CLINICAL INVESTIGATION Morphologic changes in the pulmonary arteries after percutaneous balloon angioplasty for pulmonary arterial stenosis

The pathologic appearance of pulmonary arteries subjected to balloon dilation was studied in four subjects with stenosis of pulmonary arteries. Nine vessels were dilated. Successful dilation in seven vessels was accompanied by intimal disruption and tearing of the media. In one vessel, at the site of a previous surgical procedure, dilation could not be accomplished. Histologically, this vessel was encased by reactive fibrous tissue, which may have precluded successful dilation. In one case, simultaneous rupture of the dilating balloon and the left pulmonary artery occurred. Morphologic examination could not adequately explain the cause of vessel rupture. Among the six vessels successfully dilated and studied 4 to 14 months after the dilation, the postdilation luminal diameter had been maintained. Tears in the intima and media as seen histologically had been filled in by scar tissue. In one artery a dilated segment distal to a residual obstruction revealed marked intimal proliferation. Circulation 71, No. 2, 195-201, 1985. THE MORPHOLOGIC changes in human vessels after balloon angioplasty are not well defined. Dotter and Judkins' described the first transluminal angioplasty procedure in 1964. Later, percutaneous transluminal balloon angioplasty was introduced. The new technique was used initially to treat obstructive arterial disease derived from atherosclerosis and has since been applied to treat many causes of vascular obstruction of various types and in many vessels of the body. Although balloon dilation of stenotic pulmonary arteries is being increasingly used clinically, we are unaware of any published reports dealing with pathologic findings after this procedure in patients with pulmonary arterial stenosis. The purpose of this report is to define the gross and histologic sequelae of transluminal balloon angioplasty performed in nine pulmonary arterial branches among four children in whom death occurred from various causes. From the Departments of Pediatric Cardiology and Pathology, University of Minnesota, Minneapolis, and the Department of Pathology, United Hospitals, St. Paul. Supported by research grant 5 ROI HL05694 from the National Heart, Lung, and Blood Institute and by the Dwan Family fund. Address for correspondence: Jesse E. Edwards, M.D., Department of Pathology, United Hospitals, 333 North Smith Ave., St. Paul,. MN 55102. Received April 13, 1984; revision accepted Oct. 18, 1984. *Established Investigator of the American Heart Association. Current Address: Department of Cardiology, Children's Hospital, 300 Longwood Ave., Boston, MA 02115. Materials and methods The four patients were part of a group of 25 children at the University of Minnesota who underwent balloon dilation angioplasty for hypoplastic or stenotic pulmonary arteries. Protocol for dilation angioplasty. Before recommendation of balloon angioplasty of a pulmonary artery, the criteria described by Lock et al.2 were followed. The diameter of the hypoplastic or stenotic pulmonary artery was measured directly from biplane cineangiograms. A polyethylene balloon catheter with an inflatable diameter three to four times that of the narrowed segment was introduced into the affected pulmonary arterial segment and inflated to 1 atmosphere of pressure. The catheter was manipulated until the stenotic segment indented the balloon. The balloon was then inflated to a pressure of 7 to 8 atmospheres and maintained for 30 sec. Assessment of effects of dilation angioplasy. The anatomic and hemodynamic effects of balloon angioplasty were assessed by one or more of the following: (1) direct measurement of the diameter of the narrowed segment angiographically before and after dilation, (2) assessment of the gradient across the stenotic segment or segments before and after balloon dilation, and (3) lung scan assessment of blood flow to the lung served by the dilated vessel or vessels before and after balloon dilation. Case summaries Patient 1. In this female patient, cyanosis was apparent in infancy. Cardiac catheterization revealed hypoplasia of the right and left pulmonary arteries with systemic pressures in the right ventricle. The intracardiac structures appeared normal. At 32 months of age the patient underwent successful balloon angioplasty dilation of the right pulmonary artery (table 1). At 35 months of age, dilation of the left pulmonary artery was performed in which a 12 mm dilating balloon was inflated to 9 atmospheres in the left lower pulmonary artery. Simultaneous rupture of the balloon and the left lower pulmonary artery occurred. The child exsanguinated and died despite massive transfusions and an emergency thoracotomy. Vol. 71, No. 2, February 1985 195