Technical factors in mitral valve surgery (MVS) which may influence neurological complications, trauma to the left atrium and formation of atrial mural thrombi have not previously been described in detail. We have reviewed the records of 146 patients (pts) undergoing MVS through the superior approach between January 1974 and May 1981. The series consisted of 97 females and 49 males with a mean age of 57 +/- 18 years. All but 4 pts were in New York Heart Association functional class III or IV. Twenty-five pts underwent open mitral commissurotomy, 116 had valve replacement and 5 had annuloplasty. Concomitant procedures were coronary bypass in 47, aortic valve replacement in 18 and resection of left ventricular aneurysm in 3. Left atrial thrombi were removed in 21 pts. Thirteen pts (9%) died postoperatively. The causes of death were left ventricular failure in 7, arrhythmia in 4 and atrio-ventricular disruption in 2. Two of these pts also had cerebral dysfunction. Autopsy examination in 8 pts failed to reveal formation of fresh left atrial septal or posterior mural thrombus. Postoperative complications included transient neurologic injury presumed to be due to air embolus in 3 and postoperative bleeding from atrial suture line in one. The mean follow-up for the survivors has been 30 months. There have been 16 (12%) late deaths from 1 to 72 months (mean 15). Autopsy examination of 4 pts and surgical exploration in one other pt which failed to reveal organized left atrial mural thrombus. Only one late death was related to prosthetic thrombosis. This occurred following cessation of anticoagulations.(ABSTRACT TRUNCATED AT 250 WORDS)