Circulation is a scientific journal published by Lippincott Williams & Wilkins for the American Heart Association. The journal publishes articles related to research in and the practice of cardiovascular diseases, including observational studies, clinical trials, epidemiology, health services and outcomes studies, and advances in applied (translational) and basic research. From 1996 to 2004, its impact factor has remained close to 10. As of 2009, its impact factor is 14.595 and it ranks first among journals in the Cardiac and Cardiovascular Systems, Hematology, Peripheral Vascular Disease categories. 2008 saw the appearance of six subspecialty journals. The first edition of Circulation: Arrhythmia and Electrophysiology (Circ Arrhythm Electrophysiol) appeared in April 2008, followed by an edition dedicated to heart failure in May titled Circulation: Heart Failure (Circ Heart Fail). The remaining four journals launched once per month from July through October 2008. In order of release they were, Circulation: Cardiovascular Imaging (Circ Cardiovasc Imaging), Circulation: Cardiovascular Interventions (Circ Cardiovasc Intervent), Circulation: Cardiovascular Quality and Outcomes (Circ