Aortic root expansion follows a precise chronology during systole and becomes more cylindrical - probably to maximize ejection. These findings might stimulate a more physiologic approach to aortic valve and aortic root surgical procedures.
Recent developments in aortic valve replacement include the truly stentless pericardial bioprostheses with single point attached commissures (SPAC) implantation technique. The leaflet geometry available for the SPAC valves can either be a simple tubular or a complex three-dimensional structure molded using specially designed molds. Our main objective was to compare these two leaflet designs, the tubular vs. the molded, by dynamic finite element simulation. Time-varying physiological pressure loadings over a full cardiac cycle were simulated using ABAQUS. Dynamic leaflet behavior, leaflet coaptation parameters, and stress distribution were compared. The maximum effective valve orifice area during systole is 633.5 mm(2) in the molded valve vs. 400.6 mm(2) in the tubular valve, and the leaflet coaptation height during diastole is 4.5 mm in the former, in contrast to 1.6 mm in the latter. Computed compressive stress indicates high magnitudes at the commissures and inter-leaflet margins of the tubular valve, the highest being 3.83 MPa, more than twice greater than 1.80 MPa in the molded valve. The molded leaflet design which resembles the native valve exerts a positive influence on the mechanical performance of the SPAC pericardial valves compared with the simple tubular design. This may suggest enhanced valve efficacy and durability.
Hepatitis B virus (HBV) reactivation is a well-described event in HBV surface antigen (HbsAg)-positive patients undergoing immunosuppression. There are only few data about the risk of HBV reactivation in HBsAg-negative solid-organ transplant recipients with resolved HBV infection. We conducted a systematic screening of serum and liver samples from 38 HBsAg-negative and anti-HBV core antigen (anti-HBc)-positive patients for the presence of HBV-DNA and for serologic HBV markers before and after solid-organ transplantation (kidney, n=23; liver, n=9; heart, n=6). Pretransplant prevalence of HBV-DNA was 24% (6/25) in serum and 33% (3/9) in liver samples. Forty-four percent (15/34) of the recipients were viremic after transplantation; this finding was more common in patients coinfected with hepatitis C (P=0.011) and in patients negative for anti-HBs (P=0.001). Two recipients became antigenemic (HBsAg-positive), but none developed clinical signs of hepatitis. In conclusion, subclinical reactivation of HBV infection was detected in a significant proportion of HBsAg-negative solid-organ-transplant recipients.
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