Direct endoscopy-guided mitral valve repair in the beating heart: An acute animal study

Objective: The purpose of this study was to develop a new method for minimally invasive mitral valve repair under direct endoscopic visualization in the beating heart. Methods: Fiberoptic cardioscopy of the left heart was conducted in 12 calves. Systemic perfusion was maintained by cardiopulmonary bypass through a median sternotomy. A clear solution (Ringer's lactate) was temporarily administered via the pulmonary artery to flush out the pulmonary vasculature, and additional perfusion of the left heart chambers enhanced visualization of the intracardiac anatomy. The endoscope, with an open-ended transparent flexible outer sheath, was inserted through the left ventricular apex, and an endoscopic clip was used for edge-to-edge mitral valve repair. Hemodilution was avoided by the drainage of irrigation fluid via a left ventricular cannula. Results: Direct endoscopic visualization of the mitral valve in an in vivo beating heart was obtained clearly, avoiding systemic hemodilution. In the last experiment, edge-to-edge repair using an endoscopic clip was successfully performed. Use of an effective intracardiac irrigation method was important for successful image acquisition and achievement of repair procedures. Conclusions: This acute animal study showed the technical feasibility of beating-heart mitral valve surgery under direct endoscopic imaging. Although this study was performed under open-chest conditions, our successful experiment is a first step toward closed-chest intracardiac surgery with direct endoscopic visualization.