A catheter includes a balloon and a shaft having a coaxial portion including an outer tubular member having a bore, a transition neck, an access fitting adjacent the proximate end of the catheter shaft for directing a guidewire into the catheter shaft, an inflation port, a guidewire tubular member disposed coaxially in the outer tubular member, the outer tubular member and guidewire tubular member defining a first, annular inflation/deflation lumen fluid communication with the inflation port, at least one second inflation/deflation lumen separate from and non-coaxial with the guidewire tubular member and having a cross-sectional area less than the cross-sectional area of the first inflation/deflation lumen and opening at a proximate end into the first inflation/deflation lumen and at the distal end of the transition neck.