Abstract 3086: Transcatheter Pulmonic Valve Replacement in Sheep using a Grafted Self-Expanding Stent with Tissue Valve
Background: The initial repair of tetralogy of Fallot (TOF) involves placement of a trans-annular patch (TAP) in the majority of patients. Over time, however, TAP often causes free pulmonary insufficiency (PI), necessitating follow-up treatment. Importantly, TAP also leads to an enlargement of the right ventricular (RV) outflow tract, which precludes a less-invasive approach to treat PI with currently available trans-catheter techniques. To address this unmet clinical need, a new trans-catheter device was created and tested in an animal model.
Methods: Six sheep underwent echocardiography and were chosen to have the device implant on the basis of their pulmonary artery (PA) size (>28 mm). A dumb-bell shaped, self-expanding covered stent with a central valve-baring portion of 22 mm diameter was developed. This device was mounted on a 22F delivery system, introduced via a jugular approach and delivered in native pulmonary position. Hemodynamic data, echocardiograms and magnetic resonance images (MRI) were acquired at baseline, immediately post-implant and at term (4wks: n=2; 5wks: n=1; 8wks: n=2; 19wks: n=1). Gross pathologic and ultra-structural (Faxitron®) evaluations were performed at term.
Results: The device was successfully implanted in 6/6 (100%) sheep with procedure times of less than 20 minutes and fluoroscopy times less than 5 minutes. Immediately post-implant, all animals had good valve function on echocardiography (‘none’: n=5, ‘trivial’: n=1). Mean RV-to-PA gradients were slightly increased from baseline to post-implant and term (3.3, 4.7 and 7.5 mmHg, respectively). One animal showed moderate tricuspid regurgitation (TR), which was caused during device delivery. Chronically, TR and PI remained unchanged at term. While stent fractures were observed at term (n=3), no device migration or related complications were observed. On ultra-structural evaluation, valve leaflets were pliable and displayed no-to-minimal fibrin deposition and mineralization at term.
Conclusion: Trans-catheter delivery and implantation of a self-expanding grafted stent with tissue valve was successful in a chronic sheep model. Stent design and material properties merit further investigation for the application in humans.