A Non-Invasive Technique to Quantify In Vitro Bioprosthetic Valvular Coaptation

Abstract

The functional relationship between valvular leaflet stress and coaptive geometry may provide insight into a bioprosthetic heart valve's ability to maintain coaptation under a broad range of physiologic operating conditions. Previous investigators have only indirectly measured coaptation geometry. A non-invasive in vitro technique is demonstrated to directly quantify the coaptive geometry of bioprosthetic heart valves. A discussion is provided detailing the use of this information in a finite element model to determine the functional relationship between valvular leaflet stress and coaptation geometry. Video images of the stent post deflections and coaptive geometry for size 21 mm, 23 mm, and 25 mm Hancock Aortic Pericardial heart valves are obtained based on back light illumination of each valve's coaptive area at discrete back pressures. The resulting images are analyzed using image processing and motion analysis techniques. Results indicate that at back pressures greater than 50-75 mmHg the coaptive area remains constant. There is a decrease in coaptive depth at the valve's periphery, whereas the point of maximum coaptation maintains position approximately midway along the free margin. Good agreement is found between the experimentally determined and finite element model's predicted coaptation geometry.