A small pericardial effusion is a marker of increased mortality.

Objective: the study aimed to evaluate the prognostic importance of an incidental small pericardial effusion found on echocardiography.

Methods: we identified 10,067 consecutive patients undergoing echocardiography at 1 of 3 laboratories. Patients were excluded if they were referred for evaluation of the pericardium (n = 133), had cardiac surgery within the previous 60 days (n = 393), had a moderate or greater pericardial effusion (>1 cm if circumferential, n = 29), had no follow-up (n = 153), or had inadequate visualization of the pericardial space (n = 9). The Social Security Death Index was used to determine survival.

Results: a small pericardial effusion was noted in 534 (5.7%) of 9,350 patients. Compared to patients without a small effusion, those with an effusion were slightly older (68 ± 13 vs 67 ± 12 years, P = .02) and had a lower ejection fraction (52% vs 55%, P < .0001). Mortality at 1 year was greater for patients with a small effusion (26%) compared to those without an effusion (11%, P < .0001). After adjustment for demographics, medical history, patient location, and other echocardiographic findings, small pericardial effusion remained associated with higher mortality (hazard ratio 1.17, 95% CI 1.09-1.28, P = .0002). Of 211 with an effusion and follow-up echocardiography (mean 547 days), 136 (60%) had resolution, 63 (28%) showed no change, and 12 (5%) had an increase in size, although no patient developed a large effusion or cardiac tamponade.

Conclusion: the presence of a small asymptomatic pericardial effusion is associated with increased mortality.