Early and late tamponade with the Novacor left ventricular assist system. Cardiac tamponade can be a major complication after implantation of the Novacor left ventricular assist system (LVAS). Between 1987 and 1989, 14 patients received an LVAS as a bridge to cardiac transplantation: 3 developed early tamponade (33 +/- 12 hr postoperatively) and 5 were diagnosed with a late tamponade (9.4 +/- 3.2 days postoperatively). One patient had both early and late tamponade. Early tamponade was more common in those with increased perioperative blood loss (5,270 +/- 1,942 ml vs. 1,420 +/- 1,160 ml in other patients, p less than 0.05). Early tamponade was suggested by reduction in mean arterial pressure (74 +/- 1 to 64 +/- 3 mmHg), LVAS output (5 +/- 0.5 to 2.7 +/- 0.7 L/min), LVAS stroke volume (55 +/- 4 to 23 +/- 5 ml), and an increase in central venous pressure (13 +/- 1 to 21 +/- 1 mmHg, p less than 0.05 for all values). Late tamponade was associated with a marked rise in central venous pressure (14 +/- 1 to 22 +/- 2 mmHg, p less than 0.05), with only a mild decrease in LVAS output (4.9 +/- 1 to 3.8 +/- 0.9 L/min) and stroke volume (49 +/- 8 to 36 +/- 3 ml), without a significant change in mean arterial pressure. Two of these five late episodes occurred in patients who were anticoagulated with heparin (PTT 52 and 100 sec), and in one other with warfarin (PT 27 sec, PTT 55 sec); two patients were not on any anticoagulants. Surgical drainage of pericardial effusions, and especially of clotted blood found frequently posterior to the left ventricle in the space created by the LVAS decompressed left ventricle, resulted in an immediate return of all hemodynamic measurements to normal in both early and late tamponade. 