Abstract. Objective: To determine whether there are patterns in the incidence of emergency department (ED) visits for congestive heart failure (CHF) by month of the year, day of the week, or hour of the day. Methods: This was a retrospective analysis of a computerized billing database of ED visits, involving seven northern New Jersey hospitals EDs. Consecutive patients seen by emergency physicians over an 11-year period (January 1, 1988-December 31, 1998) were included. Chi-square tests were used to evaluate for significant differences (p < 0.05). Results: There were a total of 2,370,233 patients in the database, of whom 26,224 had a primary ED diagnosis of CHF. The chi-square test rejected uniformity for month of the year, for day of the week, and for hour of the day (p < 0.0001). Visits for CHF were increased in the winter months. Compared with the average of the other months, December was the highest (14.3% above, p < 0.0001) and August was the lowest (15.5% below, p < 0.0001). There was also a day-of-the-week variation. Compared with the average of the other days, Monday was the highest (14.5% above, p < 0.0001) and Saturday was the lowest (9.6% below, p < 0.0001). There was also an hour-ofthe-day pattern, with a rapid rise after 8 AM and a downtrend after 3 PM. Conclusions: These data revealed a higher incidence of ED visits for CHF in the winter months, on Mondays, and during the hours of 8 AM to 3 PM. In comparison with previous studies, these data revealed a similar pattern by month of the year and a different pattern by hour of the day. Key words: congestive heart failure; pulmonary edema; seasonal; weekly; circadian. ACADEMIC EMERGENCY MEDICINE 2001; 8:682-685 Hypertensive heart disease malignant with congestive heart disease 402.11Hypertensive heart disease benign with congestive heart failure 402.91Hypertensive heart disease unspecified with congestive heart failure 428.9Heart failure unspecified 404.91Hypertensive heart and renal disease unspecified with congestive heart failure 404. 93 Hypertensive heart and renal disease with congestive heart failure and renal failure 518.4Acute edema of lung, unspecified 398.91Rheumatic heart failure (congestive)Temporal patterns in the incidence of congestive heart failure (CHF) may offer clues to precipitating factors, particularly the influence of climate and other stresses. There are only a few studies 1-5 that have analyzed the incidence of CHF by sea- analyzed data from an emergency department (ED) in the United States, and that study included just 103 patients. These studies found a predominance of visits in the winter and a peak late in the day and in the early hours of the morning. The objective of our study was to determine whether our cohort showed similar patterns in the incidence of ED visits for CHF by month of the year and hour of the day, and if a pattern exists by day of the week. METHODSStudy Design. This study was a retrospective analysis of a computerized billing database of ED visits. The institutional review board at the authors' inst...