs 340 ± 81 ms; P < 0.05). In the remaining nine patients (45%; group III), there was no change in the refractory period (270 ± 65 ms vs 273 ± 74 ms), although tachycardia was not inducible. A shortcut link between the fast and slow pathways was examined by comparing the A-H intervals over the slow pathway during the tachycardia and during atrial pacing at the tachycardia cycle length. Prior to ablation, a shortcut link was assumed in 1 of group I patients, 2 of group II patients, and 8 of group III patients. Of the 9 patients in whom the slow pathway was not impaired after ablation (group III), 8 patients were found to have a shortcut link, while 8 of 11 patients with impairment of the slow pathway after ablation (groups I and II) had no shortcut link between the fast and slow pathways (P < 0.05). Conclusion: In patients with a shortcut link between the fast and slow pathways, slow pathway conduction itself does not need to be impaired to eliminate the AVNRT, whereas in patients without this shortcut link, slow pathway conduction must be impaired.     

Atrioventricular Nodal Reentrant Tachycardia Ablation in the Setting of Bilateral Femoral Vein Occlusion

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common supraventricular tachycardia. Ablation of the slow pathway is the treatment of choice for recurrent episodes despite adequate medical therapy. We present an uncommon case of AVNRT ablation using a superior vena cava approach in a patient with bilateral common femoral vein occlusion. This approach appears to be a safe alternative in patients with an absence of an inferior venous access.     

Cryoablation versus Radiofrequency Ablation for Atrioventricular Nodal Reentrant Tachycardia: Patient Pain Perception and Operator Stress

Background: Cryoablation (CRYO) is an alternative to radiofrequency (RF) ablation in the treatment of atrioventricular nodal reentrant tachycardia (AVNRT). This study aims to evaluate the differences in patient pain perception and operator stress between CRYO and RF ablation in the treatment of AVNRT. Methods: Patients with supraventricular tachycardia underwent electrophysiology study. Twenty patients (eight males, age 46.5 ± 12.5 years) diagnosed with AVNRT were randomized to receive CRYO (11) with a 6‐mm‐tip catheter or RF (nine) with a 4‐mm‐tip catheter. Patients’ pain perception and operator stress were assessed with a visual analogue scale (VAS) from 0 to 10 at the end of procedure. Results: There was no significant difference in acute procedural success (CRYO 100% vs RF 89%, P = 0.257). There was no complication of permanent atrioventricular block in either group. The number of energy applications was significantly higher in the CRYO group (2.8 ± 1.2 vs 1.6 ± 0.9, P = 0.02). The fluoroscopic time was significantly reduced in the CRYO group (6.0 ± 4.9 vs 10.9 ± 5.4 minutes, P = 0.049) with no difference in procedure time (CRYO 49.3 ± 12.5 vs RF 54.5 ± 17.0 minutes, P = 0.462). Patients in the CRYO group experienced significantly less pain than patients in the RF group (VAS 2.3 ± 2.8 vs 5.4 ± 3.4, P = 0.024). The operator also experienced significantly less stress during CRYO than RF (VAS 1.9 ± 0.8 vs 6.2 ± 1.6, P < 0.001). There was no recurrence in both groups at 6‐month follow‐up. Conclusions: CRYO, as compared with RF, produces less pain in patients and less stress in operator in the treatment of AVNRT. (PACE 2011; 2–7)     

Atrial Ectopy Originating from the Posteroinferior Atrium During Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia

Atrial ectopy sometimes appears during RF ablation of the slow pathway in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its origin, characteristics, and significance are still unclear. To examine these issues, we analyzed 67 consecutive patients with AVNRT (60 with slow-fast AVNRT and 7 with fast-slow AVNRT), which was successfully eliminated by RF ablation to the sites with a slow potential in 63 patients and with the earliest activations of retrograde slow pathway conduction in 4 patients. During successful RF ablation, junctional ectopy with the activation sequence showing H-A-V at the His-bundle region appeared in 52 patients (group A) and atrial ectopy with negative P waves in the inferior leads preceding the QRS and the activation sequence showing A-H-V at the His-bundle region appeared in 15 patients (group B). Atrial ectopy was associated with (10 patients) or without junctional ectopy (5 patients). Before RF ablation, retrograde slow pathway conduction induced during ventricular burst and/or extrastimulus pacing was more frequently demonstrated in group B than in group A (9/15 [60%] vs 1/52 [2%], P < 0.001). Successful ablation site in group A was distributed between the His-bundle region and coronary sinus ostium, while that in group B was confined mostly to the site anterior to the coronary sinus ostium. In group B, atrial ectopy also appeared in 21% of the unsuccessful RF ablations. In conclusion, atrial ectopy is relatively common during slow pathway ablation and observed in 8% of RF applications overall and 22% of RF applications that successfully eliminated inducible AVNRT. Atrial ectopy appears to be closely related to successful slow pathway ablation among patients with manifest retrograde slow pathway function.     

Acute Radiation Dermatitis Following Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia

Radiation exposure during fluoroscopic imaging poses potential risks to patients and physicians, especially during protracted cardiovascular or radiological interventional procedures. We describe a woman with refractory paroxysmal supraventricular tachycardia who underwent radiofrequency catheter ablation of the slow pathway involved in atrioventricular nodal reentrant tachycardia. The patient subsequently returned 4 weeks later with acute radiation dermatitis that was retrospectively attributed to a malfunction in the fluoroscopy unit that lacked a maximum current output cut-off switch. Using dose reconstruction studies and her estimated biological response, we determined that she received between 15 and 20 Gy (1 Gy = 100 rods) to the skin on her back during the procedure. The exposure will result in an increase in her lifelong risk of skin and lung cancer. This article underscores the potential for radiation-induced injury during lengthy therapeutic procedures using x-ray equipment.