Balloon catheter apparatus and method

A balloon catheter for enlarging a flow passage within a vascular conduit, said balloon catheter comprising:

• a catheter tube having a longitudinal axis extending between a proximal end and a distal end;
• an inner member extending coaxially within said catheter tube, said inner member being longitudinally slidable within said catheter tube and configured such that a longitudinal passageway is created between said inner member and said catheter tube for passage of a fluid therethrough;
• a balloon disposed coaxially about said inner member, said balloon having a proximal balloon end connected to said distal end of said catheter tube and a distal balloon end connected to said inner member to define an annular balloon chamber in fluid connection with said longitudinal passageway, said balloon having properties for inflating and deflating in response to the fluid passing through the longitudinal passageway;
• an outer sleeve surrounding said balloon, said sleeve having a proximal sleeve end connected to said distal end of said catheter tube and a distal sleeve end connected to the distal end of said inner member such that said outer sleeve is radially expandable and collapsible independent of said balloon through movement of the inner member relative to the catheter tube;
• and
• the outer sleeve being radially expandable to a predetermined configuration comprising a pair of spaced-apart annular chambers, and said balloon, upon inflation, being limited to the predetermined configuration by said outer sleeve.