Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, but pathophysiological processes underlying AF remain incompletely understood, despite extensive basic and clinical researches. They involve alterations of ion channels, gap junctions and intracellular Ca2+ handling by the sarcoplasmic reticulum at the cellular level, and various changes at the organ level affecting atrial tissue architecture. In addition, there is evidence supporting that inflammation, oxidative stress, metabolic disorders and changes in autonomic nervous function contribute to abnormal electrical activities leading to AF. It is well stablished that the paroxysmal type of AF is related to focal sources mainly in the extra-atrial tissue (e.g., pulmonary vein myocardium), as confirmed by the clinical efficacy of electrical isolation of these foci from the atrial tissue. In contrast, the mechanisms maintaining long-lasting AF are still controversial and may involve both ectopic focal impulse generation and various forms of reentry. Two conflicting hypotheses have been proposed as a reentrant mechanism: stable rotors at fixed locations produce sustained electrical activity of AF (mother rotor hypothesis), and breakup of random excitation waves generating multiple wavelets maintains AF (multiple wavelet hypothesis). The progression of paroxysmal AF to persistent AF is mediated by electrical and structural remodeling, the former highlights an abbreviation of atrial refractory period and cell-to-cell electrical uncoupling, and the latter includes proliferation of myofibroblasts and interstitial fibrosis. In this symposium, four distinguished speakers will give talks on these issues and discuss the initiation and perpetuation mechanisms of AF.

Recently, the therapeutic and diagnostic tools and devices in atrial fibrillation make remarkable progress as follows.

• Contact-force sensing technology in RF catheter ablation has the potentials to increase the durability of pulmonary vein isolation (PVI) and to improve the learning curve of young physicians. And recent new parameters such as Ablation Index (CARTO) and LSI (Navx) were correlated to the ablation lesion depth and were promising to improve the ablation procedure.
• Balloon ablation technology (Cryoballoon, Hot balloon and Laser balloon) was remarkably advanced. Especially, Cryoballoon ablation was able to create the durable PVI and to reduce the procedure time. Several reports indicated that the efficacy of each balloon ablation for paroxysmal atrial fibrillation was as same as RF catheter ablation. However, balloon ablation has the potential risk of pulmonary vein stenosis and phrenic nerve palsy. So, the further examinations to avoid these complications are required.
• 3D mapping system was very useful and essential to catheter ablation for atrial fibrillation. Recently, auto mapping system was developed on each 3D mapping system (Confidense(CARTO),Auto-mapping(Navx), and Rhythmia). Each system was able to represent the reentrant circuit and the focal source of atrial tachycardia and fibrillation. Especially, the ORION catheter of Rhythmia system has the 64 small electrodes and can clearly record the fractionated potential on slow conduction area without far field potential.

This session will present recent advances in these novel therapeutic and diagnostic tools and devices in atrial fibrillation. These advances aim to improve the procedure time and optimize procedural outcomes.

In contrast to the well-established treatment for paroxysmal atrial fibrillation, catheter ablation for persistent or long-standing persistent AF (PerAF/LSPAF) is still a big challenge with various controversies remained.
Firstly, indication of ablation is still debatable, because most of PerAF/LSPAF patients are asymptomatic. Although regardless of the absence of serious symptoms in these patients, their poorer QOL than paroxysmal AF patients has been shown, which can be improved by restoring sinus rhythm by ablation treatment through the increase of LV systolic function and the exercise tolerance capability.
Optimal ablation strategies for PerAF/LSPAF also remain to be debatable. Less advanced persistent cases have been shown to be cured by a simple pulmonary vein isolation technique, however additional techniques to reduce the substrates perpetuating AF are necessary to conquer PerAF/LSPAF. Although various methods have been developed so far (linear ablation, CFAE, GP, Rotor/Driver, LVZ, etc), there has been no established method demonstrating obvious advantages to others. An order-made therapy with the selection of appropriate treatment in each case will be necessary to improve the outcome of ablation for PerAF/LSPAF patients.
In this symposium, we want to discuss the indications, meanings, and the strategy issues of catheter ablation to conquer PerAF/LSPAF.

The history of implantable pacemaker is over a half century, and approximately 60,000 patients receive pacemakers annually in Japan. However, conventional pacemakers are known to be associated with several adverse events. Majority of the adverse events are related with the lead or subcutaneous pocket. The leadless pacemaker was invented to overcome these known complications. The approval of the leadless pacemaker in Japan was in September, 2017. Japanese patients are small and often have known risk factors for cardiac perforation. As more patients receive the leadless pacemaker, possibly DDD in future, we would like to discuss the current status, future direction and possible procedure tips for the safe implant.

Cardiovascular implantable electronic device (CIED)-associated infection is a serious and sometimes fatal problem after device implantation. It has been reported to occur around 1-7% of cases, but it is gradually increasing recently because of expanded function and device indication. For prevention, appropriate management before/during the implantation (patient selection, preventative maneuver and choice of device) is important. But once infection occurred, the mainstream of the management is a total removal of these devices, however it sometimes causes fatal complication including death. From the early 1990s, lead extraction system for CIED has progressed. Excimer laser system has approved in 2010 and now a standard therapy for CIED-associated infection in yearly 500 cases in Japan. J-LEX (Japanese registry of Lead Extraction) will provide a current situation in this filed.
In this session, we will make a discussion with experts about the prevention and the appropriate management for CIED-associated infection, especially focus on the patient selection and the recent advancement of lead extraction system.

In Japan, implantable cardioverter-defibrillators (ICDs) were approved by the Japanese Ministry of Health, Labor and Welfare in 1996. Then, the first guidelines for ICDs were published by the Japanese Circulation Society in 2001. CRT-P and CRT with an ICD (CRT-D) were also approved in 2004 and 2006, respectively. The ICDs were a first grade therapy to prevent sudden cardiac death worldwide, even in Japan. The indication for ICDs seemed to have been confirmed. The indication for ICDs for secondary prevention, in particular, for sudden cardiac death, had already been established nearly 20 years after the approval of ICDs in Japan. However, Japan is now aging and is about to enter an unprepared for super-aging society. Therefore, new problems are arising as to how to consider ICD indications not only for primary prevention, but also for secondary prevention in patients with comorbidities and that are super-aged and frail. In this symposium, we would like to reconsider how to consider these problems and the indications for ICDs.

Although cardiac resynchronization therapy (CRT) has been proven to improve the prognosis of patients with a reduced cardiac function and wide QRS complex, a substantial number of candidates do not have a favorable clinical response. The exact rate of non-responders is still unclear because various definitions of non-responders have been used among the studies. The recent trials are prone to using a clinical composite score, which includes the clinical response (NYHA class and exercise duration), reverse remodeling (increase in the LVEF and a reduction in the systolic or diastolic dimension of the LV), and outcome measurements (hospitalization, morbidity, and mortality).
Since the causes of non-responders are multifactorial (patient selection, inadequate AV and/or V-V timing, a sub-optimal left ventricular lead position, and a conduction delay within the LV), various efforts to resolve these problems have been challenged. Owing to the advanced CRT features for heart failure, the rate of non-responders has seemed to improve. In this symposium, the most advanced technologies to obtain cardiac synchronization and the near future of CRT will be discussed.

Most cardiovascular implantable electronic devices (CIEDs) currently use leads that connect the generator to cardiac tissue. Lead management is an important issue, given the lead failures, generator changes, and clinical conditions that can directly affect CIEDs. The previous expert consensus ‘Transvenous Lead Extraction: Heart Rhythm Society Expert Consensus on Facilities, Training, Indications, and Patient Management’ was published in 2009. In that consensus document the complete removal of the entire CIED system was recommended in cases with confirmed or suspected pocket infections of the implanted devices. Regarding non-infectious indications, chronic pain induced by the device system and undergoing specific imaging such as MRI were class IIa indications for a lead extraction. Further, this statement also provided several conditions involving thrombosis or venous stenosis, and functional or non-functional leads, as class I or IIa indications. Moreover, that document delivered detailed recommendations for facilities and training on lead extractions that remain appropriate.
In September 2017, the new statement ‘2017 HRS Expert Consensus Statement on Cardiovascular Implantable Electronic Device Lead Management and Extraction’ was announced. The main focus of this new statement is to provide practical clinical guidance in the broad field of lead management, including lead extractions. Therefore, we can learn a lot about the latest management of CIED systems. However, regarding non-infectious indications, the optimal decision-making process regarding lead extractions for noninfectious indications is less clarified, because it is unclear whether the risk of an extraction outweighs the benefit of having the lead removed in many situations, for example with ‘recalled leads’, ‘abandoned or non-functional leads’, ‘taking MRI imaging in patients with non-MRI conditioned devices’, and even ‘functional leads’. In this session, we would like to discuss the non-infectious indications of lead extractions

The autonomic nervous system is involved in regulation of electrophysiological properties in cardiac tissues. Abnormal autonomic states have been shown as a strong prognostic marker of increased mortality and propensity to lethal arrhythmias. Activation of the sympathetic nervous system enhances automaticity or triggered activity, accelerates conduction and shortens refractory period, thereby leading to induction of atrial as well as ventricular tachyarrhythmias. Activation of the parasympathetic nervous system exerts protective effects against ventricular tachyarrhythmias. However, activation of the parasympathetic nervous system is associated with induction of atrial fibrillation in apparently healthy subjects and ventricular fibrillation in patients with Brugada syndrome. Modulation of the autonomic nervous activity with invasive techniques is now becoming promising treatment strategies for some specific tachyarrhythmias. For instance, ablation of the atrial epicardial ganglionated plexus is effective in suppressing paroxysms of atrial fibrillation. Additionally, cervical vagal nerve stimulation, left stellate ganglionectomy and renal sympathetic denervation could be now promising, adjunctive treatment techniques for refractory arrhythmias. Indeed, left stellate ganglionectomy is effective in suppressing ventricular tachyarrhythmias in patients with catecholaminergic polymorphic ventricular tachycardia as well as long QT syndrome. In this symposium, arrhythmogenic mechanisms of neurocardiac interactions and recent progress in modulation of the autonomic nervous activity for treatment of refractory arrhythmias will be discussed.

As more complex rhythm disturbance has become the target of EP study and catheter ablation, the technology of electro-anatomical mapping (EAM) system has been rapidly developed. At present, we have several different EAM systems with some specific features, such as capability to make a prompt mapping for non-sustained unstable arrhythmias, ability to display all catheters’ positions and rapid depiction of cardiac geometry. For the procedural success, it is essential to use each EAM system with a deep understanding of the characteristics of the system as well as to make a careful interpretation for the acquired data. In this session, with regard to the clinically available EAM systems, how to master the new technology to make a profit for the patients will be discussed. Further the new system currently under the development will be introduced, particularly focusing on the principal benefits and future perspective in this field.

Cardiomyopathy is cardiac disorder that causes heart failure and rhythm disorders such as supraventricular and ventricular arrhythmias. Sudden cardiac death (SCD) is primarily caused by ventricular tachycardia (VT)/fibrillation (VF). Therefore, the prevention of VT/VF is a key issue in the treatment of patients at risk for SCD. Atrial fibrillation (AF) frequently occurs in patients with cardiomyopathy. It is recognized that AF leads to clinical deterioration and worsened hemodynamics. However, the mechanisms of arrhythmias associated with various cardiomyopathies are complex and heterogeneous. The etiology of arrhythmias associated with dilated cardiomyopathies is known to be the result of a variety of electrical abnormalities, but the primary cause is not well understood. Arrhythmogenic right ventricular cardiomyopathy is slowly progresses to more diffuse ventricular dysfunction. In the early phase of this cardiomyopathy, structural change is absent or minor, but patients may be at risk of SCD. For hypertrophic cardiomyopathy, the predictive value of each of established clinical risk factors is poor and risk stratification for SCD remains a challenge. Drug therapy including beta-blockers and amiodarone, implantable cardioverter-defibrillator and radiofrequency ablation are important tools in the management of arrhythmia and SCD in patients with cardiomyopathy, but further investigation is necessary. Thus, each cardiomyopathy also results in different risk assessment and treatment approaches for arrhythmia. There are still many unresolved problems about cardiomyopathy and arrhythmias. In this symposium, we would like to discuss topics related to these issues, ranging from the basic sciences to clinical managements.