Evolution of the postoperative pericardial effusion after day 15: the problem of the late tamponade

STUDY OBJECTIVES: To evaluate, through clinical and transthoracic echocardiography (TTE) follow-up, the natural history of persistent pericardial effusion (PE) after postoperative day 15 in patients who were given and were not given anticoagulant therapy. DESIGN AND PATIENTS: We retrospectively studied a cohort of 1,277 patients who were hospitalized between May 1997 and May 1999 in our center a mean (+/- SD) time period of 15 +/- 3 days after undergoing coronary artery bypass graft (CABG) surgery (856 patients) or valve replacement (VR) surgery (421 patients). MEASUREMENTS: TTE was performed on mean (+/- SD) postoperative day 20 +/- 1 (TTE(1)) and postoperative day 30 +/- 2 (TTE(2)). PE severity was classified on a scale from grade 1 to grade 4. RESULTS: On postoperative day 20 +/- 1, PE was present in 22% of the 1,277 patients and was more frequent after patients underwent CABG surgery than after undergoing VR surgery (25% vs 17%, respectively; p < 0.01). On postoperative day 30 +/- 2, the overall incidence of late tamponade in patients with PE was 4%. The incidence increased with the severity grade of PE at TTE(1) (p < 0.001). The negative predictive value of a severity grade < 2 at TTE(1) for late tamponade was 100%. Late tamponade incidence was higher after VR surgery than after CABG surgery (11% vs 2%, respectively; p < 0.01), and was higher in patients who had received anticoagulation therapy than in those who had not (8% vs 2%, respectively; p < 0.05). CONCLUSION: Persisting PE is common after postoperative day 15 and is more frequent after undergoing CABG surgery than after undergoing VR surgery. The incidence of late tamponade is usually underestimated, and it increases with the presence of VR, anticoagulation therapy, and/or higher postoperative TTE severity grade. Our data suggest that only patients with a PE severity grade of >/= 2 (< 10% of patients) require TTE follow-up after postoperative day 20.