We have investigated angiographically and histologically the vascular response to implantation of intravascular stents in normal puppies. Eight balloon-expandable stents were placed in six mongrel puppies (weight 6.4–10.5 kg) under anesthesia. Four stents were successfully placed in the pulmonary arteries and three in the aorta. In one case, the strut of the stent was hooked by a leaflet of the tricuspid valve at the time of placement and eventually had to be implanted in the inferior caval vein. Two puppies died, one from bleeding from the femoral artery and the other from thrombotic obstruction at the superior mesenteric artery, both after successful implantation. The former was due to repeat arterial puncture and the latter wasdue to failure to use aspirin. Angiographic studies showed satisfactory opacities of the branch arteries in all but one puppy. The diameter of the arteries prior to implantation was 7.5±1.5 mm. The diameters at the middle of the stents immediately after implantation and during the period of follow-up were 6.9±1.7mm and 6.9±2.1 mm, respectively. Histologic studies revealed that neogenic endothelial layers of 30 to 40 pm in thickness had formed over the struts of the stent without formation of thrombusthree weeks after implantation. Scanning electron microscopy revealed that the endothelial cells of the neoendothelial layer had almost identical characteristics to those of normal arteries. These results indicate that clinical application of this stent is feasible but that use of anticoagulants is mandatory during and after implantation in the treatment of selected patients with aortic coarctation or pulmonary arterial stenosis. Relative progression of stenosis may occur, however, and the inability for re-expansion is a major disadvantage of this stent.

In recent years, percutaneous placement of stents has been used as an alternative to surgery or balloon angioplasty for the treatment of adults with peripheral pulmonary arterial stenosis. This therapy has also been proposed for children, but questions still remain about its indications in this group of patients. We describe here the results of intravascular placement of stents in a group of 29 patients, with a mean age of 12±7 (range 3–31) years and weighing 35 ±19 (range 11–74) kg. All were affected by postsurgical or congenital isolated pulmonary arterial stenosis, and have now been followed for 38 ±19 (range 6–65) months. The early hemodynamic results have been excellent, with a significant reduction of the pulmonary arterial systolic pressure, the systolic pressure gradient, and the ratio of systolic pressures in the pulmonary and systemic circuits, and with a significant increase of the diameter of the stented vessels in all the patients. Of the 29 patients, 24 have been recatheterized 18 ± 10 months after the procedure, demonstrating the stability of the results, with a low incidence of late restenosis, this seen in only 1 patient (2°). Lung perfusion scanning, performed in 17 patients each year after the follow-up catheterization, has showed that the results are maintained at long-term follow-up (51 ±9 months).

We report the first case, to the best of our knowledge, of a child with the unusual association of Moya-Moya disease and both systemic and pulmonary hypertension. Histological examination revealed fibromuscular dysplasia as the common denominator for a diffuse arteriopathy.

Aims: We investigated the incidence and outcome of cardiac malformations in 53 patients with Williams syndrome. Methods and results:The mean age, and period of follow-up, were 3.6 and 5.3 years, with standard deviations of 4.0 and 5.6 years, respectively. Of the patients, 45 (85%) had cardiovascular anomalies, often combined. Males presented earlier than females, at the ages of 2.1 years, with standard deviation of 2.8 years, as opposed to 4.5 years, with standard deviation of 4.2 years (p < 0.01). Supravalvar aortic stenosis occurred in 32 patients (71%), pulmonary arterial stenosis in 17 (38%), and mitral valvar prolapse in 12 (27%), 9 of these having regurgitant valves. Pulmonary valvar stenosis, ventricular septal defect, coarctation of the aorta, persistent patency of the arterial duct, hypertrophic cardiomyopathy, and subaortic stenosis all occurred less frequently. In 21 patients (47%), 24 surgical or catheter interventions had been made, most often for repair of supravalvar aortic stenosis, undertaken on 16 occasions with just one recurrence, and in 4 along with surgery to the mitral valve. Other lesions requiring intervention were pulmonary valvar stenosis, pulmonary arterial stenosis, coarctation of the aorta, and subaortic stenosis. We lost 3 patients (7%), with severe supravalvar aortic stenosis and moderate or severe mitral regurgitation, 2 early and one late after surgery. Conclusion: The most frequent cardiovascular anomalies in Williams syndrome were supravalvar aortic stenosis, pulmonary arterial stenosis, and mitral valvar prolapse, which occurred more frequently in our patients than previously observed. Patients with left ventricular pressure and volume overload were at greater risk.