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.     

Radiofrequency Catheter Ablation of a Posteroseptal Accessory Pathway along the Morphologic Tricuspid Valve in a Patient with Congenitally Corrected Transposition of the Great Arteries and Complete Atrioventricular Block

We report a patient with Congenitally Corrected Transposition of the Great Arteries, complete atrioventricular block and a posteroseptal accessory pathway across the morphologic tricuspid valve. Ablation of the accessory pathway was performed for her symptomatic palpitations.     

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.     

Corrected Transposition of the Great Arteries, Common Atrioventricular Valve, and Dextrocardia

Corrected transposition of the great arteries with a common atrioventricular valve is a rare congenital anomaly. In the presence of two well-defined, atrioventricular valves, cross-sectional echocardiography is the method of choice for the diagnosis of this cardiac defect. The presence of a common atrioventricular valve can be a limitation of the method. Angiocardiography provides additional information for the diagnosis. (ECHOCARDIOGRAPHY, Volume 8, September 1991)     

Successful Percutaneous Ablation of Ventricular Tachycardia in Congenitally Corrected Transposition of the Great Arteries, a Case Report

Ventricular tachycardia (VT) is rarely recognized in patients with congenitally corrected transposition of the great arteries (CCTGA). We describe a 48-year-old woman with CCTGA, systemic atrioventricular valve replacement for Ebsteinoid malformation of the valve, ventricular dysfunction and ventricular tachycardia related to the previous surgical scar. The patient had successful non-contact mapping and radiofrequency ablation of the offending tachycardia substrate.     

Slowing of the Ventricular Rate During Atrial Fibrillation by Ablation of the Slow Pathway of AV Nodal Reentrant Tachycardia

Influence of Slow Pathway Ablation on Atrial Fibrillation. Introduction : The mechanisms whereby radiofrequency catheter modification of AV nodal conduction slows the ventricular response are not well defined. Whether a successful modification procedure can be achieved by ablating posterior inputs to the AV node or by partial ablation of the compact AV node is unclear. We hypothesized that ablation of the well-defined slow pathway in patients with AV nodal reentrant tachycardia would slow the ventricular response during atrial fibrillation.
Methods and Results : In 34 patients with dual AV physiology and inducible AV nodal reentrant tachycardia, atrial fibrillation was induced at baseline and immediately after successful slow pathway ablation and at 1-week follow-up. The minimal, maximal, and mean RR intervals during atrial fibrillation increased from 353 ± 76,500 ± 121, and 405 ± 91 msec to 429 ± 84 (P < 0.01), 673 ± 161 (P < 0.01), and 535 ± 98 msec (P < 0.01), respectively. These effects remained stable during follow-up at 1 week. The AV block cycle length increased from 343 ± 68 msec to 375 ± 60 msec (P < 0.05) immediately and to 400 ± 56 msec (P < 0.01) at 1-week follow-up. The effective refractory period of the AV node prolonged from 282 ± 83 msec to 312 ± 89 msec and to 318 ± 81 msec after 1 week (P < 0.05), respectively.
Conclusion : This study shows a decrease in ventricular response to pacing-induced atrial fibrillation after ablation of the slow pathway in patients with AV nodal reentrant tachycardia. Since the AV nodal conduction properties could be defined, this study supports the hypothesis that the main mechanism of AV nodal modification in chronic atrial fibrillation is caused by ablation of posterior inputs to the AV node.     

Case Report: Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia in a Patient with Heart Transplantation

Ten years after orthotopic cardiac transplantation, a 56-year-old man developed recurrent presyncope and syncope. A 24-hour ambulatory electrocardiographic recording did not document significant arrhythmic events. A head-up tilt table test was negative. An electrophysiologic study revealed dual atrioventricular (AV) nodal physiology and inducible typical atrioventricular nodal reentrant tachycardia (AVNRT). The patient became hypotensive and presyncopal during AVNRT. Radiofrequency (RF) catheter ablation successfully eliminated AVNRT without complications. The patient remained free of symptoms at nine months follow-up.     

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.     

Radiofrequency Catheter Ablation of Atrioventricular Nodal Reentrant Tachycardia after Orthotopic Heart Transplantation

Patients with orthotopic heart transplantation may develop a variety of arrhythmias. Successful radiofrequency catheter ablation for tachyarrhythmias from manifest and concealed accessory bypass tracts in transplant patients has been previously reported. We present a patient with orthotopic heart transplantation who developed typical atrioventricular nodal tachycardia, which was successfully treated by radiofrequency catheter ablation.     

Electrophysiologic Spectrum of Atrioventricular Nodal Behavior in Patients with Atrioventricular Nodal Reentrant Tachycardia Undergoing Selective Fast or Slow Pathway Ablation

AV Nodal Behavior After Ablation. Introduction; The objective of this report is to delineate the atrioventricular (AV) nodal electrophysiologic behavior in patients undergoing fast or slow pathway ablation for control of their AV nodal reentrant tachycardia (AVNRT).
Methods and Results: One hundred sixteen consecutive patients with symptomatic AVNRT were included. Twenty-two patients underwent fast pathway ablation with complete abolition of AVNRT in all and development of complete AV block in five patients. Of 17 patients with intact AV conduction postablation, 12 had demonstrated antegrade dual pathway physiology during baseline study, which was maintained in three and lost in nine patients postablation. Two patients with successful fast pathway ablation developed uncommon AVNRT necessitating a slow pathway ablation. Twenty-one patients demonstrated both common and uncommon forms of AV nodal reentry during baseline study. The earliest site of atrial activation was close to the His-bundle recording site (anterior interatrial septum) during common variety and the coronary sinus ostium (posterior interatrial septum) during the uncommon AV nodal reentry in all 21 patients. Ninety-six patients underwent successful slow pathway ablation. Among these, the antegrade dual pathway physiology demonstrable during baseline study (60 patients) was maintained in 25 and lost in 35 patients postablation.
Conclusion: These data suggest that: (1) dual pathway physiology may persist after successful ablation, which might be a reflection of multiple reentrant pathways in patients with AVNRT: and (2) the retrograde pathways during common and uncommon AVNRT have anatomically separate atrial breakthroughs. These findings have important electrophysiologic implications regarding the prevailing concept of the AV nodal physiology in patients with AVNRT.     

Persistence of Single Echo Beat Inducibility After Selective Ablation of the Slow Pathway in Patients with Atrioventricular Nodal Reentrant Tachycardia:

Residual Slow Pathway Conduction Effects on AVN Function. Introduction : Residual slow pathway conduction with or without reentrant echo beats has been reported in 25% to 30% of patients undergoing ablation for AV nodal reentrant tachycardia (AVNRT).
Methods and Results : Fifty-eight consecutive patients (aged 45 ± 12 years) with slow-fast AVNRT underwent radiofrequency catheter ablation of the slow AV nodal pathway (SP). Residual slow-fast echo beat was documented in 21 (36%) of 58 patients (group A). The pre-and postablation AH intervals triggering the echo beats were similar (346 ± 8 msec vs 352 ± 6 msec, P = NS), as were the pre-and postablation echo zones (55 ± 6 msec vs 52 ± 5 msec, P = NS) and functional refractory period of the SP. A consistent prolongation of the AV nodal effective refractory period (AVN-ERP; from 265 ± 28 msec to 340 ± 50 msec, P < 0.001) and the Wenckebach cycle length (WBCL; from 298 ± 41 msec to 438 ± 43 msec, P < 0.001) was observed in all patients with abolition of SP conduction (group B). In group A patients, the prolongation of WBCL was less (285 ± 33 msec preablation, and 334 ± 41 msec postablation, P < 0.001). Additional pulses abolished the residual echo in 16 of 21 patients, and further prolongation of the AVN-ERP and WBCL comparable to those found in patients without a residual echo beat was observed. During 19 ± 8 months follow-up, no patient had clinical recurrence of AVNRT.
Conclusion : Residual single echo beat after SP ablation for AVNRT reflects the persistence of some portion of the SP with unchanged functional conduction properties whose prognostic significance is uncertain. A consistent increase of WBCL can be a reliable marker of complete abolition of slow pathway conduction and termination of AVNRT.     

Atrioventricular Nodal Reentrant Tachycardia with Paroxysmal Atrial Fibrillation: Clinical and Electrophysiological Features and Predictors of Atrial Fibrillation Recurrence Following Elimination of Atrioventricular Nodal Reentrant Tachycardia

Introduction: Clinical and electrophysiological characteristics of patients with atrioventricular nodal reentrant tachycardia (AVNRT) and paroxysmal atrial fibrillation (AF) have not been studied in a large patient cohort. We aimed to define the clinical features and cardiac electrophysiological characteristics of these patients, and to examine the incidence and identify predictors of AF recurrences after elimination of AVNRT. Methods and Results: Thirty-six patients with AVNRT and documented paroxysmal AF (Group 1) and 497 patients with AVNRT alone undergoing ablation in the same period (Group 2) were studied. There were no significant differences between groups regarding clinical features, except age, which was higher in Group 1 (p < 0.001). Presence of atrial vulnerability (induction of AF lasting > 30 seconds) and multiple AH jumps (≥50 ms) before ablation were significantly more prevalent in Group 1 (p < 0.001, p = 0.010 respectively). During follow-up of 34 ± 11 months, AF recurred in 10 patients (28%) in Group 1, while 2 patients in Group 2 (0.4%) developed paroxysmal AF (p < 0.001). Univariate predictors of AF were: left atrial diameter > 40 mm (p = 0.001), presence of mitral or aortic calcification (p = 0.003), atrial vulnerability after ablation (p = 0.015) and valvular disease (p = 0.042). However, independent predictors of AF recurrences were left atrial diameter > 40 mm (p = 0.002) and the presence of atrial vulnerability after ablation (p = 0.034). Conclusion: In patients with both AVNRT and paroxysmal AF, the recurrence rate of AF after elimination of AVNRT is 28%. Left atrial diameter greater than 40 mm and atrial vulnerability after elimination of AVNRT are independent predictors of AF recurrences in the long term.     

射频消融慢径后心动过速复发与房室结电生理特性变化的关系

为揭示房室结折返性心动过速（ＡＶＮＲＴ）复发的机制，对４５例射频消融治疗成功的慢－快型ＡＶＮＲＴ患者在消融术前、术后即刻及术后逾三个月行电生理检查。结果１０例复发（复发组）。复发组术前心房早搏刺激时的最大心房－Ｈｉｓ束间期（Ａ２Ｈ２ｍａｘ）较非复发组明显延长（４１３±６０ｍｓｖｓ３１１±１１０ｍｓ，Ｐ＜０．０１）；两组术后即刻Ａ２Ｈ２ｍａｘ较术前均明显缩短（Ｐ均＜０．０１）；术后三个月复发组的Ａ２Ｈ２ｍａｘ较术后即刻明显延长（３５６±９３ｍｓｖｓ２９８±９６ｍｓ，Ｐ＜０．０５），非复发组则有进一步缩短趋势，两组术后三个月的Ａ２Ｈ２ｍａｘ比较有显著性差异（３５６±９３ｍｓｖｓ２２２±７３ｍｓ，Ｐ＜０．００５）；非复发组术后三个月Ａ２Ｈ２ｍａｘ较术前明显缩短（２２２±７３ｍｓｖｓ３１１±１１０ｍｓ，Ｐ＜０．０１），房室结前传文氏周期及有效不应期较术前明显延长（４０５±９１ｍｓｖｓ３６６±８４ｍｓ，３３２±７５ｍｓｖｓ２６９±６３ｍｓ，Ｐ＜０．０１及＜０．０００１），复发组消融术前后比较差异则无显著性。结果提示部分ＡＶＮＲＴ复发可能与其房室结本身电生理特性有关，基础状态下Ａ２Ｈ２ｍａｘ长的患者心动过速更易复发。     

Elimination of AV Nodal Reentrant Tachycardia with 2:1 VA Block by Posteroseptal Ablation

AV Nodal Reentrant Tachycardia. AV nodal reentry capable of VA block during tachycardia was successfully eliminated using a posteroseptal ablation pulse delivered well away from the site of earliest atrial activation during tachycardia. A possible explanation is that the arrhythmia represented typical AV nodal reentrant tachycardia with transient intra atrial conduction block during tachycardia.     

Atrioventricular Nodal Reentrant Tachycardia with Advanced Infra-Hisian Atrioventricular Block

We report a case of 78-year-old man admitted to the hospital due to palpitations and lightheadedness. On EKG advanced atrioventricular block with ventricular rate of 37 beats per minute was noted. On electrophysiology study a common type of atrioventricular nodal reentrant tachycardia was inducible with maintenance of advanced AV block. Radiofrequency ablation of slow pathway followed by placement of a permanent pacemaker resulted in elimination of tachycardia and resolution of symptoms.     

Dimension and Related Anatomical Distance of Koch's Triangle in Patients with Atrioventricular Nodal Reentrant Tachycardia

Koch's Triangle in AVNRT. Introduction: The dimension of Koch's triangle in patients with AV nodal reentrant tachycardia has not been well described. Understanding the dimension and anatomical distance related to Koch's triangle might be useful in avoiding accidental AV block during ablation of the slow pathway. The purposes of this study were to define the dimension of Koch's triangle and its related anatomical distance and correlate these parameters with the successful ablation sites in patients with AV nodal reentrant tachycardia. Methods and Results: We studied 218 patients with AV nodal reentrant tachycardia. The distance between the presumed proximal His-bundle area and the base of the coronary sinus orifice (D_His-Os) measured in the right anterior oblique view was used to define the dimension of Koch's triangle. The distance of the proximal His-bundle recording site from the successful ablation site (D_His-Ab) and the distance as a fraction of the entire length of Koch's triangle (D_His-Ab/D_His-Os) were determined. The mean D_His-Os, and D_His-Ab were 25.9 ± 7.9 and 13.4 ± 3.8 mm, respectively. D_His-os negatively correlated with patient age (r = -0.41, P < 0.0001) and body mass index (r = -0.18, P = 0.004). Among the patients with successful ablation sites in the medial area, D_His-Os was longer (27.2 ± 6.6 vs 24.6 ± 8.4 mm, P < 0.005), D_His–Ab was similar (12.9 ± 3.1 vs 13.9 ± 4.0, P > 0.05) and D_His-Ab/D_His-Os was smaller (0.48 ± 0.04 vs 0.74 ± 0.11, P < 0.05). Furthermore, the patients with successful ablation sites in the medial location needed more radiofrequency pulse numbers than those in the posterior location (6 ± 4 vs 4 ± 3, P < 0.05). Conclusion: The site of successful slow pathway ablation was consistently about 13 mm from the site recording the proximal His-bundle deflection in patients with AV nodal reentrant tachycardia despite marked variability in the dimensions of Koch's triangle: therefore, patients with large triangles required ablation in the medial region rather than the posterior region. Care should be taken when delivering radiofrequency energy to the posteroseptal area in patients with shorter D_His-Os to avoid injury to AV node.     

AV Nodal Reentrant Tachycardia with Unusual Characteristics:

AV Nodal Reentrant Tachycardia. There are still some AV nodal reentrant tachycardias with unusual AV nodal properties that need further study to understand these complexities. Accordingly, the two-dimensional model with alpha and beta pathways in the AV nodal reentrant tachycardia circuit certainly is an oversimplification and does not explain adequately the anatomic and physiologic complexity of the AV junctional area. The modern concept suggests that this arrhythmia takes place in a highly complex three-dimensional model with nonuniform anisotropy and discontinuous conduction property in the AV junctional area. Application of radiofrequency energy within the AV Junctional area should always he performed carefully to achieve a successful ablation procedure and to minimize possible injury of AV nodal conduction.     

The Electrophysiologic Characteristics in Patients with Only Ventricular-Pacing Inducible Slow–Fast Form Atrioventricular Nodal Reentrant Tachycardia

Background: Atrioventricular nodal reentrant tachycardia (AVNRT) can be usually induced by atrial pacing or extrastimulation. However, it is less commonly induced only by ventricular pacing or extrastimulation. Objective: The purpose of this retrospective study was to investigate the electrophysiologic characteristics in patients with slow–fast form AVNRT that could be induced only by ventricular pacing or extrastimulation. Methods: The total population was 1497 patients associated with AVNRT. There were 1373 (91.7%) patients who had slow–fast form AVNRT included in our study. Group 1 (n = 45) could be induced only by ventricular pacing or extrastimulation, and Group 2 (n = 1328) could be induced by only atrial stimulation or both atrial and ventricular stimulation. The electrophysiologic characteristics of the group 1 and group 2 patients were compared. Results: Group 1 patients had a significantly lower incidence of both antegrade and retrograde dual AV nodal pathways. The pacing cycle length (CL) of the antegrade 1:1 fast pathway (FP) and antegrade ERP of the FP were both significantly shorter in Group 1 patients. Mean antegrade FRP of the fast and slow pathways were significantly shorter in Group 1 patients. The differences of pacing CL of 1:1 antegrade conduction, antegrade ERP and FRP were much longer in Group 2 patients. Conclusion: This study demonstrated the patients with slow–fast form AVNRT that could be induced only by ventricular stimulation had a lower incidence of dual AV nodal pathways and the different electrophysiologic characteristics (shorter pacing CL of the antegrade 1:1 FP, antegrade ERP of the FP and the differences of pacing CL of 1:1 antegrade conduction, antegrade ERP and FRP) from the other patients. The specific electrophysiologic characteristics in such patients could be the reason that could be induced only by ventricular stimulation.     

Double Retrograde Atrial Response After Radiofrequency Ablation of Typical AV Nodal Reentrant Tachycardia

Double Atrial Response. This case report describes a patient in whom a single ventricular depolarization resulted in a double atrial response and the initiation of atypical A V nodal reentrant tachycardia after successful radiofrequency ablation of typical AV nodal reentrant tachycardia using the slow pathway approach. (J Cardiovasc Electrophysiol, Vol. 4, pp. 695–701, December 1993)     

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.