It is known that pulmonary veins（PVs）are an origin of the most frequent arrhythmia, atrial fibrillation. However, molecular characteristics of the arrhythmogenicity unique to PV myocytes is still unclear. We have investigated the molecular mechanism of catecholamine-induced arrhythmia using both electrophysiology and molecular biology with isolated PV cardiomyocytes of rats. In this paper, I mainly discuss cross-talk among a cluster of Ca²⁺-releasing channels on the sarcoplasmic reticulum and Na⁺-Ca²⁺ exchanger on T-tubule（Ca²⁺ releasing-NCX coupling）, a hyperpolarization activated Cl^－ current originated in ClC-2/HSPA8 complex, and influence of the adenylate cyclase.

Several lines of evidence have shown that epicardial adipose tissue（EAT）is related to the presence, severity, and outcome of atrial fibrillation（AF）. Mechanistically, studies have suggested that the effects of EAT may be mediated by local cytokines/chemokines, inflammation, and fatty infiltration. Here, we discuss the role of EAT, especially in its effect on atrial myocardial fibrosis. Prevention of qualitative alteration of EAT may be a novel therapeutic target for AF.

Pulmonary vein isolation is a cornerstone treatment for atrial fibrillation（AF）. Ablation centers have reported the efficacy of catheter ablation of AF. However, there are few reports examining the effects of time from onset or diagnosis of AF to catheter ablation procedure on clinical outcomes by primary care physicians. We examined the difference in treatment effect depending on the time from onset or diagnosis of paroxysmal or persistent AF to catheter ablation procedure to clarify the appropriate implementation time of AF treatment and role of primary care physicians. A total of 97 patients including 82 patients with paroxysmal AF and 15 patients with persistent AF were evaluated. The cure rate after the first catheter ablation procedure increased as the time from onset or diagnosis of AF to catheter ablation procedure decreased, regardless of age and degree of CHADS₂ score. It is important to determine the indication of catheter ablation as early as possible rather than rely on indeterminate antiarrhythmic medications alone. Early referring to a hospital that performs catheter ablation is an important thing primary care physicians can do to improve the prognosis of patients with AF.