Registry for Long-Term Outcomes After Catheter Ablation in Nagano Prefecture　― The Shinshu Catheter Ablation (Shinshu-AB) Registry Rationale and Design ―

Abstract

Background: Catheter ablation (CA) is a well-established therapy for arrhythmia, but the impact of CA strategies has not been thoroughly investigated. Nagano Prefecture comprises a large geographical area and some hospitals do not have cardiac surgeons, thus limiting the application of CA strategies. The aim of this study was to investigate the detailed strategies for CA in Nagano Prefecture and to clarify their efficacy and safety.

Methods and Results: The Shinshu Catheter Ablation (Shinshu-AB) Registry is a multicenter prospective observational registry. Patients treated with CA for any type of arrhythmia are included. Data on the target arrhythmia(s), CA strategy, outcomes, and complications were collected and analyzed at Shinshu University Hospital. The study was approved by the institutional review boards of all investigational sites and registered in the UMIN Clinical Trials Registry (UMIN-55562). Primary endpoints were the composite incidence of arrhythmia recurrence, procedure-related adverse events, and cardiovascular events. The secondary endpoints were acute success, chronic success for >12 months, and all-cause death.

Conclusions: The Shinshu-AB Registry provides real-world data from the Nagano Prefecture on the outcomes and complications of CA for various types of arrhythmias.

Central Figure

Catheter ablation (CA) is an established treatment for arrhythmias that is performed on 70,000 patients annually in Japan, with that number continuing to increase.¹ Nagano Prefecture is approximately 200 km from Tokyo and has poor access to major cities. Some hospitals do not have cardiac surgeons, which limits the use of CA strategies, but the effect of CA strategies or their absence on arrhythmia therapy outcomes has not been sufficiently investigated. Furthermore, Nagano Prefecture is a “prefecture of longevity”, so the age group undergoing CA is expected to be older. Many regional cities have aging populations and thus clinicians implementing CA strategies are expected to encounter challenges similar to those in Nagano Prefecture. Atrial fibrillation (AF), a common arrhythmia, may worsen frailty in older individuals, but has also not been sufficiently investigated.

The Japanese Catheter Ablation (J-AB) Registry, established by the Japanese Heart Rhythm Society (JHRS) in collaboration with the National Cerebral and Cardiovascular Center, is a nationwide, multicenter, prospective observational registry.^2–5 It is the largest clinical study of its kind ever conducted in Japan and provides insights into the current state of CA therapy nationwide. However, the Registry did not collect data on the CA strategy used or detailed findings during the procedure. Although numerous clinical studies have investigated CA strategies for AF, there is a paucity of research focusing on conditions such as paroxysmal supraventricular tachycardia, premature ventricular contraction, and ventricular tachycardia.

Therefore, we established a registry of all arrhythmias to investigate the prognostic impact of CA strategies in the Nagano Prefecture, Japan. Our registry collected data on the target arrhythmias, CA strategies, procedural outcomes, and complications. It is estimated that these data will help build evidence for CA therapy.

Methods

Study Design

The Shinshu-AB Registry is a multicenter, prospective, observational registry from Nagano Prefecture (Figure). Recruitment began in May 2021 and is expected to enroll patients undergoing CA until May 2026; all enrolled patients will be followed up for ≥3 years. A total of 12 hospitals will participate in the registry and patients treated with CA for any type of arrhythmia will be included. Patients who decline to participate will be excluded.

Figure.

The medical systems of the facilities participating in the study and the population of each medical region. Nagano Prefecture is geographically divided into 4 medical regions by the Japan Alps mountain range: Hokushin (North), Toshin (East), Chushin (Central), and Nanshin (South). The availability of cardiovascular surgeons and arrhythmia specialists, availability of balloon catheter ablation, and the 3-D mapping system that can be used are shown schematically. CA, catheter ablation.

Study Population

Data on patient characteristics (age, sex, height, weight, past medical history, medication, frailty score, blood pressure, pulse rate), laboratory data, transthoracic echocardiography, ankle-brachial index, target arrhythmias, outcomes of the procedure (pulmonary vein isolation (PVI) for AF, inferior vena cava–tricuspid valve isthmus block for isthmus-dependent atrial flutter [common atrial flutter], atrial flutter of unusual type [uncommon atrial flutter] or atrial tachycardia, atrioventricular nodal reentrant tachycardia, accessory pathway ablation of atrioventricular reciprocal tachycardia, premature ventricular contractions, and ventricular tachycardia) will be collected. Three-dimensional (3D) mapping systems, catheters, and other devices will be investigated as the CA strategies. Ablation data, including procedure time, energization time, fluoroscopy time, fluoroscopic dose, success/failure, ablation index, lesion size index, and number of ablation sites, are collected. Data on the recurrence of arrhythmia and complications, including major or minor bleeding, cardiac tamponade, cerebral and systemic embolism, phrenic nerve paralysis, esophageal injury, pericarditis, sick sinus syndrome, atrioventricular block, and cardiac and noncardiac death, are also collected. For this study, major bleeding was defined as Bleeding Academic Research Consortium ≥2, indicating any overt, actionable sign of hemorrhage. Complete acute success was defined as the elimination of the targeted arrhythmia or the establishment of PVI in the case of AF. Partial success of premature ventricular contractions was defined as a reduction of <0% of the total daily heartbeat on the Holter ECG.

Study Schedule

All patients undergo preadmission testing within 3 months before ablation (Table 1). Ablation strategies and data are shown in Table 2. All cases of AF, common atrial flutter, uncommon atrial flutter/atrial tachycardia, premature ventricular contractions, and ventricular tachycardia are followed up for 1 month, 3–6 months, 1 year, and 2 years after ablation. The atrioventricular nodal reentrant tachycardia and atrioventricular reciprocal tachycardia groups are to be followed up at 1 month, 1 year, and 2 years after ablation (Table 3).

Table 1.

Collection of Preadmission Data

Patient characteristics

Age, sex, height, weight, past medical history, medication, frailty score, blood pressure, pulse, medication adherence

Laboratory data

Red blood cell count, white blood cell count, hematocrit, platelet count, hemoglobin, sodium, potassium, chlorine, total protein, albumin, blood urea nitrogen, creatinine, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, creatine phosphorus kinase, total bilirubin, hemoglobin A1c, D-dimer, C-reactive protein, total cholesterol, B-type natriuretic peptide

Transthoracic echocardiography

Left atrial dimension, left atrial volume, left atrial volume index, LV end-diastolic diameter, LV ejection fraction, E/e′ (lateral, septal), evaluation of structural heart disease

Ankle-brachial index

12-lead ECG

Holter ECG

ECG, electrocardiography; LV, left ventricular.

Table 2.

Procedural Investigation Data

Ablation strategy

3D mapping system, multi-electrode catheter, confirmation of high-density mapping, radiofrequency catheter, balloon catheter, sheath, sedation method, sedative medication, respiratory management

Procedural data checklist

Common to all arrhythmia ablations

Procedure time, fluoroscopy time, energizing power, contact force, ablation index, lesion size index, additional procedure, success/unsuccess, complication(s)

Atrial flutter, AT

Dragging or point-by-point ablation, confirmation of AT origin, number of AT types

Atrial fibrillation

Presence or absence of sinus rhythm during catheter ablation, availability of PV autoactivation after PVI, cryoballoon ablation cool-down time, maximum temperature of hot/laser balloon ablation, additional ablation (SVC isolation, CFAE, CARTOFINDER, BOX isolation), confirmation of dormant conduction (using adenosine), induced atrial fibrillation (using isoproterenol and/or burst pacing), left tuft pressure, and pre-procedural arterial pressure

Atrioventricular nodal reentrant tachycardia

Confirmation of junctional rhythm and ablation site

Accessory pathway ablation of atrioventricular reciprocal tachycardia

Confirmation of accessory pathway site, number of accessory pathways, left tuft pressure, and arterial pressure

Premature ventricular contractions

Number of target sites, pace map guide ablation

Ventricular tachycardia

Activation map during tachycardia, confirmation of slow conduction

AT, atrial tachycardia; CFAE, complex fractionated arterial endogram; PV, pulmonary vein; PVI, pulmonary vein isolation; SVC, superior vena cava.

Table 3.

Study Schedule

Item(s) recorded	Registration*	Ablation	1 month†	3–6 months†,‡	12 months†	24 months†	36 months†
Patient information	○
Physical examination including blood pressure and pulse	○		○	○	○
Laboratory test	○			○	○‡
12-lead ECG	○		○‡		○‡
Holter ECG	○			○
Transthoracic echocardiography	○			○	○‡
Ablation procedure details		○
Medication status			○	○	○	○	○
Adverse clinical events Recurrence of arrhythmia

*Within 3 months of ablation. ^†Within 1 month of ablation. ^‡Excluding cases of paroxysmal supraventricular tachycardia.

Primary and Secondary Endpoints

The primary endpoint has been defined as the composite incidences of arrhythmia recurrence, procedure-related adverse events, and cardiovascular events. The secondary endpoints include acute success, chronic success over 12 months, and all-cause death.

Sample Size

This study aims to clarify the status of CA therapy in Nagano Prefecture, Japan, with the goal of incorporating the maximum number of cases that could be studied to reflect daily clinical practice. Based on the number of CA therapies administered in the previous year, we set the number of cases to 2,500. Assuming a recurrence rate of 20% for the most common AF ablations, the number of observed recurrences is estimated to be 500, allowing for a total of 50 explanatory variables in the search for risk factors using a multivariate analysis. Thus, the sample size appears to be sufficient.

Statistical Analysis

The frequency and descriptive statistics of CA therapy practices in the included cases will be calculated. The impact of baseline and disease-specific variables on outcomes during the follow-up period will be analyzed using a logistic regression model. Additionally, a logistic model will be used to analyze the facility and operator factors as hierarchical factors. IBM SPSS Statistics 27 software will be used to analyze the data.

Ethics

This study complies with the ethical standards outlined in the Declaration of Helsinki, and was approved by the institutional review boards of Shinshu University Hospital (approval number: 5164; 27 May 2021) and all participating hospitals. All participants provide informed consent and can withdraw their consent at any time during the study.

Data Collection in the Registry

The attending physician or research assistant will collect data under the supervision of the lead clinician at each participating hospital. Patient data will be recorded on standardized data collection forms at each hospital and subsequently submitted to the Shinshu University Hospital.

The study schedule for data collection before admission, during hospitalization, and after discharge is summarized in Table 3. During hospitalization, investigators will register the patients and collect information on their medical history, current medications, echocardiographic findings, 12-lead ECG, Holter ECG (within 6 months prior to admission), ankle–brachial index, and frailty assessment. Data on medication use at admission and discharge will be documented.

During the CA procedure, data will be collected using 3D mapping systems, multi-electrode catheters, ablation catheters, balloon catheters, and variable sheaths. In addition, details of sedation and respiratory management during CA are recorded. Key procedural parameters, including procedure time, fluoroscopy time, energy delivery, contact force, ablation index, lesion size index, procedural success/failure, and complications, are documented by the operating physician, who will also report specific procedural details based on the type of arrhythmia, as outlined in Table 2. As a standard protocol, ECG monitoring will be maintained throughout the patient’s hospitalization.

No adjudication committee has been established for event verification. Instead, data will be collected based on reports from the attending physician or the physician responsible for the patient. Recurrent arrhythmias will be confirmed using either 12-lead or Holter ECG.

Discussion

The number of patients who have undergone CA for cardiac arrhythmia has increased and exceeded 89,609 per year, as reported by the J-AB Registry in 2021.⁵ Few large-scale prospective studies examining CA have been conducted in Japan, with the exception of the JHRS-led project that registers all CA cases (J-AB Registry), representing a regional survey of CA.^2–5 Although the J-AB Registry is the cornerstone of Japan’s CA therapy strategy, it does not capture detailed intraprocedural data. The Shinshu-AB Registry, although smaller in sample size, is unique in its inclusion of comprehensive procedural details and post-CA evaluations such as echocardiographic and frailty assessments.

AF is the most common target arrhythmia and PVI is a well-established treatment option^6,7 that is also performed for persistent AF; however, owing to the high recurrence rate, other therapeutic strategies have been devised.^8–12 Recurrent AF is caused by reconduction in the ablated area, and contact force technology is now being used to improve the effectiveness of CA.^13,14 The 3 main CA systems used are the EnSite (Abbott), CARTO (Biosense Webster), and RHYTHMIA (Boston Scientific) systems. 3D imaging guides are available, with 3D imaging-guided CA expected to improve safety and outcomes, as well as reducing radiation exposure. The usefulness of high-density mapping for various arrhythmias has been reported previously,^15–17 and the Shinshu-AB Registry will also assess the usefulness of high-density mapping using multi-electrode catheters for various arrhythmias.

Point-by-point CA can require a procedure time of up to 3 h, as each point between the left atrium and PV is cauterized for several tens of seconds. Balloon ablation, which has been performed at many institutions in recent years, shortens the procedure time;¹⁸ 3 types of balloon ablation systems have been approved in Japan: cryoballoon, hot balloon, and endoscopic laser balloon, each with its own characteristics. PVI is accomplished by balloon occlusion of the PV followed by cryothermal, radiofrequency or laser energy application to isolate the left atrial muscle.^19–22 In hospitals without a full-time arrhythmia specialists, there may be limitations on available equipment, potentially affecting CA outcomes.²³ Therefore, a registry should investigate whether these differences are related to procedural outcomes and safety.

The incidence of complications associated with CA for all arrhythmias reported in the J-AB Registry was approximately 2.5%.⁵ It is well known that AF increases cardiovascular events and deaths.^24,25 CA is expected to have benefits that outweigh these risks and should be performed as early as possible after the onset of the arrhythmia.

In particular, Nagano Prefecture is a “prefecture of longevity”, so the age group undergoing CA is expected to be older. Thus, examining the prognoses of older patients with CA in this study will help build evidence. Stratifying outcomes by age may help refine CA therapy strategies in different patient populations. In this registry, post-CA follow-up confirms the frailty score, which is expected to reveal changes in frailty after CA, particularly in patients with AF. Moreover, Nagano Prefecture covers a large area and some hospitals do not have cardiac surgeons, thus limiting the use of CA strategies. The differences in the outcomes of the CA strategies should also be examined.

The J-AB Registry is the largest ablation registry in Japan, but does not collect data on CA strategies or detailed intraprocedural findings. Although the Shinshu-AB Registry is smaller than the J-AB Registry, it includes detailed investigation of the 3D-mapping system used, contact force, ablation index/lesion size index, energization output, number of energizations, and catheters used. Therefore, the Shinshu-AB Registry will clarify the status of CA use in the Nagano Prefecture.

Study Limitations

At the time the Shinshu-AB Registry was designed in 2021, no hospital in Nagano Prefecture had access to pulsed field ablation (PFA). Consequently, data on PFA have not been collected to date. However, once PFA becomes available, it will be included in future data collection to ensure the registry reflects evolving CA practices.

Conclusions

The Shinshu-AB Registry is a prospective multicenter observational study that will provide real-world data on the success rates, acute outcomes, and complications of CA for arrhythmias in the Nagano Prefecture.

Acknowledgments

The authors thank Yuka Ichihara, Minako Aono, and Mebae Kobayashi for their assistance with this study. We thank Editage (www.editage.jp) for English language editing.

Disclosures

K.K. is a member of Circulation Reports’ Editorial Team. No other authors have conflicts of interest to disclose. This research received no specific grants from any funding agency in the public, commercial, or not-for-profit sectors.

IRB Information

IRB approval (code No. 5164) was obtained from Shinshu University School of Medicine.

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