Non-destructive assessment of 62 Dutch Björk-Shiley convexo-concave heart valves

Non-destructive assessment of 62 Björk-Shiley convexo-concave heart valves in view of the risk of fracture and possible detection of defects by means of X-ray or acoustics. Scanning electron microscopy and stereomicroscopy of an unselected sample of valves, representing approximately 70% of the valves explanted between 1991 and 1996. Mean duration of implantation was 10.7 +/- 1.9 years. Six of the 62 valves had a fracture with disk escape. Of the remaining 56 valves, 11 (19.6%) had a single-leg fracture and seven (12.5%) showed a crack. Valves, 24 (42.8%), revealed no significant defect. After 4600 days of implantation, large valves (i.e. > or = 29 mm) showed a 6.7 time increase in the risk of crack or single-leg fracture compared with smaller valves (OR 6.7, 95% CI 1.8-24.6, P = 0.04). In a small in-vitro experiment with single-leg fracture, rapid smearing occurred, resulting in strut leg separation upon some movement. After approximately 400 x 10(6) cycles, 42.5% of the retrieved intact valves was without significant defect, while 32% had a serious prefracture defect. Time evolution from defect to fracture remains unpredictable. Also, detection of prefracture defects, including single-leg fracture, remains difficult, because a "well-detectable' fracture with dislocation is just a brief condition. However, technical knowledge can enhance the epidemiological and manufacturing information used for clinical decision making