Electroactive polymers show promising characteristic such as lightness, compactness, flexibility and large displacements making them a candidate for application in cardiac assist devices. This revives the need for quasi- square wave voltage supply switching between 0 and several kilo-Volts, that must be efficient, to limit the heat dissipation, and compact in order to be implanted. The high access resistance, associated to compliant electrodes, represents an additional difficulty. Here, a solid-state Marx modulator is adapted to cope with electroactive polymer characteristics, taking advantage of an efficient energy transfer over a sequential multistep charge/discharge process. To ensure compactness, efficiency as well as the needs of an implanted device, a wireless magnetic field based communication, and power transfer system has been implemented. This work demonstrates the benefit of this design through simulations, and experimental validation on a cardiac assist device. At a voltage of 7 kV, an efficiency of up to 88% has been achieved over a complete charge/discharge cycle.