a through 3d show a variety of balloon inner members which help to provide axial length stability to the balloon 112 shown in fig1 a and 1b and maintain the lumen within the valve region in general colinear relationship with the lumen of the more proximal portions of the catheter assembly fig3 a shows a simple balloon inner member 114 as was included in the devices shown in fig1 a and 1b balloon inner member 114 is made up of two ends 116 and a spring 118 the ends serve to allow mounting of the balloon inner member 114 in the sections of the catheter having reasonably constant diameter the inner diameter may be large enough to pass the valve plug 104 therethrough or may be smaller to allow only the guidewire to pass the ends have of course a lumen allowing a guidewire to pass completely through the ends and through the intermediate coil 118 the ends 116 may be attached to the coil 118 by any suitable means including gluing shrink wrapping heat welding solvent welding and a host of other ways the coil 118 involved is one having an inside diameter at least larger than that of.