Thrombomodulin and angiotensin-converting enzyme activity during pediatric open heart operations

Background. Thrombomodulin and angiotensin-converting enzyme are endothelial glycoproteins. The metabolism of these substances is altered when endothelial cells are damaged. Methods. Serum thrombomodulin level was assayed in 56 children and angiotensin-converting enzyme activity determined in 27 children with congenital heart disease before, during, and after open heart operations. Results. The thrombomodulin level was significantly higher in children with a high pulmonary blood flow who had pulmonary hypertension than in those with a normal pressure (p < 0.01), and although all patients showed an increase in serum thrombomodulin after coming off cardiopulmonary bypass, the increase was greater in those with preoperative pulmonary hypertension (p < 0.05). Serum angiotensin-converting enzyme activity was normal preoperatively in all children, irrespective of pulmonary arterial pressure, and decreased in all after coming off cardiopulmonary bypass but decreased to a significantly greater extent in those who had pulmonary hypertension preoperatively (p < 0.05). Conclusions. These findings are compatible with the presence of pulmonary endothelial cell injury and dysfunction before intracardiac repair, which is exacerbated by cardiopulmonary bypass.