Objective: To evaluate the feasibility of a valved stent on closure patent ductus arteriosus in a Chinese miniswine model.
Methods: Self-expandable nitinol stents were made of Ni-Ti shape memory alloy (9 mm in diameter). Bovine pericardium was shaped and sutured onto the stents. Fluid passing test, pre-releasing test and static test of pressure in tube were performed in all devices before use. In eight Chinese miniswine, vascular grafts (PTFE vascular prosthesis) were surgically inserted between the descending thoracic aorta and pulmonary artery for establishment of patent ductus arteriosus model. Valved stents were deployed to occlude the patent ductus arteriosus. Echocardiography was performed two hours post operation. Aortic angiography was made 30 days post operation in survived animals. Animals were then sacrificed for autopsy and electron microscopy examinations.
Results: In vitro testing showed that the closure of the valved stent leaflets was satisfactory and fluid flows were not restricted in the opposite direction. The valved stents could be released through catheter, expanded completely, rapidly fixed in the tube. Closure of patent ductus arteriosus was succeeded in 6 out of 8 animals. One animal died of respiratory failure 2 hours post operation, another one died of pulmonary embolism due to valved stent displacement. Resident shunt was not evidenced by echocardiography, aortic angiography and dissection examinations in the remaining 6 animals. The new endothelial tissue fully covered the pulmonary and aortic sides of patent ductus arteriosus in 4 and 3 animals respectively. The electron microscopic observation revealed endothelial coverage of dives.
Conclusion: The valved stent could effectively close artificial patent ductus arteriosus in vivo with satisfactory new intima covering on both sides of patent ductus arteriosus.