Although long-term effects have been studied, the immediate effect of surgery for acquired heart disease on left ventricular function is not well defined. Accordingly, 44 adults with acquired heart disease underwent intraoperative two-dimensional echocardiography with a gas-sterilized transducer before and immediately after cardiopulmonary bypass. Ejection fraction was measured by short-axis area change at the maximum left ventricular cross section (SAAC-EF) and also by a method using multiple sections. Correction of both mitral and aortic regurgitation produced a significant intraoperative decrease in ejection fraction from 0.49 +/- 19 (SD) to 0.32 +/- 0.16 (p less than .02) and from 0.41 +/- 0.13 to 0.30 +/- 0.17 (p less than .0005), respectively. Relief of aortic stenosis and mitral stenosis resulted in an intraoperative increase in ejection fraction from 0.45 +/- 0.10 to 0.55 +/- 0.09 (p less than .02) and from 0.41 +/- 0.05 to 0.50 +/- 0.07 (p less than .05), respectively. Ejection fraction after coronary artery bypass grafting was unchanged. Preload (end-diastolic area) was significantly decreased after correction of aortic regurgitation (p less than .02) but unchanged in other lesions. We conclude that (1) correction of pure mitral and aortic valvular lesions produces characteristic alterations in ejection fraction in the immediate postoperative period; (2) with the possible exception of patients with aortic regurgitation, the observed change in ejection fraction does not appear to reflect changes in preload; (3) noninvasive assessment of left ventricular function by two-dimensional echocardiography during cardiac surgery appears feasible and could provide data important for clinical decision making in the early postoperative period.