Background-A growing population of patients with coronary artery disease experiences angina that is not amenable to revascularization and is refractory to medical therapy. Preclinical studies have indicated that human CD34 ϩ stem cells induce neovascularization in ischemic myocardium, which enhances perfusion and function. Methods and Results-Twenty-four patients (19 men and 5 women aged 48 to 84 years) with Canadian Cardiovascular Society class 3 or 4 angina who were undergoing optimal medical treatment and who were not candidates for mechanical revascularization were enrolled in a double-blind, randomized (3:1), placebo-controlled dose-escalating study. Patients received granulocyte colony-stimulating factor 5 g · kg Ϫ1 · d Ϫ1 for 5 days with leukapheresis on the fifth day. Selection of CD34ϩ cells was performed with a Food and Drug Administration-approved device. Electromechanical mapping was performed to identify ischemic but viable regions of myocardium for injection of cells (versus saline). The total dose of cells was distributed in 10 intramyocardial, transendocardial injections. Patients were required to have an implantable cardioverterdefibrillator or to temporarily wear a LifeVest wearable defibrillator. No incidence was observed of myocardial infarction induced by mobilization or intramyocardial injection. The intramyocardial injection of cells or saline did not result in cardiac enzyme elevation, perforation, or pericardial effusion. No incidence of ventricular tachycardia or ventricular fibrillation occurred during the administration of granulocyte colony-stimulating factor or intramyocardial injections. One patient with a history of sudden cardiac death/ventricular tachycardia/ventricular fibrillation had catheter-induced ventricular tachycardia during mapping that required cardioversion. Serious adverse events were evenly distributed. Efficacy parameters including angina frequency, nitroglycerine usage, exercise time, and Canadian Cardiovascular Society class showed trends that favored CD34 ϩ cell-treated patients versus control subjects given placebo. Conclusions-A randomized trial of intramyocardial injection of autologous CD34ϩ cells in patients with intractable angina was completed that provides evidence for feasibility, safety, and bioactivity. A larger phase IIb study is currently under way to further evaluate this therapy. (Circulation. 2007;115:3165-3172.)

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Background-Although previous studies have suggested that competitive athletes have a higher risk of atrial fibrillation than the general population, limited and inconsistent data are available on the association between regular physical activity and the risk of atrial fibrillation. Methods and Results-A systematic, comprehensive literature search was performed using MEDLINE, EMBASE, and COCHRANE until 2011. Extracted data from the eligible studies were meta-analyzed using fixed effects model. Four studies, which included 95 526 subjects, were eligible for meta-analysis. For all of the studies included, the extreme groups (ie, maximum versus minimal amount of physical activity) were used for the current analyses. The total number of participants belonging to the extreme groups was 43 672. The pooled odds ratio (95% confidence interval) for atrial fibrillation among regular exercisers was 1.08 (0.97-1.21). Conclusions-Our data do not support a statistically significant association between regular physical activity and increased incidence of atrial fibrillation. (Circ Arrhythm Electrophysiol. 2013;6:252-256.)