Devices and methods for providing localized pressure to a region of a patient's heart to improve heart functioning. The devices include a cardiac jacket made of a flexible biocompatible material and at least one inflatable bladder disposed on an interior surface of the jacket. Inflation of the bladder causes the bladder to expand to exert localized pressure against a region of the heart. In some cases, a phase-change material is filled into the bladder as a liquid and the material solidifies at body temperature. In some cases, a positioning tool is used prior to the implantation of the jacket in order to determine effective positions for the inflatable bladder(s) to be located on the heart to improve heart functioning.