Abstract
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 (6) 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 (10% vs 44%, 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.