Abstract: A catheter system (100) for treating a treatment site (106) within or adjacent to a vessel wall (108) or heart valve includes a balloon (104) having a balloon length (204L). The balloon (104) is configured to be movable between an inflated state (135) and a deflated state. The balloon (104) includes (i) a balloon proximal region (250), (ii) a balloon distal region (254), and (iii) a balloon transition region (252). The balloon proximal region (250) has a balloon proximal end (204P) and a substantially constant balloon proximal region diameter (256) while the balloon (104) is in the inflated state (135). The balloon distal region (254) has a balloon distal end (104D), and a substantially constant balloon distal region diameter (262) while the balloon (104) is in the inflated state (135). The balloon distal region diameter (262) is different than the balloon proximal region diameter (256). The balloon transition region (252) has a balloon transition region diameter (260) that varies.