The value and extent of valve area increase by balloon dilatation of the stenosed bioprosthesis: in vitro studies.

The value and extent in which balloon dilatation increases the valve area in severe bioprosthesis stenosis has not been defined. In-vitro double balloon dilatation, using 15 to 20 mm diameter Meditech balloon catheters, simultaneously inflated to 5 atmospheres, was attempted in 10 intact, stenosed, surgically excised bioprosthetic valves, 7 mitral and 3 aortic, size 21 to 35 mm. Radiological studies and calculation of the valve area, using a conical sizer, were performed both before and after balloon dilatation. After balloon dilatation the valve area was increased from 1.1 +/- 0.4 to 2.0 +/- 0.5 cm2 (p less than 0.001). The valve area increase was due to improved leaflet mobility in all cases. Leaflet calcium fractures were noted in 9 valves, 5 exhibited leaflet tears and the valve annulus was distorted in 3. A control group of balloon dilatation in 10 unused bioprostheses of the same sizes showed no leaflet tears. The mechanism of valve area increase, (80%), of stenotic bioprostheses by balloon dilatation, is improvement in leaflet mobility, partially secondary to leaflet calcium fractures and tears. Despite the marked increase in the bioprosthesis valve area the induction of leaflet tears will limit the clinical use of this technique for the dilatation of stenosed bioprosthetic valve.