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.     

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.     

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.     

Preserved Autonomic Modulation of the Sinus and Atrioventricular Nodes Following Posteroseptal Ablation for Treatment of Atrioventricular Nodal Reentrant Tachycardia

Autonomic Control of the AV Node. Introduction : Following radiofrequency catheter ablation of AV nodal reentrant tachycardia (AVNRT), inappropriate sinus tachycardia may occur, possibly due to damage to autonomic cardiac nerve fibers. Furthermore, inducibility of AVNRT is often critically dependent on the autonomic balance. We investigated whether successful ablation of AVNRT is associated with an alteration of autonomic input to the sinus and AV nodes.
Methods and Results : To estimate changes in the automatic modulation of the sinus and AV nodes, power spectra of beat-to-beat PP and PR intervals were analyzed from high-quality nighttime ECG recordings of 11 patients before and after radiofrequency application. Normalized HF power (nHF) of PP and PR intervals was used as an index of efferent vagal modulation and the LF/HF ratio as an index of sympathovagal balance of the sinus node (PP) and AV node (PR). Before ablation, LF/HF_PP was 3.2 and nHF_PP was 0.3 in the sinus node, For the A/V node, LF/HF_PR was 1.2 and nHF^PR was 0.5. Following ablation. LF/HF_PP (3.5) and nHF_PP (0.3) of the PP intervals did not change. Similarly to the sinus node, there were no changes in the autonomic modulation of the AV node, as both LF/HF_PR (1.2) and nHF_PR (0.5) remained unchanged.
Conclusion : Our results indicate that autonomic control of the sinus und AV nodes is preserved following successful radiofrequency ablation of AVNRT. The effects of posteroseptal radiofrequency current application are not necessarily mediated by changes in the autonomic input to the 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.     

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.     

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.     

Differential Effect of Adenosine on Anterograde and Retrograde Fast Pathway Conduction in Patients with Atrioventricular Nodal Reentrant Tachycardia

Adenosine and Retrograde Fast Pathway Conduction . Introduction : Several studies have shown that the fast pathway is more responsive to adenosine than the slow pathway in patients with AV nodal reentrant tachycardia. Little information is available regarding the effect of adenosine on anterograde and retrograde fast pathway conduction.
Methods and Results : The effects of adenosine on anterograde and retrograde fast pathway conduction were evaluated in 116 patients (mean age 47 ± 16 years) with typical AV nodal reentrant tachycardia. Each patient received 12 mg of adenosine during ventricular pacing at a cycle length 20 msec longer than the fast pathway VA block cycle length and during sinus rhythm or atrial pacing at 20 msec longer than the fast pathway AV block cycle length. Anterograde block occurred in 98% of patients compared with retrograde fast pathway block in 62% of patients ( P < 0.001). Unresponsiveness of the retrograde fast pathway to adenosine was associated with a shorter AV block cycle length (374 ± 78 vs 333 ± 74 msec, P < 0.01), a shorter VA block cycle length (383 ± 121 vs 307 ± 49 msec, P < 0.001), and a shorter VA interval during tachycardia (53 ± 23 vs 41 ± 17 msec, P < 0.01).
Conclusion : Although anterograde fast pathway conduction is almost always blocked by 12 mg of adenosine, retrograde fast pathway conduction is not blocked by adenosine in 38% of patients with typical AV nodal reentrant tachycardia. This indicates that the anterograde and retrograde fast pathways may be anatomically and/or functionally distinct. Unresponsiveness of VA conduction to adenosine is not a reliable indicator of an accessory pathway.     

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.     

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.     

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.     

房室结折返性心动过速患者房室结功能曲线连续性的电生理分析

分析房室结折返性心动过速 (AVNRT)中房室结功能曲线呈连续性者的电生理特点。将AVNRT分为房室结功能曲线连续组 (Ⅰ组 )及房室结功能曲线不连续组 (Ⅱ组 ) ,行慢径消融 ,进行消融前后和组间的电生理比较 ,分析房室结功能曲线呈连续性者的特点。结果 :I组心房程序刺激对AVNRT的诱发率仅 42 % (5 / 12 ) ,低于Ⅱ组的 6 6 %(2 3/ 35 )。Ⅰ组房室结前传有效不应期 (ERP AVN)消融前后无显著变化 (2 18.2± 2 9.3msvs 2 5 3.3± 80 .3ms,P >0 .0 5 ) ;心房程序刺激最长A2 H2 间期 (AHmax)消融前后无显著变化 (2 2 5 .8± 71.8msvs 175 .4± 41.9ms,P >0 .0 5 )。Ⅱ组ERP AVN消融后显著延长 (2 78.9± 5 8.9msvs 2 35 .8± 39.6ms,P <0 .0 5 ) ;AHmax消融后显著缩短 (172 .0± 6 7.1msvs 331.6± 86 .6ms ,P <0 .0 5 ) ;消融后房室结快径前传有效不应期 (ERP FP)显著缩短 (2 78.9± 5 8.9msvs 330 .0±5 5 .3ms,P <0 .0 5 )。消融前Ⅰ组AHmax短于Ⅱ组 (P <0 .0 5 ) ,Ⅰ组心动过速时A2 H2 间期 (AHSVT)与消融前AHmax比较差异无显著性 (P >0 .0 5 ) ;Ⅱ组AHSVT短于消融前AHmax(P <0 .0 5 )。结论 :房室结功能曲线连续性者较难经常规心房程序刺激诱发心动过速 ;慢径消融后曲线“尾巴”消失可作为消融终点的一项指     

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.     

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.     

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。     

A Quantitative Fluoroscopic Comparison of the Coronary Sinus Ostium in Patients With and Without AV Nodal Reentrant Tachycardia

Coronary Sinus Ostium. Introduction : The purpose of this study was to perform a quantitative fluoroscopic analysis of the coronary sinus ostium and its relationship to the His bundle in patients with and without AV nodal reentrant tachycardia. Sites of slow pathway ablation are often near the coronary sinus ostium, which can be located within a few millimeters of the His bundle. Whether such close proximity of the coronary sinus ostium to the His bundle is unique to patients with AV nodal reentrant tachycardia is unknown.
Methods and Results : Fifty consecutive patients (mean age 39 ± 14 years) with no structural heart disease underwent electrophysiologic testing and radiofrequency ablation. The study group consisted of 28 patients with inducible AV nodal reentrant tachycardia or dual AV nodal physiology and 22 patients in the control group. A coronary sinus venogram was performed in each patient. The coronary sinus ostium was similar in size in the study group (11.4 ± 4.5 mm) and in the control group (10.5 ± 3.6 mm, P = 0.2). The coronary sinus ostium was funnel shaped in half of the study patients and in half of the control patients (P = 1.0). The mean distance from the upper lip of the coronary sinus ostium to the tip of the His bundle catheter was 9.7 ± 5.5 mm in the study group and 10.4 ± 5.1 mm in the control group (P = 0.7). The mean distance from the lower lip of the coronary sinus ostium to the tip of the His-bundle catheter in the study group was 20.1 ± 6.1 mm and 19.5 ± 5.6 mm in the control group (P =0.7).
Conclusion : This study demonstrates a wide range of normal coronary sinus ostium diameters, morphology, and anatomic relationships with surrounding structures, with no demonstrable correlation to the presence or absence of dual AV node physiology or AV nodal reentrant tachycardia.     

P Wave Dispersion Predicts Recurrence of Paroxysmal Atrial Fibrillation in Patients with Atrioventricular Nodal Reentrant Tachycardia Treated with Radiofrequency Catheter Ablation

Background: Paroxysmal atrial fibrillation (AF) recurs in up to one‐third of patients with atrioventricular nodal reentrant tachycardia (AVNRT) treated with slow pathway ablation. Therefore, identification of patients at risk for recurrence of AF after slow pathway ablation is important because of the necessity for additional therapies. The purpose of this study was to determine whether successful slow pathway ablation influences P wave parameters and whether these parameters predict the recurrence of paroxysmal AF in patients with both AVNRT and paroxysmal AF after ablation. Methods: Thirty‐six patients with AVNRT and documented paroxysmal AF (Group 1) were compared to 36 age‐matched controls with AVNRT only (Group 2). P wave durations and P dispersion were measured before and after ablation. Results: No significant differences were observed between P wave parameters observed before and after ablation. Maximum P wave durations (Pmax) and P dispersion (Pdisp) were significantly higher in Group 1 than in Group 2 (P < 0.001 for both) whereas minimum P wave durations did not differ between groups, both before and after ablation. Ten patients (28%) in Group‐1 had recurrence of AF during a mean follow‐up of 34 ± 11 months. Univariate predictors of AF recurrence were Pdisp ≥35.5 ms (P < 0.010), left atrial diameter >40 mm (P < 0.010), mitral or aortic calcification (P < 0.010), Pmax ≥112 ms (P < 0.050), valvular heart disease (P < 0.050), and atrial vulnerability (induction of AF lasting >30 second) after ablation (P < 0.050). However, only Pdisp ≥35.5 ms (P < 0.050) and left atrial diameter >40 mm (P < 0.010) were independent predictors of AF recurrences. Conclusion: This study suggests that P wave dispersion could identify patients with AVNRT susceptible to recurrence of AF after slow pathway ablation.     

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.