Percutaneous pulmonary valve replacement: 3-month evaluation of self-expanding valved stents

Purpose. In a recent study our group established an acute animal model of percutaneous pulmonary valve replacement using self-expanding nitinol stents. The present study was performed to evaluate these valved stents over a 3-month period. Description. Bovine jugular xenografts were sutured into nitinol stents. Transfemoral implantation in the pulmonary position using a modified commercially available application device (with a 22-French outer diameter) was evaluated in 9 sheep. Evaluation. Two sheep died shortly after successful valved stent implantation due to internal venous hemorrhage. Another 1 sheep died 2.5 months after the procedure due to vegetations on the neovalve leading to subtotal stenosis. All other animals survived the 3-month study time (n = 6). An orthotopic pulmonary valved stent position was achieved in 4 animals and a supravalvular position in 1. During the deployment procedure, rhythm disturbances occurred in all animals, and mean arterial blood pressure dropped from 83.9 +/- 26.0 mm Hg to 68.3 +/- 22.3 mm Hg (p = 0.006) (n = 5). The peak-to-peak transvalvular gradient was 5.1 +/- 4.0 mm Hg initially (n = 5), and 3.6 +/- 1.6 mm Hg at follow-up (n = 5). Three-month angiographic and echocardiographic follow-up confirmed competent neovalves without paravalvular leakages. Conclusions. After 3 months of implantation, percutaneously implanted memory nitinol valved stents demonstrated good function in the sheep.