Unsuspected left-to-right shunt: is routine use of hydrogen platinum electrode system indicated in shunt detection?

Unsuspected left-to-right shunt was found in 6 of 1,500 adult patients undergoing diagnostic cardiac catheterization. In 3 patients were found unsuspected secundum atrial septal defects (1 associated with mitral stenosis and 2 with coronary artery disease). In 3 patients, unsuspected partial anomalous pulmonary venous drainage was found (1 associated with aortic valve disease and 2 with severe coronary artery disease). It is concluded that the incidence of unsuspected left-to-right shunt diagnosed during routine cardiac catheterization is very low. Careful physical examination and the application of conventional techniques during cardiac catheterization should suggest the possibility of such a shunt. Hydrogen platinum electrode system (HPES) should be reserved for patients in whom the right heart catheter takes an abnormal course or when the pulmonary artery oxygen saturation is high and the arteriovenous oxygen difference is small.