In vivo comparison of hemocompatibility of materials used in mechanical heart valves.
OBJECTIVE
Most studies of mechanical heart valve prostheses in recent years have focused on the hydrodynamic and clinical performance of different valve designs. Little attention has been paid to the hemocompatibility (thrombogenicity) of materials used in the prostheses.


METHODS
In the present study, three materials currently used in mechanical heart valves, titanium, cobalt-chromium alloy (Haynes 25) and pyrolytic carbon (Pyrolite), together with a surface-modified (methylated) titanium, were evaluated and compared for their hemocompatibility in a sheep model. The test materials in the form of discs were glued to plastic buttons and implanted into the intrathoracic venae cavae of anesthetized sheep. Four different materials were tested simultaneously in each animal: two in the superior and two in the inferior vena cava. Eight animals were used. After two hours of exposure to flowing blood, the discs were explanted and evaluated for their hemocompatibility using close-up photography and scanning electron microscopy (SEM). Thrombus formation and blood cell adhesion were studied quantitatively.


RESULTS
The results showed that there was significantly more thrombus on pyrolytic carbon and methylated titanium than on titanium and cobalt-chromium (p < 0.05). More leukocytes adhered on pyrolytic carbon and cobalt-chromium than on titanium and methylated titanium (p < 0.05).


CONCLUSIONS
The results indicate that titanium and cobalt-chromium under the present condition were more hemocompatible than pyrolytic carbon. The clinical significance of the finding remains to be investigated.
Department of Cardiothoracic Surgery, Linköping Heart Center, University Hospital, Sweden.
Y
Y
Yang
S F
SF
Franzen
C L
CL
Olin
D000268:Adhesiveness; D000818:Animals; D001672:Biocompatible Materials; D001792:Blood Platelets / Q000648:ultrastructure; D002244:Carbon; D002858:Chromium Alloys; D006350:Heart Valve Prosthesis / Q000295:instrumentation*; D007962:Leukocytes / Q000648:ultrastructure; D008422:Materials Testing / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D012756:Sheep; D013924:Thrombophlebitis / Q000209:etiology / Q000473:pathology; D014025:Titanium; D014684:Venae Cavae / Q000601:surgery
D001672:Biocompatible Materials; D002858:Chromium Alloys; C009139:pyrolytic carbon; D002244:Carbon; D014025:Titanium