Catheter modification of the atrioventricular junction with radiofrequency energy for control of atrioventricular nodal reentry tachycardia

The underrecognized and neglected compact atrioventricular nodal potential: clinical significance for preventing atrioventricular block during so-called slow pathway radiofrequency ablation

BACKGROUND

The radiofrequency (RF) ablation target may be located at the compact atrioventricular node (AVN) region during so-called slow pathway (SP) RF ablation, potentially leading to transient or permanent atrioventricular block (AVB). However, related data are rare.

METHODS

Among 715 index consecutive patients who underwent RF ablation for atrioventricular nodal re-entry tachycardia, 17 patients subsequently experienced transient or permanent AVB and were included in this retrospective observational study.

RESULTS

Among the 17 patients, two patients (11.8%) developed transient first-degree AVB, four patients (23.5%) developed transient second-degree AVB, seven patients (41.2%) developed transient third-degree AVB, and four patients (23.5%) developed permanent third-degree AVB. During baseline sinus rhythm before the start of RF ablation, no His-bundle potential was recorded from the RF ablation catheter. During the so-called SP RF ablation that led to transient or permanent AVB, junctional rhythm with ventriculoatrial (VA) conduction block followed by subsequent AVB was observed in 14 of 17 patients (82.4%), and a low-amplitude, low-frequency hump-shaped atrial potential was recorded before the start of RF ablation in 7 of the 17 patients (41.2%). Direct AVB occurred in 3 of the 17 patients (17.6%), and a low-amplitude, low-frequency hump-shaped atrial potential was recorded before the start of RF ablation in all 3 patients.

CONCLUSIONS

The low-amplitude, low-frequency hump-shaped atrial potential recorded at the so-called SP region may reflect the electrogram of compact AVN activation, and RF ablation to this site heralds impending AVB even when a His-bundle potential is not recorded.

The Safety and Feasibility of Pulsed-Field Ablation in Atrioventricular Nodal Re-Entrant Tachycardia: First-in-Human Pilot Trial

BACKGROUND

The incidence of atrioventricular conduction system damage during the catheter ablation procedure has long been a safety concern in patients with atrioventricular nodal re-entrant tachycardia (AVNRT). Pulsed-field ablation (PFA) with high tissue selectivity is a promising technique to address this problem in patients with AVNRT.

OBJECTIVES

This study aimed to evaluate the safety and feasibility of PFA in patients with AVNRT.

METHODS

This was an investigator-initiated, single-center, single-arm, prospective study performed in West China Hospital, Sichuan University. Patients diagnosed with AVNRT by electrophysiological examination were included and treated using PFA. The primary outcome was the ability to achieve acute ablation success. The secondary outcomes were ablation success after 6 months and safety incidents reported.

RESULTS

A total of 30 patients with AVNRT with a mean age of 47.9 ± 13.9 years were included and underwent PFA. Acute ablation success was achieved in all patients. The skin-to-skin procedure time was 109.1 ± 32.1 minutes, and fluoroscopy time was 4.1 ± 0.9 minutes. A median of 8 (range: 6.5 to 11.0) PFA applications were delivered. The average distance of the closest ablation site to the His bundle was 6.5 ± 2.5 mm, with a minimum distance of 2.0 mm. All patients maintained sinus rhythm after 6 months. No adverse events occurred in any patient during the ablation or the 6-month follow-up.

CONCLUSIONS

PFA showed favorable feasibility and safety in patients with AVNRT in this pilot study. Further study with larger population and longer follow-up time is warranted to verify the results.

Personalized Definition of Surgical Targets in Major Depression and Obsessive-Compulsive Disorder: A Potential Role for Low-Intensity Focused Ultrasound?

Major Depressive Disorder (MDD) and Obsessive-Compulsive Disorder (OCD) are common and potentially incapacitating conditions. Even when recognized and adequately treated, in over a third of patients with these conditions the response to first-line pharmacological and psychotherapeutic measures is not satisfactory. After more assertive measures including pharmacological augmentation (and in the case of depression, transcranial magnetic stimulation, electroconvulsive therapy, or treatment with ketamine or esketamine), a significant number of individuals remain severely symptomatic. In these persons, different ablation and deep-brain stimulation (DBS) psychosurgical techniques have been employed. However, apart from the cost and potential morbidity associated with surgery, on average only about half of patients show adequate response, which limits the widespread application of these potentially life-saving interventions. Possible reasons are considered for the wide variation in outcomes across different series of patients with MDD or OCD exposed to ablative or DBS psychosurgery, including interindividual anatomical and etiological variability. Low-intensity focused ultrasound (LIFU) is an emerging technique that holds promise in its ability to achieve anatomically circumscribed, noninvasive, and reversible neuromodulation of deep brain structures. A possible role for LIFU in the personalized presurgical definition of neuromodulation targets in the individual patient is discussed, including a proposed roadmap for clinical trials addressed at testing whether this technique can help to improve psychosurgical outcomes.

A prospective evaluation of the impact of individual RF applications for slow pathway ablation for AVNRT: Markers of acute success

BACKGROUND

Catheter ablation is highly effective for atrioventricular nodal re-entrant tachycardia (AVNRT). Generally junctional rhythm (JR) is an accepted requirement for successful ablation however there is a lack of detailed prospective studies to determine the characteristics of JR and the impact on slow pathway conduction.

METHODS

Multicentre prospective observational study evaluating the impact of individual radiofrequency (RF) applications in typical AVNRT (slow/fast). Characteristics of JR during ablation were documented and detailed testing was performed after every RF application to determine outcome. Procedural success was defined as ≤1 AV nodal echo.

RESULTS

Sixty-seven patients were included (mean age 53 ± 18years, 57% female and a history of SVT 2.9 ± 4.7 years). RF (50w, 60°) ablation for AVNRT was applied in 301 locations with JR in 178 (59%). Successful slow pathway modification was achieved in 66 (99%) patients with slow pathway block in 30 (46%). Success was associated with JR in all patients. Success was achieved in six patients with RF < 10 s. There was no significant difference in the CL of JR during RF between effective (587 ± 150 ms) versus ineffective (611 ± 193 ms, p = .4) applications. Inadvertent junctional beat-atrial (JA) block with immediate termination of RF was observed in 19 (28%) patients with AVNRT no longer inducible in 14 (74%). Freedom from SVT was achieved in 66 (99%) patients at a mean follow up of 15 ± 6 months.

CONCLUSION

In this prospective study, JR was required during RF for acute success in AVNRT. Cycle length of JR during RF was not predictive of success. Although unintended JA block during faster JR was associated with slow pathway block, this is a precursor to fast pathway block and should not be intentionally targeted.

[History of catheter ablation]

After His bundle electrography was established in 1967, the step from invasive electrophysiologic diagnosis of arrhythmias to interventional treatment by catheter ablation was imminent. The time interval of 15 years between the diagnosis and treatment of arrhythmias was even shorter than the 19 years between the first selective coronary angiography in 1958 at the Cleveland Clinic in the USA and the first percutaneous coronary intervention in 1977 in Zurich. During each time period, a great amount of knowledge was gained in cardiac surgery, which proved to be very helpful for the development of the interventional treatment. The history of endovascular treatment is an impressive reminder that the preparation and support of cardiovascular surgeons and their handling of complications played a decisive role in the further development of cardiovascular internal medicine. The history of catheter ablation teaches us that the joint work of cardiologists and cardiovascular surgeons is of great importance for the choice and further development of the best possible treatment as for future development of the techniques of therapy.

High incidence of atrial fibrillation after successful catheter ablation of atrioventricular nodal reentrant tachycardia: a 15.5-year follow-up

Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common type of supraventricular tachycardia. Slow pathway (SP) ablation is the treatment of choice with a high acute success rate and a negligible periprocedural risk. However, long-term outcome data are scarce. The aim of this study was to assess long-term outcome and arrhythmia free survival after SP ablation. In this study, 534 consecutive patients with AVNRT, who underwent SP ablation between 1994 and 1999 were included. During a mean follow-up of 15.5 years, 101 (18.9%) patients died unrelated to the procedure or any arrhythmia. Data were collected by completing a questionnaire and/or contacting patients. Clinical information was obtained from 329 patients (61.6%) who constitute the final study cohort. During the electrophysiological study, sustained 1:1 slow AV nodal pathway conduction was eliminated in all patients. Recurrence of AVNRT was documented in 9 patients (2.7%), among those 7 patients underwent a successful repeat ablation procedure. New-onset atrial fibrillation (AF) was documented in 39 patients (11.9%) during follow-up. Pre-existing arterial hypertension (odds ratio 2.61, 95% CI 1.14–5.97, p = 0.023), age (odds ratio 1.05, 95% CI 1.02–1.09, p = 0.003) and the postinterventional AH interval (odds ratio 1.02, 95% CI 1.00–1.04, p = 0.038) predicted the occurrence of AF. The present long-term observational study after successful SP ablation of AVNRT confirms its clinical value reflected by low recurrence and complication rates. The unexpectedly high incidence of new-onset AF (11.9%) may impact long-term follow-up and requires further clinical attention.

Should fast pathway ablation be reconsidered in typical atrioventricular nodal re-entrant tachycardia?

INTRODUCTION

Atrioventricular nodal re-entry tachycardia (AVNRT) is the most common, regular narrow-complex tachycardia. The established treatment is catheter ablation of the AV nodal slow pathway (SP). However, in a select group of patients with long PR intervals in sinus rhythm, SP ablation can lead to AV block due to the absence of robust anterograde conduction through the fast pathway (FP). This report aims to demonstrate that AV nodal FP ablation is a reasonable approach in patients with AVNRT and poor or absent anterograde FP conduction.

METHODS AND RESULTS

Standard electrophysiology study techniques were used in the electrophysiology laboratory. Catheter ablations were performed using radiofrequency energy. Mapping of intracardiac activation was performed with electroanatomical mapping systems. Outcomes were assessed acutely during the procedure and during routine clinical follow-up. Six patients with first-degree AV block and recurrent AVNRT who underwent ablation of their tachycardia at our institution are presented. One patient underwent ablation of AV nodal SP resulting in high-degree AV block necessitating pacemaker implantation. The remaining five patients underwent ablation of the AV nodal FP guided by electroanatomical mapping of the earliest atrial activation in tachycardia. These five had successful treatment of the tachycardia with preservation of anterograde AV nodal conduction. Mapping and ablation approach to eliminate retrograde FP conduction are described.

CONCLUSION

In select patients with AVNRT and poor anterograde FP conduction, retrograde FP ablation is reasonable and is less likely to result in AV block and pacemaker dependency.

Biophysics and clinical utility of irrigated-tip radiofrequency catheter ablation

Catheter ablation by radiofrequency (RF) energy has successfully eliminated cardiac tachyarrhythmias. RF ablation lesions are created by thermal energy. Electrode catheters with 4-mm-tips have been adequate to ablate arrhythmias located near the endocardium; however, the 4-mm-tip electrode does not readily ablate deeper tachyarrhythmia substrate. With 8- and 10-mm-tip RF electrodes, ablation lesions were larger; yet, these catheters are associated with increased risk for coagulum, char and thrombus formation, as well as myocardial steam rupture. Cooled-tip catheter technology was designed to cool the electrode tip, prevent excessive temperatures at the electrode tip-tissue interface, and thus allow continued delivery of RF current into the surrounding tissue. This ablation system creates larger and deeper ablation lesions and minimizes steam pops and thrombus formation. The purpose of this article is to review cooled-tip RF ablation biophysics and outcomes of clinical studies as well as to discuss future technological improvements.

Aging is a primary risk factor for cardiac arrhythmias: disruption of intracellular Ca2+ regulation as a key suspect

Aging is an inevitable time-dependent progression associated with a functional decline of the cardiovascular system even in 'healthy' individuals. Age positively correlates with an increasing risk of cardiac problems including arrhythmias. Not only the prevalence but also the severity of arrhythmias escalates with age. The reasons for this are multifactorial but dysregulation of intracellular calcium within the heart is likely to play a key role in initiating and perpetuating these life-threatening events. We now know that several aspects of cardiac calcium regulation significantly change with advancing age - changes that could produce electrical instability. Further development of knowledge of the mechanisms underlying these changes will allow us to reduce what currently is an inevitable increase in the incidence of arrhythmias in the elderly.

The significance of repetitive ventricular responses induced by radiofrequency energy application for idiopathic left ventricular tachycardia

In radiofrequency (RF) ablation for idiopathic left ventricular tachycardia (ILVT), the termination of tachycardia during RF ablation is considered a hallmark of success. However, in cases of patients with difficulty of induction of ventricular tachycardia (VT), the evaluation of procedural success can be problematic. We have observed thermal responses reflected as ventricular rhythm change to RF energy delivered on sinus rhythm for ILVT. We therefore describe the significance of repetitive ventricular responses. The study subjects were 11 ILVT patients for whom RF energy was delivered during sinus rhythm because of difficulty in re-induction of tachycardia. During each energy delivery, we focused on the occurrence of repetitive ventricular responses especially exhibiting a similar morphology to clinical VT. The repetitive ventricular responses were noted in 10 of 11 patients. Two patients received a second procedure due to the recurrence of ILVT. The mean follow-up period was 36.2+/-12.8 months. The clinical course of the remaining patients was favorable and without recurrence of ILVT. Based on the favorable clinical outcomes, ablation-induced repetitive ventricular responses with similar QRS morphology to clinical ILVT are useful markers for selecting an ablation site and could be used as an additional mapping method, termed as "thermal mapping".

Paroxysmal Supraventricular Tachycardia: A Century of Progress

This article reviews progress in the understanding of AV junctional reentrant tachycardia and accessory pathway-mediated tachycardia in the twentieth century and in the early part of the twenty-first century. Emphasis is placed on the contributions of John Uther and the department he founded at Westmead Hospital.

Atrioventricular nodal reentrant tachycardia associated with idiopathic ventricular tachycardia: clinical and electrophysiologic characteristics

BACKGROUND

Case reports have described the coexistence of ventricular tachycardia (VT) and supraventricular tachycardia in the same patient. This study examines the frequency of dual atrioventricular nodal (AVN) physiology, AVN echo beats, and atrioventricular nodal reentrant tachycardia (AVNRT) in patients with VT.

METHODS

Programmed atrial and ventricular stimulation was performed in 132 consecutive patients referred for electrophysiologic study of symptomatic VT. Of the 132, 99 patients had structural heart disease, and 33 patients had idiopathic ventricular tachycardia (IVT).

RESULTS

Among the 33 patients with IVT, 23 had dual AVN physiology. Compared with patients with structural heart disease undergoing VT ablation, dual AVN pathways (70% vs 27%, P < .0001), dual AVN pathways with echo beats (24% vs 8%, P = 0.03), and AVNRT (21% vs 1%, P = .0002) were more common in patients with IVT.

CONCLUSION

Dual AVN physiology and AVNRT appear to be associated with IVT. This finding suggests that patients with IVT should undergo a complete electrophysiologic evaluation, and the diagnosis of coexistent AVNRT should be considered in this population.

Incidence and Mechanism of Dislocated Fast Pathway in Various Forms of Atrioventricular Nodal Reentrant Tachycardia

BACKGROUND

The incidence and mechanism of the dislocated antegrade fast pathway (A-FP) were examined in various forms of atrioventricular nodal reentrant tachycardia (AVNRT).

METHODS AND RESULTS

To localize the A-FP, 5 atrial sites comprising the inferior coronary sinus ostium (CSOS), apex of the triangle of Koch (A-TOK), and 3 equidistant sites on the atrioventricular junction extending from A-TOK to CSOS (site S, M, and I) were pace mapped at 100 beats/min in 71 patients with slow-fast (n=49), fast-slow (n=7) and slow-intermediate (n=15) forms of AVNRT. The site with the shortest interval between the stimulus and His potential recorded at the A-TOK (shortest St-H) was defined as the A-FP site. The A-FP was located at A-TOK in 31 patients (nondislocated group), and inferior to A-TOK in 40 patients (site S in 26, M in 13, and I in one patient; dislocated group). There was no significant difference in the location of the A-FP among the 3 forms of AVNRT. Although the shortest St-H did not differ between groups, the St-H at A-TOK in the dislocated group was significantly longer than that in the nondislocated group. Additionally, the His potential preceding that of the A-TOK was observed more frequently inferior to the A-TOK in the dislocated group than in the nondislocated group, suggesting that the A-FP dislocation was accompanied by displacement of the His bundle.

CONCLUSIONS

Dislocated A-FP was frequently and uniformly observed among various forms of AVNRT, and is probably caused by inferior displacement of the entire atrioventricular node - His bundle apparatus.

The history of AV nodal reentry

Though patients with AV nodal reentry are now routinely cured by catheter ablation, the basic mechanism of this disorder is still under debate. The putative mechanism of AV node reentry was first discovered by the elegant work of Gordon Moe. He demonstrated the existence of dual pathways and echo beats in rabbits. Building on these seminal observations, the mechanism of AVNRT has burgeoned to include the possibility of left atrial input into the node. The first curative nonpharmacologic procedures involved surgical dissection around the AV node and the procedure was rapidly supplanted by catheter ablation procedures. The initial ablative procedure targeted the fast pathway, but later observations showed that ablation of the slow pathway was more effective and safer. Cure of AV nodal reentry which is the most common cause of paroxysmal supraventricular tachycardia became possible through the cooperative efforts of anatomists, physiologists, surgeons, and clinical electrophysiologists.

Use of advanced mapping systems to guide ablation in complex cases: experience with noncontact mapping and electroanatomic mapping systems

OBJECTIVE

This report describes our experience with noncontact mapping and electroanatomic mapping in complex ablations, which are defined as ablations done after failure of conventional ablation.

MATERIAL AND METHODS

Patients were included (N = 68; 49% with structural heart disease) in whom previous ablation failed and in whom a second procedure was done with advanced mapping. Non-contact mapping was used in 17 patients, electroanatomic mapping in 36, and both noncontact and electroanatomic mapping in 15. Arrhythmias included focal atrial tachycardia (n = 16), reentrant atrial tachycardia (n = 14), right ventricular outflow tachycardia (n = 10), post-myocardial infarction ventricular tachycardia (n = 9), and others (n = 19).

RESULTS

Acute success at the second ablation was achieved in 79% of patients. At 20 +/- 9 months after the procedure, 69% of these patients reported having significantly fewer symptoms than before the second ablation, and 51% were free of symptoms. Only 16% were using antiarrhythmic medications. Complications included a small pericardial effusion in two patients, hypotension in one patient, and a femoral pseudoaneurysm in another.

CONCLUSIONS

Advanced mapping is a useful and safe adjunct for catheter ablation after ablation has failed in patients with complex substrate.

Acute and Long-Term Results of Slow Pathway Ablation in Patients with Atrioventricular Nodal Reentrant Tachycardia-An Analysis of the Predictive Factors for Arrhythmia Recurrence

BACKGROUND

Predictors of atrioventricular nodal reentrant tachycardia (AVNRT) recurrence after radiofrequency ablation including the importance of residual slow pathway conduction are not known. The aim of this study was to report the acute and long-term results of slow pathway ablation in a large series of consecutive patients with AVNRT and to analyze the potential predictors of arrhythmia recurrence with a particular emphasis on the residual slow pathway conduction after ablation.

METHODS

The study included 506 consecutive patients with AVNRT (mean age 52.6 +/- 16 years, 315 women) who underwent slow pathway ablation using a combined electrophysiological and anatomical approach. The end point of ablation procedure was noninducibility of the arrhythmia. The primary end point of the study was the recurrence of AVNRT.

RESULTS

Acute success was achieved in 500 patients (98.8%). After ablation, 471 patients (93%) were followed up for a mean of 903 +/- 692 days. Of the 465 patients with successful ablation, 24 patients (5.2%) developed AVNRT recurrences during the follow-up. No significant differences in the cumulative rates of AVNRT recurrence were observed in groups with or without electrophysiological evidence of residual slow pathway conduction (P = 0.25, log-rank test). Multivariate analysis identified only age as an independent predictor of AVNRT recurrence (hazard ratio 0.96, 95% confidence interval 0.94-0.99, P = 0.004) with younger patients being at an increased risk for arrhythmia recurrence.

CONCLUSIONS

Our study demonstrated that only younger age, but not other clinical or electrophysiological parameters including residual slow pathway conduction predicted an increased risk for AVNRT recurrence after slow pathway radiofrequency ablation.

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.

Long-term efficacy of slow-pathway catheter ablation in patients with documented but noninducible supraventricular tachycardia

BACKGROUND

The long-term efficacy of radiofrequency catheter ablation of slow pathway in patients with dual atrioventricular node pathway and a documented but noninducible paroxysmal supraventricular tachycardia (PSVT) is not entirely clear.

METHODS

Forty nine patients (Group A) with documented but noninducible PSVT and dual atrioventricular node pathway were prospectively studied. Programmed electrical stimulation induced a single atrioventricular node echo beat in 13 patients, and double echo beats in 9 at baseline or during isoproterenol infusion. Clinical and electrophysiological characteristics of Group A patients were compared with that of age- and gender-matched patients with dual atrioventricular node pathway but inducible PSVT (Group B).

RESULTS

There was no significant difference in the electrophysiological properties of the fast and slow pathways between the two groups. Catheter ablation eliminated the slow pathway in all patients. There was no recurrence of PSVT in either Group A or Group B during the follow-up of 38 +/- 5 months.

CONCLUSIONS

In patients with dual atrioventricular node pathway and a documented but noninducible PSVT, catheter ablation of slow pathway is highly effective in preventing tachycardia in long term.

Cardiac arrhythmias: the quest for a cure: a historical perspective

During the last 40 years, much progress has been made in our understanding and management of cardiac arrhythmias. A major step in the late 1960s was to combine programmed electrical stimulation of the heart with intracardiac activation recording. This allowed: 1) localization of the site of the block in the atrioventricular conduction system in patients with bradycardia; and 2) identification of the site of origin and the mechanism of supraventricular and ventricular tachycardia. Combining information from intracardiac studies with findings on the 12-lead electrocardiogram (ECG) resulted in much better localization of conduction abnormalities and arrhythmias using the ECG. This new knowledge led to the development of new therapies, such as bradycardia and antitachycardia pacing, and surgery for supraventricular and ventricular tachycardia. A very important development in the treatment of life-threatening arrhythmias was the implantable defibrillator. Growing concern about failure to protect patients at risk for dying suddenly with antiarrhythmic drugs led to a rapid increase in their number. Cure by catheter ablation became possible for patients with different types of arrhythmias. Genetic analysis allowed the identification of different monogenic arrhythmic diseases. Several challenges remain: the epidemic of atrial fibrillation, arrhythmias in heart failure, and sudden death out-of-hospital. One-fifth of all deaths are sudden and unexpected. The important issue is how we are going to prevent these unnecessary deaths from occurring.

Cardiac Surgery for Arrhythmias

Cardiac arrhythmia surgery was initiated in 1968 with the first successful division of an accessory AV connection for the Wolff-Parkinson-White Syndrome. Subsequent surgical procedures included the left atrial isolation procedure and the right atrial isolation procedure for automatic atrial tachycardias, discrete cryosurgery of the AV node for AV nodal reentry tachycardia, the atrial transection procedure, corridor procedure and Maze procedure for atrial fibrillation, the right ventricular disconnection procedure for arrhythmogenic right ventricular tachycardia, the encircling endocardial ventriculotomy, subendocardial resection procedure, endocardial cryoablation, the Jatene procedure, and the Dor procedure for ischemic ventricular tachycardia. Because of monumental strides in the treatment of most refractory arrhythmias by endocardial catheter techniques during the past decade, the only remaining viable surgical procedures for cardiac arrhythmias are the Maze procedure for atrial fibrillation and the Dor procedure for ischemic ventricular tachycardia. Nevertheless, the 25-30 years of intense activity in the field of cardiac arrhythmia surgery provided the essential foundation for the development of these catheter techniques and represent one of the most exciting and productive eras in the history of medicine. In one short professional career, we have witnessed the birth of arrhythmia surgery, its adolescence as an "esoteric" specialty, its prime as an enlightening yet exhausting period, and finally its waning years as a source of knowledge and wisdom on which better methods of treatment have been founded. One could hardly ask for a more rewarding experience.

Cardiac Surgery for Arrhythmias

Cardiac arrhythmia surgery was initiated in 1968 with the first successful division of an accessory AV connection for the Wolff-Parkinson-White syndrome. Subsequent surgical procedures included the left atrial isolation procedure and right atrial isolation procedure for automatic atrial tachycardias, discrete cryosurgery of the AV node for AV nodal reentrant tachycardia, the atrial transection procedure, the corridor procedure, and the maze procedure for atrial fibrillation, the right ventricular disconnection procedure for arrhythmogenic right ventricular tachycardia, and the encircling endocardial ventriculotomy, subendocardial resection procedure, endocardial cryoablation, the Jatene procedure, and the Dor procedure for ischemic ventricular tachycardia. Because of monumental strides in the treatment of most refractory arrhythmias by endocardial catheter techniques during the past decade, the only remaining viable surgical procedures for cardiac arrhythmias are the maze procedure for atrial fibrillation and the Dor procedure for ischemic ventricular tachycardia. Nevertheless, the 25 to 30 years of intense activity in the field of cardiac arrhythmia surgery provided the essential foundation for the development of these catheter techniques and represent one of the most exciting and productive eras in the history of medicine. In one short professional career, we have witnessed the birth of arrhythmia surgery, its adolescence as an "esoteric" specialty, its prime as an enlightening yet exhausting period, and finally its waning years as a source of knowledge and wisdom upon which better methods of treatment have been founded. One could hardly ask for a more rewarding experience.

Statistical accuracy of a moving equivalent dipole method to identify sites of origin of cardiac electrical activation

While radio frequency (RF) catheter ablation (RCA) procedures for treating ventricular arrhythmias have evolved significantly over the past several years, the use of RCA has been limited to treating slow ventricular tachycardias (VTs). In this paper, we present preliminary results from computer and animal studies to evaluate the accuracy of an algorithm that uses the single equivalent moving dipole (SEMD) model in an infinite homogeneous volume conductor to guide the RF catheter to the site of origin of the arrhythmia. Our method involves measuring body surface electrocardiographic (ECG) signals generated by arrhythmic activity and by bipolar current pulses emanating from a catheter tip, and representing each of them by a SEMD model source at each instant of the cardiac cycle, thus enabling rapid repositioning of the catheter tip requiring only a few cycles of the arrhythmia. We found that the SEMD model accurately reproduced body surface ECG signals with a correlation coefficients > 0.95. We used a variety of methods to estimate the uncertainty of the SEMD parameters due to measurement noise and found that at the time when the arrhythmia is mostly localized during the cardiac cycle, the estimates of the uncertainty of the spatial SEMD parameters (from ECG signals) are between 1 and 3 mm. We used pacing data from spatially separated epicardial sites in a swine model as surrogates for focal ventricular arrhythmic sources and found that the spatial SEMD estimates of the two pacing sites agreed with both their physical separation and orientation with respect to each other. In conclusion, our algorithm to estimate the SEMD parameters from body surface ECG can potentially be a useful method for rapidly positioning the catheter tip to the arrhythmic focus during an RCA procedure.

Slow:fast and slow:slow AV nodal reentry in the rabbit resulting from longitudinal dissociation within the posterior AV nodal input

OBJECTIVE

The anatomic and electrophysiologic bases for multiple forms of sustained AV nodal tachycardia were determined in the rabbit.

METHODS

Intracellular microelectrode recordings were used to identify antegrade and retrograde conduction limbs of sustained tachycardias observed in 23 of 152 superfused rabbit AV junctions.

RESULTS

Slow:slow tachycardias (196 +/- 12 msec cycle length) with nearly equal AH and HA intervals (99 +/- 12; 97 +/- 11 msec, respectively) and early atrial activation near the coronary sinus os were observed in 14 preparations and slow:fast tachycardias (189 +/- 11 msec cycle length) with an AH > HA interval (141 +/- 12; 48 +/- 10 msec, respectively) and early atrial activation along the anterior limbus of the fossa ovalis were observed in 11 preparations. Both tachycardias were associated with longitudinal dissociation and localized reentry within the triangle of Koch. Slow:fast and slow:slow tachycardias exhibited counterclockwise and clockwise reentry circuits, respectively. Both circuits were present in two preparations. Slow:fast AV nodal reentrant tachycardias could be reset with stimuli introduced near the coronary sinus os and the anterior AV nodal input. Slow:slow tachycardias could be reset only by stimuli introduced near the coronary sinus os. The fraction of the tachycardia cycle length contained within the compact AV node was greater for slow:fast (0.35 +/- 0.07) than slow:slow reentry (0.15 +/- 0.05, p = 0.026), suggesting a longer lower common pathway for slow:fast tachycardia.

CONCLUSIONS

Longitudinal dissociation within the posterior AV nodal input incorporating the AV node can provide the reentrant substrate for two different clinical forms of sustained AV nodal tachycardias.

Selective atrionodal input ablation for induction of proximal complete heart block with stable junctional escape rhythm in patients with uncontrolled atrial fibrillation

BACKGROUND

The study tests the hypothesis that ablating all inputs to the atrioventricular (AV) node can result in complete heart block with stable junctional escape rhythm.

METHODS AND RESULTS

We attempted atrionodal input ablation in 76 consecutive patients with uncontrolled atrial fibrillation. Fast and slow pathways were first ablated. If there was no AV block, additional energy applications were done between fast and slow pathway locations. The patients were followed for 42 +/- 11 months. Group I (n = 57) comprised patients with complete heart block and junctional escape rhythm (53 +/- 4 beats/min) at the end of the procedure. The escape rhythm remained stable throughout follow-up. Group II (n = 15) were patients who failed the stepwise atrionodal input ablation and required AV junctional ablation guided by His bundle potential to achieve complete heart block. Four patients showed a slow escape rhythm after ablation (33 +/- 4 beats/min). Others had no escape rhythm. All 15 pts remained pacemaker dependent. The total death rate of groups I and II was 18/57 (31.6%) vs 10/15 (66.7%), respectively (p < 0.02). These differences could not be explained by a difference of left ventricular ejection fraction (0.42 +/- 0.07 vs 0.41 +/- 0.04, respectively, p = NS).

CONCLUSIONS

(1) In most patients, ablation of both fast and slow pathways did not result in complete heart block, indicating the presence of multiple atrionodal inputs. (2) Ablation of all atrionodal inputs may result in complete heart block with stable junctional escape rhythm. (3) As compared with AV junctional ablation, atrionodal input ablation was associated with a lower mortality rate on long-term follow up.

Predictors of long-term success in catheter ablation of atrioventricular nodal reentrant tachycardia: a multivariate regression analysis

BACKGROUND

To investigate the predictors of long-term success after catheter ablation of atrioventricular nodal reentrant tachycardia (AVNRT).

METHODS

One-hundred and fourteen consecutive patients underwent slow pathway ablation using anteroseptal (n=24), midseptal (n=65) and posteroseptal approach (n=25). The correlation between ablation approaches, electrophysiological characteristics during and after ablation and the recurrence rate of AVNRT was analyzed by a multivariate regression analysis.

RESULTS

During ablation, transient AV block in the anteroseptal, midseptal and posteroseptal approach occurred in 8.3, 4.6 and 0%, respectively (P<0.01). AVNRT recurred in seven patients after 5 years follow-up. Five recurrences (20.8%) were from anteroseptal approach group and two (3.1%) were from midseptal approach group. Multivariate regression analysis revealed that anteroseptal ablation approach and residual dual atrioventricular nodal pathway following apparently successful ablation were the predictors for recurrence of AVNRT (R=0.645, P<0.001).

CONCLUSION

Anteroseptal approach of slow pathway ablation is associated with a higher incidence of transient AV block and AVNRT recurrence than other approaches. Residual dual atrioventricular nodal pathway after apparently successful ablation also carries a high risk of recurrence.

Is electrical stimulation during administration of catecholamines required for the evaluation of success after ablation of atrioventricular node re-entrant tachycardias?

OBJECTIVES

The purpose of this study was to answer the question of whether stimulation after administration of catecholamines is mandatory for identifying unsuccessful ablations of atrioventricular node re-entrant tachycardia (AVNRT).

BACKGROUND

The success of radiofrequency (RF) catheter ablation in AVNRT is confirmed in many centers by noninducibility of tachycardias during stimulation after the administration of catecholamines.

METHODS

A total of 131 patients (81 women and 50 men; mean age 53.6 +/- 13.7 years [range 20 to 77]) were studied. Electrical stimulation was performed without and with the beta-adrenergic amine Orciprenaline (metaproterenol) before and after RF catheter ablation.

RESULTS

In 100 patients (76.3%; confidence interval [CI] 68.1% to 83.3%) an AVNRT was inducible without administration of Orciprenaline. Thirty minutes after the initially successful ablation in 95 patients, tachycardia was inducible in none of these patients, not even after Orciprenaline administration. In the 31 patients (23.7%; CI 16.7% to 31.9%) in whom there was no tachycardia inducible before ablation, Orciprenaline was given, and the stimulation protocol was repeated. In only five patients (3.8%; CI 1.3% to 8.7%) was there still no tachycardia inducible. After an initially successful ablation in the 26 patients who had inducible tachycardias with Orciprenaline before ablation, no tachycardia could be re-induced. After Orciprenaline, the tachycardia was inducible again in only one patient.

CONCLUSIONS

Only patients who require catecholamines for tachycardia induction before ablation need catecholamines for control of the success of the ablation of AVNRT.

Atrioventricular node reentry tachycardia in pediatric patients

Atrioventricular node reentry tachycardia (AVNRT) is a significant cause of paroxysmal supraventricular tachycardia (SVT) in the pediatric population. Symptoms can include palpitations, chest pain, fatigue, light-headedness and syncope. AVNRT is a reentry tachycardia that is comprised of dual conduction pathways through the AV node. On electrocardiogram, AVNRT usually manifests as a regular tachycardia with a narrow QRS complex and P waves that are either absent or distort the terminal portion of the QRS complex. Electrophysiology study will reveal dual AV node pathways: a fast pathway with a short AH interval and a long effective refractory period (ERP); and a slow pathway with a longer AH interval and a shorter ERP. During tachycardia, electrophysiologic signals will reveal conduction up the midline. Introduction of premature ventricular contractions and measurement of the HA interval during SVT can help distinguish AVNRT from a SVT utilizing an accessory pathway. Radiofrequency catheter ablation (RFA) has been used increasingly in children as treatment for AVNRT. The initial approach to RFA of AVNRT was modification of AV fast pathway conduction by lesions placed near the anterosuperior aspect of the triangle of Koch, known as the anterior approach method. However, this technique was associated with a significant risk of complete AV block. Now, the posterior approach slow pathway modification is used more commonly, which positions the ablation catheter along the tricuspid annulus immediately anterior to the coronary sinus ostium. This has been associated with a lower risk of complete AV block. Using this technique, RFA should be considered the method of choice for curative therapy of AVNRT in pediatric patients.

Complications associated with radiofrequency catheter ablation of cardiac arrhythmias

Catheter ablation using radiofrequency energy has evolved as a safe and effective means for the treatment of various supraventricular and ventricular arrhythmias. Despite the overall efficacy of radiofrequency catheter ablation, cardiovascular complications can occur in a small number of patients. The purpose of this article is to review the current understanding of the risks and complications that can occur during catheter ablation procedures.

Catheter ablation for cardiac arrhythmias

The safety and efficacy of catheter ablation for treatment of most types of cardiac arrhythmias are well established. These arrhythmias and arrhythmia substrates include AVNRT, accessory pathways, focal atrial tachycardia, atrial flutter, idiopathic ventricular tachycardia, and bundle-branch re-entry. Catheter ablation is considered as an alternative to pharmacologic therapy in the treatment of these cardiac arrhythmias.

Diagnosis and ablation of atrial flutter using a high resolution, noncontact mapping system

The ablation of atrial flutter can sometimes be time consuming and unsuccessful using conventional catheter techniques especially in patients with recurrences after previous ablation procedures. Simultaneous high resolution mapping from multiple sites may overcome some of the limitations. Therefore, a new high resolution noncontact mapping system was used for diagnosis and ablation of atrial flutter in 15 patients. The mapping system consists of a catheter-mounted multielectrode array, an amplifier, and a computer workstation. Far-field potentials recorded by the multielectrode catheter are amplified, digitized, and sampled at 1.2 kHz, and digitally filtered to construct high resolution activation maps during tachycardia. Ablation catheters can be steered to target sites without fluoroscopy. In 12 of the 15 patients the analysis of the activation sequence during tachycardia showed a counter-clockwise, and in 1 of 15 patients a clockwise, rotating wavefront using the isthmus as part of the reentrant circuit. In two patients no tachycardia could be induced. In 3 of the 15 patients with previous conventional ablation procedures the gap in the line of block in the isthmus region was identified and marked on the animation model. The isthmus in the right atrium was ablated and isthmus block verified by the mapping system in all patients. No complications were observed. No recurrences of atrial flutter occurred during follow-up of 4 +/- 1.7 months. The total procedure and fluoroscopy time was 171 +/- 50.0 minutes and 24 +/- 12.7 minutes, respectively. In conclusion, the use of the new high resolution noncontact mapping system in patients with right atrial flutter is safe and highly effective. In patients with previously failed conventional ablation procedures the use of a noncontact mapping system may facilitate the identification of the gap in the line of block in the isthmus region and reablation of atrial flutter.

Catheter ablation in the year 2000

After its introduction in 1987, radiofrequency catheter ablation became established as a safe and effective therapy for the cure of many cardiac arrhythmias in people. The possibility of assessing the relationship between the anatomical target and the electrophysiologic changes produced by radiofrequency pulse delivery has also provided significant improvement in the physician's knowledge of the pathophysiology of the underlying rhythm disturbance. Nowadays, using this therapy, success rates well above 90% with recurrence rates lower than 5% are expected after treatment of most regular supraventricular arrhythmias. As catheter ablation techniques develop, success rates in the range of those obtained for regular supraventricular arrhythmias are expected in the future in the treatment of regular ventricular and irregular supraventricular arrhythmias.