[Left atrial thrombus in the early postoperative period after mitral valve replacement].

Left atrial thrombus after mitral valve surgery is believed to be relatively rare. However, we previously reported on cases of left atrial thrombus (LAT) with spontaneous regression in the early postoperative period. Forty two patients who underwent mitral valve replacement were studied using computerized tomography (CT). Early postoperative LAT was found in 11 patients out of 42 (26.2%); all of whom had an uneventful postoperative course. The mean preoperative atrial diameter in the LAT group (81.4 mm) was greater than that in the non-LAT group (57.0 mm). This was the most decisive factor significant enough for discriminating between the two groups. Other factors, including age, sex, length of symptoms, preoperative NYHA classification, cardiac rhythms, preoperative cardiac index, duration of cardiopulmonary bypass, type of artificial valve used, duration of intubation and period prior to anticoagulant therapy were not significant. From March 1988, 10,000 U/day of heparin was administered to 20 of the 42 patients. LAT developed in 2 cases (10%). Of the 22 patients who did not accept heparin therapy, 9 (41%) developed LAT. Of the 11 patients having postoperative LAT, 6 were treated by fibrinolytic therapy (urokinase plus heparin). A decrease in thrombus size was observed in 3 cases, and no change in the other 3. Postoperative anticoagulant therapy with warfarin and dipyridamole was administered to all 11 LAT patients, in 8 cases, LAT disappeared for 3 to 42 months period. We therefore conclude as follows: 1) The incidence of early postoperative LAT was 26.2% (11/42). 2) Postoperative thrombus was more likely to occur in the left atrium with a large diameter. 3) Heparin dose of 10,000 U/day seemed to be an effective prophylactic therapy for LAT. 4) Fibrinolytic therapy with urokinase and heparin was not always favorable in LAT cases. 5) In 8 cases out of 11, LAT was resolved under standard anticoagulant therapy with warfarin and dipyridamole in long-term period.