Transapical mitral valved stent implantation: Early survival

Objectives: Transcatheter valve replacement procedures can result in favorable outcomes for selected patients. The present study investigates outcomes one month after implanting pigs with a novel mitral valved stent using the off-pump technique.

Methods: A novel nitinol mitral valved stent was custom-designed for this study. Five pigs underwent trans-catheter stent implantation. Hemodynamic stability and valve function were assessed after implantation (n=5), after one and four weeks (n=4) using transesophageal echocardiography, ventriculography and cardiac computed tomography (CT). Three surviving pigs were sacrificed after 1 month and one after 8 weeks. The valved stent was evaluated micro- and macroscopically.

Results: Precise deployment and accurate positioning of the stent was established in all but one animal. The average mean transvalvular gradient and mean gradient across the left ventricular outflow tract (LVOT) recorded immediately after deployment, 1 week and 4 weeks were 1.8±0.2, 3.5±0.4, 4.2±0.3 and 1.5±0.7, 2.0±0.4, 2.1±0.5. Mild regurgitation was present 1h after implantation (1/5), after 6h (1/5) and none thereafter. One animal died of unrecognized imperfect valved stent positioning after 24 hours. Valved stent migration, embolization, systolic anterior movement and LVOT obstruction were not evident after 4 weeks. Gross evaluation revealed ca. 70% of tissue growth after 4 weeks and atrial elements were partially fractured close to the aortic root in two pigs.

Conclusions: The new mitral valved stent demonstrated reliable stent stability, minimal gradients across the LVOT and adequate function without paravalvular leakage after 1 month.