Effect of fibroblast growth factor-2 on pannus formation in replacement prosthetic heart valves

Fibroblast growth factor-2 (FGF-2) is a multifunctional protein which plays a role in smooth muscle cell growth, wound healing, tissue repair and angiogenesis. FGF-2 is also released by mechanically wounded cells. Herein, the importance of FGF-2 release from periannular tissue in the mechanism of pannus formation in obstructed mechanical prostheses was investigated.

Between January 1993 and December 2002, 35 patients with an obstructed bileaflet prosthetic mitral valve were classified according to the nature of obstruction as either thrombus or pannus. Data were related to patient age and gender, prosthesis model and size, intraoperative and pathology findings, and interval between implant and thrombosis. FGF-2 release was monitored immunohistochemically in all cases.

Thrombus formation was found in 19 patients, and pannus formation in 16. Patients were reoperated on after 3.10 +/- 0.7 years in the thrombus group, and after 6.3 +/- 0.46 years in the pannus group (p = 0.04). A foreign body reaction was found 78.9% of thrombus patients and 81.2% of pannus patients (p = 0.602), chronic inflammation in 31.5% and 50%, respectively (p = 0.317), and FGF-2 release in 78.9% and 87.5%, respectively (p = 0.582).

As FGF-2 release was similar in both patient groups, the duration of FGF-2 release from injured periannnular tissue was considered to form part of the chronic healing process, and was not attributed to mitral valve obstruction by pannus formation.