The diagnosis of patent ductus arteriosus (PDA) usually requires catheterization, as does percutaneous treatment of the disorder. To obtain pressure gradients, a catheter can be passed in either direction through the PDA, from the pulmonary artery to the aorta or via the more common route of aorta to pulmonary artery. Several types of catheters have been used, but to date there have been no reports showing the use of a left internal mammary artery (LIMA) angiographic catheter for this purpose. We report successful passage of this catheter from the aorta across a PDA to the pulmonary artery in 15 adult patients who were observed to have no complications. (C) 1999 Wiley-Liss, Inc.