Heart valve function: a biomechanical perspective

Heart valves (HVs) are cardiac structures whose physiological function is to ensure directed blood flow through the heart over the cardiac cycle. While primarily passive structures that are driven by forces exerted by the surrounding blood and heart, this description does not adequately describe their elegant and complex biomechanical function. Moreover, they must replicate their cyclic function over an entire lifetime, with an estimated total functional demand of least 3×109 cycles. As in many physiological systems, one can approach HV biomechanics from a multi-length-scale approach, since mechanical stimuli occur and have biological impact at the organ, tissue and cellular scales. The present review focuses on the functional biomechanics of HVs. Specifically, we refer to the unique aspects of valvular function, and how the mechanical and mechanobiological behaviours of the constituent biological materials (e.g. extracellular matrix proteins and cells) achieve this remarkable feat. While we focus on the work from the authors' respective laboratories, the works of most investigators known to the authors have been included whenever appropriate. We conclude with a summary and underscore important future trends

Improving mitral valve coaptation with adjustable rings: outcomes from a European multicentre feasibility study with a new-generation adjustable annuloplasty ring system

OBJECTIVES: To evaluate the performance and safety of an adjustable semi-rigid annuloplasty ring for mitral regurgitation (MR) in a multicentre study. METHODS: Between March 2010 and December 2011, 30 subjects underwent mitral valve (MV) repair using the Cardinal adjustable annuloplasty ring. This device is a semi-rigid ring allowing postimplantation size adjustment, under beating-heart conditions, to optimize leaflet coaptation under echocardiographic guidance. Coaptation length was determined before and after adjustment by transoesophageal echocardiography. RESULTS: The study enrolled 21 (70%) male and 9 (30%) female subjects with a mean age of 64 years. The approach was conventional midline sternotomy or mini-invasive right thoracotomy. Leaflet resection was done in 17 subjects, and chordal repair was used in 13. Concomitant procedures included coronary artery bypass grafting in 2 (7%) subjects, atrial ablation in 4 (13%) and tricuspid repair in 4 (13%). There was 1 (3%) early death unrelated to the study device. Intraoperative ring adjustment was performed in 24 of the 30 subjects. Residual MR was detected prior to adjustment in 6 subjects (4 mild and 2 moderate MR). Following adjustment, 5 subjects had no MR and 1 had trace MR. After adjustment, mean coaptation length improved from 7 ± 3 to 10 ± 3 mm (P < 0.0001). All patients who completed 1-year follow-up had less-than-mild MR, with the exception of 1 patient with ring dehiscence (and resultant 2+ MR) and 1 functional MR patient who developed recurrent 2+ MR due to persistent leaflet tethering. CONCLUSIONS: MV repair with the Cardinal adjustable annuloplasty ring is a reliable technique that enables the adjustment of the ring diameter on a beating heart under echocardiographic control. Such technology allows the optimization of leaflet coaptation, providing minimal residual MR and durable repair