Haemodynamically irrelevant pericardial effusion is associated with increased mortality in patients with chronic heart failure. 
Pericardial effusion (PE) is a common finding in cardiac patients with chronic heart failure.  The prognostic relevance of a small, haemodynamically non-compromising PE in such patients, however, remains to be determined.  All patients referred to our heart failure clinic and having a baseline echocardiography and follow-up clinical visits were included.  Patients with a haemodynamically relevant PE, acute myo-/pericarditis, systemic sclerosis, rheumatoid arthritis, heart transplantation, heart surgery within the last 6 months or malignancies within the last 3 years were excluded.  Patients with or without a haemodynamically irrelevant PE were compared regarding all-cause mortality as the primary and cardiovascular death or need for heart transplantation as secondary outcomes.  A total of 897 patients (824 patients in the control vs. 73 patients in the PE group) were included.  In the PE group, left ventricular ejection fraction (LVEF) was lower [31%, interquartile range (IQR): 18.0-45.0] than in controls (34%, IQR: 25.0-47.0; P = 0.04), while the end-systolic diameters of the left ventricle and the left atrium were larger (P = 0.01 and P = 0.001, respectively).  Similarly, in patients with PE, the right ventricle (RV) systolic function was lower (P < 0.005 for both the fractional area change and the tricuspid annulus movement), the dimensions of RV and right atrium (RA) were larger (P < 0.05 for RV and P < 0.01 for RA), and the degree of tricuspid regurgitation was higher (P < 0.0001).  Furthermore, in the PE group, the heart rate was higher (P < 0.001) and the leukocyte count as well as CRP values were increased (P = 0.004 and P < 0.0001, respectively); beta-blocker use was less frequent (P = 0.04), while spironolactone use was more frequent (P = 0.03).  The overall survival was reduced in the PE group compared with controls (P = 0.02).  Patients with PE were more likely to suffer cardiovascular death (1-year estimated event-free survival: 86 ± 5 vs. 95 ± 1%; P = 0.01) and to require heart transplantation (1-year estimated event-free survival: 88 ± 4 vs. 95 ± 1%; P = 0.009).  A multivariate Cox proportional hazard model revealed the following independent predictors of mortality: (a) PE (P = 0.04, hazard ratio (HR): 1.95, 95% confidence interval (CI): 1.0-3.7), (b) age (P = 0.04, HR: 1.02, 95% CI: 1.0-1.04) and (c) LVEF <35% (P = 0.03, HR: 1.7, 95% CI: 1.1-2.8).  In chronic heart failure, even minor PEs are associated with an increased risk of all-cause mortality, cardiac death, and need for transplantation.