Transcutaneous angioplasty of experimental aortic coarctation.

A dilatable form of juxtaductal aortic coarctation was surgically created in 29 newborn lambs. Of the 17 long-term survivors, four lambs served as controls and 13 underwent transcutaneous balloon dilation angioplasty with either polyvinylchloride or polyethylene catheters after 7--10 weeks of recovery. During growth before dilation, there was little change in the systolic gradient across the coarctation (36.6-35.3 mm Hg) despite an increase in animal weight from 3.8 to 19.3 kg. This systolic gradient remained constant in undilated lambs throughout a 6-month follow-up. Dilation produced an immediate 65% increase in the diameter of the coarctation and a 68% decrease in the systolic gradient across the coarctation site. Successful dilation required very high (6--8 atmospheres) dilating pressures. This gradient relief persisted throughout a follow-up of up to 1 year. Although no late sequelae could be attributed to the angioplasty, one lamb suffered an anterior aortic tear (associated with a difficult postdilation wire passage across the dilation site), which resulted in fatal intrathoracic hemorrhage. Cross pathologic inspection demonstrated intimal and medial tears in successfully dilated lambs in the first 3 days after dilation; on late pathologic examination, the intima appeared completely healed, without evidence of aneurysm or accelerated atheroma formation, within 2 months. These results, in conjunction with previous human in vitro studies, support the hypothesis that human aortic coarctation may be a dilatable lesion, although the safe limits and optimal protocols for dilating human coarctations are not known.