Dynamic right ventricular outflow tract obstruction in cardiac surgery

Background: Right ventricular outflow tract obstruction can be a cause of hemodynamic instability but it has not been described in non-congenital cardiac surgery. Methods: The prevalence of right ventricular outflow tract obstruction was retrospectively studied in 670 consecutive patients undergoing cardiac surgery. Significant right ventricular outflow tract obstruction was diagnosed if the right ventricular systolic to pulmonary artery peak gradient was more than 25 mm Hg. The diagnosis was based on measurement of the right ventricular and pulmonary artery systolic pressure through the paceport and distal opening of the pulmonary artery catheter. To further validate the prevalence and the importance of right ventricular outflow tract obstruction, 130 patients were prospectively studied over a 12-month period. Results: In the retrospective cohort, 6 patients ( 1%) undergoing various types of cardiac surgical procedures were found to have significant dynamic right ventricular outflow tract obstruction with a mean gradient of 31 +/- 4 mm Hg ( 26 to 35 mm Hg). In the prospective study significant dynamic right ventricular outflow tract obstruction was identified in 5 patients ( 4%) ( average peak: 37 +/- 15 mm Hg; range: 27 to 60 mm Hg). The typical transesophageal echocardiography finding was end-systolic obliteration of the right ventricular outflow tract. In patients with significant dynamic right ventricular outflow tract obstruction, hemodynamic instability was present in 10/11 patients ( 91%). Conclusions: Right ventricular outflow tract obstruction is easily diagnosed using the paceport of the pulmonary artery catheter and should be considered as a potential cause of hemodynamic instability especially when transesophageal echocardiography reveals systolic right ventricular cavity obliteration.