Implantable pulse generator for two-stage therapy

An implantable medical device for generating electrical stimulations, wherein the medical device is embodied to generate and emit, a first therapy treatment via a first stimulation phase, wherein at least one first stimulation that has a first amplitude is generated by means of energy from an energy storage element, and a second therapy treatment via a second stimulation phase following the first stimulation phase when it is determined that the at least one first stimulation does not result in a therapy treatment success, wherein at least one second stimulation that has a second amplitude is generated by means of energy from the energy storage element, wherein the energy storage element is charged prior to the generation of the at least one first stimulation and after the generation of the at least one first stimulation but before generation of the at least one second stimulation, wherein the medical device is embodied not to completely discharge the energy storage element by generating the at least one first stimulation, wherein the energy of the at least one first stimulation is less than the energy of the at least one second stimulation, or the total energy of a plurality of first stimulations in the first stimulation phase is less than the total energy of a plurality of second stimulations in the second stimulation phase, and wherein the implantable medical device includes a control unit configured for terminating the first stimulation phase and continuing with the second stimulation phase when a predefined quantity of energy of the at least one first stimulation has been used without therapy success and/or when the first stimulation phase has not demonstrated any therapy success over a predefined or programmed period, wherein the first stimulation phase is divided into subphases with a parameter set for a highest therapy success in a first subphase followed by additional subphases with parameters sets in the sequence of decreasing chances of success.