Wisconsin Heart Hospital

Mitral and tricuspid valves are essential for unidirectional blood flow in the heart. They are derived from similar cell sources, and yet congenital dysplasia affecting both valves is clinically rare, suggesting the presence of differential regulatory mechanisms underlying their development. Here, we specifically inactivated Dicer1 in the endocardium during cardiogenesis and found that Dicer1 deletion caused congenital mitral valve stenosis and regurgitation, whereas it had no impact on other valves. We showed that hyperplastic mitral valves were caused by abnormal condensation and extracellular matrix (ECM) remodeling. Our single-cell RNA sequencing analysis revealed impaired maturation of mesenchymal cells and abnormal expression of ECM genes in mutant mitral valves. Furthermore, expression of a set of miRNAs that target ECM genes was significantly lower in tricuspid valves compared to mitral valves, consistent with the idea that the miRNAs are differentially required for mitral and tricuspid valve development. We thus reveal miRNA-mediated gene regulation as a novel molecular mechanism that differentially regulates mitral and tricuspid valve development, thereby enhancing our understanding of the non-association of inborn mitral and tricuspid dysplasia observed clinically.

Transcatheter valve-in-valve and valve-in-ring implantation has become a common approach to treating patients with failed bioprosthetic tricuspid valves as well as failed surgical repairs of the tricuspid valve where an annuloplasty ring has been utilized. We describe a case where a Melody valve was percutaneously implanted in a native tricuspid valve with severe stenosis following surgical repair without a supporting annuloplasty ring.

Robotically assisted coronary artery bypass grafting is gaining again the interest of cardiac surgeons. The use of the CE-marked and FDA-cleared C-Port Flex A® anastomotic connector facilitates the mission critical anastomosis between the bypass graft and the target coronary artery. Anastomotic times are significantly shorter, and technical reliability is high. Midterm results of facilitated anastomoses created with the C-Port product line are comparable with those obtained with hand-sewn anastomoses; long-term results are awaited. This technique can become an integral part of the totally endoscopic coronary artery bypass grafting procedure.