Cardiac arrhythmias are cardiac rhythm disorders that comprise an important epidemiological and public health problem. Cardiac arrhythmias are significantly associated with increased risks of cardiovascular complications and sudden death, consequently leading to decreased quality of life, disability, high mortality, and healthcare expense. Atrial fibrillation (AF) is the most common sustained arrhythmia, and has been further increasing with the aging of society. Although the prevalence is relatively lower in Asians than in Westerners, the prognostic impacts on stroke and mortality in Asians are comparable. Sudden cardiac death (SCD) occurs in approximately 40 cases per 100,000 persons annually in each country of Asia. Most cases are caused by myocardial infarction and ventricular fibrillation in out-of-hospital cardiac arrest cases, but the proportion of myocardial infarction is lower in Asia than in Western countries. The primary electrophysiological disorders related to channelopathies, such as long QT syndrome, short QT syndrome, Brugada syndrome, early repolarization syndrome, and catecholaminergic polymorphic ventricular tachycardia, are estimated to be responsible for 10% of SCDs. Implantable cardioverter-defibrillator implantation has become established as an effective secondary prevention for SCD, and numbers have been increasing annually worldwide. New insights into arrhythmic diseases have been emerging from epidemiological, clinical, and genetic research, and contribute to improvements in diagnosis and prognosis. (Circ J 2013; 77: 2419–2431)

Rev-erb α, known as nuclear receptor 1D1 (NR1D1), regulates circadian rhythm, modulates glucose and lipid metabolism, and inflammatory response. However, little is known about the effect of Rev-erb agonist on the progression of myocardial infarction (MI) and heart failure. To investigate it, wild-type male mice underwent sham-operation or permanent ligation of the left anterior descending coronary artery to create MI model. Rev-erb agonist SR9009 (100 mg/kg/day) or vehicle was intraperitoneally administered. Echocardiography was performed to evaluate cardiac function 1 week after surgery. The gene and protein expression levels in the left ventricles (LVs) were determined with real-time PCR, western blotting, and immunofluorescence. Moreover, immune cell infiltration into the LVs was analyzed by flow cytometry. Survival rate and reduced LV function were significantly improved by the treatment with SR9009 after MI. The expression level and plasma concentration of brain natriuretic peptide were significantly lower in MI mice treated with SR9009 (MI+SR) than in MI mice treated with vehicle (MI+V). Moreover, the mRNA expression levels of inflammatory-related molecules such as Il6, Mcp1, Ly6g, Cd11b, matrix metallopeptidase (Mmp)9, and the protein expression levels of phosphorylated NF-κB p65, phosphorylated ERK, and phosphorylated p38 were also significantly lower in MI+SR than in MI+V. Immunofluorescence intensity for MMP-9 was enhanced in the LVs, but was less so in MI+SR than in MI+V. Furthermore, infiltrations of neutrophils and proinflammatory macrophages in the LVs were dramatically increased in MI+V and were significantly suppressed in MI+SR. Rev-erb agonist SR9009 treatment inhibited post-MI mortality and improved cardiac function through modulating inflammation and remodeling process.

The long-term prognosis of subjects with supraventricular premature complexes (SVPCs) remains unclear in the general population. The aim of this study was to examine the prognostic significance of SVPCs in community-based health checkups. We assessed 63 197 individuals (mean age, 58.8 ± 9.9 years; 67.6% women) who participated in annual community-based health checkups in 1993 and were followed until 2008. The primary endpoint was stroke death, cardiovascular death (CVD), or all-cause death during a 14-year mean follow-up, and the secondary endpoint was first atrial fibrillation (AF) event in subjects without self-reported heart diseases or AF at baseline. Compared with subjects without SVPCs, the multivariate-adjusted hazard ratios (HRs) [95% confidence interval (CI)] of stroke death, CVD, and all-cause death in subjects with SVPCs were 1.24 (0.98–1.56) for men and 1.63 (1.30–2.05) for women, 1.22 (1.04–1.44) for men and 1.48 (1.25–1.74) for women, and 1.08 (0.99–1.18) for men and 1.21 (1.09–1.34) for women, respectively. Atrial fibrillation occurred in 386 subjects during the follow-up (1.05/1000 person-years). The presence of SVPCs at baseline was the significant predictor of AF onset [HRs (95% CI): 4.87 (3.61–6.57) for men and 3.87 (2.69–5.57) for women]. Propensity score matched analyses also revealed the presence of SVPCs was significantly associated with increased risks of AF incidence and CVD even after adjusting the potential confounders. The presence of SVPCs in 12-lead electrocardiograms was a strong predictor of AF development, and associated with increased risk of CVD in general population.

Neutrophils are recruited into the heart at an early stage following a myocardial infarction (MI). These secrete several proteases, one of them being neutrophil elastase (NE), which promotes inflammatory responses in several disease models. It has been shown that there is an increase in NE activity in patients with MI; however, the role of NE in MI remains unclear. Therefore, the present study aimed to investigate the role of NE in the pathogenesis of MI in mice. NE expression peaked on day 1 in the infarcted hearts. In addition, NE deficiency improved survival and cardiac function post-MI, limiting fibrosis in the noninfarcted myocardium. Sivelestat, an NE inhibitor, also improved survival and cardiac function post-MI. Flow cytometric analysis showed that the numbers of heart-infiltrating neutrophils and inflammatory macrophages (CD11b⁺F4/80⁺CD206^low cells) were significantly lower in NE-deficient mice than in wild-type (WT) mice. At the border zone between intact and necrotic areas, the number of terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic cells was lower in NE-deficient mice than in WT mice. Western blot analyses revealed that the expression levels of insulin receptor substrate 1 and phosphorylation of Akt were significantly upregulated in NE-knockout mouse hearts, indicating that NE deficiency might improve cardiac survival by upregulating insulin/Akt signaling post-MI. Thus, NE may enhance myocardial injury by inducing an excessive inflammatory response and suppressing Akt signaling in cardiomyocytes. Inhibition of NE might serve as a novel therapeutic target in the treatment of MI.