The role of anticoagulation in the development of pericardial effusion and late tamponade after cardiac surgery.

This study aimed at elucidating the role of anticoagulation in the genesis of late pericardial effusion and tamponade after cardiac surgery. Using serial 2-D echocardiography, 141 patients undergoing surgery for coronary artery bypass (56), valvular (69) or congenital (16) [corrected] heart disease were studied postoperatively. Group 1 (74 patients) received full anticoagulation (warfarin 73; heparin 1) and group 2 (67 patients) received either antithrombotic agents (aspirin plus dipyridamole), or no treatment. Fifty percent (70/141) of patients developed effusion. There was no significant difference between the two groups in the incidence of either effusion in general (43/74; 58% vs 27/67; 40%, respectively) or small or medium sized effusion. However, a large effusion was significantly more common in group 1 than in group 2 (32% vs 4%, P < 0.005). Twelve patients (12/141; 8.5%) developed late tamponade, 7 to 33 (15 +/- 7.3 mean +/- SD) days after surgery. All had a large effusion demonstrated by echo, drained by pericardiocentesis, and none died. All 12 patients with tamponade belonged to group 1 (P < 0.001). Excess anticoagulation was detected at least once in 41 of the 74 group 1 patients (55%). When compared to properly anticoagulated patients, excessively anticoagulated patients had a similar overall incidence of effusion and a similar incidence of small or moderate effusion, but a higher incidence of large effusion (18% vs 44%, [corrected] P < 0.05) and tamponade (3% vs 27%, P < 0.025). We conclude that, unlike small or medium-sized effusions, large pericardial effusions and tamponade are more likely to occur among anticoagulated patients, especially if they are excessively anticoagulated.