Congestive heart failure (CHF) is the end stage of many cardiac diseases, and one of the leading causes of mortality and morbidity around the world. Coronary heart disease and hypertension (either singly or together) are the main etiology for CHF. It has been reported that major acute cardiovascular events (myocardial infarction, sudden death, cardiac arrest, ischemic and hemorrhagic stroke, pulmonary embolism, rupture/dissection of aortic aneurysms) do not occur randomly through time, but exhibit a specific temporal periodicity characterized by seasonal (winter), weekly (Monday), and circadian (morning) patterns of onset. Thus, because the major causes of CHF present a temporal pattern, in the past several years some studies have investigated the temporal variation of CHF hospitalization and mortality, with results indicating the possibility of a preference for winter months, Mondays, and nighttime, respectively.