Is Vagal Innervation to the Atrioventricular Node Impaired After Radiofrequency Ablation of the Slow Atrioventricular Nodal Pathway?

To assess the potentially adverse effects of RF catheter ablation (RFCA) of the slow AV nodal pathway on the parasympathetic innervation to the AV node in patients with AV nodal reentrant tachycardia (AVNRT), AV nodal conduction was evaluated following vagal stimulation by means of a phenylephrine bolus injection (200 μg) before and after RFCA in ten patients (mean age, 37 ± 14 years). Nine patients with AV reentrant tachycardia (AVRT) due to a left free wall accessory pathway served as a control group (mean age of 37 ± 12 years). Whereas no prolongation of the AH interval was observed in the AVNRT group following the phenylephrine bolus during sinus rhythm, despite a significant slowing in sinus rate, phenylephrine administration in AVRT patients was associated with both slowing of the sinus rate and prolongation of the AH interval. Following successful RFCA, the same responses were observed. To delineate the indirect effect of heart rate on AV conduction in response to the phenylephrine bolus, the AH interval was also measured during fixed atrial pacing. A marked prolongation of the AH interval occurred in both groups following phenylephrine administration. This prolongation was biphasic in 50% of A VNRT patients before ablation, suggesting a predominant effect of vagal stimulation on the fast AV nodal pathway. RFCA was associated with disappearance of discontinuous AV conduction in all but one patient with AVNRT. Vagal stimulation caused the same amount of AH interval prolongation as before RFCA in both study groups. In conclusion, patients with AVNRT have a preserved modulation of AV nodal conduction in response to vagal stimulation during sinus rhythm. In addition, vagal stimulation seems to exert a predominant effect on the fast A V nodal pathway. RFCA of the slow AV nodal pathway in patients with A VNRT does not cause detectable damage to the vagal innervation to the AV node.     

Usefulness of Intravenous Propofol Anesthesia for Radiofrequency Catheter Ablation in Patients with Tachyarrhythmias: Infeasibility for Pediatric Patients with Ectopic Atrial Tachycardia

General anesthesia is sometimes required during radiofrequency catheter ablation (RFCA) of various tachyarrhythmias because of an anticipated prolonged procedure and the need to ensure stability during critical ablation. In this study, we examine the feasibility of using propofol anesthesia for RFCA procedure. There were 150 patients (78 male, 72 female; mean age 30 years, range 4-96 years) in the study. Electrophysiologic study was performed before and during propofol infusion in the initial 20 patients and was performed only during propofol infusion in the remaining 130 patients. In the initial 20 patients, propofol infusion increased the sinus rate and facilitated AV nodal conduction. The accessory pathway effective refractory period, as well as the sinus node recovery time, atrial effective refractory period, and ventricular effective refractory period were not significantly changed. There were 152 tachyarrhythmias in 150 patients (24 atrial flutter, 31 AV nodal reentrant tachycardia, 68 AV reciprocating tachycardia, 12 ventricular tachycardia, and 17 atrial tachycardia). Most (148/152) tachycardias remained inducible after anesthesia and RFCA was performed uneventfully. However, in four of the seven pediatric patients with ectopic atrial tachycardia, the tachycardia terminated after propofol infusion and could not be induced by isoproterenol infusion. Consequently, RFCA could not be performed. Intravenous propofol anesthesia is feasible during RFCA for most tachyarrhythmias except for ectopic atrial tachycardia in children.     

Electrophysiological characteristics of junctional rhythm during ablation of the slow pathway in different types of atrioventricular nodal reentrant tachycardia

BACKGROUND: Junctional rhythm (JR) is commonly observed during radiofrequency (RF) ablation of the slow pathway for atrioventricular (AV) nodal reentrant tachycardia. However, the atrial activation pattern and conduction time from the His-bundle region to the atria recorded during JR in different types of AV nodal reentrant tachycardia have not been fully defined. METHODS: Forty-five patients who underwent RF ablation of the slow pathway for AV nodal reentrant tachycardia were included; 27 patients with slow-fast, 11 patients with slow-intermediate, and 7 patients with fast-slow AV nodal reentrant tachycardia. The atrial activation pattern and HA interval (from the His-bundle potential to the atrial recording of the high right atrial catheter) during AV nodal reentrant tachycardia (HA(SVT)) and JR (HA(JR)) were analyzed. RESULTS: In all patients with slow-fast AV nodal reentrant tachycardia, the atrial activation sequence recorded during JR was similar to that of the retrograde fast pathway, and transient retrograde conduction block during JR was found in 1 (4%) patient. The HA(JR) was significantly shorter than the HA(SVT) (57 +/- 24 vs 68 +/- 21 ms, P < 0.01). In patients with slow-intermediate AV nodal reentrant tachycardia, the atrial activation sequence of the JR was similar to that of the retrograde fast pathway in 5 (45%), and to that of the retrograde intermediate pathway in 6 (55%) patients. Transient retrograde conduction block during JR was noted in 1 (9%) patient. The HA(JR) was also significantly shorter than the HA(SVT) (145 +/- 27 vs 168 +/- 29 ms, P = 0.014). In patients with fast-slow AV nodal reentrant tachycardia, retrograde conduction with block during JR was noted in 7 (100%) patients. The incidence of retrograde conduction block during JR was higher in fast-slow AV nodal reentrant tachycardia than slow-fast (7/7 vs 1/11, P < 0.01) and slow-intermediate AV nodal reentrant tachycardia (7/7 vs 1/27, P < 0.01). CONCLUSIONS: In patients with slow-fast and slow-intermediate AV nodal reentrant tachycardia, the JR during ablation of the slow pathway conducted to the atria through the fast or intermediate pathway. In patients with fast-slow AV nodal reentrant tachycardia, there was no retrograde conduction during JR. These findings suggested there were different characteristics of the JR during slow-pathway ablation of different types of AV nodal reentrant tachycardia.     

室上性心动过速射频消融疑难病例分析

目的：分析６例特殊疑难射频消融病例,探讨安全有效的消融策略。方法：３例为右侧旁道,其中１例为右侧显性旁道,术中导管机械刺激诱发心房颤动,采用单极标测消融成功．另２例为右侧隐匿性旁道,采用“窦－室－窦”标测法,于窦律下放电阻断旁道。２例左侧隐匿性旁道,其中１例为房室折返性心动过速伴终止时长时间窦性停搏,反复晕厥,即“快一慢”型室上性心律失常,射频消融后,其伴随症状也消失．另１例为左后间隔隐匿性慢传导旁道,测△ＨＡ为３２ｍｓ,得以确诊。１例为慢一快型房室结折返性心动过速,胸廓畸形,心血管严重移位．导管操作困难。结果：所有患者均消融成功。结论：特殊类型疑难病例消融成功的关键是,根据各自特殊的电生理和解剖特点,采取针对性消融策略。     

The Role of Isoproterenol Testing Following Radiofrequency Catheter Ablation of Accessory Pathways in Children

LIBERMAN, L., et al .: The Role of Isoproterenol Testing Following Radiofrequency Catheter Ablation of Accessory Pathways in Children. Isoproterenol (ISO) testing following radiofrequency catheter ablation (RFCA) of accessory pathways (APs) in children is often performed to assess efficacy. However, its role in postablative testing for this indication has not been previously studied. In view of a recent national shortage of ISO, this study reviewed the results of ISO testing in pediatric patients after acutely successful RFCA to evaluate its role in postablative testing. Seventy patients (median age 13.0 years, range 2.8–24 years) underwent acutely successful RFCA for APs. If AP conduction was not present and tachycardia was not inducible with programmed stimulation 30 minutes following RFCA, repeat testing was performed during continuous infusion ISO. ISO infusion resulted in the induction of arrhythmias in 3 (4%) of 70 patients that required further ablative therapy. None of these patients had inducible arrhythmias or AP conduction during postablative testing without ISO infusion. One patient, with the permanent form of junctional reciprocating tachycardia (PJRT), had persistence of AP conduction requiring further RFCA applications. Two patients had inducible AV nodal reentrant tachycardia (AVNRT) that was treated with slow pathway modification. At a median follow-up of 7.3 months, two (3%) patients had recurrence of tachycardia. These patients did not have inducible tachycardia, AP conduction, or dual AVN physiology with ISO testing. Although ISO may improve AP conduction in patients with PJRT and uncover AVNRT, these results suggest that ISO testing after an apparently successful AP ablation may not be necessary to confirm acute success. In addition, lack of AP conduction on ISO did not rule out the possibility of medium-term recurrence. (PACE 2003; 26[Pt. I]:559–561)     

Transcoronary chemical ablation of arrhythmias.

BACKGROUND: Chemical or electrical ablation of an arrhythmogenic ventricular area and the atrioventricular (AV) node is still an experimental technique. After we introduced alcohol ablation in the clinical situation we conducted this study to develop the catheter technique for delivering alcohol in patients with incessant ventricular tachycardia after myocardial infarction and patients with atrial fibrillation and flutter with uncontrollable ventricular rates. METHODS: In patients with incessant ventricular tachycardia, the coronary artery supplying blood to the site of origin of the tachycardia could be identified by the combined information from coronary and left ventricular angiography and from programmed electrical stimulation, including endocardial mapping and pace mapping. In the 12 patients with incessant ventricular tachycardia we selected, the coronary artery supplying blood to the site of origin of the tachycardia could be identified and catheterized in ten patients. Ethanol ablation was successful in all of them. With a follow-up from 2 to 44 months, seven of the ten treated patients are still alive and six remain free of tachycardia. In patients with atrial fibrillation or flutter and uncontrollable ventricular rates, the AV artery could be catheterized and ethanol injected in 13 of the 19 patients. Complete block was produced in ten patients and AV conduction was sufficiently modified to control symptoms in three patients. Long-term results with ethanol ablation have remained excellent in this setting. CONCLUSION: Chemical ablation is a technique that may be of enormous value and even lifesaving for patients with an incessant form of tachycardia not responding to any form of medical therapy. Transcoronary ablation of AV conduction should be considered in patients with a right dominant coronary circulation in whom radiofrequency ablation has failed.     

慢旁道参与的室上性心动过速的电生理特点和导管射频消融治疗

方法 :对 6例慢旁道参与的心动过速的电生理和导管射频消融 (RFCA)治疗。结果 :6例患者的室上性心动过速特点为窄形QRS波 ,RP间期 >PR间期。电生理特点为 :右心室刺激时有与心动过速相同激动顺序的逆传性心房活动 ;心动过速的最短RP间期 >110ms;旁道的逆传具有递减性传导的性质 ;心动过速时与H波同步刺激心室可逆传到心房并使之提前激动并且激动顺序与心动过速时相同 ;6例患者中 ,旁道位于右后间隔 4例、左后间隔 1例、左后侧 1例 ;RFCA可成功阻断所有 6例患者的旁道 ,靶图的特点是VA提前而不融合。结论 :RFCA治疗慢旁道参与的心动过速安全、有效     

Novel Form of Atrial Tachycardia Originating at the Atrioventricular Annulus

We report two patients with reentrant atrial tachycardia that originated at the AV annulus. Atrial tachycardia originated in the posterior portion of mitral annulus in one patient (case 1) and the posterolateral portion of tricuspid annulus in one patient (case 2). Tachycardia was successfully eliminated by RF catheter ablation in both patients, with the catheter placed underneath the mitral valve in case 1 and on the tricuspid annulus in case 2. Spiky potentials were recorded in the diastolic phase of the atrium during tachycardia at the sites of successful ablation. Spiky potentials were also recorded after atrial electrogram during sinus rhythm, and showed decremental properties during atrial pacing. An accelerated atrial rhythm was observed during RF application, and tachycardia could not be induced after ablation in either patient. Tachycardia in these patients seemed to be due to reentrant tachycardia originating in the accessory AV node (Mahaim fiber) without ventricular connection.     

Inappropriate detection of supraventricular arrhythmias by implantable dual chamber defibrillators: a comparison of four different algorithms

Inappropriate therapy of supraventricular tachyarrhythmias by an ICD is still a common problem. Dual chamber (DDD) ICDs provide additional atrial sensing and should result in higher specificity for detection of supraventricular tachyarrhythmias. However, a direct comparison of different dual chamber algorithms has not been reported. The detection algorithms of four different DDD ICDs were tested: Phylax AV, Defender IV, Ventak AV III DR, and Gem DR 7271. Based on arrhythmias recorded from patients undergoing invasive electrophysiological studies and in many cases of catheter ablation at our institution, a library consisting of 71 supraventricular and 15 ventricular tachyarrhythmias was created. The library consists of episodes of atrial fibrillation, atrial flutter with different AV conduction, typical and atypical AV nodal reentrant tachycardia, AV reentrant tachycardia, sinus tachycardia, and ventricular tachycardia with and without ventriculoatrial conduction. Atrial fibrillation was appropriately classified by all four algorithms. However, the specificity for detection of other supraventricular tachyarrhythmias achieved by the Biotronik (12%) and the Guidant (11%) devices was significantly lower compared to the specificity of the ELA (28%) and the Medtronic DDD ICD (20%). This is due to the fact that the Biotronik and the Guidant algorithm classified all supraventricular tachyarrhythmias resulting in a stable ventricular rate as ventricular tachycardia, whereas the ELA and Medtronic algorithms performed a more detailed analysis by assessment of PR association, atrial onset, or timing of the atrial event relative to the ventricular event, respectively. Atrial fibrillation, the most common supraventricular tachyarrhythmia in patients with ICD, was detected by all devices.     

Catheter Ablation for Recurrent Tachyarrhythmias. Clinical Experience with Two Different Techniques of Ablation in 21 Patients

Between 1984 and 1988, 21 patients underwent catheter ablation for drug refractory arrhythmias. Nine patients presented atrial flutter, atrial fibrillation or atrial tachycardia, nine had supraventricular tachycardia (one AV nodal reentrant tachycardia, one reciprocating tachycardia due to concealed accessory pathway and seven XMPW syndrome). Three had ventricular tachycardia. Fourteen patients were treated with direct current shock ablation (DC) and seven patients with radiofrequency ablation (RF). Eight patients underwent ablation of the His bundle. In six patients permanent AV block could be induced and in two first-degree AV block. All became asymptomatic (two with additional antiarrhythmic drug therapy). In four patients with WPW syndrome DC ablation of the accessory pathway was attempted. In one patient a permanent block in the accessory pathway and in another an intermittent block were obtained. In the two remaining patients with accessory pathways the ablation failed to interrupt the retrograde conduction in one the retrograde conduction was modified: however, in the other no change could be demonstrated. Two patients underwent ventricular foci ablation, with one partial success (arrhythmia controlled with associated drug therapy) and one failure. Three patients had RF His bundle ablation (two for atrial flutter and one for atrial fibrillation). One complete atrioventricular block, one first degree AV block and one first degree AV block associated with right bundle branch block were induced. Recurrence of tachyarrhythmias was prevented only in the patient with complete atrioventricular block. RF ablation of accessory pathway was performed in three patients. It resulted in anterograde block in the accessory pathway in the first patient; a slight modification of the retrograde refractory period in the second and no change was noted in the last one. The first of these three patients could then be controlled with drug therapy. The other two patients underwent surgical dissection of the pathway. One patient underwent an unsuccessful attempt of ventricular focus ablation with RF energy. Complications were more common with DC than with RF ablation but serious ventricular arrhythmias were also observed during RF ablation. Thus, DC ablation was completely successful in eight of 14 patients (57%), partially successful with the addition of drug therapy in three patients (21%) and failed in 22%. HF ablation was successful in only one patient (14.5%) and partially successful in another one (14.5%). This relatively low success rate is due in part to the design of the device and the electrodes used in this study. With technical improvements of RF ablation it seems reasonable to expect that this method will play a significant role in the management of drug refractory arrhythmias, since RF ablation, when compared to DC ablation, has the major advantage not to require general anesthesia during the procedure.     

Specificity of Retrograde Conduction in Screening for Atrioventricular Nodal Reentrant Tachycardia

Baseline AV conduction properties (antegrade and retrograde) are often used to assess the presence of dual AV nodal physiology or concealed AV accessory pathways. Although retrograde conduction (RET) is assumed to be a prerequisite for AV nodal reentrant tachycardia (AVNRT), its prevalence during baseline measurements has not been evaluated. We reviewed all cases of AVNRT referred for radiofrequency ablation to determine the prevalence of RET at baseline evaluation and after isoproterenol infusion. Results: Seventy-three patients with AVNRT underwent full electrophysiological evaluation. Sixty-six patients had manifest RET and inducible AVNRT during baseline atrial and ventricular stimulation. Seven patients initially demonstrated complete RET block despite antegrade evidence of dual AV nodal physiology. In 3 of these 7 patients AVNRT was inducible at baseline despite the absence of RET. In the other four patients isoproterenol infusion was required for induction of AVNRT, however only 3 of these 4 patients developed RET. One of these remaining patients had persistent VA block after isoproterenol. Conclusions: The induction of AVNRT in the absence of RET suggests that this is not an obligatory feature of this arrhythmia. Therefore, baseline AV conduction properties are unreliable in assessing the presence of AVNRT and isoproterenol infusions should be used routinely to expose RET and reentrant tachycardia.     

Pacemaker-like syndrome complicating slow pathway ablation for AV nodal reentrant tachycardia

This case report describes pacemaker-like syndrome after successful slow pathway ablation for atrioventricular (AV) nodal reentrant tachycardia due to recurrence of single AV nodal echo beats during sinus rhythm. The resultant AV dyssynchrony was responsible for the symptom complex. Following ablation of retrograde ventriculoatrial conduction, the AV nodal echo beats were eliminated and the pacemaker-like syndrome resolved.     

Transvenous Ablation with High Frequency Energy for Atrioventricular Junctional (AV Nodal) Reentrant Tachycardia

We performed transcatheter AV junction ablation with high frequency energy in four patients with AV nodal reentrant tachycardia where extensive trials of several antiarrhythmic drugs failed to prevent further recurrences of tachycardia. Initially high frequency catheter ablation induced complete AV block in all patients. A recuperation of AV 1:1 conduction followed some time later, persisting in follow-up. No complications have been encountered in either the acute phase or the follow-up (from 6 to 8 months; mean +/- SD: 8.7 +/- 2.5 months). The electrophysiological study was carried out 6 weeks following ablation, and all patients showed AV 1:1 conduction. No dual nodal pathway was encountered and no tachycardia could be triggered. With refinement of the method, the potential application of high frequency energy to interrupt intranodal or perinodal connections responsible for reentrant supraventricular tachycardia or to retard AV nodal conduction appears promising.     

A Wide QRS Complex Tachycardia with Different Initiation Patterns: What is the Mechanism?

A 47-year-old man with palpitations underwent electrophysiologic testing (EPS). Burst atrial pacing while infusing isoproterenol induced non-reproducible wide QRS tachycardias with an unusual pattern of an H-A-V activation with the same tachycardia cycle length and two different initiation patterns. The tachycardia had the earliest atrial activation at the His bundle region. No dual atrioventricular (AV) nodal physiology was demonstrated by programmed atrial stimulation. Though a definite diagnosis of AV nodal reentrant tachycardia was not obtained, slow pathway ablation was performed in order to avoid inadvertent AV block as a complication. Thereafter, no tachycardias were induced by repeat burst atrial pacing.     

Computer Model of the Atrioventricular Node Predicts Reentrant Arrhythmias

Introduction: Following atrial premature beats, the AV node may exhibit sustained reentrant tachyarrhyth-mias, isolated echo beats, or discontinuities in the recovery curve (the plot of conduction time versus atrial cycle length). A computer model was used to examine the hypothesis that spatial variation of AV nodal passive electrical resistance may account for these phenomena. Methods and Results: A computer model of a rectangular lattice of elecirotonically linked elements whose ionic kinetics simulated nodal ionic flux was developed. the model showed that there exists a resistance value that minimizes the effective refractory period, because high resistance prevents depolarization of distal elements, while low resistance allows leakage of depolarizing current by electrotonic transmission, preventing activation of proximal elements. High resistances stabilized reentry by slowing conduction. Simulations incorporating equal resistance values between elements predicted increased AV nodal conduction times with increasing prematurity of atrial impulses. A model with a gradual change in resistance between fibers produced discontinuities and tachycardia, but not both simultaneously. Uniform anisotropy produced preferential transverse block, leading to echo beats and “fast-slow” tachycardia, but not recovery curve discontinuities. Nonuniform anisotropy could produce reentry, but tachycardia often occurred without discontinuities. Dividing the lattice into two electrotonically linked parallel pathways with different resistance values (“dual pathway model”) predicted recovery curve discontinuities, echo beats, and tachycardia. At critical atrial cycle lengths, only the (high resistance) slow pathway conducted antegradely, while the fast pathway conducted retrogradely, to generate the typical “slow-fast” tachycardia. Responses of the dual pathway model to ablation were consistent with clinical data, including the previous observation of a decrease in fast pathway effective refractory period after slow pathway ablation. Conclusion: Differences in passive electrical resistance of electrotonically linked dual pathways within the AV node may account for functional longitudinal dissociation, reentrant arrhythmias, and responses to catheter ablation therapy.     

Radiofrequency ablation of cardiac arrhythmias using a three-dimensional real-time position management and mapping system

A recently developed three-dimensional real-time position management system (RPM) uses an ultrasound ranging technique that enables multiple distance measurements between two reference catheters and a mapping catheter each equipped with ultrasound transducers. In addition to three-dimensional representation of the catheters and ablation sites it displays real-time movements of catheters (including the tip and shaft). A recently released version of the system enables additional geometry reconstruction of the heart chamber and activation mapping. This study included 21 patients (mean age 59 +/- 14.5 years) referred for radiofrequency catheter ablation of various arrhythmias. Geometry was reconstructed by tracing the endocardial contour of the respective heart chambers. Global and local color coded activation maps were constructed to confirm the nature of arrhythmia and to guide ablation. Spontaneous or induced arrhythmias were typical atrial flutter (n = 8), atypical atrial flutter (n = 3), atrioventricular nodal reentrant tachycardia (n = 3), atrial tachycardia (n = 2), atrial fibrillation (n = 2), ventricular tachycardia (n = 2), and Wolff-Parkinson-White syndrome (n = 1). Geometry reconstruction and mapping of arrhythmias were possible in 20 of 21 patients. RPM-guided radiofrequency ablation was successful in 19 (95%) of 20 patients. Due to difficulties in steering the RPM mapping/ablation catheter, in 6 (28%) successfully mapped patients, radiofrequency ablation was performed using another catheter. In one patient, the RPM-guided map was inconclusive and in another patient, ablation failed due to multiple reentrant circuits. No complications were observed. In conclusion, the new RPM system enables geometry reconstruction and three-dimensional positioning of the ablation catheters, reconstruction of the activation maps, marking of anatomic structures and reproducible tracking of multiple ablation sites. The system could be used to guide radiofrequency ablation of atrial and ventricular arrhythmias.     

Relation between the AH interval and the ablation site in patients with atrioventricular nodal reentrant tachycardia

The determinants of slow pathway conduction in patients with AV nodal reentrant tachycardia (AVNRT) are still unknown, and great differences in the AH interval during slow pathway conduction are observed between patients. In 35 patients with typical AVNRT who underwent successful slow pathway ablation (defined as complete elimination of dual pathway physiology), the A2H2 interval at the "jump" during programmed atrial stimulation and the AH interval during AVNRT (as a reflection of slow pathway conduction time) and the fluoroscopic distance between the successful ablation site and the His-bundle recording site and between the coronary sinus ostium (CSO) and the His-bundle recording site were determined. The mean (+/- SEM) AH interval during slow pathway conduction was 323 +/- 12 ms with programmed stimulation and 310 +/- 10 ms during AVNRT. The mean number of energy applications was 8 +/- 1 (range 1-21). The mean distances between (1) the successful ablation site and the His bundle recording site and (2) between the CSO and the His-bundle recording site were 24 +/- 1 and 28 +/- 1 mm in the RAO and 23 +/- 1 and 28 +/- 1 mm in the LAO projections, respectively. The AH interval during slow pathway conduction correlated significantly with the distance between the successful ablation site and the His-bundle (P < 0.001) but not with the distance between CSO and His-bundle recording site. There is a significant correlation between the AH interval during slow pathway conduction and the distance of the successful ablation site from the His bundle. This relationship (1) suggests that, in addition to functional factors, anatomic factors influence slow pathway conduction and (2) may be helpful in determining the initial energy application site during slow pathway ablation.     

Fast pathway ablation in a patient with PR prolongation

The classical form of typical atrioventricular node reentrant tachycardia (AVNRT) is a “slow-fast” pathways tachycardia, and the usual therapy is an ablation of the slow pathway since it carries a low risk of atrioventricular (AV) block. In patients with long PR interval and/or living on the anterograde slow pathway, an alternative technique is required. We report a case of a 42-year-old lady with idiopathic restrictive cardiomyopathy, persistent atrial fibrillation status post pulmonary vein isolation, and premature ventricular complex ablation with a systolic dysfunction, who presented with incessant slow narrow complex tachycardia of 110 bpm that appeared to be an AVNRT. Her baseline EKG revealed a first-degree AV block with a PR of 320 ms. EP study showed no evidence of anterograde fast pathway conduction. Given this fact, the decision was to attempt an ablation of the retrograde fast pathway. The fast pathway was mapped during tachycardia to its usual location into the anteroseptal region, then radiofrequency ablation in this location terminated tachycardia. After ablation, she continued to have her usual anterograde conduction through slow pathway and the tachycardia became uninducible. In special populations with prolonged PR interval or poor anterograde fast pathway conduction, fast pathway ablation is the required ablation for typical AVNRT.     

A Nodoventricular Fiber Associated with Dual AV Nodal Conduction, AV Nodal Reentrant Tachycardia, and Anterior Location of the Slow AV Nodal Pathway

We present a case of a patient with a nodoventricular tract, associated with dual AV nodal conduction and AV nodal reentrant tachycardia, and an anteroseptal location of the slow AV nodal pathway. The remarkable feature of this case is the site of successful ablation, in the anteroseptum just anterior and superior to the His bundle, where both preexcitation and dual AV nodal physiology were abolished.     

Acute effects of simvastatin to terminate fast reentrant tachycardia through increasing wavelength of atrioventricular nodal reentrant tachycardia circuit

Simvastatin (SV) leads to reduction of ventricular rhythm during atrial fibrillation on rabbit atrioventricular (AV) nodes. The aim of our study was (i) to determine the frequency‐dependent effects of SV in a functional model, and (ii) to assess the effects of SV to suppress experimental AV nodal reentrant tachycardia (AVNRT). Selective stimulation protocols were used with two different pacing protocols, His to atrial, and atrial to atrial (AA). An experimental AVNRT model with various cycle lengths was created in three groups of perfused rabbit AV nodal preparations (n = 24) including: SV 3 μm , SV 7 μm , and verapamil 0.1 μm . SV increased nodal conduction time and refractoriness by AA pacing. Different simulated models of slow/fast and fast/slow reentry were induced. SV caused inhibitory effects on the slow anterograde conduction (origin of refractoriness) more than on the fast anterograde conduction time, leading to an increase of tachycardia cycle length, tachycardia wavelength and termination of slow/fast reentrant tachyarrhythmia. Verapamil significantly suppressed the basic and frequency‐dependent intrinsic nodal properties. In addition, SV decreased the incidence of gap and echo beats. The present study showed that SV in a concentration and rate‐dependent manner increased the AV effective refractory period and reentrant tachycardia wavelength that lead to slowing or termination of experimental fast AVNRT. The direction‐dependent inhibitory effect of SV on the anterograde and retrograde dual pathways explains its specific antireentrant actions.