Seasonal variation in patients with acute heart failure: prognostic impact of admission in the summer.

There have been few reports discussing the clinical significance of the season of admission of acute heart failure (AHF) patients. The data of 661 patients with AHF admitted to the intensive care unit were analyzed. Patients were assigned to a summer admission (Group-S, n = 113, between July and September), a winter admission (Group-W, n = 214, between December and February), or to the other seasons admission group (Group-O, n = 334). We evaluated the relationships between the seasonal variations and the clinical profiles, and the long-term prognosis. There were significantly more patients with cardiomyopathy and New York Heart Association class 4, and the serum levels of total bilirubin were significantly higher in Group-S (85.8, 24.8 %, and 0.60 [0.50-0.90]) than in Group-W (75.2, 15.4 %, and 0.60 [0.40-0.78]). The left ventricular ejection fraction on admission was significantly reduced and intravenous administration of dobutamine was used more frequently in Group-S (30.0 [25.0-46.0], 31.9 %) than in Group-W (34.4 [25.2-48.0], 20.6 %) and Group-O (35.0 [25.0-46.0], 19.8 %). The multivariate Cox regression model found that summer admission was independently associated with cardiovascular death (HR: 1.58, 95 % CI 1.01-2.48; p = 0.044) and heart failure (HF) events (HR: 1.55, 95 % CI 1.05-2.28; p = 0.028). The Kaplan-Meier curves showed that the cardiovascular death rate was significantly higher in Group-S than in Group-W and Group-O, and the HF events were significantly higher in Group-S than in Group-O. The summer admission AHF patients included sicker patients, and the prognosis in these patients was worse than in the patients admitted at other times.