Echocardiographic evidence of persistent pericardial effusion after open heart surgery

Cross-sectional and M-mode echocardiography were used to review 33 patients 6-28 months (mean 19 months) after open heart surgery. Eleven patients had had echocardiographic signs of pericardial effusion during the first week after open heart surgery (Group A), and 22 had not (Group B). At review, pericardial effusion was found in 73% of subjects in Group A compared with 18% of those in Group B (P < 0.01). On average, posterior effusions were small (mean dimension in systole 0.9 cm) but they were detected reproducibly (interobserver agreement 97%). Anterior echo-free spaces (< 0.5 cm) were found frequently, but interobserver variation in their detection was high (agreement in 68%). Symptoms did not correlate with the presence of a late post-operative effusion but the groups were not matched for rhythm or ventricular function. Five patients in Group A had developed atrial fibrillation in association with their early post-operative effusion, and four of these had persisting atrial fibrillation at this review. These results suggest that echo-free spaces around the heart, suggestive of small pericardial effusions, may persist for many months after open heart surgery.