Off-pump transapical mitral valve replacement: evaluation after one month

Abstract

Objectives: The present study investigates outcomes one month after implanting pigs with a novel mitral valved stent.

Methods: A novel nitinol stent custom designed for this study included a bovine pericardial valve. Six pigs received a valved stent into the mitral position by means of the transapical implantation technique. Afterwards, haemodynamic stability and valve function were assessed, immediately after implantation (n = 6), 4 weeks (n = 4) and 8 weeks (n = 1) thereafter using transoesophageal echocardiography (TEE), ventriculography and cardiac computed tomography (CT). Four of 6 surviving pigs were sacrificed at 4 weeks after implantation and one at 8 weeks thereafter.

Results: Optimal deployment and positioning were obtained in all but one animal. This animal died of unrecognized imperfect valved stent positioning after 4 days. The average mean gradient across the new valves and the left ventricular outflow tract (LVOT) were small. Mild regurgitation developed after valved stent deployment in one of six animals just after 1 h, and in none thereafter. All animals exhibited normal haemodynamics after mitral valved stent implantation, and stability was maintained throughout the monitoring period. Migration, embolization and paravalvular leakage were not evident in the remaining animals after 4 and 8 weeks. Gross evaluation revealed that 50-70% of the atrial element was covered by tissue growth at 4 weeks/8 weeks.

Conclusions: This study demonstrates adequate deployment and anchorage of a unique, repositionable mitral valved stent. A good valve function was revealed in animals observed for 4 weeks and in one pig after 8 weeks.