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[Coronary flow obstruction in percutaneous aortic valve replacement using self-expandable valved stent: an in vitro study].

OBJECTIVE
To study the effects of self-expandable and orthotopically implanted percutaneous aortic valved stent on coronary artery flow in vitro.


METHODS
Self-expandable valved stent was developed with nitinol stent and bovine pericardium. The ascending aorta of Chinese mini swine hearts was cut proximal to the brachiocephalic trunk. The right and left main coronary arteries were dissected. In vitro coronary flow tests were performed. Firstly, baseline coronary flow with the native aortic valve was measured (n = 12). Secondly, the valved stent was deployed orthotopically. The commissures of prosthesis were positioned randomly. Through an endoscope, the effects of valved stent and native valve on coronary ostium were obtained and coronary flow measurements repeated (valve preservation group, n = 12). Then the distance from coronary ostium to native leaflet free edge was measured. Native leaflets were removed before similar valved stent deployment. Coronary flow measurements and endoscopic inspections were repeated post-implantation (valve removal group, n = 12).


RESULTS
In valve preservation group, valved stent implantation resulted in a significant decrease in left coronary flow (29.46%, P < 0.05). The obstruction was due to native leaflets sandwiched between the stent and aortic wall. The left ostia were obstructed totally in 3 and partially in 4. The flow of right coronary decreased 7.34% (P > 0.05). The right ostia were obstructed partially in 3. In valve removal group, 6.82% and 5.37% decrement in left and right coronary flow were observed after valved stent placement (P > 0.05). The distances from right coronary ostia to annulus were farther than from left coronary ostia. In two groups, the commissures of prosthesis obstructed partially left coronary ostia in 4 and right coronary ostia in 1.


CONCLUSION
Orthotopic implantation of a percutaneous self-expandable aortic valved stent would obstruct the left coronary ostium with the native valve. Coronary ostium may be obstructed partly by the commissures of prosthesis.