Developments in cardiovascular valve technology - Biomaterials and Devices for the Circulatory System - page 107

(a) (b)

4.16 Autopsy specimens of two cases of thromboembolic
complications. (a) Atrial aspect of a cloth-covered Tefl on disc Beall
valve with thrombotic occlusion. The ventricular side of this valve was
almost completely covered by the thrombus. From reference 82;
courtesy of Chest . (b) Thrombotic occlusion of a Björk-Shiley aortic
prosthesis.

mortality. Prosthetic valve endocarditis (PVE) is a rare event with an inci-
dence of 1% in most institutions, but carries a mortality rate of 18%. By
defi nition PVE is divided into early phase ( ≤ 60 days postoperative) and late

phase ( 60 days postoperative). The most common organisms associated

with PVE are coagulase-negative staphylococcus (52%), fungi (13%),
Staphylococcus aureus (10%), and enterococci (8%). 88 In a series of 1200
St. Jude medical prostheses implanted from 1982 to 1991, Fernandez et al.
reported an incidence of early-onset prosthetic valve endocarditis of 0.7%,
and 1.4% for late-onset infections. 89 The pathological process of PVE
appears to occur at the annulus with destruction of the annular anchor
sutures, thus leading to partial valve dehiscence and paravalvular leaks.
Other complications include the formation of pseudoaneurysms, prosthetic
obstruction by vegetations, septic systemic emboli, and conduction
abnormalities. 90,91
Pyrolytic carbon-based valves, although somewhat thromboresistant, can
have variable susceptibility to prosthetic valve infections. The formation of
a bacterial biofi lm is dependent on the interaction of surface free energy
and roughness properties of the pyrolytic carbon. Litzler et al. analyzed
three different pyrolytic carbon valves in current clinical use, and found
marked differences in roughness and surface free energy measured by
interferential microscopy and contact angle technique, respectively. The
rougher the pyrolytic surface the more likely bacteria were to adhere and

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