Patent ID: 8591461

Claim:
A balloon catheter comprising: a catheter shaft extending along a longitudinal axis; a first balloon mounted on the catheter shaft, the first balloon having a middle working region; and a second balloon mounted around at least a portion of the first balloon, the second balloon having a middle working length, and a plurality of holes formed in the middle working length to define a perforated portion, each of the first and second balloons movable to an expanded configuration to define an annular space therebetween, the annular space being in communication with the plurality of holes of the second balloon, the annular space comprising an annular working region disposed between the perforated portion of the middle working length of the second balloon and a corresponding portion of the middle working region of the first balloon, the corresponding portion comprising a series of longitudinal segments defining a plurality of steps each having a different cross-sectional area, the cross-sectional area of a first longitudinal segment being less than the cross-sectional area of a second longitudinal segment positioned distal to the first longitudinal segment, wherein the annular working region has an increasingly smaller cross-sectional area along the longitudinal axis in a distal direction.