No fibrous cap and pannus formation in an On-X mechanical aortic valve.

Mechanical cardiac valves placed in the aortic position can show different amounts of pannus under the aortic ring. A 68-year-old patient had undergone mitral annuloplasty with a 30-mm rigid ring and aortic valve replacement with a 21-mm On-X mechanical valve for mitral regurgitation and aortic valve stenosis 10 years and 3 months previously. In the second cardiac surgery for mitral valve replacement to treat mitral stenosis, the previously replaced On-X mechanical valve revealed no fibrous cap on the sewing cuff and no pannus on the lower border of the valve ring. These characteristic findings can be attributed to the unique design elements of this valve.